Reducing latency in video encoding and decoding

In a computer system that implements a video encoder, a method comprising:

• setting one or more syntax elements that indicate a constraint on frame reordering latency;
• outputting, as part of a bitstream, the one or more syntax elements that indicate the constraint on frame reordering latency;
• receiving a frame;
• encoding the frame, thereby producing encoded data for the frame;
• and
• outputting the encoded data for the frame as part of the bitstream, thereby enabling a video decoder to perform operations to decode the encoded data for the frame to reconstruct the frame, store the reconstructed frame in a decoded picture buffer (“DPB”), determine when the reconstructed frame in the DPB is ready for output, and output the reconstructed frame, the reconstructed frame in the DPB being ready for output if latency status of the reconstructed frame in the DPB is equal to the constraint on frame reordering latency upon determining the latency status of the reconstructed frame in the DPB and comparing the latency status of the reconstructed frame in the DPB to the constraint on frame reordering latency.

One or more computer-readable memory or storage devices having stored thereon encoded data in in a bitstream, the encoded data in the bitstream including one or more syntax elements that indicate a constraint on frame reordering latency, the encoded data in the bitstream further including encoded data for a frame, the encoded data in the bitstream having been produced, with a computer system that implements a video encoder, by operations comprising:

• setting the one or more syntax elements that indicate the constraint on frame reordering latency;
• outputting, as part of the bitstream, the one or more syntax elements that indicate the constraint on frame reordering latency;
• receiving the frame;
• encoding the frame, thereby producing the encoded data for the frame;
• and
• outputting the encoded data for the frame as part of the bitstream, thereby enabling a video decoder to perform operations to decode the encoded data for the frame to reconstruct the frame, store the reconstructed frame in a decoded picture buffer (“DPB”), determine when the reconstructed frame in the DPB is ready for output, and output the reconstructed frame, the reconstructed frame in the DPB being ready for output if latency status of the reconstructed frame in the DPB is equal to the constraint on frame reordering latency upon determining the latency status of the reconstructed frame in the DPB and comparing the latency status of the reconstructed frame in the DPB to the constraint on frame reordering latency.