This enables the second frame of the test video to be decoded.
It appears that the test video uses a superframe (group of multiple
frames) for the first chunk of the file, but we haven't implemented
superframe parsing.
We also ignore the show_frame flag, so for now, this
means that the second frame read out is shown when it should not be. To
fix this, another error type needs to be implemented that is "thrown" to
decoder's client so they know to send another sample buffer.
