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Commit 43016062 by andrewlewis Committed by Oliver Woodman
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Add a BufferProcessor for resampling. 

This initial version of the BufferProcessor interface assumes that buffers are
handled in their entirety on each invocation.

Move PCM resampling out of AudioTrack into a BufferProcessor.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=146128411
parent 3edeec24
Inline Side-by-side
Showing with 218 additions and 146 deletions
library/src/main/java/com/google/android/exoplayer2/audio/AudioTrack.java
...@@ -25,7 +25,6 @@ import android.os.ConditionVariable; ...@@ -25,7 +25,6 @@ import android.os.ConditionVariable;
import android.os.SystemClock; import android.os.SystemClock;
import android.util.Log; import android.util.Log;
import com.google.android.exoplayer2.C; import com.google.android.exoplayer2.C;
import com.google.android.exoplayer2.Format;
import com.google.android.exoplayer2.util.Assertions; import com.google.android.exoplayer2.util.Assertions;
import com.google.android.exoplayer2.util.MimeTypes; import com.google.android.exoplayer2.util.MimeTypes;
import com.google.android.exoplayer2.util.Util; import com.google.android.exoplayer2.util.Util;
...@@ -271,9 +270,9 @@ public final class AudioTrack { ...@@ -271,9 +270,9 @@ public final class AudioTrack {
@C.StreamType @C.StreamType
private int streamType; private int streamType;
@C.Encoding @C.Encoding
private int sourceEncoding; private int inputEncoding;
@C.Encoding @C.Encoding
private int targetEncoding; private int outputEncoding;
private boolean passthrough; private boolean passthrough;
private int pcmFrameSize; private int pcmFrameSize;
private int bufferSize; private int bufferSize;
...@@ -299,12 +298,12 @@ public final class AudioTrack { ...@@ -299,12 +298,12 @@ public final class AudioTrack {
private long latencyUs; private long latencyUs;
private float volume; private float volume;
private byte[] temporaryBuffer; private ByteBuffer inputBuffer;
private int temporaryBufferOffset; private ByteBuffer outputBuffer;
private ByteBuffer currentSourceBuffer; private byte[] preV21OutputBuffer;
private int preV21OutputBufferOffset;
private ByteBuffer resampledBuffer; private BufferProcessor resampler;
private boolean useResampledBuffer;
private boolean playing; private boolean playing;
private int audioSessionId; private int audioSessionId;
...@@ -470,17 +469,17 @@ public final class AudioTrack { ...@@ -470,17 +469,17 @@ public final class AudioTrack {
channelConfig = AudioFormat.CHANNEL_OUT_STEREO; channelConfig = AudioFormat.CHANNEL_OUT_STEREO;
} }
@C.Encoding int sourceEncoding; @C.Encoding int inputEncoding;
if (passthrough) { if (passthrough) {
sourceEncoding = getEncodingForMimeType(mimeType); inputEncoding = getEncodingForMimeType(mimeType);
} else if (pcmEncoding == C.ENCODING_PCM_8BIT || pcmEncoding == C.ENCODING_PCM_16BIT } else if (pcmEncoding == C.ENCODING_PCM_8BIT || pcmEncoding == C.ENCODING_PCM_16BIT
|| pcmEncoding == C.ENCODING_PCM_24BIT || pcmEncoding == C.ENCODING_PCM_32BIT) { || pcmEncoding == C.ENCODING_PCM_24BIT || pcmEncoding == C.ENCODING_PCM_32BIT) {
sourceEncoding = pcmEncoding; inputEncoding = pcmEncoding;
} else { } else {
throw new IllegalArgumentException("Unsupported PCM encoding: " + pcmEncoding); throw new IllegalArgumentException("Unsupported PCM encoding: " + pcmEncoding);
} }
if (isInitialized() && this.sourceEncoding == sourceEncoding && this.sampleRate == sampleRate if (isInitialized() && this.inputEncoding == inputEncoding && this.sampleRate == sampleRate
&& this.channelConfig == channelConfig) { && this.channelConfig == channelConfig) {
// We already have an audio track with the correct sample rate, channel config and encoding. // We already have an audio track with the correct sample rate, channel config and encoding.
return; return;
...@@ -488,28 +487,31 @@ public final class AudioTrack { ...@@ -488,28 +487,31 @@ public final class AudioTrack {
reset(); reset();
this.sourceEncoding = sourceEncoding; this.inputEncoding = inputEncoding;
this.passthrough = passthrough; this.passthrough = passthrough;
this.sampleRate = sampleRate; this.sampleRate = sampleRate;
this.channelConfig = channelConfig; this.channelConfig = channelConfig;
targetEncoding = passthrough ? sourceEncoding : C.ENCODING_PCM_16BIT;
pcmFrameSize = 2 * channelCount; // 2 bytes per 16-bit sample * number of channels. pcmFrameSize = 2 * channelCount; // 2 bytes per 16-bit sample * number of channels.
outputEncoding = passthrough ? inputEncoding : C.ENCODING_PCM_16BIT;
resampler = outputEncoding != inputEncoding ? new ResamplingBufferProcessor(inputEncoding)
: null;
if (specifiedBufferSize != 0) { if (specifiedBufferSize != 0) {
bufferSize = specifiedBufferSize; bufferSize = specifiedBufferSize;
} else if (passthrough) { } else if (passthrough) {
// TODO: Set the minimum buffer size using getMinBufferSize when it takes the encoding into // TODO: Set the minimum buffer size using getMinBufferSize when it takes the encoding into
// account. [Internal: b/25181305] // account. [Internal: b/25181305]
if (targetEncoding == C.ENCODING_AC3 || targetEncoding == C.ENCODING_E_AC3) { if (outputEncoding == C.ENCODING_AC3 || outputEncoding == C.ENCODING_E_AC3) {
// AC-3 allows bitrates up to 640 kbit/s. // AC-3 allows bitrates up to 640 kbit/s.
bufferSize = (int) (PASSTHROUGH_BUFFER_DURATION_US * 80 * 1024 / C.MICROS_PER_SECOND); bufferSize = (int) (PASSTHROUGH_BUFFER_DURATION_US * 80 * 1024 / C.MICROS_PER_SECOND);
} else /* (targetEncoding == C.ENCODING_DTS || targetEncoding == C.ENCODING_DTS_HD */ { } else /* (outputEncoding == C.ENCODING_DTS || outputEncoding == C.ENCODING_DTS_HD */ {
// DTS allows an 'open' bitrate, but we assume the maximum listed value: 1536 kbit/s. // DTS allows an 'open' bitrate, but we assume the maximum listed value: 1536 kbit/s.
bufferSize = (int) (PASSTHROUGH_BUFFER_DURATION_US * 192 * 1024 / C.MICROS_PER_SECOND); bufferSize = (int) (PASSTHROUGH_BUFFER_DURATION_US * 192 * 1024 / C.MICROS_PER_SECOND);
} }
} else { } else {
int minBufferSize = int minBufferSize =
android.media.AudioTrack.getMinBufferSize(sampleRate, channelConfig, targetEncoding); android.media.AudioTrack.getMinBufferSize(sampleRate, channelConfig, outputEncoding);
Assertions.checkState(minBufferSize != ERROR_BAD_VALUE); Assertions.checkState(minBufferSize != ERROR_BAD_VALUE);
int multipliedBufferSize = minBufferSize * BUFFER_MULTIPLICATION_FACTOR; int multipliedBufferSize = minBufferSize * BUFFER_MULTIPLICATION_FACTOR;
int minAppBufferSize = (int) durationUsToFrames(MIN_BUFFER_DURATION_US) * pcmFrameSize; int minAppBufferSize = (int) durationUsToFrames(MIN_BUFFER_DURATION_US) * pcmFrameSize;
...@@ -531,15 +533,15 @@ public final class AudioTrack { ...@@ -531,15 +533,15 @@ public final class AudioTrack {
releasingConditionVariable.block(); releasingConditionVariable.block();
if (tunneling) { if (tunneling) {
audioTrack = createHwAvSyncAudioTrackV21(sampleRate, channelConfig, targetEncoding, audioTrack = createHwAvSyncAudioTrackV21(sampleRate, channelConfig, outputEncoding,
bufferSize, audioSessionId); bufferSize, audioSessionId);
} else if (audioSessionId == C.AUDIO_SESSION_ID_UNSET) { } else if (audioSessionId == C.AUDIO_SESSION_ID_UNSET) {
audioTrack = new android.media.AudioTrack(streamType, sampleRate, channelConfig, audioTrack = new android.media.AudioTrack(streamType, sampleRate, channelConfig,
targetEncoding, bufferSize, MODE_STREAM); outputEncoding, bufferSize, MODE_STREAM);
} else { } else {
// Re-attach to the same audio session. // Re-attach to the same audio session.
audioTrack = new android.media.AudioTrack(streamType, sampleRate, channelConfig, audioTrack = new android.media.AudioTrack(streamType, sampleRate, channelConfig,
targetEncoding, bufferSize, MODE_STREAM, audioSessionId); outputEncoding, bufferSize, MODE_STREAM, audioSessionId);
} }
checkAudioTrackInitialized(); checkAudioTrackInitialized();
...@@ -611,8 +613,10 @@ public final class AudioTrack { ...@@ -611,8 +613,10 @@ public final class AudioTrack {
* @throws InitializationException If an error occurs initializing the track. * @throws InitializationException If an error occurs initializing the track.
* @throws WriteException If an error occurs writing the audio data. * @throws WriteException If an error occurs writing the audio data.
*/ */
@SuppressWarnings("ReferenceEquality")
public boolean handleBuffer(ByteBuffer buffer, long presentationTimeUs) public boolean handleBuffer(ByteBuffer buffer, long presentationTimeUs)
throws InitializationException, WriteException { throws InitializationException, WriteException {
Assertions.checkArgument(inputBuffer == null || buffer == inputBuffer);
if (!isInitialized()) { if (!isInitialized()) {
initialize(); initialize();
if (playing) { if (playing) {
...@@ -620,27 +624,12 @@ public final class AudioTrack { ...@@ -620,27 +624,12 @@ public final class AudioTrack {
} }
} }
boolean hadData = hasData;
hasData = hasPendingData();
if (hadData && !hasData && audioTrack.getPlayState() != PLAYSTATE_STOPPED) {
long elapsedSinceLastFeedMs = SystemClock.elapsedRealtime() - lastFeedElapsedRealtimeMs;
listener.onUnderrun(bufferSize, C.usToMs(bufferSizeUs), elapsedSinceLastFeedMs);
}
boolean result = writeBuffer(buffer, presentationTimeUs);
lastFeedElapsedRealtimeMs = SystemClock.elapsedRealtime();
return result;
}
@SuppressWarnings("ReferenceEquality")
private boolean writeBuffer(ByteBuffer buffer, long presentationTimeUs) throws WriteException {
boolean isNewSourceBuffer = currentSourceBuffer == null;
Assertions.checkState(isNewSourceBuffer || currentSourceBuffer == buffer);
currentSourceBuffer = buffer;
if (needsPassthroughWorkarounds()) { if (needsPassthroughWorkarounds()) {
// An AC-3 audio track continues to play data written while it is paused. Stop writing so its // An AC-3 audio track continues to play data written while it is paused. Stop writing so its
// buffer empties. See [Internal: b/18899620]. // buffer empties. See [Internal: b/18899620].
if (audioTrack.getPlayState() == PLAYSTATE_PAUSED) { if (audioTrack.getPlayState() == PLAYSTATE_PAUSED) {
// We force an underrun to pause the track, so don't notify the listener in this case.
hasData = false;
return false; return false;
} }
...@@ -653,27 +642,25 @@ public final class AudioTrack { ...@@ -653,27 +642,25 @@ public final class AudioTrack {
} }
} }
if (isNewSourceBuffer) { boolean hadData = hasData;
// We're seeing this buffer for the first time. hasData = hasPendingData();
if (hadData && !hasData && audioTrack.getPlayState() != PLAYSTATE_STOPPED) {
long elapsedSinceLastFeedMs = SystemClock.elapsedRealtime() - lastFeedElapsedRealtimeMs;
listener.onUnderrun(bufferSize, C.usToMs(bufferSizeUs), elapsedSinceLastFeedMs);
}
if (!currentSourceBuffer.hasRemaining()) { if (inputBuffer == null) {
// We are seeing this buffer for the first time.
if (!buffer.hasRemaining()) {
// The buffer is empty. // The buffer is empty.
currentSourceBuffer = null;
return true; return true;
} }
useResampledBuffer = targetEncoding != sourceEncoding;
if (useResampledBuffer) {
Assertions.checkState(targetEncoding == C.ENCODING_PCM_16BIT);
// Resample the buffer to get the data in the target encoding.
resampledBuffer = resampleTo16BitPcm(currentSourceBuffer, sourceEncoding, resampledBuffer);
buffer = resampledBuffer;
}
if (passthrough && framesPerEncodedSample == 0) { if (passthrough && framesPerEncodedSample == 0) {
// If this is the first encoded sample, calculate the sample size in frames. // If this is the first encoded sample, calculate the sample size in frames.
framesPerEncodedSample = getFramesPerEncodedSample(targetEncoding, buffer); framesPerEncodedSample = getFramesPerEncodedSample(outputEncoding, buffer);
} }
if (startMediaTimeState == START_NOT_SET) { if (startMediaTimeState == START_NOT_SET) {
startMediaTimeUs = Math.max(0, presentationTimeUs); startMediaTimeUs = Math.max(0, presentationTimeUs);
startMediaTimeState = START_IN_SYNC; startMediaTimeState = START_IN_SYNC;
...@@ -695,21 +682,31 @@ public final class AudioTrack { ...@@ -695,21 +682,31 @@ public final class AudioTrack {
listener.onPositionDiscontinuity(); listener.onPositionDiscontinuity();
} }
} }
inputBuffer = buffer;
outputBuffer = resampler != null ? resampler.handleBuffer(inputBuffer, outputBuffer)
: inputBuffer;
if (Util.SDK_INT < 21) { if (Util.SDK_INT < 21) {
// Copy {@code buffer} into {@code temporaryBuffer}. int bytesRemaining = outputBuffer.remaining();
int bytesRemaining = buffer.remaining(); if (preV21OutputBuffer == null || preV21OutputBuffer.length < bytesRemaining) {
if (temporaryBuffer == null || temporaryBuffer.length < bytesRemaining) { preV21OutputBuffer = new byte[bytesRemaining];
temporaryBuffer = new byte[bytesRemaining];
} }
int originalPosition = buffer.position(); int originalPosition = outputBuffer.position();
buffer.get(temporaryBuffer, 0, bytesRemaining); outputBuffer.get(preV21OutputBuffer, 0, bytesRemaining);
buffer.position(originalPosition); outputBuffer.position(originalPosition);
temporaryBufferOffset = 0; preV21OutputBufferOffset = 0;
} }
} }
buffer = useResampledBuffer ? resampledBuffer : buffer; if (writeOutputBuffer(presentationTimeUs)) {
int bytesRemaining = buffer.remaining(); inputBuffer = null;
return true;
}
return false;
}
private boolean writeOutputBuffer(long presentationTimeUs) throws WriteException {
int bytesRemaining = outputBuffer.remaining();
int bytesWritten = 0; int bytesWritten = 0;
if (Util.SDK_INT < 21) { // passthrough == false if (Util.SDK_INT < 21) { // passthrough == false
// Work out how many bytes we can write without the risk of blocking. // Work out how many bytes we can write without the risk of blocking.
...@@ -718,18 +715,21 @@ public final class AudioTrack { ...@@ -718,18 +715,21 @@ public final class AudioTrack {
int bytesToWrite = bufferSize - bytesPending; int bytesToWrite = bufferSize - bytesPending;
if (bytesToWrite > 0) { if (bytesToWrite > 0) {
bytesToWrite = Math.min(bytesRemaining, bytesToWrite); bytesToWrite = Math.min(bytesRemaining, bytesToWrite);
bytesWritten = audioTrack.write(temporaryBuffer, temporaryBufferOffset, bytesToWrite); bytesWritten = audioTrack.write(preV21OutputBuffer, preV21OutputBufferOffset, bytesToWrite);
if (bytesWritten >= 0) { if (bytesWritten > 0) {
temporaryBufferOffset += bytesWritten; preV21OutputBufferOffset += bytesWritten;
outputBuffer.position(outputBuffer.position() + bytesWritten);
} }
buffer.position(buffer.position() + bytesWritten);
} }
} else if (tunneling) {
bytesWritten = writeNonBlockingWithAvSyncV21(audioTrack, outputBuffer, bytesRemaining,
presentationTimeUs);
} else { } else {
bytesWritten = tunneling bytesWritten = writeNonBlockingV21(audioTrack, outputBuffer, bytesRemaining);
? writeNonBlockingWithAvSyncV21(audioTrack, buffer, bytesRemaining, presentationTimeUs)
: writeNonBlockingV21(audioTrack, buffer, bytesRemaining);
} }
lastFeedElapsedRealtimeMs = SystemClock.elapsedRealtime();
if (bytesWritten < 0) { if (bytesWritten < 0) {
throw new WriteException(bytesWritten); throw new WriteException(bytesWritten);
} }
...@@ -741,7 +741,6 @@ public final class AudioTrack { ...@@ -741,7 +741,6 @@ public final class AudioTrack {
if (passthrough) { if (passthrough) {
submittedEncodedFrames += framesPerEncodedSample; submittedEncodedFrames += framesPerEncodedSample;
} }
currentSourceBuffer = null;
return true; return true;
} }
return false; return false;
...@@ -885,7 +884,7 @@ public final class AudioTrack { ...@@ -885,7 +884,7 @@ public final class AudioTrack {
submittedPcmBytes = 0; submittedPcmBytes = 0;
submittedEncodedFrames = 0; submittedEncodedFrames = 0;
framesPerEncodedSample = 0; framesPerEncodedSample = 0;
currentSourceBuffer = null; inputBuffer = null;
avSyncHeader = null; avSyncHeader = null;
bytesUntilNextAvSync = 0; bytesUntilNextAvSync = 0;
startMediaTimeState = START_NOT_SET; startMediaTimeState = START_NOT_SET;
...@@ -1094,7 +1093,7 @@ public final class AudioTrack { ...@@ -1094,7 +1093,7 @@ public final class AudioTrack {
*/ */
private boolean needsPassthroughWorkarounds() { private boolean needsPassthroughWorkarounds() {
return Util.SDK_INT < 23 return Util.SDK_INT < 23
&& (targetEncoding == C.ENCODING_AC3 || targetEncoding == C.ENCODING_E_AC3); && (outputEncoding == C.ENCODING_AC3 || outputEncoding == C.ENCODING_E_AC3);
} }
/** /**
...@@ -1129,82 +1128,6 @@ public final class AudioTrack { ...@@ -1129,82 +1128,6 @@ public final class AudioTrack {
sessionId); sessionId);
} }
/**
* Converts the provided buffer into 16-bit PCM.
*
* @param buffer The buffer containing the data to convert.
* @param sourceEncoding The data encoding.
* @param out A buffer into which the output should be written, if its capacity is sufficient.
* @return The 16-bit PCM output. Different to the out parameter if null was passed, or if the
* capacity was insufficient for the output.
*/
private static ByteBuffer resampleTo16BitPcm(ByteBuffer buffer, @C.PcmEncoding int sourceEncoding,
ByteBuffer out) {
int offset = buffer.position();
int limit = buffer.limit();
int size = limit - offset;
int resampledSize;
switch (sourceEncoding) {
case C.ENCODING_PCM_8BIT:
resampledSize = size * 2;
break;
case C.ENCODING_PCM_24BIT:
resampledSize = (size / 3) * 2;
break;
case C.ENCODING_PCM_32BIT:
resampledSize = size / 2;
break;
case C.ENCODING_PCM_16BIT:
case C.ENCODING_INVALID:
case Format.NO_VALUE:
default:
// Never happens.
throw new IllegalStateException();
}
ByteBuffer resampledBuffer = out;
if (resampledBuffer == null || resampledBuffer.capacity() < resampledSize) {
resampledBuffer = ByteBuffer.allocateDirect(resampledSize);
}
resampledBuffer.position(0);
resampledBuffer.limit(resampledSize);
// Samples are little endian.
switch (sourceEncoding) {
case C.ENCODING_PCM_8BIT:
// 8->16 bit resampling. Shift each byte from [0, 256) to [-128, 128) and scale up.
for (int i = offset; i < limit; i++) {
resampledBuffer.put((byte) 0);
resampledBuffer.put((byte) ((buffer.get(i) & 0xFF) - 128));
}
break;
case C.ENCODING_PCM_24BIT:
// 24->16 bit resampling. Drop the least significant byte.
for (int i = offset; i < limit; i += 3) {
resampledBuffer.put(buffer.get(i + 1));
resampledBuffer.put(buffer.get(i + 2));
}
break;
case C.ENCODING_PCM_32BIT:
// 32->16 bit resampling. Drop the two least significant bytes.
for (int i = offset; i < limit; i += 4) {
resampledBuffer.put(buffer.get(i + 2));
resampledBuffer.put(buffer.get(i + 3));
}
break;
case C.ENCODING_PCM_16BIT:
case C.ENCODING_INVALID:
case Format.NO_VALUE:
default:
// Never happens.
throw new IllegalStateException();
}
resampledBuffer.position(0);
return resampledBuffer;
}
@C.Encoding @C.Encoding
private static int getEncodingForMimeType(String mimeType) { private static int getEncodingForMimeType(String mimeType) {
switch (mimeType) { switch (mimeType) {
......
library/src/main/java/com/google/android/exoplayer2/audio/BufferProcessor.java 0 → 100644
/*
* Copyright (C) 2017 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.android.exoplayer2.audio;
import java.nio.ByteBuffer;
/**
* Interface for processors of buffers, for use with {@link AudioTrack}.
*/
public interface BufferProcessor {
/**
* Processes the data in the specified input buffer in its entirety. Populates {@code output} with
* processed data if is not {@code null} and has sufficient capacity. Otherwise a different buffer
* will be populated and returned.
*
* @param input A buffer containing the input data to process.
* @param output A buffer into which the output should be written, if its capacity is sufficient.
* @return The processed output. Different to {@code output} if null was passed, or if its
* capacity was insufficient.
*/
ByteBuffer handleBuffer(ByteBuffer input, ByteBuffer output);
}
library/src/main/java/com/google/android/exoplayer2/audio/ResamplingBufferProcessor.java 0 → 100644
/*
* Copyright (C) 2017 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.android.exoplayer2.audio;
import com.google.android.exoplayer2.C;
import com.google.android.exoplayer2.Format;
import com.google.android.exoplayer2.util.Assertions;
import java.nio.ByteBuffer;
/**
* A {@link BufferProcessor} that converts PCM input buffers from a specified input bit depth to
* {@link C#ENCODING_PCM_16BIT} in preparation for writing to an {@link android.media.AudioTrack}.
*/
/* package */ final class ResamplingBufferProcessor implements BufferProcessor {
@C.PcmEncoding
private final int inputEncoding;
/**
* Creates a new buffer processor for resampling input in the specified encoding.
*
* @param inputEncoding The PCM encoding of input buffers.
* @throws IllegalArgumentException Thrown if the input encoding is not PCM or its bit depth is
* not 8, 24 or 32-bits.
*/
public ResamplingBufferProcessor(@C.PcmEncoding int inputEncoding) {
Assertions.checkArgument(inputEncoding == C.ENCODING_PCM_8BIT
|| inputEncoding == C.ENCODING_PCM_24BIT || inputEncoding == C.ENCODING_PCM_32BIT);
this.inputEncoding = inputEncoding;
}
@Override
public ByteBuffer handleBuffer(ByteBuffer input, ByteBuffer output) {
int offset = input.position();
int limit = input.limit();
int size = limit - offset;
int resampledSize;
switch (inputEncoding) {
case C.ENCODING_PCM_8BIT:
resampledSize = size * 2;
break;
case C.ENCODING_PCM_24BIT:
resampledSize = (size / 3) * 2;
break;
case C.ENCODING_PCM_32BIT:
resampledSize = size / 2;
break;
case C.ENCODING_PCM_16BIT:
case C.ENCODING_INVALID:
case Format.NO_VALUE:
default:
// Never happens.
throw new IllegalStateException();
}
ByteBuffer resampledBuffer = output;
if (resampledBuffer == null || resampledBuffer.capacity() < resampledSize) {
resampledBuffer = ByteBuffer.allocateDirect(resampledSize);
}
resampledBuffer.position(0);
resampledBuffer.limit(resampledSize);
// Samples are little endian.
switch (inputEncoding) {
case C.ENCODING_PCM_8BIT:
// 8->16 bit resampling. Shift each byte from [0, 256) to [-128, 128) and scale up.
for (int i = offset; i < limit; i++) {
resampledBuffer.put((byte) 0);
resampledBuffer.put((byte) ((input.get(i) & 0xFF) - 128));
}
break;
case C.ENCODING_PCM_24BIT:
// 24->16 bit resampling. Drop the least significant byte.
for (int i = offset; i < limit; i += 3) {
resampledBuffer.put(input.get(i + 1));
resampledBuffer.put(input.get(i + 2));
}
break;
case C.ENCODING_PCM_32BIT:
// 32->16 bit resampling. Drop the two least significant bytes.
for (int i = offset; i < limit; i += 4) {
resampledBuffer.put(input.get(i + 2));
resampledBuffer.put(input.get(i + 3));
}
break;
case C.ENCODING_PCM_16BIT:
case C.ENCODING_INVALID:
case Format.NO_VALUE:
default:
// Never happens.
throw new IllegalStateException();
}
resampledBuffer.position(0);
return resampledBuffer;
}
}
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