Question

在Android 4.4.2中，我使用MediaCodec来解码mp3个文件。我正在使用queueInputBuffer()对输入的mp3编码帧进行排队，并使用dequeueOutputBuffer()来获取已解码的帧。但解码器从第8帧开始提供解码输出（基于bufferInfo.presentationTimeUs）并跳过最初的7帧。此方案仅针对少数流而不针对所有流发生。此外，这种行为在许多运行中都是一致的。

我想要所有帧的解码输出，我不希望跳过任何帧。任何人都可以帮助我理解为什么帧被跳过？我保证流不会被破坏。因为我得到INFO_TRY_AGAIN到第7帧，当`dequeueOutputBuffer'返回有效的缓冲区索引时，它的呈现时间总是第8帧。

以下是排队代码：

Log.e(TAG, "audptOffset = "+audptOffset+"input PT = "+audpt);
                audcodec.queueInputBuffer(audInbufIndex, 0, audchunkSize, audpt, 0);

以下是我如何调用dequeue并写入AudioTrack：

if(!audoutputDone ){
                if(!waitForAudioRelease){
                    auoutBufIndex  = audcodec.dequeueOutputBuffer(auinfo, 100);
                    Log.e(TAG, "Output PT = " + auinfo.presentationTimeUs+"auoutBufIndex = "+auoutBufIndex);
                }
                if (auoutBufIndex >= 0) {
                    waitForAudioRelease = true;
                } else if (auoutBufIndex == MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED) {
                    auddecOutBufArray = audcodec.getOutputBuffers();
                } else if (auoutBufIndex == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
                    MediaFormat newFormat = audcodec.getOutputFormat();
                    int sampleRate1 = newFormat.getInteger(MediaFormat.KEY_SAMPLE_RATE);
                    int channelCount1 =newFormat.getInteger(MediaFormat.KEY_CHANNEL_COUNT);
                    Log.e(TAG, "INFO_OUTPUT_FORMAT_CHANGED");
                    int minBufSize1 = AudioTrack.getMinBufferSize(sampleRate1, (channelCount1==2)?
                            AudioFormat.CHANNEL_OUT_STEREO:AudioFormat.CHANNEL_OUT_MONO, AudioFormat.ENCODING_PCM_16BIT);
                    audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC,
                            sampleRate1, (channelCount1==2)?AudioFormat.CHANNEL_OUT_STEREO:AudioFormat.CHANNEL_OUT_MONO,
                            AudioFormat.ENCODING_PCM_16BIT, minBufSize1,
                            AudioTrack.MODE_STREAM);
                    audioTrack.play();
                    waitForAudioRelease = false;
                }
                audionowUs = System.currentTimeMillis();
                if (auoutBufIndex >= 0) {               
                    auwhenRealUs = (auinfo.presentationTimeUs/1000) + mStartTimeRealMs - (audptOffset/1000);
                    aulateByUs = audionowUs - auwhenRealUs;


                    if(!audioWaitTillStartTime){
                        while((mStartTimeRealMs+((auinfo.presentationTimeUs/1000) - (audptOffset/1000))) >= audionowUs){
                            try {
                                Thread.sleep(10);
                            } catch (InterruptedException e) {
                                // TODO Auto-generated catch block
                                e.printStackTrace();
                            }
                            audionowUs = System.currentTimeMillis();
                        }
                        Log.e(TAG,"Play is going to start PT Difference = "+((auinfo.presentationTimeUs/1000) - (audptOffset/1000)));
                    }

添加更多日志：

02-22 17:46:03.164: E/CL(28650): received play command from server
02-22 17:46:03.209: E/RealTimeClient(28650): created decoder for audio/mpeg
02-22 17:46:03.234: E/Music(28650): Output PT = 0
02-22 17:46:03.234: E/Music(28650): pt of first frame received 1215000
02-22 17:46:03.234: E/Music(28650): Input PT = 1215000
02-22 17:46:03.234: E/Music(28650): Output PT = 0
02-22 17:46:03.234: E/Music(28650): Input PT = 1241122
02-22 17:46:03.239: E/Music(28650): Output PT = 0
02-22 17:46:03.239: E/Music(28650): Input PT = 1267244
02-22 17:46:03.239: E/Music(28650): Output PT = 0
02-22 17:46:03.239: E/Music(28650): Input PT = 1293367
02-22 17:46:03.239: E/Music(28650): Output PT = 0
02-22 17:46:03.239: E/Music(28650): Input PT = 1319489
02-22 17:46:03.239: E/Music(28650): Output PT = 0
02-22 17:46:03.244: E/Music(28650): INFO_OUTPUT_FORMAT_CHANGED
02-22 17:46:03.249: I/Reverb(28650):  getpid() 28650, IPCThreadState::self()->getCallingPid() 28650
02-22 17:46:03.249: E/Reverb(28650): Reverb::StartElementHandler, wrong element or attributes: boolean
02-22 17:46:03.249: E/Music(28650): Input PT = 1345612
02-22 17:46:03.254: E/Music(28650): Output PT = 1293367
02-22 17:46:03.259: E/Music(28650): Input PT = 1371734
02-22 17:46:03.259: E/Music(28650): Input PT = 1397857
02-22 17:46:03.259: E/Music(28650): Input PT = 1423979
02-22 17:46:03.259: E/Music(28650): Input PT = 1450102
02-22 17:46:03.264: E/Music(28650): Input PT = 1476224
02-22 17:46:03.269: E/Music(28650): Input PT = 1502346
02-22 17:46:03.269: E/Music(28650): Input PT = 1528469
02-22 17:46:03.269: E/Music(28650): Input PT = 1554591
02-22 17:46:03.269: E/Music(28650): Input PT = 1580714
02-22 17:46:03.269: E/Music(28650): Input PT = 1606836
02-22 17:46:03.269: E/Music(28650): Input PT = 1632959
02-22 17:46:03.269: E/Music(28650): Input PT = 1659081
02-22 17:46:04.124: W/AudioTrack(28650): releaseBuffer() track 0x5e2faf28 name=0x3 disabled, restarting
02-22 17:46:04.129: E/Music(28650): Output PT = 1319489
02-22 17:46:04.129: E/Music(28650): Input PT = 1685204
02-22 17:46:04.159: E/Music(28650): Output PT = 1345612

Answer 1

MPEG-1 Layer III（MP3）具有相关帧，您不能从任何帧开始，如第I层或第II层。引用提供的link，“在最坏的情况下，在能够解码一个帧之前可能需要9个输入帧。”这很可能就是你所看到的。虽然前7帧中的每一帧都有一个与之相关的PTS，但直到你到达第8帧时，解码器实际上才能完全解码帧并开始播放。播放从第8帧PTS开始。您需要手动解析有问题的流的字节以完全验证这是发生了什么，但我怀疑您实际上正在播放所有帧。

Android MediaCodec不解码所有输入缓冲区

1 个答案: