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Change SilenceSkippingAudioProcessor to not rely on the frame MSB.

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PiperOrigin-RevId: 309925306
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samrobinson 2020-05-05 13:04:58 +01:00 committed by Oliver Woodman
parent 918963c2b4
commit d944f32f24
1 changed files with 9 additions and 15 deletions
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24
library/core/src/main/java/com/google/android/exoplayer2/audio/SilenceSkippingAudioProcessor.java
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@ -17,11 +17,13 @@ package com.google.android.exoplayer2.audio;
import androidx.annotation.IntDef; import androidx.annotation.IntDef;
import com.google.android.exoplayer2.C; import com.google.android.exoplayer2.C;
import com.google.android.exoplayer2.util.Assertions;
import com.google.android.exoplayer2.util.Util; import com.google.android.exoplayer2.util.Util;
import java.lang.annotation.Documented; import java.lang.annotation.Documented;
import java.lang.annotation.Retention; import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy; import java.lang.annotation.RetentionPolicy;
import java.nio.ByteBuffer; import java.nio.ByteBuffer;
import java.nio.ByteOrder;
/** /**
* An {@link AudioProcessor} that skips silence in the input stream. Input and output are 16-bit * An {@link AudioProcessor} that skips silence in the input stream. Input and output are 16-bit
@ -39,19 +41,9 @@ public final class SilenceSkippingAudioProcessor extends BaseAudioProcessor {
* not exceed {@link #MINIMUM_SILENCE_DURATION_US}. * not exceed {@link #MINIMUM_SILENCE_DURATION_US}.
*/ */
private static final long PADDING_SILENCE_US = 20_000; private static final long PADDING_SILENCE_US = 20_000;
/** /** The absolute level below which an individual PCM sample is classified as silent. */
* The absolute level below which an individual PCM sample is classified as silent. Note: the
* specified value will be rounded so that the threshold check only depends on the more
* significant byte, for efficiency.
*/
private static final short SILENCE_THRESHOLD_LEVEL = 1024; private static final short SILENCE_THRESHOLD_LEVEL = 1024;
/**
* Threshold for classifying an individual PCM sample as silent based on its more significant
* byte. This is {@link #SILENCE_THRESHOLD_LEVEL} divided by 256 with rounding.
*/
private static final byte SILENCE_THRESHOLD_LEVEL_MSB = (SILENCE_THRESHOLD_LEVEL + 128) >> 8;
/** Trimming states. */ /** Trimming states. */
@Documented @Documented
@Retention(RetentionPolicy.SOURCE) @Retention(RetentionPolicy.SOURCE)
@ -325,9 +317,10 @@ public final class SilenceSkippingAudioProcessor extends BaseAudioProcessor {
* classified as a noisy frame, or the limit of the buffer if no such frame exists. * classified as a noisy frame, or the limit of the buffer if no such frame exists.
*/ */
private int findNoisePosition(ByteBuffer buffer) { private int findNoisePosition(ByteBuffer buffer) {
Assertions.checkArgument(buffer.order() == ByteOrder.LITTLE_ENDIAN);
// The input is in ByteOrder.nativeOrder(), which is little endian on Android. // The input is in ByteOrder.nativeOrder(), which is little endian on Android.
for (int i = buffer.position() + 1; i < buffer.limit(); i += 2) { for (int i = buffer.position(); i < buffer.limit(); i += 2) {
if (Math.abs(buffer.get(i)) > SILENCE_THRESHOLD_LEVEL_MSB) { if (Math.abs(buffer.getShort(i)) > SILENCE_THRESHOLD_LEVEL) {
// Round to the start of the frame. // Round to the start of the frame.
return bytesPerFrame * (i / bytesPerFrame); return bytesPerFrame * (i / bytesPerFrame);
} }
@ -340,9 +333,10 @@ public final class SilenceSkippingAudioProcessor extends BaseAudioProcessor {
* from the byte position to the limit are classified as silent. * from the byte position to the limit are classified as silent.
*/ */
private int findNoiseLimit(ByteBuffer buffer) { private int findNoiseLimit(ByteBuffer buffer) {
Assertions.checkArgument(buffer.order() == ByteOrder.LITTLE_ENDIAN);
// The input is in ByteOrder.nativeOrder(), which is little endian on Android. // The input is in ByteOrder.nativeOrder(), which is little endian on Android.
for (int i = buffer.limit() - 1; i >= buffer.position(); i -= 2) { for (int i = buffer.limit() - 2; i >= buffer.position(); i -= 2) {
if (Math.abs(buffer.get(i)) > SILENCE_THRESHOLD_LEVEL_MSB) { if (Math.abs(buffer.getShort(i)) > SILENCE_THRESHOLD_LEVEL) {
// Return the start of the next frame. // Return the start of the next frame.
return bytesPerFrame * (i / bytesPerFrame) + bytesPerFrame; return bytesPerFrame * (i / bytesPerFrame) + bytesPerFrame;
} }