private bool GetNextBox(out MpegBox mpegBox, long endPosition, MpegBox parentBox)
{
// return empty object when we reach data endPosition. If endPosition is set
// to zero, return empty object if we reach EOF.
if (this.br.BaseStream.Position == (0 == endPosition ? this.br.BaseStream.Length : endPosition))
{
mpegBox = null;
return(false);
}
// create new box, fill in the byte offset
MpegBox ma = new MpegBox(parentBox, null, MpegBox.BoxType.Unknown, this.br.BaseStream.Position, 0);
// now get the size and type
ma.Size = BU.ReverseToUInt32(this.br.ReadBytes(4)); // size
// special size values aren't handled yet
if (ma.Size < 2)
{
throw new MsvDecoderException("Special MPEG box size values are not yet supported.");
}
// type
try
{
ma.Type = (MpegBox.BoxType)BU.ReverseToInt32(this.br.ReadBytes(4));
}
catch
{
ma.Type = MpegBox.BoxType.Unknown;
}
// check the type to see if it has data or child boxes that we care about
switch (ma.Type)
{
case MpegBox.BoxType.moov:
{
// now that we've picked up the moov box, leave br's pointer
// at the start of the moov data and read in all its child boxes
ma.Children = GetBoxes(br, ma.Offset + ma.Size, ma);
break;
}
case MpegBox.BoxType.trak:
{
// read in all its child boxes
ma.Children = GetBoxes(br, ma.Offset + ma.Size, ma);
break;
}
case MpegBox.BoxType.mdia:
{
// read in all its child boxes
ma.Children = GetBoxes(br, ma.Offset + ma.Size, ma);
break;
}
case MpegBox.BoxType.minf:
{
// read in all its child boxes
ma.Children = GetBoxes(br, ma.Offset + ma.Size, ma);
break;
}
case MpegBox.BoxType.stbl:
{
// read in all its child boxes
ma.Children = GetBoxes(br, ma.Offset + ma.Size, ma);
break;
}
case MpegBox.BoxType.uuid: // may have data we want
{
// note current br pointer location
long dataStartPos = this.br.BaseStream.Position;
// get the 16 byte UUID value from the start of data
ma.UuidType = GetUuidType(this.br.ReadBytes(16));
// return pointer to previous location
this.br.BaseStream.Position = dataStartPos;
// if this is a uuid we care about, copy its data into the box
if (!(MpegBox.BoxUuidType.Unknown == ma.UuidType ||
MpegBox.BoxUuidType.None == ma.UuidType))
{
// TODO: throw exception if ma.Size is bigger than an Int32 can hold
// read data into ma, then leave br's pointer at the end of this data/box
ma.Data = br.ReadBytes((int)ma.Size - 8); // box size, less size/tag bytes
}
else
{
// don't care about this uuid, move br's pointer to the end of this box
this.br.BaseStream.Seek(ma.Size - 8, SeekOrigin.Current);
break;
}
break;
}
case MpegBox.BoxType.stco: // contains list of mdat data chunk offsets
{
// read data into ma, then leave br's pointer at the end of this data/box
ma.Data = br.ReadBytes((int)ma.Size - 8); // box size, less size/tag bytes
break;
}
default: // unrecognized, don't read any data from this box
{
// just move br's pointer to the end of this box
this.br.BaseStream.Seek(ma.Size - 8, SeekOrigin.Current);
break;
}
}
// all done, verify br's pointer is where it should be
// return finished box
mpegBox = ma;
return(true);
}
private bool GetNextAtom(out MpegAtom mpegAtom, long endPosition, MpegAtom parentAtom)
{
// return empty object when we reach data endPosition. If endPosition is set
// to zero, return empty object if we reach EOF.
if (this.br.BaseStream.Position == (0 == endPosition ? this.br.BaseStream.Length : endPosition))
{
mpegAtom = null;
return(false);
}
// create new atom, fill in the byte offset
MpegAtom ma = new MpegAtom(null, null, MpegAtom.AtomType.Unknown, this.br.BaseStream.Position, 0);
// now get the size and type
ma.Size = BU.ReverseToUInt32(this.br.ReadBytes(4)); // size
// type
try
{
ma.Type = (MpegAtom.AtomType)BU.ReverseToInt32(this.br.ReadBytes(4));
}
catch
{
ma.Type = MpegAtom.AtomType.Unknown;
}
/*
* switch (BU.ReverseToInt32(this.br.ReadBytes(4))) // type
* {
* case 0x6D6F6F76: ma.Type = MpegAtom.AtomType.moov; break; // "moov"
* case 0x75756964: ma.Type = MpegAtom.AtomType.uuid; break; // "uuid"
* default: ma.Type = MpegAtom.AtomType.Unknown; break; // uninteresting to us
* }
*/
// check the type to see if it has data or child atoms that we care about
switch (ma.Type)
{
case MpegAtom.AtomType.moov:
{
// now that we've picked up the moov atom, leave br's pointer
// at the start of the moov data and read in all its child atoms
ma.Children = GetAtoms(br, ma.Offset + ma.Size);
// TODO: verify br's pointer is now at end of moov data
break;
}
case MpegAtom.AtomType.trak:
{
// now that we've picked up the moov atom, leave br's pointer
// at the start of the moov data and read in all its child atoms
ma.Children = GetAtoms(br, ma.Offset + ma.Size);
// TODO: verify br's pointer is now at end of moov data
break;
}
case MpegAtom.AtomType.uuid: // may have data we want
{
// note current br pointer location
long dataStartPos = this.br.BaseStream.Position;
// get the 16 byte UUID value from the start of data
ma.UuidType = GetUuidType(this.br.ReadBytes(16));
// return pointer to previous location
this.br.BaseStream.Position = dataStartPos;
// if this is a uuid we care about, copy its data into the atom
if (!(MpegAtom.AtomUuidType.Unknown == ma.UuidType ||
MpegAtom.AtomUuidType.None == ma.UuidType))
{
// TODO: throw exception if ma.Size is bigger than an Int32 can hold
// read data into ma, then leave br's pointer at the end of this data/atom
ma.Data = br.ReadBytes((int)ma.Size - 8); // atom size, less size/tag bytes
}
else
{
// don't care about this uuid, move br's pointer to the end of this atom
this.br.BaseStream.Seek(ma.Size - 8, SeekOrigin.Current);
break;
}
break;
}
default: // unrecognized, don't read any data from this atom
{
// just move br's pointer to the end of this atom
this.br.BaseStream.Seek(ma.Size - 8, SeekOrigin.Current);
break;
}
}
// all done, verify br's pointer is where it should be
// return finished atom
mpegAtom = ma;
return(true);
}
