Ejemplo n.º 1
0
        private Mp3FileReader(Stream inputStream, FrameDecompressorBuilder frameDecompressorBuilder, bool ownInputStream)
        {
            if (inputStream == null)
            {
                throw new ArgumentNullException(nameof(inputStream));
            }
            if (frameDecompressorBuilder == null)
            {
                throw new ArgumentNullException(nameof(frameDecompressorBuilder));
            }
            this.ownInputStream = ownInputStream;
            try
            {
                mp3Stream = inputStream;
                Id3v2Tag  = Id3v2Tag.ReadTag(mp3Stream);

                dataStartPosition = mp3Stream.Position;
                var firstFrame = Mp3Frame.LoadFromStream(mp3Stream);
                if (firstFrame == null)
                {
                    throw new InvalidDataException("Invalid MP3 file - no MP3 Frames Detected");
                }
                double bitRate = firstFrame.BitRate;
                xingHeader = XingHeader.LoadXingHeader(firstFrame);
                // If the header exists, we can skip over it when decoding the rest of the file
                if (xingHeader != null)
                {
                    dataStartPosition = mp3Stream.Position;
                }

                // workaround for a longstanding issue with some files failing to load
                // because they report a spurious sample rate change
                var secondFrame = Mp3Frame.LoadFromStream(mp3Stream);
                if (secondFrame != null &&
                    (secondFrame.SampleRate != firstFrame.SampleRate ||
                     secondFrame.ChannelMode != firstFrame.ChannelMode))
                {
                    // assume that the first frame was some kind of VBR/LAME header that we failed to recognise properly
                    dataStartPosition = secondFrame.FileOffset;
                    // forget about the first frame, the second one is the first one we really care about
                    firstFrame = secondFrame;
                }

                mp3DataLength = mp3Stream.Length - dataStartPosition;

                // try for an ID3v1 tag as well
                mp3Stream.Position = mp3Stream.Length - 128;
                byte[] tag = new byte[128];
                mp3Stream.Read(tag, 0, 128);
                if (tag[0] == 'T' && tag[1] == 'A' && tag[2] == 'G')
                {
                    Id3v1Tag       = tag;
                    mp3DataLength -= 128;
                }

                mp3Stream.Position = dataStartPosition;

                // create a temporary MP3 format before we know the real bitrate
                Mp3WaveFormat = new Mp3WaveFormat(firstFrame.SampleRate,
                                                  firstFrame.ChannelMode == ChannelMode.Mono ? 1 : 2, firstFrame.FrameLength, (int)bitRate);

                CreateTableOfContents();
                tocIndex = 0;

                // [Bit rate in Kilobits/sec] = [Length in kbits] / [time in seconds]
                //                            = [Length in bits ] / [time in milliseconds]

                // Note: in audio, 1 kilobit = 1000 bits.
                // Calculated as a double to minimize rounding errors
                bitRate = (mp3DataLength * 8.0 / TotalSeconds());

                mp3Stream.Position = dataStartPosition;

                // now we know the real bitrate we can create an accurate MP3 WaveFormat
                Mp3WaveFormat = new Mp3WaveFormat(firstFrame.SampleRate,
                                                  firstFrame.ChannelMode == ChannelMode.Mono ? 1 : 2, firstFrame.FrameLength, (int)bitRate);
                decompressor   = frameDecompressorBuilder(Mp3WaveFormat);
                waveFormat     = decompressor.OutputFormat;
                bytesPerSample = (decompressor.OutputFormat.BitsPerSample) / 8 * decompressor.OutputFormat.Channels;
                // no MP3 frames have more than 1152 samples in them
                bytesPerDecodedFrame = 1152 * bytesPerSample;
                // some MP3s I seem to get double
                decompressBuffer = new byte[bytesPerDecodedFrame * 2];
            }
            catch (Exception)
            {
                if (ownInputStream)
                {
                    inputStream.Dispose();
                }
                throw;
            }
        }
Ejemplo n.º 2
0
        /// <summary>
        /// Load Xing Header
        /// </summary>
        /// <param name="frame">Frame</param>
        /// <returns>Xing Header</returns>
        public static XingHeader LoadXingHeader(Mp3Frame frame)
        {
            XingHeader xingHeader = new XingHeader();

            xingHeader.frame = frame;
            int offset = 0;

            if (frame.MpegVersion == MpegVersion.Version1)
            {
                if (frame.ChannelMode != ChannelMode.Mono)
                {
                    offset = 32 + 4;
                }
                else
                {
                    offset = 17 + 4;
                }
            }
            else if (frame.MpegVersion == MpegVersion.Version2)
            {
                if (frame.ChannelMode != ChannelMode.Mono)
                {
                    offset = 17 + 4;
                }
                else
                {
                    offset = 9 + 4;
                }
            }
            else
            {
                return(null);
                // throw new FormatException("Unsupported MPEG Version");
            }

            if ((frame.RawData[offset + 0] == 'X') &&
                (frame.RawData[offset + 1] == 'i') &&
                (frame.RawData[offset + 2] == 'n') &&
                (frame.RawData[offset + 3] == 'g'))
            {
                xingHeader.startOffset = offset;
                offset += 4;
            }
            else
            {
                return(null);
            }

            XingHeaderOptions flags = (XingHeaderOptions)ReadBigEndian(frame.RawData, offset);

            offset += 4;

            if ((flags & XingHeaderOptions.Frames) != 0)
            {
                xingHeader.framesOffset = offset;
                offset += 4;
            }
            if ((flags & XingHeaderOptions.Bytes) != 0)
            {
                xingHeader.bytesOffset = offset;
                offset += 4;
            }
            if ((flags & XingHeaderOptions.Toc) != 0)
            {
                xingHeader.tocOffset = offset;
                offset += 100;
            }
            if ((flags & XingHeaderOptions.VbrScale) != 0)
            {
                xingHeader.vbrScale = ReadBigEndian(frame.RawData, offset);
                offset += 4;
            }
            xingHeader.endOffset = offset;
            return(xingHeader);
        }