Android MediaCodec: how to request a key frame when encoding

Question

In Android4.1, a key frame is often requested in a real-time encoding application. But how to do it using MediaCodec object? The current Android4.2 SDK seems not support it.

Answer 1

You can produce random keyframe by specifying MediaCodec.BUFFER_FLAG_SYNC_FRAME when queuing input buffers:

MediaCodec codec = MediaCodec.createDecoderByType(type);
codec.configure(format, ...);
codec.start();
ByteBuffer[] inputBuffers = codec.getInputBuffers();
for (;;) {
  int inputBufferIndex = codec.dequeueInputBuffer(timeoutUs);
  if (inputBufferIndex >= 0) {
    // fill inputBuffers[inputBufferIndex] with valid data
    ...
    codec.queueInputBuffer(inputBufferIndex, 0, inputBuffers[inputBufferIndex].limit(), presentationTime,
        isKeyFrame ? MediaCodec.BUFFER_FLAG_SYNC_FRAME : 0);
  }

}

Stumbled upon the need to insert random keyframe when encoding video on Galaxy Nexus. On it, MediaCodec didn't automatically produce keyframe at the start of the video.