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 bool HasResultNode(IResultNode resultNode, Func <IResultNode, bool> predicate)
{
if (predicate(resultNode))
{
return(true);
}
if (resultNode.HasChildren())
{
foreach (IResultNode childNode in resultNode.Children)
{
if (HasResultNode(childNode, predicate))
{
return(true);
}
}
}
return(false);
}
private static uint GetValidSliceCount(IResultNode resultNode)
{
uint count = 0;
if (IsSlice(resultNode))
{
uint?firstMacroblockInSlice = GetFirstMacroblockInSlice(resultNode);
if ((firstMacroblockInSlice == 0) || (firstMacroblockInSlice >= 60))
{
// TODO: check other attributes
++count;
}
}
if (resultNode.HasChildren())
{
foreach (IResultNode childNode in resultNode.Children)
{
count += GetValidSliceCount(childNode);
}
}
return(count);
}
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);
}
public static IResultNode GetLastDescendant(this IResultNode resultNode)
{
return(resultNode.HasChildren() ? resultNode.GetLastChild().GetLastDescendant() : resultNode);
}
