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@rohitjoins
rohitjoins committed Nov 27, 2023
1 parent 853862a commit 70d4eb5
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Showing 2 changed files with 41 additions and 29 deletions.
62 changes: 37 additions & 25 deletions libraries/extractor/src/main/java/androidx/media3/extractor/ts/AdtsReader.java
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Original file line number Diff line number Diff line change
Expand Up @@ -285,12 +285,18 @@ private void setCheckingAdtsHeaderState() {
bytesRead = 0;
}

/** Sets the state to STATE_READING_AAC_PCE. */
/**
* Sets the state to STATE_READING_AAC_PCE.
*
* @param outputToUse TrackOutput object to write the sample to
* @param currentSampleDuration Duration of the sample to be read
* @param sampleSize Size of the sample
*/
private void setReadingAacPceState(
TrackOutput outputToUse, long currentSampleDuration, int sampleSize) {
state = STATE_READING_AAC_PCE;
bytesRead = 0;
currentOutput = outputToUse;
this.currentOutput = outputToUse;
this.currentSampleDuration = currentSampleDuration;
this.sampleSize = sampleSize;
pceBuffer = new ParsableBitArray(new byte[min(sampleSize, AAC_PCE_MAX_SIZE)]);
Expand Down Expand Up @@ -567,46 +573,52 @@ private void parseAdtsHeader() throws ParserException {

@RequiresNonNull({"pendingOutputFormat", "pceBuffer"})
void readAacProgramConfigElement() {
// See ISO 13818-7 Advanced Audio Coding (2006) Table 36 for PCE tag encoding.
if (pceBuffer.readBits(3) == 5 /* PCE tag */) {
// See `ISO 13818-7 Advanced Audio Coding (2006) Table 25` for format of a PCE
pceBuffer.skipBits(10); // Element instance tag, profile, sample frequency index
// See ISO 13818-7 Advanced Audio Coding (2006) Table 25 for syntax of a PCE.
pceBuffer.skipBits(10); // element_instance_tag(4), profile(2), element_instance_tag(4)

int channelBits = 0;
channelBits += pceBuffer.readBits(4) * 5; // Front channel elements
channelBits += pceBuffer.readBits(4) * 5; // Side channel elements
channelBits += pceBuffer.readBits(4) * 5; // Back channel elements
channelBits += pceBuffer.readBits(2) * 4; // LFE channel elements
channelBits += pceBuffer.readBits(3) * 4; // Data elements
channelBits += pceBuffer.readBits(4) * 5; // Coupling channel elements

if (pceBuffer.readBit()) {
pceBuffer.skipBits(4); // Mono mixdown
// num_front_channel_elements, front_element_is_cpe(1), front_element_tag_select(4)
channelBits += pceBuffer.readBits(4) * 5;
// num_side_channel_elements, side_element_is_cpe(1), side_element_tag_select(4)
channelBits += pceBuffer.readBits(4) * 5;
// num_back_channel_elements, back_element_is_cpe(1), back_element_tag_select(4)
channelBits += pceBuffer.readBits(4) * 5;
// num_lfe_channel_elements, lfe_element_tag_select(4)
channelBits += pceBuffer.readBits(2) * 4;
// num_assoc_data_elements, assoc_data_element_tag_select(4)
channelBits += pceBuffer.readBits(3) * 4;
// num_valid_cc_elements, cc_element_is_ind_sw(1), valid_cc_element_tag_select(4)
channelBits += pceBuffer.readBits(4) * 5;

if (pceBuffer.readBit()) { // mono_mixdown_present
pceBuffer.skipBits(4); // mono_mixdown_element_number
}

if (pceBuffer.readBit()) {
pceBuffer.skipBits(4); // Stereo mixdown
if (pceBuffer.readBit()) { // stereo_mixdown_present
pceBuffer.skipBits(4); // stereo_mixdown_element_number
}

if (pceBuffer.readBit()) {
pceBuffer.skipBits(3); // Matrix mixdown
if (pceBuffer.readBit()) { // matrix_mixdown_idx_present
pceBuffer.skipBits(3); // matrix_mixdown_idx(2), matrix_mixdown_idx(1)
}

// Beyond this point, pceBuffer may be empty, so check before consuming.
int numAlignmentBits =
8 - (pceBuffer.getPosition() + channelBits + 7) % 8 - 1; // byte_alignment
int commentSizeBits = 8; // comment_field_bytes

int numAlignmentBits = 8 - (pceBuffer.getPosition() + channelBits + 7) % 8 - 1;

if (pceBuffer.bitsLeft() >= channelBits + numAlignmentBits + 8)
{
// Beyond this point, pceBuffer may be empty, so check before consuming.
if (pceBuffer.bitsLeft() >= channelBits + numAlignmentBits + commentSizeBits) {
pceBuffer.skipBits(channelBits);

// Store PCE size excluding initial PCE tag, alignment bits and comment for later.
int numPceBits = pceBuffer.getPosition() - 3 /* PCE tag */;

pceBuffer.skipBits(numAlignmentBits);
int commentSize = pceBuffer.readBits(8);
int commentSize = pceBuffer.readBits(commentSizeBits);

if (sampleSize >= pceBuffer.getBytePosition() + commentSize)
{
if (sampleSize >= pceBuffer.getBytePosition() + commentSize) {
// Append PCE to format's audio specific config.
byte[] oldConfig = pendingOutputFormat.initializationData.get(0);

Expand Down
8 changes: 4 additions & 4 deletions libraries/extractor/src/test/java/androidx/media3/extractor/ts/AdtsReaderTest.java
View file
Original file line number Diff line number Diff line change
Expand Up @@ -65,8 +65,7 @@ public class AdtsReaderTest {
TestUtil.createByteArray(0xff, 0xf1, 0x50, 0x00, 0x02, 0x1f, 0xfc);

private static final byte[] AAC_PCE_ADTS_CONTENT =
TestUtil.createByteArray(
0xa0, 0x99, 0x01, 0x20, 0x00, 0x21, 0x19, 0x00, 0x00);
TestUtil.createByteArray(0xa0, 0x99, 0x01, 0x20, 0x00, 0x21, 0x19, 0x00, 0x00);

private static final byte[] AAC_PCE_TEST_DATA =
Bytes.concat(AAC_PCE_ADTS_HEADER, AAC_PCE_ADTS_CONTENT);
Expand Down Expand Up @@ -202,16 +201,17 @@ public void adtsDataOnly() throws ParserException {
@Test
public void aacPceData() throws ParserException {
data = new ParsableByteArray(AAC_PCE_TEST_DATA);

feed();

assertSampleCounts(0, 1);
adtsOutput.assertSample(0, AAC_PCE_ADTS_CONTENT, 0, C.BUFFER_FLAG_KEY_FRAME, null);
}

@Test(expected = IllegalStateException.class)
public void aacPceDataFail() throws ParserException {
data = new ParsableByteArray(AAC_PCE_TEST_DATA);
data = new ParsableByteArray(Arrays.copyOf(AAC_PCE_TEST_DATA, AAC_PCE_TEST_DATA.length));
byte[] bytes = data.getData();

// Remove PCE tag (first 3 bits of content).
bytes[AAC_PCE_ADTS_HEADER.length] &= 0x1f;
// Replace with CPE tag.
Expand Down

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