📷 A modern, cross-platform, 2D Graphics library for .NET
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// Copyright (c) Six Labors.
// Licensed under the Six Labors Split License.
using SixLabors.ImageSharp.Formats;
using SixLabors.ImageSharp.Formats.Heif.Av1;
using SixLabors.ImageSharp.Formats.Heif.Av1.OpenBitstreamUnit;
using SixLabors.ImageSharp.Memory;
namespace SixLabors.ImageSharp.Tests.Formats.Heif.Av1;
[Trait("Format", "Avif")]
public class ObuFrameHeaderTests
{
/// <summary>
/// Identifies one reference sequence-header conformance condition used by the malformed-input theory.
/// </summary>
public enum InvalidSequenceHeaderCase
{
/// <summary>
/// Encodes the otherwise valid baseline.
/// </summary>
None,
/// <summary>
/// Encodes an unassigned sequence-level index.
/// </summary>
UndefinedSequenceLevel,
/// <summary>
/// Encodes an initial display delay greater than ten frames.
/// </summary>
InitialDisplayDelayAboveTen,
/// <summary>
/// Encodes a frame identifier wider than sixteen bits.
/// </summary>
FrameIdentifierLengthAboveSixteen,
/// <summary>
/// Encodes a zero display-tick unit.
/// </summary>
ZeroDisplayTick,
/// <summary>
/// Encodes a zero time scale.
/// </summary>
ZeroTimeScale,
/// <summary>
/// Encodes the unsigned-variable-length overflow sentinel.
/// </summary>
OverflowingTicksPerPicture,
/// <summary>
/// Encodes the sRGB identity-matrix tuple with the main profile.
/// </summary>
MainProfileSrgbIdentity,
/// <summary>
/// Encodes an identity matrix with subsampled components.
/// </summary>
SubsampledIdentityMatrix
}
private static readonly byte[] DefaultSequenceHeaderBitStream =
[0x0a, 0x06, 0b001_1_1_000, 0b00_1000_01, 0b11_110101, 0b001_11101, 0b111_1_1_1_0_1, 0b1_0_0_1_1_1_10];
// This complete temporal-delimiter and sequence-header prefix comes from the color item in libavif's
// draw_points_idat_progressive.avif. Its operating points select spatial layers 0+1 and layer 0 respectively.
private static ReadOnlySpan<byte> ProgressiveSequenceHeaderBitStream =>
[
0x12, 0x00,
0x0A, 0x0F, 0x20, 0x13, 0x01, 0x00, 0x80, 0x81, 0x4E, 0x0A, 0x36, 0xBE, 0x48, 0x08, 0x20, 0x34, 0x80
];
// Bits Syntax element Value
// 1 obu_forbidden_bit 0
// 4 obu_type 2 (OBU_TEMPORAL_DELIMITER)
// 1 obu_extension_flag 0
// 1 obu_has_size_field 1
// 1 obu_reserved_1bit 0
// 8 obu_size 0
private static readonly byte[] DefaultTemporalDelimiterBitStream = [0x12, 0x00];
[Theory]
// [InlineData(TestImages.Heif.IrvineAvif, 0x0198, 0x6bd1)]
[InlineData(TestImages.Heif.XnConvert, 0x010e, 0x03cc)]
[InlineData(TestImages.Heif.Orange4x4, 0x010e, 0x001d)]
public void ReadFrameHeader(string filename, int fileOffset, int blockSize)
{
// Assign
string filePath = Path.Combine(TestEnvironment.InputImagesDirectoryFullPath, filename);
byte[] content = File.ReadAllBytes(filePath);
Span<byte> span = content.AsSpan(fileOffset, blockSize);
Av1BitStreamReader reader = new(span);
IAv1TileReader decoder = new Av1TileDecoderStub();
ObuReader obuReader = new();
// Act
obuReader.ReadAll(ref reader, blockSize, () => decoder);
// Assert
Assert.NotNull(obuReader.SequenceHeader);
Assert.NotNull(obuReader.FrameHeader);
Assert.NotNull(obuReader.FrameHeader.TilesInfo);
Assert.Equal(reader.Length * 8, reader.BitPosition);
Assert.Equal(reader.Length, blockSize);
}
[Theory]
[InlineData(TestImages.Heif.Orange4x4, 0x010e, 0x001d)]
[InlineData(TestImages.Heif.XnConvert, 0x010e, 0x03cc)]
public void BinaryIdenticalRoundTripFrameHeader(string filename, int fileOffset, int blockSize)
{
// Assign
string filePath = Path.Combine(TestEnvironment.InputImagesDirectoryFullPath, filename);
byte[] content = File.ReadAllBytes(filePath);
Span<byte> span = content.AsSpan(fileOffset, blockSize);
Av1TileDecoderStub tileStub = new();
Av1BitStreamReader reader = new(span);
ObuReader obuReader = new();
// Act 1
obuReader.ReadAll(ref reader, blockSize, () => tileStub);
// Assign 2
MemoryStream encoded = new();
// Act 2
ObuWriter obuWriter = new();
obuWriter.WriteAll(Configuration.Default, encoded, obuReader.SequenceHeader, obuReader.FrameHeader, tileStub);
// Assert
byte[] encodedArray = encoded.ToArray();
Assert.Equal((ReadOnlySpan<byte>)span, encodedArray);
}
[Theory]
[InlineData(TestImages.Heif.Orange4x4, 0x010e, 0x001d)]
[InlineData(TestImages.Heif.XnConvert, 0x010e, 0x03cc)]
public void ThreeTimeRoundTripFrameHeader(string filename, int fileOffset, int blockSize)
{
// Assign
string filePath = Path.Combine(TestEnvironment.InputImagesDirectoryFullPath, filename);
byte[] content = File.ReadAllBytes(filePath);
Span<byte> span = content.AsSpan(fileOffset, blockSize);
Av1TileDecoderStub tileStub = new();
Av1BitStreamReader reader = new(span);
ObuReader obuReader1 = new();
// Act 1
obuReader1.ReadAll(ref reader, blockSize, () => tileStub);
// Assign 2
MemoryStream encoded = new();
// Act 2
ObuWriter obuWriter = new();
obuWriter.WriteAll(Configuration.Default, encoded, obuReader1.SequenceHeader, obuReader1.FrameHeader, tileStub);
// Assign 2
Span<byte> encodedBuffer = encoded.ToArray();
IAv1TileReader tileDecoder2 = new Av1TileDecoderStub();
Av1BitStreamReader reader2 = new(span);
ObuReader obuReader2 = new();
// Act 2
obuReader2.ReadAll(ref reader2, encodedBuffer.Length, () => tileDecoder2);
// Assert
Assert.Equal(ObuPrettyPrint.PrettyPrintProperties(obuReader1.SequenceHeader.ColorConfig), ObuPrettyPrint.PrettyPrintProperties(obuReader2.SequenceHeader.ColorConfig));
Assert.Equal(ObuPrettyPrint.PrettyPrintProperties(obuReader1.SequenceHeader), ObuPrettyPrint.PrettyPrintProperties(obuReader2.SequenceHeader));
Assert.Equal(ObuPrettyPrint.PrettyPrintProperties(obuReader1.FrameHeader), ObuPrettyPrint.PrettyPrintProperties(obuReader2.FrameHeader));
Assert.Equal(ObuPrettyPrint.PrettyPrintProperties(obuReader1.FrameHeader.TilesInfo), ObuPrettyPrint.PrettyPrintProperties(obuReader2.FrameHeader.TilesInfo));
}
[Fact]
public void ReadTemporalDelimiter()
{
// Arrange
Av1BitStreamReader reader = new(DefaultTemporalDelimiterBitStream);
ObuReader obuReader = new();
IAv1TileReader tileDecoder = new Av1TileDecoderStub();
// Act
obuReader.ReadAll(ref reader, DefaultTemporalDelimiterBitStream.Length, () => tileDecoder);
// Assert
Assert.Null(obuReader.SequenceHeader);
Assert.Null(obuReader.FrameHeader);
}
[Fact]
public void ReadAnnexBHeaderWithoutSizeField()
{
// Arrange
// Annex B's outer obu_length is one byte and covers the size-less temporal-delimiter header.
byte[] bitStream = [0x01, 0x10];
Av1BitStreamReader reader = new(bitStream);
ObuReader obuReader = new();
IAv1TileReader tileDecoder = new Av1TileDecoderStub();
// Act
obuReader.ReadAll(ref reader, bitStream.Length, () => tileDecoder, isAnnexB: true);
// Assert
Assert.Null(obuReader.SequenceHeader);
Assert.Null(obuReader.FrameHeader);
}
/// <summary>
/// Verifies that a final low-overhead frame OBU may use the enclosing image-item boundary instead of an OBU size field.
/// </summary>
[Fact]
public void ReadFinalLowOverheadFrameWithoutSizeField()
{
const int itemDataOffset = 0x010E;
const int itemDataLength = 0x001D;
string filePath = Path.Combine(TestEnvironment.InputImagesDirectoryFullPath, TestImages.Heif.Orange4x4);
byte[] fileContent = File.ReadAllBytes(filePath);
byte[] sizedBitStream = fileContent.AsSpan(itemDataOffset, itemDataLength).ToArray();
int frameOffset = DefaultTemporalDelimiterBitStream.Length;
Av1BitStreamReader sequenceSizeReader = new(sizedBitStream.AsSpan(frameOffset + 1));
ulong sequencePayloadLength = sequenceSizeReader.ReadLittleEndianBytes128(out int sequenceSizeLength);
frameOffset += 1 + sequenceSizeLength + (int)sequencePayloadLength;
Av1BitStreamReader sizeReader = new(sizedBitStream.AsSpan(frameOffset + 1));
ulong framePayloadLength = sizeReader.ReadLittleEndianBytes128(out int encodedSizeLength);
byte[] bitStream = new byte[sizedBitStream.Length - encodedSizeLength];
// Preserve the independently encoded frame payload while changing only the final OBU's legal boundary form.
sizedBitStream.AsSpan(0, frameOffset).CopyTo(bitStream);
bitStream[frameOffset] = (byte)(sizedBitStream[frameOffset] & ~0x02);
sizedBitStream.AsSpan(frameOffset + 1 + encodedSizeLength).CopyTo(bitStream.AsSpan(frameOffset + 1));
Assert.Equal(framePayloadLength, (ulong)(bitStream.Length - frameOffset - 1));
ReadObuStream(bitStream);
}
[Fact]
public void ReadSequenceHeader()
{
// Arrange
byte[] bitStream = DefaultSequenceHeaderBitStream;
Av1BitStreamReader reader = new(bitStream);
ObuReader obuReader = new();
IAv1TileReader tileDecoder = new Av1TileDecoderStub();
ObuSequenceHeader expected = GetDefaultSequenceHeader();
// Act
obuReader.ReadAll(ref reader, bitStream.Length, () => tileDecoder);
// Assert
Assert.NotNull(obuReader.SequenceHeader);
Assert.Null(obuReader.FrameHeader);
Assert.Equal(ObuPrettyPrint.PrettyPrintProperties(expected), ObuPrettyPrint.PrettyPrintProperties(obuReader.SequenceHeader));
}
/// <summary>
/// Verifies reference sequence-header conformance failures through the complete bounded OBU parser.
/// </summary>
/// <param name="invalidCase">The single invalid syntax condition encoded into an otherwise valid sequence header.</param>
[Theory]
[InlineData(InvalidSequenceHeaderCase.UndefinedSequenceLevel)]
[InlineData(InvalidSequenceHeaderCase.InitialDisplayDelayAboveTen)]
[InlineData(InvalidSequenceHeaderCase.FrameIdentifierLengthAboveSixteen)]
[InlineData(InvalidSequenceHeaderCase.ZeroDisplayTick)]
[InlineData(InvalidSequenceHeaderCase.ZeroTimeScale)]
[InlineData(InvalidSequenceHeaderCase.OverflowingTicksPerPicture)]
[InlineData(InvalidSequenceHeaderCase.MainProfileSrgbIdentity)]
[InlineData(InvalidSequenceHeaderCase.SubsampledIdentityMatrix)]
public void ReadSequenceHeaderRejectsConformanceFailure(InvalidSequenceHeaderCase invalidCase)
{
byte[] bitStream = CreateNonReducedSequenceHeaderObu(invalidCase);
Assert.Throws<InvalidImageContentException>(() => ReadObuStream(bitStream));
}
/// <summary>
/// Verifies that reserved OBU header fields are ignored consistently by container validation and syntax parsing.
/// </summary>
/// <param name="hasExtension">Whether the sequence header also carries nonzero reserved extension bits.</param>
[Theory]
[InlineData(false)]
[InlineData(true)]
public void ReadSequenceHeaderIgnoresReservedObuHeaderBits(bool hasExtension)
{
byte[] bitStream;
if (hasExtension)
{
bitStream = new byte[DefaultSequenceHeaderBitStream.Length + 1];
bitStream[0] = (byte)(DefaultSequenceHeaderBitStream[0] | 0x05);
bitStream[1] = 0x07;
DefaultSequenceHeaderBitStream.AsSpan(1).CopyTo(bitStream.AsSpan(2));
}
else
{
bitStream = [.. DefaultSequenceHeaderBitStream];
bitStream[0] |= 0x01;
}
Av1CodecConfiguration configuration = new([0x81, 0x00, 0x00, 0x00], new DecoderOptions());
configuration.ValidateItemData(
bitStream,
null,
null,
new DecoderOptions(),
out _,
out _);
ReadObuStream(bitStream);
}
/// <summary>
/// Verifies that metadata-type LEB128 values obey the reference decoder's shared unsigned 32-bit limit.
/// </summary>
[Fact]
public void ValidateItemDataRejectsMetadataTypeAboveLimit()
{
byte[] bitStream =
[
.. DefaultSequenceHeaderBitStream,
// Metadata type 2^32 followed by valid byte-aligned trailing bits.
0x2A, 0x06, 0x80, 0x80, 0x80, 0x80, 0x10, 0x80
];
DecoderOptions options = new() { SegmentIntegrityHandling = SegmentIntegrityHandling.Strict };
Av1CodecConfiguration configuration = new([0x81, 0x00, 0x00, 0x00], options);
Assert.Throws<InvalidImageContentException>(
() => configuration.ValidateItemData(
bitStream,
null,
null,
options,
out _,
out _));
}
/// <summary>
/// Verifies that an item cannot select an operating-point index absent from its sequence header.
/// </summary>
[Fact]
public void ReadOperatingPointRejectsIndexOutsideSequenceHeader()
{
byte[] bitStream = [.. ProgressiveSequenceHeaderBitStream];
Assert.Throws<InvalidImageContentException>(() => ReadObuStream(bitStream, 2));
}
/// <summary>
/// Verifies that an extended OBU belongs to an operating point only when both of its layer identifiers are selected.
/// </summary>
/// <param name="temporalId">The temporal-layer identifier carried by the test OBU.</param>
/// <param name="spatialId">The spatial-layer identifier carried by the test OBU.</param>
/// <param name="isIncluded">Whether operating point one selects both identifiers.</param>
[Theory]
[InlineData(0, 0, true)]
[InlineData(0, 1, false)]
[InlineData(1, 0, false)]
public void ReadOperatingPointRequiresBothLayerBits(byte temporalId, byte spatialId, bool isIncluded)
{
byte extension = (byte)((temporalId << 5) | (spatialId << 3));
byte[] bitStream = [.. ProgressiveSequenceHeaderBitStream, 0x2E, extension, 0x01, 0x00];
// A selected metadata OBU reaches ignored-payload validation, where an all-zero payload is invalid. A filtered
// OBU has nevertheless had its complete header, size and payload boundary consumed before syntax is skipped.
if (isIncluded)
{
Assert.Throws<InvalidImageContentException>(() => ReadObuStream(bitStream, 1));
}
else
{
ReadObuStream(bitStream, 1);
}
}
/// <summary>
/// Verifies that an all-zero operating-point mask includes every extended OBU.
/// </summary>
[Fact]
public void ReadZeroOperatingPointMaskIncludesExtendedObu()
{
byte[] bitStream = [.. DefaultSequenceHeaderBitStream, 0x2E, 0x08, 0x01, 0x00];
Assert.Throws<InvalidImageContentException>(() => ReadObuStream(bitStream));
}
/// <summary>
/// Verifies that an OBU without an extension header applies to every operating point.
/// </summary>
[Fact]
public void ReadOperatingPointIncludesUnextendedObu()
{
byte[] bitStream = [.. ProgressiveSequenceHeaderBitStream, 0x2A, 0x01, 0x00];
Assert.Throws<InvalidImageContentException>(() => ReadObuStream(bitStream, 1));
}
/// <summary>
/// Verifies that temporal delimiters remain part of stream framing even when their extension is outside the selected mask.
/// </summary>
[Fact]
public void ReadOperatingPointDoesNotFilterTemporalDelimiter()
{
byte[] bitStream = [.. ProgressiveSequenceHeaderBitStream, 0x16, 0x08, 0x01, 0x01];
Assert.Throws<InvalidImageContentException>(() => ReadObuStream(bitStream, 1));
}
/// <summary>
/// Verifies that an excluded OBU cannot escape validation of its declared payload boundary.
/// </summary>
[Fact]
public void ReadFilteredOperatingPointObuStillValidatesBoundary()
{
byte[] bitStream = [.. ProgressiveSequenceHeaderBitStream, 0x2E, 0x08, 0x02, 0x80];
Assert.Throws<InvalidImageContentException>(() => ReadObuStream(bitStream, 1));
}
/// <summary>
/// Verifies that the reduced sequence syntax cannot be used without declaring a still picture.
/// </summary>
[Fact]
public void ReducedHeaderWithoutStillPictureThrows()
{
const int sequenceHeaderPayloadOffset = 2;
byte[] bitStream = [.. DefaultSequenceHeaderBitStream];
// The first payload byte stores the three profile bits followed by still_picture and
// reduced_still_picture_header. Clear only still_picture so the remaining syntax stays reduced.
bitStream[sequenceHeaderPayloadOffset] &= 0b1110_1111;
Assert.Throws<InvalidImageContentException>(() => ReadObuStream(bitStream));
}
/// <summary>
/// Verifies that a declared still-picture sequence rejects frame prefixes which do not describe a shown key frame.
/// </summary>
/// <param name="invalidFramePrefix">The high nibble containing show-existing, frame-type, and show-frame syntax.</param>
[Theory]
[InlineData(0b1000_0000)] // show_existing_frame = 1
[InlineData(0b0101_0000)] // frame_type = INTRA_ONLY_FRAME, show_frame = 1
[InlineData(0b0000_0000)] // frame_type = KEY_FRAME, show_frame = 0
public void InvalidStillPicturePrefixThrows(int invalidFramePrefix)
{
ObuSequenceHeader sequenceHeader = GetDefaultSequenceHeader();
sequenceHeader.IsReducedStillPictureHeader = false;
ObuFrameHeader frameHeader = GetKeyFrameHeader();
Av1TileDecoderStub tileStub = new();
byte[] emptyTile = [];
tileStub.ReadTile(emptyTile, 0);
using MemoryStream stream = new();
ObuWriter writer = new();
writer.WriteAll(Configuration.Default, stream, sequenceHeader, frameHeader, tileStub);
byte[] bitStream = stream.ToArray();
int sequenceObuOffset = DefaultTemporalDelimiterBitStream.Length;
Av1BitStreamReader sequenceSizeReader = new(bitStream.AsSpan(sequenceObuOffset + 1));
ulong sequencePayloadLength = sequenceSizeReader.ReadLittleEndianBytes128(out int sequenceSizeLength);
int frameObuOffset = sequenceObuOffset + 1 + sequenceSizeLength + (int)sequencePayloadLength;
Av1BitStreamReader frameSizeReader = new(bitStream.AsSpan(frameObuOffset + 1));
_ = frameSizeReader.ReadLittleEndianBytes128(out int frameSizeLength);
int framePayloadOffset = frameObuOffset + 1 + frameSizeLength;
// Preserve syntax after the frame prefix so each malformed stream differs from a valid writer result only in
// show_existing_frame or the still-picture frame-type/show-frame conformance condition under test.
bitStream[framePayloadOffset] = (byte)((bitStream[framePayloadOffset] & 0x0F) | invalidFramePrefix);
Assert.Throws<InvalidImageContentException>(() => ReadObuStream(bitStream));
}
/// <summary>
/// Verifies that ignored OBU payloads are bounded and skipped before parsing the following sequence header.
/// </summary>
[Fact]
public void ReadIgnoredObusSkipsEachDeclaredPayload()
{
// 0x7A identifies padding and 0x4A identifies reserved OBU type 9. Both carry explicit sizes so their payload
// bytes must never be interpreted as another OBU header.
byte[] bitStream =
[
0x7A, 0x02, 0x80, 0x00,
0x4A, 0x01, 0x80,
.. DefaultSequenceHeaderBitStream
];
Av1BitStreamReader reader = new(bitStream);
ObuReader obuReader = new();
IAv1TileReader tileDecoder = new Av1TileDecoderStub();
obuReader.ReadAll(ref reader, bitStream.Length, () => tileDecoder);
Assert.NotNull(obuReader.SequenceHeader);
Assert.Equal(bitStream.Length * 8, reader.BitPosition);
}
/// <summary>
/// Verifies that a four-byte tile size cannot wrap into an empty first tile.
/// </summary>
[Fact]
public void ReadTileGroupRejectsFourByteTileSizeOverflow()
{
byte[] bitStream = CreateTwoTileFrame(GetDefaultSequenceHeader(), GetKeyFrameHeader(), 4);
Span<byte> encodedTileSize = bitStream.AsSpan(bitStream.Length - 6, 4);
encodedTileSize.Fill(byte.MaxValue);
Assert.Throws<InvalidImageContentException>(() => ReadObuStream(bitStream));
}
/// <summary>
/// Verifies the reference decoder's doubled minimum inner-tile width for a super-resolution-scaled frame.
/// </summary>
[Fact]
public void ReadTileInfoRejectsNarrowSuperResolutionInnerTile()
{
ObuSequenceHeader sequenceHeader = GetDefaultSequenceHeader();
sequenceHeader.Use128x128Superblock = false;
sequenceHeader.EnableSuperResolution = true;
sequenceHeader.FrameWidthBits = 8;
sequenceHeader.MaxFrameWidth = 192;
ObuFrameHeader frameHeader = GetKeyFrameHeader();
frameHeader.FrameSize.FrameWidth = 96;
frameHeader.FrameSize.SuperResolutionUpscaledWidth = 192;
frameHeader.FrameSize.RenderWidth = 192;
frameHeader.FrameSize.SuperResolutionDenominator = 16;
frameHeader.ModeInfoColumnCount = 24;
byte[] bitStream = CreateTwoTileFrame(sequenceHeader, frameHeader, 1);
Assert.Throws<InvalidImageContentException>(() => ReadObuStream(bitStream));
}
/// <summary>
/// Verifies that an intra-only frame cannot signal the all-slots refresh mask reserved for key and switch frames.
/// </summary>
[Fact]
public void ReadFrameHeaderRejectsIntraOnlyAllSlotsRefresh()
{
byte[] sequenceHeader = CreateNonReducedSequenceHeaderObu(default);
using AutoExpandingMemory<byte> frameMemory = new(Configuration.Default, 8);
Av1BitStreamWriter frameWriter = new(frameMemory);
frameWriter.WriteBoolean(false);
frameWriter.WriteLiteral((uint)ObuFrameType.IntraOnlyFrame, 2);
frameWriter.WriteBoolean(true);
frameWriter.WriteBoolean(true);
frameWriter.WriteBoolean(false);
frameWriter.WriteBoolean(false);
frameWriter.WriteLiteral(byte.MaxValue, 8);
int framePayloadLength = (frameWriter.BitPosition + 7) >> 3;
frameWriter.Flush();
byte[] bitStream = new byte[sequenceHeader.Length + 2 + framePayloadLength];
sequenceHeader.CopyTo(bitStream, 0);
int frameObuOffset = sequenceHeader.Length;
bitStream[frameObuOffset] = (byte)(((byte)ObuType.FrameHeader << 3) | 0x02);
bitStream[frameObuOffset + 1] = (byte)framePayloadLength;
frameMemory.GetSpan(framePayloadLength).CopyTo(bitStream.AsSpan(frameObuOffset + 2));
Assert.Throws<InvalidImageContentException>(() => ReadObuStream(bitStream));
}
/// <summary>
/// Verifies that invalid OBU boundaries, size fields, and trailing bytes are rejected.
/// </summary>
/// <param name="bitStream">The malformed OBU stream.</param>
[Theory]
[InlineData(new byte[] { 0x7A, 0x02, 0x11 })]
[InlineData(new byte[] { 0x7A, 0x01, 0x00 })]
[InlineData(new byte[] { 0x12, 0x01, 0x01 })]
[InlineData(new byte[] { 0x7A, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80 })]
public void ReadInvalidObuBoundaryThrows(byte[] bitStream)
=> Assert.Throws<InvalidImageContentException>(() => ReadObuStream(bitStream));
/// <summary>
/// Verifies that an empty temporal delimiter may occupy a payload containing only zero padding bytes.
/// </summary>
[Fact]
public void ReadTemporalDelimiterAllowsZeroPayloadPadding()
{
byte[] bitStream = [0x12, 0x02, 0x00, 0x00];
ReadObuStream(bitStream);
}
[Fact]
public void WriteTemporalDelimiter()
{
// Arrange
using MemoryStream stream = new(2);
ObuWriter obuWriter = new();
// Act
obuWriter.WriteAll(Configuration.Default, stream, null, null, null);
byte[] actual = stream.GetBuffer();
// Assert
Assert.Equal(DefaultTemporalDelimiterBitStream, actual);
}
[Fact]
public void WriteSequenceHeader()
{
// Arrange
using MemoryStream stream = new(10);
ObuSequenceHeader input = GetDefaultSequenceHeader();
ObuWriter obuWriter = new();
// Act
obuWriter.WriteAll(Configuration.Default, stream, input, null, null);
byte[] buffer = stream.GetBuffer();
// Assert
// Skip over Temporal Delimiter header.
byte[] actual = buffer.AsSpan()[DefaultTemporalDelimiterBitStream.Length..].ToArray();
Assert.Equal(DefaultSequenceHeaderBitStream, actual);
}
/// <summary>
/// Verifies that the combined frame OBU declares exactly the payload bytes emitted by the writer.
/// </summary>
[Fact]
public void WriteFrameHeader()
{
// Arrange
using MemoryStream stream = new(10);
ObuSequenceHeader sequenceInput = GetDefaultSequenceHeader();
ObuFrameHeader frameInput = GetKeyFrameHeader();
Av1TileDecoderStub tileStub = new();
byte[] tileData = [0x80];
tileStub.ReadTile(tileData, 0);
ObuWriter obuWriter = new();
// Act
obuWriter.WriteAll(Configuration.Default, stream, sequenceInput, frameInput, tileStub);
byte[] bitStream = stream.ToArray();
// Assert
int frameOffset = DefaultTemporalDelimiterBitStream.Length + DefaultSequenceHeaderBitStream.Length;
Span<byte> frameObu = bitStream.AsSpan(frameOffset);
byte expectedHeader = (byte)(((byte)ObuType.Frame << 3) | 0x02);
Assert.Equal(expectedHeader, frameObu[0]);
Av1BitStreamReader sizeReader = new(frameObu[1..]);
ulong declaredPayloadSize = sizeReader.ReadLittleEndianBytes128(out int encodedSizeLength);
Assert.Equal(frameObu.Length - 1 - encodedSizeLength, (int)declaredPayloadSize);
Av1BitStreamReader reader = new(bitStream);
ObuReader obuReader = new();
obuReader.ReadAll(ref reader, bitStream.Length, () => new Av1TileDecoderStub());
Assert.NotNull(obuReader.SequenceHeader);
Assert.NotNull(obuReader.FrameHeader);
Assert.Equal(bitStream.Length * 8, reader.BitPosition);
}
/// <summary>
/// Encodes one non-reduced sequence header with a single selected conformance failure.
/// </summary>
/// <param name="invalidCase">The syntax condition to make invalid, or <see cref="InvalidSequenceHeaderCase.None"/>.</param>
/// <returns>The complete explicitly sized sequence-header OBU.</returns>
private static byte[] CreateNonReducedSequenceHeaderObu(InvalidSequenceHeaderCase invalidCase)
{
bool hasTimingInfo = invalidCase is
InvalidSequenceHeaderCase.ZeroDisplayTick or
InvalidSequenceHeaderCase.ZeroTimeScale or
InvalidSequenceHeaderCase.OverflowingTicksPerPicture;
bool hasInitialDisplayDelay = invalidCase == InvalidSequenceHeaderCase.InitialDisplayDelayAboveTen;
bool hasFrameIdentifiers = invalidCase == InvalidSequenceHeaderCase.FrameIdentifierLengthAboveSixteen;
bool hasColorDescription = invalidCase is
InvalidSequenceHeaderCase.MainProfileSrgbIdentity or
InvalidSequenceHeaderCase.SubsampledIdentityMatrix;
using AutoExpandingMemory<byte> payloadMemory = new(Configuration.Default, 32);
Av1BitStreamWriter writer = new(payloadMemory);
writer.WriteLiteral((uint)ObuSequenceProfile.Main, 3);
writer.WriteBoolean(false);
writer.WriteBoolean(false);
writer.WriteBoolean(hasTimingInfo);
if (hasTimingInfo)
{
writer.WriteLiteral(invalidCase == InvalidSequenceHeaderCase.ZeroDisplayTick ? 0U : 1U, 32);
writer.WriteLiteral(invalidCase == InvalidSequenceHeaderCase.ZeroTimeScale ? 0U : 1U, 32);
bool overflowingTicksPerPicture = invalidCase == InvalidSequenceHeaderCase.OverflowingTicksPerPicture;
writer.WriteBoolean(overflowingTicksPerPicture);
if (overflowingTicksPerPicture)
{
// Thirty-two leading zeros are the UVLC sentinel which the reference decoder rejects as UINT32_MAX.
writer.WriteLiteral(0U, 32);
}
writer.WriteBoolean(false);
}
writer.WriteBoolean(hasInitialDisplayDelay);
writer.WriteLiteral(0U, 5);
writer.WriteLiteral(0U, 12);
uint sequenceLevel = invalidCase == InvalidSequenceHeaderCase.UndefinedSequenceLevel ? 24U : 0U;
writer.WriteLiteral(sequenceLevel, 5);
if (sequenceLevel > 7)
{
writer.WriteBoolean(false);
}
if (hasInitialDisplayDelay)
{
writer.WriteBoolean(true);
writer.WriteLiteral(10U, 4);
}
writer.WriteLiteral(7U, 4);
writer.WriteLiteral(7U, 4);
writer.WriteLiteral(63U, 8);
writer.WriteLiteral(63U, 8);
writer.WriteBoolean(hasFrameIdentifiers);
if (hasFrameIdentifiers)
{
writer.WriteLiteral(15U, 4);
writer.WriteLiteral(0U, 3);
}
// Disable superblock and intra-edge tools.
writer.WriteBoolean(false);
writer.WriteBoolean(false);
writer.WriteBoolean(false);
// Disable the inter compound, warped, dual-filter, and order-hint tools.
writer.WriteBoolean(false);
writer.WriteBoolean(false);
writer.WriteBoolean(false);
writer.WriteBoolean(false);
writer.WriteBoolean(false);
// Select fixed disabled screen-content and integer-motion-vector behavior.
writer.WriteBoolean(false);
writer.WriteBoolean(false);
// Disable super resolution, CDEF, and restoration in the otherwise valid baseline.
writer.WriteBoolean(false);
writer.WriteBoolean(false);
writer.WriteBoolean(false);
// Encode an 8-bit, non-monochrome color configuration.
writer.WriteBoolean(false);
writer.WriteBoolean(false);
writer.WriteBoolean(hasColorDescription);
if (hasColorDescription)
{
bool isSrgbIdentity = invalidCase == InvalidSequenceHeaderCase.MainProfileSrgbIdentity;
writer.WriteLiteral((uint)(isSrgbIdentity ? ObuColorPrimaries.Bt709 : ObuColorPrimaries.Unspecified), 8);
writer.WriteLiteral((uint)(isSrgbIdentity ? ObuTransferCharacteristics.Srgb : ObuTransferCharacteristics.Unspecified), 8);
writer.WriteLiteral((uint)ObuMatrixCoefficients.Identity, 8);
}
if (invalidCase != InvalidSequenceHeaderCase.MainProfileSrgbIdentity)
{
writer.WriteBoolean(false);
writer.WriteLiteral((uint)ObuChromoSamplePosition.Unknown, 2);
}
writer.WriteBoolean(false);
writer.WriteBoolean(false);
int trailingBitCount = 8 - (writer.BitPosition & 0x07);
writer.WriteLiteral(1U << (trailingBitCount - 1), trailingBitCount);
int payloadLength = (writer.BitPosition + 7) >> 3;
writer.Flush();
byte[] obu = new byte[payloadLength + 2];
obu[0] = (byte)(((byte)ObuType.SequenceHeader << 3) | 0x02);
obu[1] = (byte)payloadLength;
payloadMemory.GetSpan(payloadLength).CopyTo(obu.AsSpan(2));
return obu;
}
/// <summary>
/// Encodes one valid reduced frame with two one-byte tile payloads.
/// </summary>
/// <param name="sequenceHeader">The sequence syntax to encode.</param>
/// <param name="frameHeader">The frame syntax to encode.</param>
/// <param name="tileSizeBytes">The number of bytes used for the first tile's size field.</param>
/// <returns>The complete temporal delimiter, sequence header, and combined frame OBU stream.</returns>
private static byte[] CreateTwoTileFrame(
ObuSequenceHeader sequenceHeader,
ObuFrameHeader frameHeader,
int tileSizeBytes)
{
frameHeader.TilesInfo.HasUniformTileSpacing = true;
frameHeader.TilesInfo.TileColumnCount = 2;
frameHeader.TilesInfo.TileRowCount = 1;
frameHeader.TilesInfo.TileSizeBytes = tileSizeBytes;
Av1TileDecoderStub tileStub = new();
tileStub.ReadTile([0x80], 0);
tileStub.ReadTile([0x80], 1);
using MemoryStream stream = new();
ObuWriter writer = new();
writer.WriteAll(Configuration.Default, stream, sequenceHeader, frameHeader, tileStub);
return stream.ToArray();
}
private static ObuSequenceHeader GetDefaultSequenceHeader()
// Offset Bits Syntax element Value
// 0 3 seq_profile 1
// 3 1 still_picture 1
// 4 1 reduced_still_picture_header 1
// 5 5 seq_level_idx[ 0 ] 0
// 10 4 frame_width_bits_minus_1 8
// 14 4 frame_height_bits_minus_1 7
// 18 9 max_frame_width_minus_1 425
// 27 8 max_frame_height_minus_1 239
// 35 1 use_128x128_superblock 1
// 36 1 enable_filter_intra 1
// 37 1 enable_intra_edge_filter 1
// 38 1 enable_superres 0
// 39 1 enable_cdef 1
// 40 1 enable_restoration 1
// 41 1 ColorConfig.BitDepth.HasHighBit 0
// 42 1 ColorConfig.IsDescriptionPresent 0
// 43 1 ColorConfig.ColorRange 1
// 44 1 ColorConfig.HasSeparateUVDelta 1
// 45 1 film_grain_present 1
// 47 2 Trailing bits 2
=> new()
{
SequenceProfile = ObuSequenceProfile.High,
IsStillPicture = true,
IsReducedStillPictureHeader = true,
TimingInfoPresentFlag = false,
InitialDisplayDelayPresentFlag = false,
FrameWidthBits = 8 + 1,
FrameHeightBits = 7 + 1,
MaxFrameWidth = 425 + 1,
MaxFrameHeight = 239 + 1,
IsFrameIdNumbersPresent = false,
Use128x128Superblock = true,
EnableFilterIntra = true,
EnableIntraEdgeFilter = true,
EnableInterIntraCompound = false,
EnableMaskedCompound = false,
EnableWarpedMotion = false,
EnableDualFilter = false,
EnableOrderHint = false,
OperatingPoint = [new()],
// EnableJountCompound = true,
// EnableReferenceFrameMotionVectors = true,
ForceScreenContentTools = 2,
ForceIntegerMotionVector = 2,
EnableSuperResolution = false,
EnableCdef = true,
EnableRestoration = true,
ColorConfig = new()
{
IsMonochrome = false,
ColorPrimaries = ObuColorPrimaries.Unspecified,
TransferCharacteristics = ObuTransferCharacteristics.Unspecified,
MatrixCoefficients = ObuMatrixCoefficients.Unspecified,
SubSamplingX = false,
SubSamplingY = false,
BitDepth = Av1BitDepth.EightBit,
HasSeparateUvDelta = true,
ColorRange = true,
},
AreFilmGrainingParametersPresent = true,
};
/// <summary>
/// Reads one complete OBU stream for malformed-input assertions that cannot capture a ref-struct reader.
/// </summary>
/// <param name="bitStream">The complete encoded OBU stream.</param>
private static void ReadObuStream(byte[] bitStream, byte operatingPointIndex = 0)
{
Av1BitStreamReader reader = new(bitStream);
ObuReader obuReader = new(operatingPointIndex);
IAv1TileReader tileDecoder = new Av1TileDecoderStub();
obuReader.ReadAll(ref reader, bitStream.Length, () => tileDecoder);
}
private static ObuFrameHeader GetKeyFrameHeader()
=> new()
{
FrameType = ObuFrameType.KeyFrame,
ShowFrame = true,
ShowableFrame = false,
DisableFrameEndUpdateCdf = false,
FrameSize = new()
{
FrameWidth = 426,
FrameHeight = 240,
RenderWidth = 426,
RenderHeight = 240,
SuperResolutionUpscaledWidth = 426,
},
PrimaryReferenceFrame = 7,
ModeInfoRowCount = 60,
ModeInfoColumnCount = 108,
RefreshFrameFlags = 0xff,
ErrorResilientMode = true,
ForceIntegerMotionVector = true,
TilesInfo = new ObuTileGroupHeader()
{
HasUniformTileSpacing = true,
TileColumnCount = 1,
TileRowCount = 1,
}
};
}