Switch all owning AVFrame* variables to av_frame_ptr for
automatic cleanup.
Use AVBufferRef to store frame data in AVFrame where appropriate
so that it can be freed automatically with it's AVFrame.
Handle allocation errors.
Remove all uses of deprecated av_init_packet() and switch any stack
based AVPackets to unique_ptrs allocated with av_packet_alloc().
Ensure that all code paths call av_packet_unref() after use to reset
before next usage.