@ -35,101 +35,219 @@ internal class ObuReader
/// <param name="isAnnexB">A value indicating whether each OBU is prefixed by an Annex B length field.</param>
public void ReadAll ( ref Av1BitStreamReader reader , int dataSize , Func < IAv1TileReader > creator , bool isAnnexB = false )
{
bool seenFrameHeader = false ;
bool frameDecodingFinished = false ;
while ( ! frameDecodingFinished )
try
{
int lengthSize = 0 ;
int payloadSize = 0 ;
if ( isAnnexB )
int availableByteCount = reader . Length - Av1Math . DivideBy8Floor ( reader . BitPosition ) ;
if ( ( reader . BitPosition & 0x7 ) ! = 0 | | ( uint ) dataSize > ( uint ) availableByteCount )
{
ReadObuSize ( ref reader , out payloadSize , out lengthSize ) ;
throw new InvalidImageContentException ( "The AV1 OBU data boundary is invalid." ) ;
}
ObuHeader header = ReadObuHeaderSize ( ref reader , out lengthSize ) ;
if ( isAnnexB )
bool seenFrameHeader = false ;
bool frameDecodingFinished = false ;
Span < byte > primaryFrameHeaderPayload = default ;
while ( dataSize > 0 & & ! frameDecodingFinished )
{
header . PayloadSize - = header . Size ;
dataSize - = lengthSize ;
lengthSize = 0 ;
}
payloadSize = header . PayloadSize ;
dataSize - = header . Size + lengthSize ;
if ( isAnnexB & & dataSize < payloadSize )
{
throw new InvalidImageContentException ( "Corrupt frame" ) ;
}
switch ( header . Type )
{
case ObuType . SequenceHeader :
this . SequenceHeader = new ( ) ;
ReadSequenceHeader ( ref reader , this . SequenceHeader ) ;
break ;
case ObuType . FrameHeader :
case ObuType . RedundantFrameHeader :
case ObuType . Frame :
if ( header . Type ! = ObuType . Frame )
{
// Nothing to do here.
}
else if ( header . Type ! = ObuType . FrameHeader )
int annexObuSize = 0 ;
if ( isAnnexB )
{
ReadObuSize ( ref reader , out annexObuSize , out int annexLengthSize ) ;
if ( annexLengthSize > dataSize | | annexObuSize < 1 )
{
Guard . IsFalse ( seenFrameHeader , nameof ( seenFrameHeader ) , "Frame header expected ") ;
throw new InvalidImageContentException ( "The Annex B AV1 OBU length is invalid." ) ;
}
else
dataSize - = annexLengthSize ;
if ( annexObuSize > dataSize )
{
Guard . IsTrue ( seenFrameHeader , nameof ( seenFrameHeader ) , "Already decoded a frame header" ) ;
throw new InvalidImageContentException ( "The Annex B AV1 OBU exceeds its temporal-unit boundary." ) ;
}
}
else if ( dataSize < 1 )
{
throw new InvalidImageContentException ( "The AV1 OBU header is truncated." ) ;
}
int obuStartBitPosition = reader . BitPosition ;
ObuHeader header = ReadObuHeaderSize ( ref reader , out _ ) ;
if ( ! isAnnexB & & ! header . HasSize )
{
// AV1 section 5 requires every low-overhead OBU to carry its own payload size. Only Annex B may
// derive the payload length from the outer obu_length field.
throw new InvalidImageContentException ( "A low-overhead AV1 OBU is missing its payload-size field." ) ;
}
int headerAndLengthSize = ( reader . BitPosition - obuStartBitPosition ) > > 3 ;
int boundedObuSize = isAnnexB ? annexObuSize : dataSize ;
if ( headerAndLengthSize > boundedObuSize )
{
throw new InvalidImageContentException ( "The AV1 OBU header exceeds its declared boundary." ) ;
}
int payloadSize = header . HasSize ? header . PayloadSize : boundedObuSize - headerAndLengthSize ;
if ( ( uint ) payloadSize > ( uint ) ( boundedObuSize - headerAndLengthSize ) )
{
throw new InvalidImageContentException ( "The AV1 OBU payload exceeds its declared boundary." ) ;
}
int completeObuSize = headerAndLengthSize + payloadSize ;
if ( isAnnexB & & completeObuSize ! = annexObuSize )
{
throw new InvalidImageContentException ( "The nested and Annex B AV1 OBU lengths do not match." ) ;
}
dataSize - = isAnnexB ? annexObuSize : completeObuSize ;
header . PayloadSize = payloadSize ;
// A dedicated payload reader prevents malformed syntax from consuming the following OBU. The parent
// advances once here, so ignored metadata, padding, and reserved OBUs are skipped without copying.
Span < byte > obuPayload = reader . ReadBytes ( payloadSize ) ;
Av1BitStreamReader payloadReader = new ( obuPayload ) ;
int decodedPayloadSize ;
switch ( header . Type )
{
case ObuType . SequenceHeader :
this . SequenceHeader = new ( ) ;
ReadSequenceHeader ( ref payloadReader , this . SequenceHeader ) ;
decodedPayloadSize = Av1Math . DivideBy8Floor ( payloadReader . BitPosition ) ;
break ;
case ObuType . FrameHeader :
if ( this . SequenceHeader is null )
{
throw new InvalidImageContentException ( "An AV1 frame header appears before its sequence header." ) ;
}
if ( seenFrameHeader )
{
throw new InvalidImageContentException ( "An AV1 frame contains more than one primary frame header." ) ;
}
if ( ! seenFrameHeader )
{
seenFrameHeader = true ;
this . FrameHeader = new ( ) ;
this . ReadFrameHeader ( ref reader , header , header . Type ! = ObuType . Frame ) ;
}
this . ReadFrameHeader ( ref payloadReader , header , trailingBit : true ) ;
decodedPayloadSize = Av1Math . DivideBy8Floor ( payloadReader . BitPosition ) ;
primaryFrameHeaderPayload = obuPayload [ . . decodedPayloadSize ] ;
break ;
case ObuType . RedundantFrameHeader :
if ( ! seenFrameHeader )
{
throw new InvalidImageContentException ( "A redundant AV1 frame header appears before its primary frame header." ) ;
}
if ( header . Type ! = ObuType . Frame )
{
break ; // For OBU_TILE_GROUP comes under OBU_FRAME
}
if ( primaryFrameHeaderPayload . Length > obuPayload . Length
| | ! obuPayload [ . . primaryFrameHeaderPayload . Length ] . SequenceEqual ( primaryFrameHeaderPayload ) )
{
throw new InvalidImageContentException ( "The redundant AV1 frame header does not match its primary header." ) ;
}
goto TILE_GROUP ;
case ObuType . TileGroup :
TILE_GROUP :
if ( ! seenFrameHeader )
{
throw new InvalidImageContentException ( "Corrupt frame" ) ;
}
// The primary header already owns the decoded frame state. Matching its encoded bytes avoids
// parsing the same adaptive frame-header syntax twice, as in libaom's decoder.
decodedPayloadSize = primaryFrameHeaderPayload . Length ;
break ;
case ObuType . Frame :
if ( this . SequenceHeader is null )
{
throw new InvalidImageContentException ( "An AV1 frame appears before its sequence header." ) ;
}
this . decoder ? ? = creator ( ) ;
if ( seenFrameHeader )
{
throw new InvalidImageContentException ( "A combined AV1 frame OBU follows a separate frame header." ) ;
}
// A combined frame OBU reaches this label after its frame-header portion has
// been consumed, leaving the same tile-group syntax as a standalone tile OBU.
this . ReadTileGroup ( ref reader , this . decoder , header , out frameDecodingFinished ) ;
if ( frameDecodingFinished )
{
seenFrameHeader = true ;
this . FrameHeader = new ( ) ;
this . ReadFrameHeader ( ref payloadReader , header , trailingBit : false ) ;
primaryFrameHeaderPayload = obuPayload [ . . Av1Math . DivideBy8Floor ( payloadReader . BitPosition ) ] ;
goto TILE_GROUP ;
case ObuType . TileGroup :
TILE_GROUP :
if ( ! seenFrameHeader )
{
throw new InvalidImageContentException ( "An AV1 tile group appears before its frame header." ) ;
}
this . decoder ? ? = creator ( ) ;
// A combined frame OBU reaches this label after its frame-header portion has
// been consumed, leaving the same tile-group syntax as a standalone tile OBU.
this . ReadTileGroup ( ref payloadReader , this . decoder , header , out frameDecodingFinished ) ;
decodedPayloadSize = Av1Math . DivideBy8Floor ( payloadReader . BitPosition ) ;
if ( frameDecodingFinished )
{
seenFrameHeader = false ;
}
break ;
case ObuType . TemporalDelimiter :
// AV1 section 5.6 defines no delimiter syntax. The common post-switch validation still permits
// zero bytes between the empty syntax and the declared payload boundary, matching libaom.
seenFrameHeader = false ;
}
decodedPayloadSize = 0 ;
break ;
case ObuType . Padding :
int lastNonzeroIndex = obuPayload . Length - 1 ;
while ( lastNonzeroIndex > = 0 & & obuPayload [ lastNonzeroIndex ] = = 0 )
{
lastNonzeroIndex - - ;
}
break ;
case ObuType . TemporalDelimiter :
// 5.6. Temporal delimiter obu syntax.
seenFrameHeader = false ;
break ;
default :
// Ignore unknown OBU types.
// throw new InvalidImageContentException($"Unknown OBU header found: {header.Type.ToString()}");
break ;
}
// AV1 padding contains only its trailing one bit and optional zero bytes. A header-only
// padding OBU is also valid, so the empty payload bypasses this final-byte check.
if ( lastNonzeroIndex > = 0 & & obuPayload [ lastNonzeroIndex ] ! = 0x80 )
{
throw new InvalidImageContentException ( "The AV1 padding OBU has invalid trailing bits." ) ;
}
dataSize - = payloadSize ;
if ( dataSize < = 0 )
{
frameDecodingFinished = true ;
if ( obuPayload . Length > 0 & & lastNonzeroIndex < 0 )
{
throw new InvalidImageContentException ( "The AV1 padding OBU is missing its trailing one bit." ) ;
}
decodedPayloadSize = payloadSize ;
break ;
default :
// Metadata, tile-list, and reserved OBUs do not contribute to this still-image reconstruction
// pass. Their declared payload has already been skipped by the parent reader. libaom rejects a
// nonempty unrecognized payload that contains only zeros because it has no trailing one bit.
if ( payloadSize > 0 )
{
int ignoredLastNonzeroIndex = payloadSize - 1 ;
while ( ignoredLastNonzeroIndex > = 0 & & obuPayload [ ignoredLastNonzeroIndex ] = = 0 )
{
ignoredLastNonzeroIndex - - ;
}
if ( ignoredLastNonzeroIndex < 0 )
{
throw new InvalidImageContentException ( "The ignored AV1 OBU is missing its trailing one bit." ) ;
}
}
decodedPayloadSize = payloadSize ;
break ;
}
// Parsed syntax may be followed only by zero bytes within its declared OBU payload. Ignored metadata
// and reserved OBUs set decodedPayloadSize to the full payload because their syntax is not consumed here.
for ( int i = decodedPayloadSize ; i < obuPayload . Length ; i + + )
{
if ( obuPayload [ i ] ! = 0 )
{
throw new InvalidImageContentException ( "The AV1 OBU contains nonzero data after its decoded syntax." ) ;
}
}
}
}
catch ( IndexOutOfRangeException exception )
{
throw new InvalidImageContentException ( "The AV1 OBU syntax exceeds its payload boundary." , exception ) ;
}
catch ( ArgumentOutOfRangeException exception )
{
throw new InvalidImageContentException ( "The AV1 OBU syntax exceeds its payload boundary." , exception ) ;
}
}
/// <summary>
@ -182,9 +300,9 @@ internal class ObuReader
private static void ReadObuSize ( ref Av1BitStreamReader reader , out int obuSize , out int lengthSize )
{
ulong rawSize = reader . ReadLittleEndianBytes128 ( out lengthSize ) ;
if ( rawSize > u int. MaxValue )
if ( rawSize > int . MaxValue )
{
throw new ImageFormatException ( "OBU block too large ." ) ;
throw new InvalidImageContentException ( "The AV1 OBU size exceeds the supported image payload limit ." ) ;
}
obuSize = ( int ) rawSize ;
James Jackson-South
1 week ago