// @VisibleForTesting
/* package */ VorbisSetup readSetupHeaders(ExtractorInput input, ParsableByteArray scratch)
throws IOException, InterruptedException {
if (vorbisIdHeader == null) {
oggReader.readPacket(input, scratch);
vorbisIdHeader = VorbisUtil.readVorbisIdentificationHeader(scratch);
scratch.reset();
}
if (commentHeader == null) {
oggReader.readPacket(input, scratch);
commentHeader = VorbisUtil.readVorbisCommentHeader(scratch);
scratch.reset();
}
oggReader.readPacket(input, scratch);
// the third packet contains the setup header
byte[] setupHeaderData = new byte[scratch.limit()];
// raw data of vorbis setup header has to be passed to decoder as CSD buffer #2
System.arraycopy(scratch.data, 0, setupHeaderData, 0, scratch.limit());
// partially decode setup header to get the modes
Mode[] modes = VorbisUtil.readVorbisModes(scratch, vorbisIdHeader.channels);
// we need the ilog of modes all the time when extracting, so we compute it once
int iLogModes = VorbisUtil.iLog(modes.length - 1);
scratch.reset();
return new VorbisSetup(vorbisIdHeader, commentHeader, setupHeaderData, modes, iLogModes);
}
private static int decodeBlockSize(byte firstByteOfAudioPacket, VorbisSetup vorbisSetup) {
// read modeNumber (https://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-730004.3.1)
int modeNumber = VorbisUtil.readBits(firstByteOfAudioPacket, vorbisSetup.iLogModes, 1);
int currentBlockSize;
if (!vorbisSetup.modes[modeNumber].blockFlag) {
currentBlockSize = vorbisSetup.idHeader.blockSize0;
} else {
currentBlockSize = vorbisSetup.idHeader.blockSize1;
}
return currentBlockSize;
}
