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AV1 Frame Header parsing

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PiperOrigin-RevId: 719253811
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dancho 2025-01-24 04:46:33 -08:00 committed by Copybara-Service
parent 1772050ece
commit 227a4d76b1
2 changed files with 134 additions and 3 deletions
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96
libraries/container/src/main/java/androidx/media3/container/ObuParser.java
View File

@ -16,6 +16,7 @@
package androidx.media3.container;
import static androidx.media3.common.util.Assertions.checkArgument;
import static java.lang.Math.min;
import androidx.annotation.Nullable;
import androidx.media3.common.util.ParsableBitArray;
@ -136,9 +137,10 @@ public final class ObuParser {
public final int orderHintBits;
/**
* Returns a {@link SequenceHeader} parsed from the input {@link #OBU_SEQUENCE_HEADER}.
* Returns a {@link SequenceHeader} parsed from the input OBU, or {@code null} if the AV1
* bitstream is not yet supported.
*
* <p>Returns {@code null} if the AV1 bitstream is not yet supported.
* @param obu The input OBU with type {@link #OBU_SEQUENCE_HEADER}.
*/
@Nullable
public static SequenceHeader parse(Obu obu) {
@ -153,7 +155,7 @@ public final class ObuParser {
private SequenceHeader(Obu obu) throws NotYetImplementedException {
checkArgument(obu.type == OBU_SEQUENCE_HEADER);
byte[] data = new byte[obu.payload.remaining()];
// Do not modify obu.payload as we read.
// Do not modify obu.payload while reading it.
obu.payload.asReadOnlyBuffer().get(data);
ParsableBitArray obuData = new ParsableBitArray(data);
obuData.skipBits(4); // seq_profile and still_picture
@ -252,6 +254,94 @@ public final class ObuParser {
}
}
/** An AV1 Frame Header. */
public static final class FrameHeader {
private static final int PROBE_BYTES = 4;
private static final int FRAME_TYPE_KEY_FRAME = 0;
private static final int FRAME_TYPE_INTRA_ONLY_FRAME = 2;
private static final int FRAME_TYPE_SWITCH_FRAME = 3;
private final boolean isDependedOn;
/** Returns whether the frame header is depended on by subsequent frames. */
public boolean isDependedOn() {
return isDependedOn;
}
/**
* Returns a {@link FrameHeader} parsed from the input OBU, or {@code null} if the AV1 bitstream
* is not yet supported.
*
* @param sequenceHeader The most recent sequence header before the frame header.
* @param obu The input OBU with type {@link #OBU_FRAME} or {@link #OBU_FRAME_HEADER}.
*/
@Nullable
public static FrameHeader parse(SequenceHeader sequenceHeader, Obu obu) {
try {
return new FrameHeader(sequenceHeader, obu);
} catch (NotYetImplementedException ignored) {
return null;
}
}
private FrameHeader(SequenceHeader sequenceHeader, Obu obu) throws NotYetImplementedException {
checkArgument(obu.type == OBU_FRAME || obu.type == OBU_FRAME_HEADER);
byte[] bytes = new byte[min(PROBE_BYTES, obu.payload.remaining())];
// Do not modify obu.payload while reading it.
obu.payload.asReadOnlyBuffer().get(bytes);
ParsableBitArray obuData = new ParsableBitArray(bytes);
throwWhenFeatureRequired(sequenceHeader.reducedStillPictureHeader);
boolean showExistingFrame = obuData.readBit();
if (showExistingFrame) {
// TODO: b/391108133 - Treat showExistingFrame as depended on. The picture was already
// decoded and the player may not save a lot of resources by rendering. Check if this
// assumption is correct!
isDependedOn = true;
return;
}
int frameType = obuData.readBits(2);
boolean showFrame = obuData.readBit();
throwWhenFeatureRequired(sequenceHeader.decoderModelInfoPresentFlag);
if (!showFrame) {
// show_frame equal to 0 specifies that this frame should not be immediately output.
// If a frame is output later, then it is depended on.
isDependedOn = true;
return;
}
boolean errorResilientMode;
if (frameType == FRAME_TYPE_SWITCH_FRAME || (frameType == FRAME_TYPE_KEY_FRAME)) {
errorResilientMode = true;
} else {
errorResilientMode = obuData.readBit();
}
obuData.skipBit(); // disable_cdf_update
throwWhenFeatureRequired(!sequenceHeader.seqForceScreenContentTools);
boolean allowScreenContentTools = obuData.readBit();
if (allowScreenContentTools) {
throwWhenFeatureRequired(!sequenceHeader.seqForceIntegerMv);
obuData.skipBit(); // force_integer_mv
}
throwWhenFeatureRequired(sequenceHeader.frameIdNumbersPresentFlag);
if (frameType != FRAME_TYPE_SWITCH_FRAME) {
obuData.skipBit(); // frame_size_override_flag
}
obuData.skipBits(sequenceHeader.orderHintBits); // order_hint
if (frameType != FRAME_TYPE_INTRA_ONLY_FRAME
&& frameType != FRAME_TYPE_KEY_FRAME
&& !errorResilientMode) {
obuData.skipBits(3); // primary_ref_frame
}
int refreshFrameFlags;
if (frameType == FRAME_TYPE_SWITCH_FRAME || (frameType == FRAME_TYPE_KEY_FRAME)) {
refreshFrameFlags = (1 << 8) - 1;
} else {
refreshFrameFlags = obuData.readBits(8);
}
isDependedOn = refreshFrameFlags != 0;
}
}
/** Full AV1 bitstream parsing is not yet implemented. */
private static void throwWhenFeatureRequired(boolean expression)
throws NotYetImplementedException {

41
libraries/container/src/test/java/androidx/media3/container/ObuParserTest.java
View File

@ -44,6 +44,12 @@ public class ObuParserTest {
private static final ByteBuffer DELIMITER_AND_HEADER_AND_PADDING_WITH_EXTENSION_AND_MISSING_SIZE =
ByteBuffer.wrap(createByteArray(0x16, 0x00, 0x00, 0x1A, 0x01, 0xC8, 0x78, 0xFF, 0xFF, 0xFF));
private static final ByteBuffer NON_REFERENCE_FRAME =
ByteBuffer.wrap(
createByteArray(
0x32, 0x1A, 0x30, 0xC0, 0x00, 0x1D, 0x66, 0x68, 0x46, 0xC9, 0x38, 0x00, 0x60, 0x10,
0x20, 0x80, 0x20, 0x00, 0x00, 0x01, 0x8B, 0x7A, 0x87, 0xF9, 0xAA, 0x2D, 0x0F, 0x2C));
@Test
public void split_sequenceHeaderAndFrame_parsesCorrectTypesAndSizes() {
List<ObuParser.Obu> obuList = ObuParser.split(SEQUENCE_HEADER_AND_FRAME);
@ -82,4 +88,39 @@ public class ObuParserTest {
assertThat(sequenceHeader.seqForceIntegerMv).isTrue();
assertThat(sequenceHeader.orderHintBits).isEqualTo(7);
}
@Test
public void parseFrameHeader_fromFrame_returnsIsDependedOn() {
List<ObuParser.Obu> obuList = ObuParser.split(SEQUENCE_HEADER_AND_FRAME);
ObuParser.Obu sequenceHeaderObu = obuList.get(0);
ObuParser.SequenceHeader sequenceHeader = ObuParser.SequenceHeader.parse(sequenceHeaderObu);
ObuParser.Obu frameObu = obuList.get(1);
ObuParser.FrameHeader frameHeader = ObuParser.FrameHeader.parse(sequenceHeader, frameObu);
assertThat(frameHeader.isDependedOn()).isTrue();
}
@Test
public void parseFrameHeader_fromFrameHeader_returnsIsDependedOn() {
ObuParser.Obu sequenceHeaderObu = ObuParser.split(SEQUENCE_HEADER_AND_FRAME).get(0);
ObuParser.SequenceHeader sequenceHeader = ObuParser.SequenceHeader.parse(sequenceHeaderObu);
ObuParser.Obu frameHeaderObu =
ObuParser.split(DELIMITER_AND_HEADER_AND_PADDING_WITH_EXTENSION_AND_MISSING_SIZE).get(1);
ObuParser.FrameHeader frameHeader = ObuParser.FrameHeader.parse(sequenceHeader, frameHeaderObu);
assertThat(frameHeader.isDependedOn()).isTrue();
}
@Test
public void parseFrameHeader_fromNonReferenceFrame_returnsNotDependedOn() {
ObuParser.Obu sequenceHeaderObu = ObuParser.split(SEQUENCE_HEADER_AND_FRAME).get(0);
ObuParser.SequenceHeader sequenceHeader = ObuParser.SequenceHeader.parse(sequenceHeaderObu);
ObuParser.Obu frameObu = ObuParser.split(NON_REFERENCE_FRAME).get(0);
ObuParser.FrameHeader frameHeader = ObuParser.FrameHeader.parse(sequenceHeader, frameObu);
assertThat(frameHeader.isDependedOn()).isFalse();
}
}