Extract Audio from Mp4 and Save to Sd Card (MediaExtractor)

Question

I have a mp4 video file in my sd card. I would like to extract the audio from the video and then save the extracted audio as a separate file on the sd card using MediaExtractor Api. Here is the code I've tried:

  MediaExtractor extractor = new MediaExtractor();
  extractor.setDataSource(MEDIA_PATH_To_File_On_SDCARD);
  for (i = 0; i < extractor.getTrackCount(); i++) {
            MediaFormat format = extractor.getTrackFormat(i);
            String mime = format.getString(MediaFormat.KEY_MIME);
            if (mime.startsWith("audio/")) {
                extractor.selectTrack(i);
                decoder = MediaCodec.createDecoderByType(mime);

                if(decoder != null)
                {
                   decoder.configure(format, null, null, 0);
                }

                break;
            }
        }

Am stuck here I have no idea of how to take the selected audio track and save it to the sd card.

Answer 1

Late to the party, this can be done by using MediaExtractor and MediaMuxer Apis together, Check out the working URL from below,

/**
     * @param srcPath the path of source video file.
     * @param dstPath the path of destination video file.
     * @param startMs starting time in milliseconds for trimming. Set to
     *            negative if starting from beginning.
     * @param endMs end time for trimming in milliseconds. Set to negative if
     *            no trimming at the end.
     * @param useAudio true if keep the audio track from the source.
     * @param useVideo true if keep the video track from the source.
     * @throws IOException
     */
    @SuppressLint("NewApi")
    public void genVideoUsingMuxer(String srcPath, String dstPath, int startMs, int endMs, boolean useAudio, boolean useVideo) throws IOException {
        // Set up MediaExtractor to read from the source.
        MediaExtractor extractor = new MediaExtractor();
        extractor.setDataSource(srcPath);
        int trackCount = extractor.getTrackCount();
        // Set up MediaMuxer for the destination.
        MediaMuxer muxer;
        muxer = new MediaMuxer(dstPath, MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4);
        // Set up the tracks and retrieve the max buffer size for selected
        // tracks.
        HashMap<Integer, Integer> indexMap = new HashMap<Integer, Integer>(trackCount);
        int bufferSize = -1;
        for (int i = 0; i < trackCount; i++) {
            MediaFormat format = extractor.getTrackFormat(i);
            String mime = format.getString(MediaFormat.KEY_MIME);
            boolean selectCurrentTrack = false;
            if (mime.startsWith("audio/") && useAudio) {
                selectCurrentTrack = true;
            } else if (mime.startsWith("video/") && useVideo) {
                selectCurrentTrack = true;
            }
            if (selectCurrentTrack) {
                extractor.selectTrack(i);
                int dstIndex = muxer.addTrack(format);
                indexMap.put(i, dstIndex);
                if (format.containsKey(MediaFormat.KEY_MAX_INPUT_SIZE)) {
                    int newSize = format.getInteger(MediaFormat.KEY_MAX_INPUT_SIZE);
                    bufferSize = newSize > bufferSize ? newSize : bufferSize;
                }
            }
        }
        if (bufferSize < 0) {
            bufferSize = DEFAULT_BUFFER_SIZE;
        }
        // Set up the orientation and starting time for extractor.
        MediaMetadataRetriever retrieverSrc = new MediaMetadataRetriever();
        retrieverSrc.setDataSource(srcPath);
        String degreesString = retrieverSrc.extractMetadata(MediaMetadataRetriever.METADATA_KEY_VIDEO_ROTATION);
        if (degreesString != null) {
            int degrees = Integer.parseInt(degreesString);
            if (degrees >= 0) {
                muxer.setOrientationHint(degrees);
            }
        }
        if (startMs > 0) {
            extractor.seekTo(startMs * 1000, MediaExtractor.SEEK_TO_CLOSEST_SYNC);
        }
        // Copy the samples from MediaExtractor to MediaMuxer. We will loop
        // for copying each sample and stop when we get to the end of the source
        // file or exceed the end time of the trimming.
        int offset = 0;
        int trackIndex = -1;
        ByteBuffer dstBuf = ByteBuffer.allocate(bufferSize);
        MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();
        muxer.start();
        while (true) {
            bufferInfo.offset = offset;
            bufferInfo.size = extractor.readSampleData(dstBuf, offset);
            if (bufferInfo.size < 0) {
                Log.d(TAG, "Saw input EOS.");
                bufferInfo.size = 0;
                break;
            } else {
                bufferInfo.presentationTimeUs = extractor.getSampleTime();
                if (endMs > 0 && bufferInfo.presentationTimeUs > (endMs * 1000)) {
                    Log.d(TAG, "The current sample is over the trim end time.");
                    break;
                } else {
                    bufferInfo.flags = extractor.getSampleFlags();
                    trackIndex = extractor.getSampleTrackIndex();
                    muxer.writeSampleData(indexMap.get(trackIndex), dstBuf, bufferInfo);
                    extractor.advance();
                }
            }
        }
        muxer.stop();
        muxer.release();
        return;
    }

You can use the above-mentioned method by using a single line: genVideoUsingMuxer(videoFile, originalAudio, -1, -1, true, false)

Also, read the comments to use this method more efficiently. GIST: https://gist.github.com/ArsalRaza/132a6e99d59aa80b9861ae368bc786d0

Answer 2

take a look at my post Decoding Video and Encoding again by Mediacodec gets a corrupted file where there is an example (just take care about the answer too). you have to use a MediaMuxer, call AddTrack for the video track and write the data to this track to the muxer after encoding each frame. You have to add track for audio too. If you just want only audio, ignore the video part, and just save the data to the muxer related to the audio. You can see some examples in grafika page, one of them could be this: https://github.com/google/grafika/

Also you can find more examples here: http://www.bigflake.com/mediacodec/

Thanks