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Use ParsableBitArray instead of ParsableByteArray

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To avoid complicated bit shifting and masking. Also makes the code more readable.

PiperOrigin-RevId: 490749482
(cherry picked from commit 3d31e094a9e802354dce2f3dc5f33062f7624248)
This commit is contained in:
rohks 2022-11-24 17:15:07 +00:00 committed by christosts
parent fda132f926
commit 5ebbdc52cb
1 changed files with 33 additions and 20 deletions
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53
libraries/extractor/src/main/java/androidx/media3/extractor/Ac3Util.java
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@ -151,16 +151,21 @@ public final class Ac3Util {
*/
public static Format parseAc3AnnexFFormat(
ParsableByteArray data, String trackId, String language, @Nullable DrmInitData drmInitData) {
int fscod = (data.readUnsignedByte() & 0xC0) >> 6;
ParsableBitArray dataBitArray = new ParsableBitArray();
dataBitArray.reset(data);
int fscod = dataBitArray.readBits(2);
int sampleRate = SAMPLE_RATE_BY_FSCOD[fscod];
int nextByte = data.readUnsignedByte();
int channelCount = CHANNEL_COUNT_BY_ACMOD[(nextByte & 0x38) >> 3];
if ((nextByte & 0x04) != 0) { // lfeon
dataBitArray.skipBits(8); // bsid, bsmod
int channelCount = CHANNEL_COUNT_BY_ACMOD[dataBitArray.readBits(3)]; // acmod
if (dataBitArray.readBits(1) != 0) { // lfeon
channelCount++;
}
// bit_rate_code - 5 bits. 2 bits from previous byte and 3 bits from next.
int halfFrmsizecod = ((nextByte & 0x03) << 3) | ((data.readUnsignedByte() & 0xE0) >> 5);
int halfFrmsizecod = dataBitArray.readBits(5); // bit_rate_code
int constantBitrate = BITRATE_BY_HALF_FRMSIZECOD[halfFrmsizecod];
// Update data position
dataBitArray.byteAlign();
data.setPosition(dataBitArray.getBytePosition());
return new Format.Builder()
.setId(trackId)
.setSampleMimeType(MimeTypes.AUDIO_AC3)
@ -185,37 +190,45 @@ public final class Ac3Util {
*/
public static Format parseEAc3AnnexFFormat(
ParsableByteArray data, String trackId, String language, @Nullable DrmInitData drmInitData) {
// 13 bits for data_rate, 3 bits for num_ind_sub which are ignored.
int peakBitrate =
((data.readUnsignedByte() & 0xFF) << 5) | ((data.readUnsignedByte() & 0xF8) >> 3);
ParsableBitArray dataBitArray = new ParsableBitArray();
dataBitArray.reset(data);
int peakBitrate = dataBitArray.readBits(13); // data_rate
dataBitArray.skipBits(3); // num_ind_sub
// Read the first independent substream.
int fscod = (data.readUnsignedByte() & 0xC0) >> 6;
int fscod = dataBitArray.readBits(2);
int sampleRate = SAMPLE_RATE_BY_FSCOD[fscod];
int nextByte = data.readUnsignedByte();
int channelCount = CHANNEL_COUNT_BY_ACMOD[(nextByte & 0x0E) >> 1];
if ((nextByte & 0x01) != 0) { // lfeon
dataBitArray.skipBits(10); // bsid, reserved, asvc, bsmod
int channelCount = CHANNEL_COUNT_BY_ACMOD[dataBitArray.readBits(3)]; // acmod
if (dataBitArray.readBits(1) != 0) { // lfeon
channelCount++;
}
// Read the first dependent substream.
nextByte = data.readUnsignedByte();
int numDepSub = ((nextByte & 0x1E) >> 1);
dataBitArray.skipBits(3); // reserved
int numDepSub = dataBitArray.readBits(4); // num_dep_sub
dataBitArray.skipBits(1); // numDepSub > 0 ? LFE2 : reserved
if (numDepSub > 0) {
int lowByteChanLoc = data.readUnsignedByte();
dataBitArray.skipBytes(6); // other channel configurations
// Read Lrs/Rrs pair
// TODO: Read other channel configuration
if ((lowByteChanLoc & 0x02) != 0) {
if (dataBitArray.readBits(1) != 0) {
channelCount += 2;
}
dataBitArray.skipBits(1); // Lc/Rc pair
}
String mimeType = MimeTypes.AUDIO_E_AC3;
if (data.bytesLeft() > 0) {
nextByte = data.readUnsignedByte();
if ((nextByte & 0x01) != 0) { // flag_ec3_extension_type_a
if (dataBitArray.bitsLeft() > 7) {
dataBitArray.skipBits(7); // reserved
if (dataBitArray.readBits(1) != 0) { // flag_ec3_extension_type_a
mimeType = MimeTypes.AUDIO_E_AC3_JOC;
}
}
// Update data position
dataBitArray.byteAlign();
data.setPosition(dataBitArray.getBytePosition());
return new Format.Builder()
.setId(trackId)
.setSampleMimeType(mimeType)