Question

我使用AudioRecord类从Microphone获取PCM数据，如何使用Android中的MediaCodec将其编码为MP3？

Answer 1

下面的代码会将pcm转换为m4a，你必须修改mp3的muxer输出格式

 private void convertAudio(String filename) throws IOException {

String outputpath =Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_MUSIC).getPath()+"/converted.m4a";
// Set up MediaExtractor to read from the source.

MediaExtractor extractor = new MediaExtractor();
extractor.setDataSource(filename);


int trackCount = extractor.getTrackCount();

// Set up MediaMuxer for the destination.
MediaMuxer muxer;
muxer = new MediaMuxer(outputpath, MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4);
// Set up the tracks.
HashMap<Integer, Integer> indexMap = new HashMap<Integer, Integer>(trackCount);
for (int i = 0; i < trackCount; i++) {
    extractor.selectTrack(i);
    MediaFormat format = extractor.getTrackFormat(i);
    format.setString(MediaFormat.KEY_MIME, MediaFormat.MIMETYPE_AUDIO_AMR_NB);

    int dstIndex = muxer.addTrack(format);
    indexMap.put(i, dstIndex);
}
// Copy the samples from MediaExtractor to MediaMuxer.
boolean sawEOS = false;
int bufferSize = 32000;
int frameCount = 0;
int offset = 100;
ByteBuffer dstBuf = ByteBuffer.allocate(bufferSize);
MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();
/* if (degrees >= 0) {
    muxer.setOrientationHint(degrees);
}*/
// Test setLocation out of bound cases

muxer.start();
while (!sawEOS) {
    bufferInfo.offset = offset;
    bufferInfo.size = extractor.readSampleData(dstBuf, offset);
    if (bufferInfo.size < 0) {

        sawEOS = true;
        bufferInfo.size = 0;
    } else {
        bufferInfo.presentationTimeUs = extractor.getSampleTime();
        bufferInfo.flags = extractor.getSampleFlags();
        int trackIndex = extractor.getSampleTrackIndex();
        muxer.writeSampleData(indexMap.get(trackIndex), dstBuf,
                bufferInfo);
        extractor.advance();
        frameCount++;

    }
}
muxer.stop();
muxer.release();

return;
}

使用MediaCodec API Android的PCM到MP3

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