Since e0da916b the ffmpeg utility has
held multiple frames output by the decoder in internal queues without
telling the decoder that it is going to do so.  When the decoder has a
fixed-size pool of frames (common in some hardware APIs where the output
frames must be stored as an array texture) this could lead to the pool
being exhausted and the decoder getting stuck.  Fix this by telling the
decoder to allocate additional frames according to the queue size.