RandomizedMp3Decoder.java
/*
* Copyright 2020 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 androidx.media3.test.utils.robolectric;
import android.media.AudioFormat;
import android.media.MediaCrypto;
import android.media.MediaFormat;
import android.view.Surface;
import androidx.annotation.RequiresApi;
import androidx.media3.common.MimeTypes;
import androidx.media3.common.util.Assertions;
import androidx.media3.common.util.UnstableApi;
import androidx.media3.common.util.Util;
import androidx.media3.extractor.MpegAudioUtil;
import androidx.media3.test.utils.TestUtil;
import com.google.common.collect.ImmutableList;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.List;
import org.robolectric.shadows.ShadowMediaCodec;
/**
* Generates randomized, but correct amount of data on MP3 audio input.
*
* <p>The decoder reads the MP3 header for each input MP3 frame, determines the number of bytes the
* input frame should inflate to, and writes randomized data of that amount to the output buffer.
* Decoder randomness can help us identify possible errors in downstream renderers and audio
* processors. The random bahavior is deterministic, it outputs the same bytes across multiple runs.
*
* <p>All the data written to the output by the decoder can be obtained by getAllOutputBytes().
*/
@RequiresApi(29)
@UnstableApi
public final class RandomizedMp3Decoder implements ShadowMediaCodec.CodecConfig.Codec {
private final List<byte[]> decoderOutput = new ArrayList<>();
private int frameSizeInBytes;
@Override
public void process(ByteBuffer in, ByteBuffer out) {
if (in.remaining() == 0) {
// An empty frame will be queued by the MediaCodecRenderer on END_OF_STREAM.
return;
}
Assertions.checkState(
in.remaining() >= 4, "Frame size too small, should be at least 4 to hold an MP3 header");
// Get the desired output size for every input.
int headerDataBigEndian = Util.getBigEndianInt(in, in.position());
int frameCount = MpegAudioUtil.parseMpegAudioFrameSampleCount(headerDataBigEndian);
int expectedNumBytes = frameCount * frameSizeInBytes;
byte[] bytesToWrite = TestUtil.buildTestData(expectedNumBytes);
out.put(bytesToWrite);
decoderOutput.add(bytesToWrite);
in.position(in.limit());
}
@Override
public void onConfigured(MediaFormat format, Surface surface, MediaCrypto crypto, int flags) {
int pcmEncoding =
format.getInteger(
MediaFormat.KEY_PCM_ENCODING, /* defaultValue= */ AudioFormat.ENCODING_PCM_16BIT);
int channelCount = format.getInteger(MediaFormat.KEY_CHANNEL_COUNT);
Assertions.checkArgument(
format.getString(MediaFormat.KEY_MIME, MimeTypes.AUDIO_MPEG).equals(MimeTypes.AUDIO_MPEG));
frameSizeInBytes = Util.getPcmFrameSize(pcmEncoding, channelCount);
}
/**
* Returns all arrays of bytes output from the decoder.
*
* @return a list of byte arrays (for each MP3 frame input) that were previously output from the
* decoder.
*/
public ImmutableList<byte[]> getAllOutputBytes() {
return ImmutableList.copyOf(decoderOutput);
}
}