The codec can consume packets without returning a frame for them; H.264
does after lost or corrupt slices (RTSP over UDP). Decode() paired each
frame with the oldest decoder_queue entry, so those entries stayed queued
for good: every later frame went to an older packet, and once the queue
passed 2 x the keyframe interval the throttle stopped sending while the
codec waited for input, so decoding stopped until zmwatch restarted zmc.
Match the frame to the entry with its pts and release the entries before
it with an earlier pts (decoded, no image), as the flush paths do. A frame
older than every entry is dropped; without a usable pts the oldest entry
is used, as before.
refs #4860
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
