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androidandroid-mediacodecmediaextractor

buffer-to-buffer encode/decode from capture in android 4.1 (API 16)

I searched for hours .. I just want a working decode/encode of a recorded movie. Is this even possible on android 4.1? Now i writes only a few kb's to my mp4 file. No errors.

After this will work, i will use KEY_FRAME_RATE and KEY_I_FRAME_INTERVAL to put it in slow motion.

I used a mediaExtractor to configure the MediaCodec. I see 3 steps (see gist for complete code):

1./

encoder.dequeueInputBuffer(5000);
extractor.readSampleData(inputBuf, offset);
ptsUsec2 = extractor.getSampleTime();
encoder.queueInputBuffer(inputBufIndex, ...);

2./

encoder.dequeueOutputBuffer(info, 5000);
ByteBuffer encodedData = encoderOutputBuffers[encoderStatus];
//i write encodedData to a FileOutputStream (to save the MP4);
decoder.queueInputBuffer(inputBufIndex, ...);

3./

decoder.dequeueOutputBuffer(info, 5000);
decoder.releaseOutputBuffer(decoderStatus, ...);

Here is the complete function i modified from google's EncodeDecodeTest file: gist

Thanks for help, Felix

Solution

  • Some additional information is available on bigflake. In particular, FAQ item #9.

    The format of frames coming out of the MediaCodec decoder is not guaranteed to be useful. Many popular devices decode data into a proprietary YUV format, which is why the checkFrame() function in the buffer-to-buffer test can't always verify the results. You'd expect the MediaCodec encoder to be able to accept the frames output by the decoder, but that's not guaranteed.

    Coding against API 18+ is generally much easier because you can work with a Surface rather than a ByteBuffer.

    Of course, if all you want is slow-motion video, you don't need to decode and re-encode the H.264 stream. All you need to do is alter the presentation time stamps, which are in the .mp4 wrapper. On API 18+, you can extract with MediaExtractor and immediately encode with MediaMuxer, without involving MediaCodec at all. On API 16, MediaMuxer doesn't exist, so you'd need some other way to wrap H.264 as .mp4.

    Unless, of course, you have some aversion to variable-frame-rate video, in which case you'll need to re-encode it with the "slow motion" frames repeated (and timestamps adjusted appropriately). The KEY_FRAME_RATE and KEY_I_FRAME_INTERVAL values will not help you -- they're set when the encoder is configured, and have no affect on frame timing.