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Extract MP4 metadata-based chapters #1851

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Extract MP4 metadata-based chapters #1851

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b32532f
Extract mp4 metadata-based chapters
MiSikora Nov 1, 2024
aacb375
Update libraries/extractor/src/test/java/androidx/media3/extractor/mp…
MiSikora Nov 1, 2024
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Apply suggestions from code review
MiSikora Nov 2, 2024
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3 changes: 3 additions & 0 deletions libraries/container/src/main/java/androidx/media3/container/Mp4Box.java
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Original file line number Diff line number Diff line change
Expand Up @@ -374,6 +374,9 @@ public abstract class Mp4Box {
@SuppressWarnings("ConstantCaseForConstants")
public static final int TYPE_xyz = 0xa978797a;

@SuppressWarnings("ConstantCaseForConstants")
public static final int TYPE_chpl = 0x6368706c;

@SuppressWarnings("ConstantCaseForConstants")
public static final int TYPE_smta = 0x736d7461;

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36 changes: 36 additions & 0 deletions libraries/extractor/src/main/java/androidx/media3/extractor/mp4/BoxParser.java
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Expand Up @@ -51,6 +51,9 @@
import androidx.media3.extractor.HevcConfig;
import androidx.media3.extractor.OpusUtil;
import androidx.media3.extractor.VorbisUtil;
import androidx.media3.extractor.metadata.id3.ChapterFrame;
import androidx.media3.extractor.metadata.id3.Id3Frame;
import androidx.media3.extractor.metadata.id3.TextInformationFrame;
import com.google.common.base.Function;
import com.google.common.collect.ImmutableList;
import com.google.common.primitives.Ints;
Expand Down Expand Up @@ -196,6 +199,9 @@ public static Metadata parseUdta(LeafBox udtaBox) {
SmtaAtomUtil.parseSmta(udtaData, atomPosition + atomSize));
} else if (atomType == Mp4Box.TYPE_xyz) {
metadata = metadata.copyWithAppendedEntriesFrom(parseXyz(udtaData));
} else if (atomType == Mp4Box.TYPE_chpl) {
udtaData.setPosition(atomPosition);
metadata = metadata.copyWithAppendedEntriesFrom(parseChpl(udtaData));
}
udtaData.setPosition(atomPosition + atomSize);
}
Expand Down Expand Up @@ -860,6 +866,36 @@ private static Metadata parseXyz(ParsableByteArray xyzBox) {
}
}

/** Parses the chapter metadata from the chpl atom. */
@Nullable
/* package */ static Metadata parseChpl(ParsableByteArray chpl) {
chpl.skipBytes(Mp4Box.HEADER_SIZE);
chpl.skipBytes(5); // version (1) + flags (3) + reservered byte (1)
ArrayList<Metadata.Entry> entries = new ArrayList<>();
int chapterCount = chpl.readInt();
for (int i = 0; i < chapterCount; i++) {
long startTimeMs = chpl.readLong() / 10_000; // Start time in 100-nanoseconds resolution
if (startTimeMs < 0 || startTimeMs > Integer.MAX_VALUE) {
startTimeMs = C.INDEX_UNSET;
}
int titleLength = chpl.readUnsignedByte();
String chapterName = chpl.readString(titleLength);
ChapterFrame chapterFrame =
new ChapterFrame(
/* chapterId= */ Integer.toString(i),
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@MiSikora MiSikora Nov 1, 2024 •
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I wasn't sure if something else or perhaps C.INDEX_UNSET should be used as the ID. MP4 chapters do not have this concept.

(int) startTimeMs,
/* endTime= */ C.INDEX_UNSET,
/* startOffset= */ C.INDEX_UNSET,
/* endOffset= */ C.INDEX_UNSET,
/* subFrames= */ new Id3Frame[] {
new TextInformationFrame(
"TIT2", /* description= */ null, ImmutableList.of(chapterName))
});
entries.add(chapterFrame);
}
return entries.isEmpty() ? null : new Metadata(entries);
}

/**
* Parses a tkhd atom (defined in ISO/IEC 14496-12).
*
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94 changes: 94 additions & 0 deletions libraries/extractor/src/test/java/androidx/media3/extractor/mp4/BoxParserTest.java
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Expand Up @@ -18,11 +18,17 @@
import static com.google.common.truth.Truth.assertThat;

import androidx.media3.common.C;
import androidx.media3.common.Metadata;
import androidx.media3.common.ParserException;
import androidx.media3.common.util.ParsableByteArray;
import androidx.media3.common.util.Util;
import androidx.media3.container.Mp4Box;
import androidx.media3.extractor.metadata.id3.ChapterFrame;
import androidx.media3.extractor.metadata.id3.Id3Frame;
import androidx.media3.extractor.metadata.id3.TextInformationFrame;
import androidx.test.ext.junit.runners.AndroidJUnit4;
import com.google.common.collect.ImmutableList;
import java.nio.ByteBuffer;
import org.junit.Test;
import org.junit.runner.RunWith;

Expand Down Expand Up @@ -288,6 +294,94 @@ public void vexuParsings() throws ParserException {
assertThat(vexuData.hasBothEyeViews()).isTrue();
}

@Test
public void chplParsing() {
byte[] data =
ByteBuffer.allocate(50)
.putInt(50) // box size
.putInt(Mp4Box.TYPE_chpl) // box type
.put(new byte[5]) // version (1), flags (3), reserved byte (1)
.putInt(2) // chapter count
// first chapter
.putLong(0) // start time in 100-nanoseconds resolution
.put((byte) 9) // Title length
.put("Chapter A".getBytes())
// second chapter
.putLong(12_340_000) // start time in 100-nanoseconds resolution
.put((byte) 6) // Title length
.put("Chap B".getBytes())
.array();

Metadata metadata = BoxParser.parseChpl(new ParsableByteArray(data));
assertThat(metadata.length()).isEqualTo(2);
assertThat(metadata.get(0))
.isEqualTo(
new ChapterFrame(
/* chapterId= */ "0",
/* startTimeMs= */ 0,
/* endTimeMs= */ -1,
/* startOffset= */ -1,
/* endOffset= */ -1,
new Id3Frame[] {
new TextInformationFrame(
"TIT2", /* description= */ null, ImmutableList.of("Chapter A"))
}));
assertThat(metadata.get(1))
.isEqualTo(
new ChapterFrame(
/* chapterId= */ "1",
/* startTimeMs= */ 1234,
/* endTimeMs= */ -1,
/* startOffset= */ -1,
/* endOffset= */ -1,
new Id3Frame[] {
new TextInformationFrame(
"TIT2", /* description= */ null, ImmutableList.of("Chap B"))
}));
}

@Test
public void chplParsingInvalidStartTime() {
byte[] data =
ByteBuffer.allocate(50)
.putInt(50) // box size
.putInt(Mp4Box.TYPE_chpl) // box type
.put(new byte[5]) // version (1), flags (3), reserved byte (1)
.putInt(2) // chapter count
// first chapter
.putLong(-10_000) // start time, negative
.put((byte) 0) // Title length
// second chapter
.putLong(Long.valueOf(Integer.MAX_VALUE) * 10_000 + 10_000) // start time, overflow
.put((byte) 0) // Title length
.array();

Metadata metadata = BoxParser.parseChpl(new ParsableByteArray(data));
assertThat(metadata.length()).isEqualTo(2);
assertThat(metadata.get(0))
.isEqualTo(
new ChapterFrame(
/* chapterId= */ "0",
/* startTimeMs= */ -1,
/* endTimeMs= */ -1,
/* startOffset= */ -1,
/* endOffset= */ -1,
new Id3Frame[] {
new TextInformationFrame("TIT2", /* description= */ null, ImmutableList.of(""))
}));
assertThat(metadata.get(1))
.isEqualTo(
new ChapterFrame(
/* chapterId= */ "1",
/* startTimeMs= */ -1,
/* endTimeMs= */ -1,
/* startOffset= */ -1,
/* endOffset= */ -1,
new Id3Frame[] {
new TextInformationFrame("TIT2", /* description= */ null, ImmutableList.of(""))
}));
}

private static void verifyStz2Parsing(Mp4Box.LeafBox stz2Atom) {
BoxParser.Stz2SampleSizeBox box = new BoxParser.Stz2SampleSizeBox(stz2Atom);
assertThat(box.getSampleCount()).isEqualTo(4);
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5 changes: 5 additions & 0 deletions .../extractor/src/test/java/androidx/media3/extractor/mp4/Mp4ExtractorParameterizedTest.java
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Expand Up @@ -88,6 +88,11 @@ public void mp4SampleWithNumericGenre() throws Exception {
assertExtractorBehavior("media/mp4/sample_with_numeric_genre.mp4");
}

@Test
public void mp4SampleWithChapters() throws Exception {
assertExtractorBehavior("media/mp4/sample_with_chapters.mp4");
}

/**
* Test case for https://github.com/google/ExoPlayer/issues/6774. The sample file contains an mdat
* atom whose size indicates that it extends 8 bytes beyond the end of the file.
Expand Down
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