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Simplify timestamp tracking

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An integer multiple/divide can be removed without loss of precision.

PiperOrigin-RevId: 315653905
This commit is contained in:
andrewlewis 2020-06-10 10:13:01 +01:00 committed by Oliver Woodman
parent 0caada8b8c
commit b0457da038
1 changed files with 18 additions and 12 deletions
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30
library/core/src/main/java/com/google/android/exoplayer2/mediacodec/C2Mp3TimestampTracker.java
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@ -19,7 +19,9 @@ import com.google.android.exoplayer2.C;
import com.google.android.exoplayer2.Format;
import com.google.android.exoplayer2.audio.MpegAudioUtil;
import com.google.android.exoplayer2.decoder.DecoderInputBuffer;
import com.google.android.exoplayer2.util.Assertions;
import com.google.android.exoplayer2.util.Log;
import java.nio.ByteBuffer;
/**
* Tracks the number of processed samples to calculate an accurate current timestamp, matching the
@ -55,17 +57,15 @@ import com.google.android.exoplayer2.util.Log;
* @return The expected output presentation time, in microseconds.
*/
public long updateAndGetPresentationTimeUs(Format format, DecoderInputBuffer buffer) {
if (seenInvalidMpegAudioHeader || buffer.data == null) {
if (seenInvalidMpegAudioHeader) {
return buffer.timeUs;
}
// These calculations mirror the timestamp calculations in the Codec2 Mp3 Decoder.
// https://cs.android.com/android/platform/superproject/+/master:frameworks/av/media/codec2/components/mp3/C2SoftMp3Dec.cpp;l=464;drc=ed134640332fea70ca4b05694289d91a5265bb46
long presentationTimeUs = processedSamples * C.MICROS_PER_SECOND / format.sampleRate;
ByteBuffer data = Assertions.checkNotNull(buffer.data);
int sampleHeaderData = 0;
for (int i = 0; i < 4; i++) {
sampleHeaderData <<= 8;
sampleHeaderData |= buffer.data.get(i) & 0xFF;
sampleHeaderData |= data.get(i) & 0xFF;
}
int frameCount = MpegAudioUtil.parseMpegAudioFrameSampleCount(sampleHeaderData);
@ -74,14 +74,20 @@ import com.google.android.exoplayer2.util.Log;
Log.w(TAG, "MPEG audio header is invalid.");
return buffer.timeUs;
}
long outSize = frameCount * format.channelCount * 2L;
boolean isFirstSample = processedSamples == 0;
long outOffset = 0;
if (isFirstSample) {
// These calculations mirror the timestamp calculations in the Codec2 Mp3 Decoder.
// https://cs.android.com/android/platform/superproject/+/master:frameworks/av/media/codec2/components/mp3/C2SoftMp3Dec.cpp;l=464;drc=ed134640332fea70ca4b05694289d91a5265bb46
if (processedSamples == 0) {
anchorTimestampUs = buffer.timeUs;
outOffset = DECODER_DELAY_SAMPLES;
processedSamples = frameCount - DECODER_DELAY_SAMPLES;
return anchorTimestampUs;
}
processedSamples += (outSize / (format.channelCount * 2L)) - outOffset;
return anchorTimestampUs + presentationTimeUs;
long processedDurationUs = getProcessedDurationUs(format);
processedSamples += frameCount;
return anchorTimestampUs + processedDurationUs;
}
private long getProcessedDurationUs(Format format) {
return processedSamples * C.MICROS_PER_SECOND / format.sampleRate;
}
}