The encoder can specify the a preferred_output_delay value to get better throughput
performance. The higher delay may get better HW performance, but it may increases
the encoder and pipeline latency.
When the output queue length is smaller than preferred_output_delay, the encoder
will not block to waiting for the encoding output. It will continue to prepare and
send more commands to GPU, which may improve the encoder throughput performance.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/4359>
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