Summary description for Page.
コード例 #1
0
		int open_seekable()
		{
            VorbisFileInstance instance = makeInstance();
			Info initial_i=new Info();
			Comment initial_c=new Comment();
			int serialno;
			long end;
			int ret;
			int dataoffset;
			Page og=new Page();
			// is this even vorbis...?
			int[] foo=new int[1];
            ret = fetch_headers(initial_i, initial_c, foo, null, instance);
			serialno=foo[0];
			dataoffset=(int)offset; //!!
			instance.os.clear();
			if(ret==-1)return(-1);
			// we can seek, so set out learning all about this file
			skable=true;
			//(callbacks.seek_func)(datasource, 0, SEEK_END);
			fseek(datasource, 0, SEEK_END);
			//offset=end=(callbacks.tell_func)(datasource);
			offset=ftell(datasource);
			end=offset;
			// We get the offset for the last page of the physical bitstream.
			// Most OggVorbis files will contain a single logical bitstream
			end=get_prev_page(og, instance);
			// moer than one logical bitstream?
			if(og.serialno()!=serialno)
			{
				// Chained bitstream. Bisect-search each logical bitstream
				// section.  Do so based on serial number only
				if(bisect_forward_serialno(0,0,end+1,serialno,0, instance)<0)
				{
					clear();
					return OV_EREAD;
				}
			}
			else
			{
				// Only one logical bitstream
				if(bisect_forward_serialno(0,end,end+1,serialno,0, instance)<0)
				{
					clear();
					return OV_EREAD;
				}
			}
			prefetch_all_headers(initial_i, initial_c, dataoffset, instance);
			//return(raw_seek(0));
            return 0;
		}
コード例 #2
0
ファイル: StreamState.cs プロジェクト: cody82/spacewar-arena
        /* This will flush remaining packets into a page (returning nonzero),
               even if there is not enough data to trigger a flush normally
               (undersized page). If there are no packets or partial packets to
               flush, ogg_stream_flush returns 0.  Note that ogg_stream_flush will
               try to flush a normal sized page like ogg_stream_pageout; a call to
               ogg_stream_flush does not gurantee that all packets have flushed.
               Only a return value of 0 from ogg_stream_flush indicates all packet
               data is flushed into pages.

               ogg_stream_page will flush the last page in a stream even if it's
               undersized; you almost certainly want to use ogg_stream_pageout
               (and *not* ogg_stream_flush) unless you need to flush an undersized
               page in the middle of a stream for some reason. */
        public int flush(Page og)
        {
            //System.out.println(this+" ---body_returned: "+body_returned);

            int i;
            int vals=0;
            int maxvals=(lacing_fill>255?255:lacing_fill);
            int bytes=0;
            int acc=0;
            long granule_pos=granule_vals[0];

            if(maxvals==0)return(0);

            /* construct a page */
            /* decide how many segments to include */

            /* If this is the initial header case, the first page must only include
                   the initial header packet */
            if(b_o_s==0)
            {  /* 'initial header page' case */
                granule_pos=0;
                for(vals=0;vals<maxvals;vals++)
                {
                    if((lacing_vals[vals]&0x0ff)<255)
                    {
                        vals++;
                        break;
                    }
                }
            }
            else
            {
                for(vals=0;vals<maxvals;vals++)
                {
                    if(acc>4096)break;
                    acc+=(lacing_vals[vals]&0x0ff);
                    granule_pos=granule_vals[vals];
                }
            }

            /* construct the header in temp storage */

            String oggs_str = "OggS";
            Encoding AE = Encoding.UTF8;
            byte[] oggs_byt = AE.GetBytes(oggs_str);
            Array.Copy(oggs_byt, 0, header, 0, oggs_byt.Length);

            /* stream structure version */
            header[4]=0x00;

            /* continued packet flag? */
            header[5]=0x00;
            if((lacing_vals[0]&0x100)==0)header[5]|=0x01;
            /* first page flag? */
            if(b_o_s==0) header[5]|=0x02;
            /* last page flag? */
            if(e_o_s!=0 && lacing_fill==vals) header[5]|=0x04;
            b_o_s=1;

            /* 64 bits of PCM position */
            for(i=6;i<14;i++)
            {
                header[i]=(byte)granule_pos;
                granule_pos>>=8;
            }

            /* 32 bits of stream serial number */
            {
            int _serialno=serialno;
            for(i=14;i<18;i++)
            {
                header[i]=(byte)_serialno;
                _serialno>>=8;
            }
            }

            /* 32 bits of page counter (we have both counter and page header
                   because this val can roll over) */
            if(pageno==-1)pageno=0;       /* because someone called
                     stream_reset; this would be a
                     strange thing to do in an
                     encode stream, but it has
                     plausible uses */
            {
            int _pageno=pageno++;
            for(i=18;i<22;i++)
            {
                header[i]=(byte)_pageno;
                _pageno>>=8;
            }
            }

            /* zero for computation; filled in later */
            header[22]=0;
            header[23]=0;
            header[24]=0;
            header[25]=0;

            /* segment table */
            header[26]=(byte)vals;
            for(i=0;i<vals;i++)
            {
                header[i+27]=(byte)lacing_vals[i];
                bytes+=(header[i+27]&0xff);
            }

            /* set pointers in the ogg_page struct */
            og.header_base=header;
            og.header=0;
            og.header_len=header_fill=vals+27;
            og.body_base=body_data;
            og.body=body_returned;
            og.body_len=bytes;

            /* advance the lacing data and set the body_returned pointer */

            lacing_fill-=vals;
            Array.Copy(lacing_vals, vals, lacing_vals, 0, lacing_fill*4);
            Array.Copy(granule_vals, vals, granule_vals, 0, lacing_fill*8);
            body_returned+=bytes;

            /* calculate the checksum */

            og.checksum();

            /* done */
            return(1);
        }
コード例 #3
0
		// uses the local ogg_stream storage in vf; this is important for
		// non-streaming input sources
        public int fetch_headers(Info vi, Comment vc, int[] serialno, Page og_ptr, VorbisFileInstance instance)
		{
			//System.err.println("fetch_headers");
			Page og=new Page();
			Packet op=new Packet();
			int ret;

			if(og_ptr==null)
			{
                ret = get_next_page(og, CHUNKSIZE, instance);
				if(ret==OV_EREAD)return OV_EREAD;
				if(ret<0) return OV_ENOTVORBIS;
				og_ptr=og;
			}
  
			if(serialno!=null)serialno[0]=og_ptr.serialno();

			instance.os.init(og_ptr.serialno());
  
			// extract the initial header from the first page and verify that the
			// Ogg bitstream is in fact Vorbis data
  
			vi.init();
			vc.init();
  
			int i=0;
			while(i<3)
			{
                instance.os.pagein(og_ptr);
				while(i<3)
				{
                    int result = instance.os.packetout(op);
					if(result==0)break;
					if(result==-1)
					{
						Console.Error.WriteLine("Corrupt header in logical bitstream.");
						//goto bail_header;
						vi.clear();
						vc.clear();
                        instance.os.clear();
						return -1;
					}
					if(vi.synthesis_headerin(vc, op)!=0)
					{
						Console.Error.WriteLine("Illegal header in logical bitstream.");
						//goto bail_header;
						vi.clear();
						vc.clear();
                        instance.os.clear();
						return -1;
					}
					i++;
				}
				if(i<3)
					if(get_next_page(og_ptr, 1, instance)<0)
					{
						Console.Error.WriteLine("Missing header in logical bitstream.");
						//goto bail_header;
						vi.clear();
						vc.clear();
                        instance.os.clear();
						return -1;
					}
			}
			return 0; 
		}
コード例 #4
0
		// last step of the OggVorbis_File initialization; get all the
		// vorbis_info structs and PCM positions.  Only called by the seekable
		// initialization (local stream storage is hacked slightly; pay
		// attention to how that's done)
		public void prefetch_all_headers(Info first_i,Comment first_c, int dataoffset,
            VorbisFileInstance instance)
		{
			Page og=new Page();
			int ret;
  
			vi=new Info[links];
			vc=new Comment[links];
			dataoffsets=new long[links];
			pcmlengths=new long[links];
			serialnos=new int[links];
  
			for(int i=0;i<links;i++)
			{
				if(first_i!=null && first_c!=null && i==0)
				{
					// we already grabbed the initial header earlier.  This just
					// saves the waste of grabbing it again
					// !!!!!!!!!!!!!
					vi[i]=first_i;
					//memcpy(vf->vi+i,first_i,sizeof(vorbis_info));
					vc[i]=first_c;
					//memcpy(vf->vc+i,first_c,sizeof(vorbis_comment));
					dataoffsets[i]=dataoffset;
				}
				else
				{
					// seek to the location of the initial header
                    seek_helper(offsets[i], instance); //!!!
                    if (fetch_headers(vi[i], vc[i], null, null, instance) == -1)
					{
						Console.Error.WriteLine("Error opening logical bitstream #"+(i+1)+"\n");
						dataoffsets[i]=-1;
					}
					else
					{
						dataoffsets[i]=offset;
						instance.os.clear();
					}
				}

				// get the serial number and PCM length of this link. To do this,
				// get the last page of the stream
				long end=offsets[i+1]; //!!!
                seek_helper(end, instance);

				while(true)
				{
					ret=get_prev_page(og, instance);
					if(ret==-1)
					{
						// this should not be possible
						Console.Error.WriteLine("Could not find last page of logical "+
							"bitstream #"+(i)+"\n");
						vi[i].clear();
						vc[i].clear();
						break;
					}
					if(og.granulepos()!=-1)
					{
						serialnos[i]=og.serialno();
						pcmlengths[i]=og.granulepos();
						break;
					}
				}
			}
		}
コード例 #5
0
        private int get_prev_page(Page page, VorbisFileInstance instance)
		{
			long begin=offset; //!!!
			int ret;
			int offst=-1;
			while(offst==-1)
			{
				begin-=CHUNKSIZE;
				if(begin<0)
					begin=0;
				seek_helper(begin, instance);
				while(offset<begin+CHUNKSIZE)
				{
					ret=get_next_page(page, begin+CHUNKSIZE-offset, instance);
					if(ret==OV_EREAD){ return OV_EREAD; }
					if(ret<0){ break; }
					else{ offst=ret; }
				}
			}
            seek_helper(offst, instance); //!!!
			ret=get_next_page(page, CHUNKSIZE, instance);
			if(ret<0)
			{
				//System.err.println("Missed page fencepost at end of logical bitstream Exiting");
				//System.exit(1);
				return OV_EFAULT;
			}
			return offst;
		}
コード例 #6
0
		public int bisect_forward_serialno(long begin, long searched, long end, int currentno, int m, VorbisFileInstance instance)
		{
			long endsearched=end;
			long next=end;
			Page page=new Page();
			int ret;

			while(searched<endsearched)
			{
				long bisect;
				if(endsearched-searched<CHUNKSIZE)
				{
					bisect=searched;
				}
				else
				{
					bisect=(searched+endsearched)/2;
				}

                seek_helper(bisect, instance);
                ret = get_next_page(page, -1, instance);
				if(ret==OV_EREAD) return OV_EREAD;
				if(ret<0 || page.serialno()!=currentno)
				{
					endsearched=bisect;
					if(ret>=0)next=ret;
				}
				else
				{
					searched=ret+page.header_len+page.body_len;
				}
			}
            seek_helper(next, instance);
            ret = get_next_page(page, -1, instance);
			if(ret==OV_EREAD) return OV_EREAD;

			if(searched>=end || ret==-1)
			{
				links=m+1;
				offsets=new long[m+2];
				offsets[m+1]=searched;
			}
			else
			{
				ret=bisect_forward_serialno(next, offset, end, page.serialno(), m+1, instance);
				if(ret==OV_EREAD)return OV_EREAD;
			}
			offsets[m]=begin;
			return 0;  
		}
コード例 #7
0
ファイル: VorbisFile.cs プロジェクト: Daramkun/ProjectLiqueur
        // seek to a sample offset relative to the decompressed pcm stream
        // returns zero on success, nonzero on failure
        public int pcm_seek(long pos)
        {
            int link=-1;
            long total=pcm_total(-1);

            if(!skable)return(-1); // don't dump machine if we can't seek
            if(pos<0 || pos>total)
            {
                //goto seek_error;
                pcm_offset=-1;
                decode_clear();
                return -1;
            }

            // which bitstream section does this pcm offset occur in?
            for(link=links-1;link>=0;link--)
            {
                total-=pcmlengths[link];
                if(pos>=total)break;
            }

            // search within the logical bitstream for the page with the highest
            // pcm_pos preceeding (or equal to) pos.  There is a danger here;
            // missing pages or incorrect frame number information in the
            // bitstream could make our task impossible.  Account for that (it
            // would be an error condition)
            {
            long target=pos-total;
            long end=offsets[link+1];
            long begin=offsets[link];
            int best=(int)begin;

            Page og=new Page();
            while(begin<end)
            {
                long bisect;
                int ret;

                if(end-begin<CHUNKSIZE)
                {
                    bisect=begin;
                }
                else
                {
                    bisect=(end+begin)/2;
                }

                seek_helper(bisect);
                ret=get_next_page(og,end-bisect);

                if(ret==-1)
                {
                    end=bisect;
                }
                else
                {
                    long granulepos=og.granulepos();
                    if(granulepos<target)
                    {
                        best=ret;  // raw offset of packet with granulepos
                        begin=offset; // raw offset of next packet
                    }
                    else
                    {
                        end=bisect;
                    }
                }
            }
            // found our page. seek to it (call raw_seek).
            if(raw_seek(best)!=0)
            {
                //goto seek_error;
                pcm_offset=-1;
                decode_clear();
                return -1;
            }
            }

            // verify result
            if(pcm_offset>=pos)
            {
                //goto seek_error;
                pcm_offset=-1;
                decode_clear();
                return -1;
            }
            if(pos>pcm_total(-1))
            {
                //goto seek_error;
                pcm_offset=-1;
                decode_clear();
                return -1;
            }

            // discard samples until we reach the desired position. Crossing a
            // logical bitstream boundary with abandon is OK.
            while(pcm_offset<pos)
            {
                float[][] pcm;
                int target=(int)(pos-pcm_offset);
                float[][][] _pcm=new float[1][][];
                int[] _index=new int[getInfo(-1).channels];
                int samples=vd.synthesis_pcmout(_pcm, _index);
                pcm=_pcm[0];

                if(samples>target)samples=target;
                vd.synthesis_read(samples);
                pcm_offset+=samples;

                if(samples<target)
                    if(process_packet(1)==0)
                    {
                        pcm_offset=pcm_total(-1); // eof
                    }
            }
            return 0;

            // seek_error:
            // dump machine so we're in a known state
            //pcm_offset=-1;
            //decode_clear();
            //return -1;
        }
コード例 #8
0
        Stream DecodeStream( Stream input, bool skipWavHeader )
        {
            int convsize = 4096 * 2;
            byte [] convbuffer = new byte [ convsize ];

            Stream output = new MemoryStream ();

            if ( !skipWavHeader )
                output.Seek ( HEADER_SIZE, SeekOrigin.Begin );

            SyncState oy = new SyncState ();
            StreamState os = new StreamState ();
            Page og = new Page ();
            Packet op = new Packet ();

            Info vi = new Info ();
            Comment vc = new Comment ();
            DspState vd = new DspState ();
            Block vb = new Block ( vd );

            byte [] buffer;
            int bytes = 0;

            oy.init ();

            while ( true )
            {
                int eos = 0;

                int index = oy.buffer ( 4096 );
                buffer = oy.data;
                bytes = input.Read ( buffer, index, 4096 );
                oy.wrote ( bytes );

                if ( oy.pageout ( og ) != 1 )
                {
                    if ( bytes < 4096 ) break;
                    throw new Exception ( "Input does not appear to be an Ogg bitstream." );
                }

                os.init ( og.serialno () );

                vi.init ();
                vc.init ();
                if ( os.pagein ( og ) < 0 )
                {
                    throw new Exception ( "Error reading first page of Ogg bitstream data." );
                }

                if ( os.packetout ( op ) != 1 )
                {
                    throw new Exception ( "Error reading initial header packet." );
                }

                if ( vi.synthesis_headerin ( vc, op ) < 0 )
                {
                    throw new Exception ( "This Ogg bitstream does not contain Vorbis audio data." );
                }

                int i = 0;

                while ( i < 2 )
                {
                    while ( i < 2 )
                    {

                        int result = oy.pageout ( og );
                        if ( result == 0 ) break;

                        if ( result == 1 )
                        {
                            os.pagein ( og );
                            while ( i < 2 )
                            {
                                result = os.packetout ( op );
                                if ( result == 0 ) break;
                                if ( result == -1 )
                                {
                                    throw new Exception ( "Corrupt secondary header.  Exiting." );
                                }
                                vi.synthesis_headerin ( vc, op );
                                i++;
                            }
                        }
                    }
                    index = oy.buffer ( 4096 );
                    buffer = oy.data;
                    bytes = input.Read ( buffer, index, 4096 );
                    if ( bytes == 0 && i < 2 )
                    {
                        throw new Exception ( "End of file before finding all Vorbis headers!" );
                    }
                    oy.wrote ( bytes );
                }

                {
                    byte [] [] ptr = vc.user_comments;
                    for ( int j = 0; j < vc.user_comments.Length; j++ )
                    {
                        if ( ptr [ j ] == null ) break;
                    }
                }

                convsize = 4096 / vi.channels;

                vd.synthesis_init ( vi );
                vb.init ( vd );

                float [] [] [] _pcm = new float [ 1 ] [][];
                int [] _index = new int [ vi.channels ];
                while ( eos == 0 )
                {
                    while ( eos == 0 )
                    {
                        int result = oy.pageout ( og );
                        if ( result == 0 ) break;
                        if ( result == -1 )
                            throw new Exception ( "Corrupt or missing data in bitstream; continuing..." );
                        else
                        {
                            os.pagein ( og );
                            while ( true )
                            {
                                result = os.packetout ( op );

                                if ( result == 0 ) break;
                                if ( result == -1 )
                                {

                                }
                                else
                                {
                                    int samples;
                                    if ( vb.synthesis ( op ) == 0 )
                                    {
                                        vd.synthesis_blockin ( vb );
                                    }

                                    while ( ( samples = vd.synthesis_pcmout ( _pcm, _index ) ) > 0 )
                                    {
                                        float [] [] pcm = _pcm [ 0 ];
                                        bool clipflag = false;
                                        int bout = ( samples < convsize ? samples : convsize );

                                        for ( i = 0; i < vi.channels; i++ )
                                        {
                                            int ptr = i * 2;
                                            int mono = _index [ i ];
                                            for ( int j = 0; j < bout; j++ )
                                            {
                                                int val = ( int ) ( pcm [ i ] [ mono + j ] * 32767.0 );
                                                if ( val > 32767 )
                                                {
                                                    val = 32767;
                                                    clipflag = true;
                                                }
                                                if ( val < -32768 )
                                                {
                                                    val = -32768;
                                                    clipflag = true;
                                                }
                                                if ( val < 0 ) val = val | 0x8000;
                                                convbuffer [ ptr ] = ( byte ) ( val );
                                                convbuffer [ ptr + 1 ] = ( byte ) ( ( uint ) val >> 8 );
                                                ptr += 2 * ( vi.channels );
                                            }
                                        }

                                        if ( clipflag )
                                        {

                                        }

                                        output.Write ( convbuffer, 0, 2 * vi.channels * bout );

                                        vd.synthesis_read ( bout );
                                    }
                                }
                            }
                            if ( og.eos () != 0 ) eos = 1;
                        }
                    }
                    if ( eos == 0 )
                    {
                        index = oy.buffer ( 4096 );
                        buffer = oy.data;
                        bytes = input.Read ( buffer, index, 4096 );
                        oy.wrote ( bytes );
                        if ( bytes == 0 ) eos = 1;
                    }
                }

                os.clear ();

                vb.clear ();
                vd.clear ();
                vi.clear ();
            }

            oy.clear ();

            output.Seek ( 0, SeekOrigin.Begin );
            if ( !skipWavHeader )
            {
                WriteHeader ( output, ( int ) ( output.Length - HEADER_SIZE ), vi.rate, ( ushort ) 16, ( ushort ) vi.channels );
                output.Seek ( 0, SeekOrigin.Begin );
            }

            return output;
        }
コード例 #9
0
ファイル: OggDecoder.cs プロジェクト: hultqvist/csvorbis
        /// <summary>
        /// Decodes a stream of Ogg Vorbis data into wav file format.
        /// </summary>
        /// <returns>
        /// A MemoryStream with the entire decoded stream.
        /// </returns>
        /// <param name='input'>
        /// Ogg Vorbis data to be decoded
        /// </param>
        /// <param name='output'>
        /// <para>Stream to write wav data.</para>
        /// <para>If writeWavHeader is true then this stream must be seekable.</para>
        /// </param>
        /// <param name='writeWavHeader'>
        /// Write wav header in the beginning of the returned stream.
        /// </param>
        public static void DecodeStream(Stream input, Stream output, bool writeWavHeader)
        {
            int convsize = 4096 * 2;
            byte[] convbuffer = new byte[convsize]; // take 8k out of the data segment, not the stack
            long start = output.Position;

            DebugWriter s_err = new DebugWriter();

            if (writeWavHeader && !output.CanSeek)
                throw new ArgumentException("To write wav header, the output stream must be seekable.", "output");

            if (writeWavHeader)
                output.Seek(HEADER_SIZE, SeekOrigin.Current); // reserve place for WAV header

            SyncState oy = new SyncState(); // sync and verify incoming physical bitstream
            StreamState os = new StreamState(); // take physical pages, weld into a logical stream of packets
            Page og = new Page(); // one Ogg bitstream page.  Vorbis packets are inside
            Packet op = new Packet(); // one raw packet of data for decode

            Info vi = new Info();  // struct that stores all the static vorbis bitstream settings
            Comment vc = new Comment(); // struct that stores all the bitstream user comments
            DspState vd = new DspState(); // central working state for the packet->PCM decoder
            Block vb = new Block(vd); // local working space for packet->PCM decode

            int bytes = 0;

            // Decode setup
            oy.init(); // Now we can read pages

            // we repeat if the bitstream is chained
            while (true)
            {
                int eos = 0;

                // grab some data at the head of the stream.  We want the first page
                // (which is guaranteed to be small and only contain the Vorbis
                // stream initial header) We need the first page to get the stream
                // serialno.

                // submit a 4k block to libvorbis' Ogg layer
                int index = oy.buffer(4096);
                bytes = input.Read(oy.data, index, 4096);
                oy.wrote(bytes);

                // Get the first page.
                if (oy.pageout(og) != 1)
                {
                    // have we simply run out of data?  If so, we're done.
                    if (bytes < 4096)
                        break;

                    // error case.  Must not be Vorbis data
                    s_err.WriteLine("Input does not appear to be an Ogg bitstream.");
                }

                // Get the serial number and set up the rest of decode.
                // serialno first; use it to set up a logical stream
                os.init(og.serialno());

                // extract the initial header from the first page and verify that the
                // Ogg bitstream is in fact Vorbis data

                // I handle the initial header first instead of just having the code
                // read all three Vorbis headers at once because reading the initial
                // header is an easy way to identify a Vorbis bitstream and it's
                // useful to see that functionality seperated out.

                vi.init();
                vc.init();
                if (os.pagein(og) < 0)
                {
                    // error; stream version mismatch perhaps
                    s_err.WriteLine("Error reading first page of Ogg bitstream data.");
                }

                if (os.packetout(op) != 1)
                {
                    // no page? must not be vorbis
                    s_err.WriteLine("Error reading initial header packet.");
                }

                if (vi.synthesis_headerin(vc, op) < 0)
                {
                    // error case; not a vorbis header
                    s_err.WriteLine("This Ogg bitstream does not contain Vorbis audio data.");
                }

                // At this point, we're sure we're Vorbis.  We've set up the logical
                // (Ogg) bitstream decoder.  Get the comment and codebook headers and
                // set up the Vorbis decoder

                // The next two packets in order are the comment and codebook headers.
                // They're likely large and may span multiple pages.  Thus we reead
                // and submit data until we get our two pacakets, watching that no
                // pages are missing.  If a page is missing, error out; losing a
                // header page is the only place where missing data is fatal. */

                int i = 0;

                while (i < 2)
                {
                    while (i < 2)
                    {

                        int result = oy.pageout(og);
                        if (result == 0)
                            break; // Need more data
                        // Don't complain about missing or corrupt data yet.  We'll
                        // catch it at the packet output phase

                        if (result == 1)
                        {
                            os.pagein(og); // we can ignore any errors here
                            // as they'll also become apparent
                            // at packetout
                            while (i < 2)
                            {
                                result = os.packetout(op);
                                if (result == 0)
                                    break;
                                if (result == -1)
                                {
                                    // Uh oh; data at some point was corrupted or missing!
                                    // We can't tolerate that in a header.  Die.
                                    s_err.WriteLine("Corrupt secondary header.  Exiting.");
                                }
                                vi.synthesis_headerin(vc, op);
                                i++;
                            }
                        }
                    }
                    // no harm in not checking before adding more
                    index = oy.buffer(4096);
                    bytes = input.Read(oy.data, index, 4096);
                    if (bytes == 0 && i < 2)
                    {
                        s_err.WriteLine("End of file before finding all Vorbis headers!");
                    }
                    oy.wrote(bytes);
                }

                // Throw the comments plus a few lines about the bitstream we're
                // decoding
                {
                    byte[][] ptr = vc.user_comments;
                    for (int j = 0; j < vc.user_comments.Length; j++)
                    {
                        if (ptr [j] == null)
                            break;
                        s_err.WriteLine(vc.getComment(j));
                    }
                    s_err.WriteLine("\nBitstream is " + vi.channels + " channel, " + vi.rate + "Hz");
                    s_err.WriteLine("Encoded by: " + vc.getVendor() + "\n");
                }

                convsize = 4096 / vi.channels;

                // OK, got and parsed all three headers. Initialize the Vorbis
                //  packet->PCM decoder.
                vd.synthesis_init(vi); // central decode state
                vb.init(vd);           // local state for most of the decode

                // so multiple block decodes can
                // proceed in parallel.  We could init
                // multiple vorbis_block structures
                // for vd here

                float[][][] _pcm = new float[1][][];
                int[] _index = new int[vi.channels];
                // The rest is just a straight decode loop until end of stream
                while (eos == 0)
                {
                    while (eos == 0)
                    {

                        int result = oy.pageout(og);
                        if (result == 0)
                            break; // need more data
                        if (result == -1)
                        {
                            // missing or corrupt data at this page position
                            s_err.WriteLine("Corrupt or missing data in bitstream; continuing...");
                        } else
                        {
                            os.pagein(og); // can safely ignore errors at
                            // this point
                            while (true)
                            {
                                result = os.packetout(op);

                                if (result == 0)
                                    break; // need more data
                                if (result == -1)
                                { // missing or corrupt data at this page position
                                    // no reason to complain; already complained above
                                } else
                                {
                                    // we have a packet.  Decode it
                                    int samples;
                                    if (vb.synthesis(op) == 0)
                                    { // test for success!
                                        vd.synthesis_blockin(vb);
                                    }

                                    // **pcm is a multichannel float vector.  In stereo, for
                                    // example, pcm[0] is left, and pcm[1] is right.  samples is
                                    // the size of each channel.  Convert the float values
                                    // (-1.<=range<=1.) to whatever PCM format and write it out

                                    while ((samples = vd.synthesis_pcmout(_pcm, _index)) > 0)
                                    {
                                        float[][] pcm = _pcm [0];
                                        bool clipflag = false;
                                        int bout = (samples < convsize ? samples : convsize);

                                        // convert floats to 16 bit signed ints (host order) and
                                        // interleave
                                        for (i = 0; i < vi.channels; i++)
                                        {
                                            int ptr = i * 2;
                                            //int ptr=i;
                                            int mono = _index [i];
                                            for (int j = 0; j < bout; j++)
                                            {
                                                int val = (int)(pcm [i] [mono + j] * 32767.0);
                                                //        short val=(short)(pcm[i][mono+j]*32767.);
                                                //        int val=(int)Math.round(pcm[i][mono+j]*32767.);
                                                // might as well guard against clipping
                                                if (val > 32767)
                                                {
                                                    val = 32767;
                                                    clipflag = true;
                                                }
                                                if (val < -32768)
                                                {
                                                    val = -32768;
                                                    clipflag = true;
                                                }
                                                if (val < 0)
                                                    val = val | 0x8000;
                                                convbuffer [ptr] = (byte)(val);
                                                convbuffer [ptr + 1] = (byte)((uint)val >> 8);
                                                ptr += 2 * (vi.channels);
                                            }
                                        }

                                        if (clipflag)
                                        {
                                            //s_err.WriteLine("Clipping in frame "+vd.sequence);
                                        }

                                        output.Write(convbuffer, 0, 2 * vi.channels * bout);

                                        vd.synthesis_read(bout); // tell libvorbis how
                                        // many samples we
                                        // actually consumed
                                    }
                                }
                            }
                            if (og.eos() != 0)
                                eos = 1;
                        }
                    }
                    if (eos == 0)
                    {
                        index = oy.buffer(4096);
                        bytes = input.Read(oy.data, index, 4096);
                        oy.wrote(bytes);
                        if (bytes == 0)
                            eos = 1;
                    }
                }

                // clean up this logical bitstream; before exit we see if we're
                // followed by another [chained]

                os.clear();

                // ogg_page and ogg_packet structs always point to storage in
                // libvorbis.  They're never freed or manipulated directly

                vb.clear();
                vd.clear();
                vi.clear();  // must be called last
            }

            // OK, clean up the framer
            oy.clear();
            s_err.WriteLine("Done.");

            if (writeWavHeader)
            {
                long end = output.Position;
                int length = (int)(end - (start + HEADER_SIZE));

                output.Seek(start, SeekOrigin.Begin);
                WriteHeader(output, length, vi.rate, (ushort)16, (ushort)vi.channels);
                output.Seek(end, SeekOrigin.Begin);
            }
        }
コード例 #10
0
ファイル: VorbisFile.cs プロジェクト: Daramkun/ProjectLiqueur
        // fetch and process a packet.  Handles the case where we're at a
        // bitstream boundary and dumps the decoding machine.  If the decoding
        // machine is unloaded, it loads it.  It also keeps pcm_offset up to
        // date (seek and read both use this.  seek uses a special hack with
        // readp).
        //
        // return: -1) hole in the data (lost packet)
        //          0) need more date (only if readp==0)/eof
        //          1) got a packet
        int process_packet(int readp)
        {
            Page og=new Page();

            // handle one packet.  Try to fetch it from current stream state
            // extract packets from page
            while(true)
            {
                // process a packet if we can.  If the machine isn't loaded,
                // neither is a page
                if(decode_ready)
                {
                    Packet op=new Packet();
                    int result=os.packetout(op);
                    long granulepos;
                    // if(result==-1)return(-1); // hole in the data. For now, swallow
                    // and go. We'll need to add a real
                    // error code in a bit.
                    if(result>0)
                    {
                        // got a packet.  process it
                        granulepos=op.granulepos;
                        if(vb.synthesis(op)==0)
                        { // lazy check for lazy
                            // header handling.  The
                            // header packets aren't
                            // audio, so if/when we
                            // submit them,
                            // vorbis_synthesis will
                            // reject them
                            // suck in the synthesis data and track bitrate
                        {
                            int oldsamples=vd.synthesis_pcmout(null, null);
                            vd.synthesis_blockin(vb);
                            samptrack+=vd.synthesis_pcmout(null, null)-oldsamples;
                            bittrack+=op.bytes*8;
                        }

                            // update the pcm offset.
                            if(granulepos!=-1 && op.e_o_s==0)
                            {
                                int link=(skable?current_link:0);
                                int samples;
                                // this packet has a pcm_offset on it (the last packet
                                // completed on a page carries the offset) After processing
                                // (above), we know the pcm position of the *last* sample
                                // ready to be returned. Find the offset of the *first*
                                //
                                // As an aside, this trick is inaccurate if we begin
                                // reading anew right at the last page; the end-of-stream
                                // granulepos declares the last frame in the stream, and the
                                // last packet of the last page may be a partial frame.
                                // So, we need a previous granulepos from an in-sequence page
                                // to have a reference point.  Thus the !op.e_o_s clause above

                                samples=vd.synthesis_pcmout(null, null);
                                granulepos-=samples;
                                for(int i=0;i<link;i++)
                                {
                                    granulepos+=pcmlengths[i];
                                }
                                pcm_offset=granulepos;
                            }
                            return(1);
                        }
                    }
                }

                if(readp==0)return(0);
                if(get_next_page(og,-1)<0)return(0); // eof. leave unitialized

                // bitrate tracking; add the header's bytes here, the body bytes
                // are done by packet above
                bittrack+=og.header_len*8;

                // has our decoding just traversed a bitstream boundary?
                if(decode_ready)
                {
                    if(current_serialno!=og.serialno())
                    {
                        decode_clear();
                    }
                }

                // Do we need to load a new machine before submitting the page?
                // This is different in the seekable and non-seekable cases.
                //
                // In the seekable case, we already have all the header
                // information loaded and cached; we just initialize the machine
                // with it and continue on our merry way.
                //
                // In the non-seekable (streaming) case, we'll only be at a
                // boundary if we just left the previous logical bitstream and
                // we're now nominally at the header of the next bitstream

                if(!decode_ready)
                {
                    int i;
                    if(skable)
                    {
                        current_serialno=og.serialno();

                        // match the serialno to bitstream section.  We use this rather than
                        // offset positions to avoid problems near logical bitstream
                        // boundaries
                        for(i=0;i<links;i++)
                        {
                            if(serialnos[i]==current_serialno)break;
                        }
                        if(i==links)return(-1); // sign of a bogus stream.  error out,
                        // leave machine uninitialized
                        current_link=i;

                        os.init(current_serialno);
                        os.reset();

                    }
                    else
                    {
                        // we're streaming
                        // fetch the three header packets, build the info struct
                        int[] foo = new int[1];
                        int ret=fetch_headers(vi[0], vc[0], foo, og);
                        current_serialno=foo[0];
                        if(ret!=0)return ret;
                        current_link++;
                        i=0;
                    }
                    make_decode_ready();
                }
                os.pagein(og);
            }
        }
コード例 #11
0
        public AudioSample OggToWav(Stream ogg, float volume, float pitch)
        {
            AudioSample sample = new AudioSample();
            TextWriter s_err = new StringWriter();
            Stream input = null;
            MemoryStream output = null;

            input = ogg;
            output = new MemoryStream();

            SyncState oy = new SyncState();
            StreamState os = new StreamState();
            Page og = new Page();
            Packet op = new Packet();

            Info vi = new Info();
            Comment vc = new Comment();
            DspState vd = new DspState();
            Block vb = new Block(vd);

            byte[] buffer;
            int bytes = 0;
            oy.init();
            while (true)
            {
                int eos = 0;
                int index = oy.buffer(4096);
                buffer = oy.data;
                try
                {
                    bytes = input.Read(buffer, index, 4096);
                }
                catch (Exception e)
                {
                    s_err.WriteLine(e);
                }
                oy.wrote(bytes);
                if (oy.pageout(og) != 1)
                {
                    if (bytes < 4096) break;
                    s_err.WriteLine("Input does not appear to be an Ogg bitstream.");
                }
                os.init(og.serialno());
                vi.init();
                vc.init();
                if (os.pagein(og) < 0)
                {
                    s_err.WriteLine("Error reading first page of Ogg bitstream data.");
                }

                if (os.packetout(op) != 1)
                {
                    s_err.WriteLine("Error reading initial header packet.");
                }

                if (vi.synthesis_headerin(vc, op) < 0)
                {
                    s_err.WriteLine("This Ogg bitstream does not contain Vorbis audio data.");
                }

                int i = 0;
                while (i < 2)
                {
                    while (i < 2)
                    {
                        int result = oy.pageout(og);
                        if (result == 0) break;
                        if (result == 1)
                        {
                            os.pagein(og);
                            while (i < 2)
                            {
                                result = os.packetout(op);
                                if (result == 0) break;
                                vi.synthesis_headerin(vc, op);
                                i++;
                            }
                        }
                    }
                    index = oy.buffer(4096);
                    buffer = oy.data;
                    try
                    {
                        bytes = input.Read(buffer, index, 4096);
                    }
                    catch (Exception e)
                    {
                        s_err.WriteLine(e);
                    }
                    oy.wrote(bytes);
                }
                sample.Channels = vi.channels;
                sample.Rate = (int)((float)vi.rate * pitch);
                convsize = 4096 / vi.channels;
                vd.synthesis_init(vi);
                vb.init(vd);
                float[][][] _pcm = new float[1][][];
                int[] _index = new int[vi.channels];
                while (eos == 0)
                {
                    while (eos == 0)
                    {
                        int result = oy.pageout(og);
                        if (result == 0) break;
                        if (result != -1)
                        {
                            os.pagein(og);
                            while (true)
                            {
                                result = os.packetout(op);
                                if (result == 0) break;
                                if (result != -1)
                                {
                                    int samples;
                                    if (vb.synthesis(op) == 0)
                                    {
                                        vd.synthesis_blockin(vb);
                                    }
                                    while ((samples = vd.synthesis_pcmout(_pcm, _index)) > 0)
                                    {
                                        float[][] pcm = _pcm[0];
                                        int bout = (samples < convsize ? samples : convsize);
                                        for (i = 0; i < vi.channels; i++)
                                        {
                                            int ptr = i * 2;
                                            int mono = _index[i];
                                            for (int j = 0; j < bout; j++)
                                            {
                                                int val = (int)(pcm[i][mono + j] * 32767.0);
                                                if (val > 32767)
                                                {
                                                    val = 32767;
                                                }
                                                if (val < -32768)
                                                {
                                                    val = -32768;
                                                }
                                                val = (int)((float)val * volume);
                                                if (val < 0) val = val | 0x8000;
                                                convbuffer[ptr] = (byte)(val);
                                                convbuffer[ptr + 1] = (byte)((uint)val >> 8);
                                                ptr += 2 * (vi.channels);
                                            }
                                        }
                                        output.Write(convbuffer, 0, 2 * vi.channels * bout);
                                        vd.synthesis_read(bout);
                                    }
                                }
                            }
                            if (og.eos() != 0) eos = 1;
                        }
                    }
                    if (eos == 0)
                    {
                        index = oy.buffer(4096);
                        buffer = oy.data;
                        try
                        {
                            bytes = input.Read(buffer, index, 4096);
                        }
                        catch (Exception e)
                        {
                            s_err.WriteLine(e);
                        }
                        oy.wrote(bytes);
                        if (bytes == 0) eos = 1;
                    }
                }
                os.clear();
                vb.clear();
                vd.clear();
                vi.clear();
                break;
            }

            oy.clear();
            input.Close();
            sample.Pcm = output.ToArray();
            return sample;
        }
コード例 #12
0
ファイル: SyncState.cs プロジェクト: Daramkun/ProjectLiqueur
        public int pageseek(Page og)
        {
            int page=returned;
            int next;
            int bytes=fill-returned;

            if(headerbytes==0)
            {
                int _headerbytes,i;
                if(bytes<27)return(0); // not enough for a header

                /* verify capture pattern */
                //!!!!!!!!!!!
                if(data[page]!='O' ||
                    data[page+1]!='g' ||
                    data[page+2]!='g' ||
                    data[page+3]!='S')
                {
                    headerbytes=0;
                    bodybytes=0;

                    // search for possible capture
                    next=0;
                    for(int ii=0; ii<bytes-1; ii++)
                    {
                        if(data[page+1+ii]=='O'){next=page+1+ii; break;}
                    }
                    //next=memchr(page+1,'O',bytes-1);
                    if(next==0) next=fill;

                    returned=next;
                    return(-(next-page));
                }
                _headerbytes=(data[page+26]&0xff)+27;
                if(bytes<_headerbytes)return(0); // not enough for header + seg table

                // count up body length in the segment table

                for(i=0;i<(data[page+26]&0xff);i++)
                {
                    bodybytes+=(data[page+27+i]&0xff);
                }
                headerbytes=_headerbytes;
            }

            if(bodybytes+headerbytes>bytes)return(0);

            // The whole test page is buffered.  Verify the checksum
            //lock(chksum)
            {
                // Grab the checksum bytes, set the header field to zero

                Array.Copy(data, page+22, chksum, 0, 4);
                data[page+22]=0;
                data[page+23]=0;
                data[page+24]=0;
                data[page+25]=0;

                // set up a temp page struct and recompute the checksum
                Page log=pageseek_p;
                log.header_base=data;
                log.header=page;
                log.header_len=headerbytes;

                log.body_base=data;
                log.body=page+headerbytes;
                log.body_len=bodybytes;
                log.checksum();

                // Compare
                if(chksum[0]!=data[page+22] ||
                    chksum[1]!=data[page+23] ||
                    chksum[2]!=data[page+24] ||
                    chksum[3]!=data[page+25])
                {
                    // D'oh.  Mismatch! Corrupt page (or miscapture and not a page at all)
                    // replace the computed checksum with the one actually read in
                    Array.Copy(chksum, 0, data, page+22, 4);
                    // Bad checksum. Lose sync */

                    headerbytes=0;
                    bodybytes=0;
                    // search for possible capture
                    next=0;
                    for(int ii=0; ii<bytes-1; ii++)
                    {
                        if(data[page+1+ii]=='O'){next=page+1+ii; break;}
                    }
                    //next=memchr(page+1,'O',bytes-1);
                    if(next==0) next=fill;
                    returned=next;
                    return(-(next-page));
                }
            }

            // yes, have a whole page all ready to go
            {
            page=returned;

            if(og!=null)
            {
                og.header_base=data;
                og.header=page;
                og.header_len=headerbytes;
                og.body_base=data;
                og.body=page+headerbytes;
                og.body_len=bodybytes;
            }

            unsynced=0;
            returned+=(bytes=headerbytes+bodybytes);
            headerbytes=0;
            bodybytes=0;
            return(bytes);
            }
            //  headerbytes=0;
            //  bodybytes=0;
            //  next=0;
            //  for(int ii=0; ii<bytes-1; ii++){
            //    if(data[page+1+ii]=='O'){next=page+1+ii;}
            //  }
            //  //next=memchr(page+1,'O',bytes-1);
            //  if(next==0) next=fill;
            //  returned=next;
            //  return(-(next-page));
        }
コード例 #13
0
ファイル: SyncState.cs プロジェクト: Daramkun/ProjectLiqueur
        // sync the stream and get a page.  Keep trying until we find a page.
        // Supress 'sync errors' after reporting the first.
        //
        // return values:
        //  -1) recapture (hole in data)
        //   0) need more data
        //   1) page returned
        //
        // Returns pointers into buffered data; invalidated by next call to
        // _stream, _clear, _init, or _buffer
        public int pageout(Page og)
        {
            // all we need to do is verify a page at the head of the stream
            // buffer.  If it doesn't verify, we look for the next potential
            // frame

            while(true)
            {
                int ret=pageseek(og);
                if(ret>0)
                {
                    // have a page
                    return(1);
                }
                if(ret==0)
                {
                    // need more data
                    return(0);
                }

                // head did not start a synced page... skipped some bytes
                if(unsynced==0)
                {
                    unsynced=1;
                    return(-1);
                }
                // loop. keep looking
            }
        }
コード例 #14
0
ファイル: StreamState.cs プロジェクト: cody82/spacewar-arena
        // add the incoming page to the stream state; we decompose the page
        // into packet segments here as well.
        public int pagein(Page og)
        {
            byte[] header_base=og.header_base;
            int header=og.header;
            byte[] body_base=og.body_base;
            int body=og.body;
            int bodysize=og.body_len;
            int segptr=0;

            int version=og.version();
            int continued=og.continued();
            int bos=og.bos();
            int eos=og.eos();
            long granulepos=og.granulepos();
            int _serialno=og.serialno();
            int _pageno=og.pageno();
            int segments=header_base[header+26]&0xff;

            // clean up 'returned data'
            {
            int lr=lacing_returned;
            int br=body_returned;

            // body data

            //System.out.println("br="+br+", body_fill="+body_fill);

            if(br!=0)
            {
                body_fill-=br;
                if(body_fill!=0)
                {
                    Array.Copy(body_data, br, body_data, 0, body_fill);
                }
                body_returned=0;
            }

            //System.out.println("?? br="+br+", body_fill="+body_fill+" body_returned="+body_returned);

            if(lr!=0)
            {
                // segment table
                if((lacing_fill-lr)!=0)
                {
                    Array.Copy(lacing_vals, lr, lacing_vals, 0, lacing_fill-lr);
                    Array.Copy(granule_vals, lr, granule_vals, 0, lacing_fill-lr);
                }
                lacing_fill-=lr;
                lacing_packet-=lr;
                lacing_returned=0;
            }
            }

            // check the serial number
            if(_serialno!=serialno)return(-1);
            if(version>0)return(-1);

            lacing_expand(segments+1);

            // are we in sequence?
            if(_pageno!=pageno)
            {
                int i;

                // unroll previous partial packet (if any)
                for(i=lacing_packet;i<lacing_fill;i++)
                {
                    body_fill-=lacing_vals[i]&0xff;
                    //System.out.println("??");
                }
                lacing_fill=lacing_packet;

                // make a note of dropped data in segment table
                if(pageno!=-1)
                {
                    lacing_vals[lacing_fill++]=0x400;
                    lacing_packet++;
                }

                // are we a 'continued packet' page?  If so, we'll need to skip
                // some segments
                if(continued!=0)
                {
                    bos=0;
                    for(;segptr<segments;segptr++)
                    {
                        int val=(header_base[header+27+segptr]&0xff);
                        body+=val;
                        bodysize-=val;
                        if(val<255)
                        {
                            segptr++;
                            break;
                        }
                    }
                }
            }

            //System.out.println("bodysize="+bodysize);

            if(bodysize!=0)
            {
                body_expand(bodysize);
                Array.Copy(body_base, body, body_data, body_fill, bodysize);
                body_fill+=bodysize;
            }

            //System.out.println("bodyfill="+body_fill);

            {
            int saved=-1;
            while(segptr<segments)
            {
                int val=(header_base[header+27+segptr]&0xff);
                lacing_vals[lacing_fill]=val;
                granule_vals[lacing_fill]=-1;

                if(bos!=0)
                {
                    lacing_vals[lacing_fill]|=0x100;
                    bos=0;
                }

                if(val<255)saved=lacing_fill;

                lacing_fill++;
                segptr++;

                if(val<255)lacing_packet=lacing_fill;
            }

            /* set the granulepos on the last pcmval of the last full packet */
            if(saved!=-1)
            {
                granule_vals[saved]=granulepos;
            }
            }

            if(eos!=0)
            {
                e_o_s=1;
                if(lacing_fill>0)
                    lacing_vals[lacing_fill-1]|=0x200;
            }

            pageno=_pageno+1;
            return(0);
        }
コード例 #15
0
		public int get_next_page(Page page, long boundary, VorbisFileInstance instance)
		{
			if(boundary>0) boundary+=offset;
			while(true)
			{
				int more;
				if(boundary>0 && offset>=boundary)return OV_FALSE;
                more = instance.oy.pageseek(page);
				if(more<0){offset-=more;}
				else
				{
					if(more==0)
					{
						if(boundary==0)return OV_FALSE;
						//	  if(get_data()<=0)return -1;
						int ret=get_data(instance);
						if(ret==0) return OV_EOF;
						if(ret<0) return OV_EREAD; 
					}
					else
					{
						int ret=(int)offset; //!!!
						offset+=more;
						return ret;
					}
				}
			}
		}
コード例 #16
0
ファイル: StreamState.cs プロジェクト: cody82/spacewar-arena
 /* This constructs pages from buffered packet segments.  The pointers
     returned are to static buffers; do not free. The returned buffers are
     good only until the next call (using the same ogg_stream_state) */
 public int pageout(Page og)
 {
     if((e_o_s!=0&&lacing_fill!=0) ||  /* 'were done, now flush' case */
         body_fill-body_returned> 4096 ||     /* 'page nominal size' case */
         lacing_fill>=255 ||          /* 'segment table full' case */
         (lacing_fill!=0&&b_o_s==0))
     {  /* 'initial header page' case */
         return flush(og);
     }
     return 0;
 }
コード例 #17
0
ファイル: SyncState.cs プロジェクト: Damian666/blasters
		public int pageseek(Page og)
		{
			int page=returned;
			int next;
			int bytes=fill-returned;
  
			if(headerbytes==0)
			{
				int _headerbytes,i;
				if(bytes<27)return(0); // not enough for a header
    
				/* verify capture pattern */
				//!!!!!!!!!!!
				if(data[page]!='O' ||
					data[page+1]!='g' ||
					data[page+2]!='g' ||
					data[page+3]!='S')
				{
					headerbytes=0;
					bodybytes=0;
  
					// search for possible capture
					next=0;
					for(int ii=0; ii<bytes-1; ii++)
					{
						if(data[page+1+ii]=='O'){next=page+1+ii; break;}
					}
					//next=memchr(page+1,'O',bytes-1);
					if(next==0) next=fill;

					returned=next;
					return(-(next-page));
				}
				_headerbytes=(data[page+26]&0xff)+27;
				if(bytes<_headerbytes)return(0); // not enough for header + seg table
    
				// count up body length in the segment table
    
				for(i=0;i<(data[page+26]&0xff);i++)
				{
					bodybytes+=(data[page+27+i]&0xff);
				}
				headerbytes=_headerbytes;
			}
  
			if(bodybytes+headerbytes>bytes)return(0);
  
			// The whole test page is buffered.  Verify the checksum
			lock(chksum)
			{
				// Grab the checksum bytes, set the header field to zero
    
				Array.Copy(data, page+22, chksum, 0, 4);
				data[page+22]=0;
				data[page+23]=0;
				data[page+24]=0;
				data[page+25]=0;
    
				// set up a temp page struct and recompute the checksum
				Page log=pageseek_p;
				log.header_base=data;
				log.header=page;
				log.header_len=headerbytes;

				log.body_base=data;
				log.body=page+headerbytes;
				log.body_len=bodybytes;
				log.checksum();

				// Compare
				if(chksum[0]!=data[page+22] ||
					chksum[1]!=data[page+23] ||
					chksum[2]!=data[page+24] ||
					chksum[3]!=data[page+25])
				{
					// D'oh.  Mismatch! Corrupt page (or miscapture and not a page at all)
					// replace the computed checksum with the one actually read in
					Array.Copy(chksum, 0, data, page+22, 4);
					// Bad checksum. Lose sync */

					headerbytes=0;
					bodybytes=0;
					// search for possible capture
					next=0;
					for(int ii=0; ii<bytes-1; ii++)
					{
						if(data[page+1+ii]=='O'){next=page+1+ii; break;}
					}
					//next=memchr(page+1,'O',bytes-1);
					if(next==0) next=fill;
					returned=next;
					return(-(next-page));
				}
			}
  
			// yes, have a whole page all ready to go
		{
			page=returned;

			if(og!=null)
			{
				og.header_base=data;
				og.header=page;
				og.header_len=headerbytes;
				og.body_base=data;
				og.body=page+headerbytes;
				og.body_len=bodybytes;
			}

			unsynced=0;
			returned+=(bytes=headerbytes+bodybytes);
			headerbytes=0;
			bodybytes=0;
			return(bytes);
		}
			//  headerbytes=0;
			//  bodybytes=0;
			//  next=0;
			//  for(int ii=0; ii<bytes-1; ii++){
			//    if(data[page+1+ii]=='O'){next=page+1+ii;}
			//  }
			//  //next=memchr(page+1,'O',bytes-1);
			//  if(next==0) next=fill;
			//  returned=next;
			//  return(-(next-page));
		}