public override IDataPacket FindReferenceHeader(IDataReader dataReader, ICodecParametersSpec codecParameters)
{
// Note: Loop to detect reference headers preceeded by a block of video frames
// (e.g. for 3GP files with 'mdat' before the 'moov' atom, so that the slices are located before the SPS/PPS pair)
while (dataReader.State == DataReaderState.Ready)
{
IScanContext scanContext = new ReferenceHeaderScanContext {
Detectors = new[] { this }
};
var dataBlock = Carve(dataReader, new ReferenceHeaderDataBlockBuilder(), scanContext);
if (dataBlock == null)
{
break; // No (more) data blocks detected
}
IResultNode videoObject = scanContext.Results.FindChild(VideoObjectName);
if ((videoObject != null) && videoObject.HasChildren())
{
IResultNode videoObjectLayer = videoObject.GetFirstChild();
if (videoObjectLayer.Name == VideoObjectLayerName)
{
return(CreateReferenceHeader(dataBlock.DataFormat, videoObject, videoObjectLayer, codecParameters));
}
}
// VideoObject or VideoObjectLayer is missing: Continue scanning after current data block ...
dataReader.Position = dataBlock.EndOffset;
}
return(null); // No reference header detected
}
private static IDataPacket CreateReferenceHeader(CodecID codec, IResultNode sequenceHeader, ICodecParametersSpec codecParameters)
{
IDataPacket data = sequenceHeader;
// Include sequence extensions
foreach (IResultNode childResultNode in sequenceHeader.Children)
{
if (!IsSequenceExtension(childResultNode.Name))
{
break;
}
data = data.Append(childResultNode);
}
// Report codec parameters for reference header
var width = GetAttribute <uint>(sequenceHeader, SequenceHeader.Attribute.HorizontalSizeValue);
var height = GetAttribute <uint>(sequenceHeader, SequenceHeader.Attribute.VerticalSizeValue);
if (sequenceHeader.HasChildren())
{
IResult sequenceExtension = sequenceHeader.GetFirstChild();
if (sequenceExtension.Name == SequenceExtension.Name)
{
width |= GetAttribute <uint>(sequenceExtension, SequenceExtension.Attribute.HorizontalSizeExtension) << 12;
height |= GetAttribute <uint>(sequenceExtension, SequenceExtension.Attribute.VerticalSizeExtension) << 12;
}
}
codecParameters.Codec = codec;
codecParameters.Width = width;
codecParameters.Height = height;
codecParameters.FrameRate = GetAttributeStringValue(sequenceHeader, SequenceHeader.Attribute.FrameRateCode);
return(data);
}
