/**
* Returns the AC-3 format given {@code data} containing the AC3SpecificBox according to ETSI TS
* 102 366 Annex F.
*/
public static MediaFormat parseAnnexFAc3Format(ParsableByteArray data) {
// fscod (sample rate code)
int fscod = (data.readUnsignedByte() & 0xC0) >> 6;
int sampleRate = SAMPLE_RATES[fscod];
int nextByte = data.readUnsignedByte();
// Map acmod (audio coding mode) onto a channel count.
int channelCount = CHANNEL_COUNTS[(nextByte & 0x38) >> 3];
// lfeon (low frequency effects on)
if ((nextByte & 0x04) != 0) {
channelCount++;
}
return MediaFormat.createAudioFormat(
MimeTypes.AUDIO_AC3, MediaFormat.NO_VALUE, channelCount, sampleRate, null);
}
/**
* Returns the AC-3 format given {@code data} containing the EC3SpecificBox according to ETSI TS
* 102 366 Annex F.
*/
public static MediaFormat parseAnnexFEAc3Format(ParsableByteArray data) {
data.skipBytes(2); // Skip data_rate and num_ind_sub.
// Read only the first substream.
// TODO: Read later substreams?
// fscod (sample rate code)
int fscod = (data.readUnsignedByte() & 0xC0) >> 6;
int sampleRate = SAMPLE_RATES[fscod];
int nextByte = data.readUnsignedByte();
// Map acmod (audio coding mode) onto a channel count.
int channelCount = CHANNEL_COUNTS[(nextByte & 0x0E) >> 1];
// lfeon (low frequency effects on)
if ((nextByte & 0x01) != 0) {
channelCount++;
}
return MediaFormat.createAudioFormat(
MimeTypes.AUDIO_EC3, MediaFormat.NO_VALUE, channelCount, sampleRate, null);
}
/**
* Returns the AC-3 format given {@code data} containing the frame header starting from the sync
* word.
*
* @param data Data to parse, positioned at the start of the syncword.
* @return AC-3 format parsed from data in the header.
*/
public static MediaFormat parseFrameAc3Format(ParsableBitArray data) {
// Skip syncword and crc1.
data.skipBits(4 * 8);
int fscod = data.readBits(2);
data.skipBits(14); // frmsizecod(6) + bsid (5 bits) + bsmod (3 bits)
int acmod = data.readBits(3);
if ((acmod & 0x01) != 0 && acmod != 1) {
data.skipBits(2); // cmixlev
}
if ((acmod & 0x04) != 0) {
data.skipBits(2); // surmixlev
}
if (acmod == 0x02) {
data.skipBits(2); // dsurmod
}
boolean lfeon = data.readBit();
return MediaFormat.createAudioFormat(
MimeTypes.AUDIO_AC3,
MediaFormat.NO_VALUE,
CHANNEL_COUNTS[acmod] + (lfeon ? 1 : 0),
SAMPLE_RATES[fscod],
null);
}
