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Standardize ALAC initialization data

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Android considers ALAC initialization data to consider of the magic
cookie only, where-as FFmpeg requires a full atom. Standardize around
the Android definition, since it makes more sense (the magic cookie
being contained within an atom is container specific, where-as the
decoder shouldn't care what container the media stream is carried in)

Issue: #5938
PiperOrigin-RevId: 261124155
This commit is contained in:
olly 2019-08-01 16:14:12 +01:00 committed by Oliver Woodman
parent 95ed5ce65d
commit cb8983afd1
2 changed files with 35 additions and 18 deletions
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47
extensions/ffmpeg/src/main/java/com/google/android/exoplayer2/ext/ffmpeg/FfmpegDecoder.java
View file

@ -172,28 +172,49 @@ import java.util.List;
private static @Nullable byte[] getExtraData(String mimeType, List<byte[]> initializationData) {
switch (mimeType) {
case MimeTypes.AUDIO_AAC:
case MimeTypes.AUDIO_ALAC:
case MimeTypes.AUDIO_OPUS:
return initializationData.get(0);
case MimeTypes.AUDIO_ALAC:
return getAlacExtraData(initializationData);
case MimeTypes.AUDIO_VORBIS:
byte[] header0 = initializationData.get(0);
byte[] header1 = initializationData.get(1);
byte[] extraData = new byte[header0.length + header1.length + 6];
extraData[0] = (byte) (header0.length >> 8);
extraData[1] = (byte) (header0.length & 0xFF);
System.arraycopy(header0, 0, extraData, 2, header0.length);
extraData[header0.length + 2] = 0;
extraData[header0.length + 3] = 0;
extraData[header0.length + 4] = (byte) (header1.length >> 8);
extraData[header0.length + 5] = (byte) (header1.length & 0xFF);
System.arraycopy(header1, 0, extraData, header0.length + 6, header1.length);
return extraData;
return getVorbisExtraData(initializationData);
default:
// Other codecs do not require extra data.
return null;
}
}
private static byte[] getAlacExtraData(List<byte[]> initializationData) {
// FFmpeg's ALAC decoder expects an ALAC atom, which contains the ALAC "magic cookie", as extra
// data. initializationData[0] contains only the magic cookie, and so we need to package it into
// an ALAC atom. See:
// https://ffmpeg.org/doxygen/0.6/alac_8c.html
// https://github.com/macosforge/alac/blob/master/ALACMagicCookieDescription.txt
byte[] magicCookie = initializationData.get(0);
int alacAtomLength = 12 + magicCookie.length;
ByteBuffer alacAtom = ByteBuffer.allocate(alacAtomLength);
alacAtom.putInt(alacAtomLength);
alacAtom.putInt(0x616c6163); // type=alac
alacAtom.putInt(0); // version=0, flags=0
alacAtom.put(magicCookie, /* offset= */ 0, magicCookie.length);
return alacAtom.array();
}
private static byte[] getVorbisExtraData(List<byte[]> initializationData) {
byte[] header0 = initializationData.get(0);
byte[] header1 = initializationData.get(1);
byte[] extraData = new byte[header0.length + header1.length + 6];
extraData[0] = (byte) (header0.length >> 8);
extraData[1] = (byte) (header0.length & 0xFF);
System.arraycopy(header0, 0, extraData, 2, header0.length);
extraData[header0.length + 2] = 0;
extraData[header0.length + 3] = 0;
extraData[header0.length + 4] = (byte) (header1.length >> 8);
extraData[header0.length + 5] = (byte) (header1.length & 0xFF);
System.arraycopy(header1, 0, extraData, header0.length + 6, header1.length);
return extraData;
}
private native long ffmpegInitialize(
String codecName,
@Nullable byte[] extraData,

6
library/core/src/main/java/com/google/android/exoplayer2/extractor/mp4/AtomParsers.java
View file

@ -1154,10 +1154,6 @@ import java.util.List;
out.format = Format.createAudioSampleFormat(Integer.toString(trackId), mimeType, null,
Format.NO_VALUE, Format.NO_VALUE, channelCount, sampleRate, null, drmInitData, 0,
language);
} else if (childAtomType == Atom.TYPE_alac) {
initializationData = new byte[childAtomSize];
parent.setPosition(childPosition);
parent.readBytes(initializationData, /* offset= */ 0, childAtomSize);
} else if (childAtomType == Atom.TYPE_dOps) {
// Build an Opus Identification Header (defined in RFC-7845) by concatenating the Opus Magic
// Signature and the body of the dOps atom.
@ -1166,7 +1162,7 @@ import java.util.List;
System.arraycopy(opusMagic, 0, initializationData, 0, opusMagic.length);
parent.setPosition(childPosition + Atom.HEADER_SIZE);
parent.readBytes(initializationData, opusMagic.length, childAtomBodySize);
} else if (childAtomSize == Atom.TYPE_dfLa) {
} else if (childAtomSize == Atom.TYPE_dfLa || childAtomType == Atom.TYPE_alac) {
int childAtomBodySize = childAtomSize - Atom.FULL_HEADER_SIZE;
initializationData = new byte[childAtomBodySize];
parent.setPosition(childPosition + Atom.FULL_HEADER_SIZE);