[FFmpeg-devel] Question: Null and Nonref frames in indeo3

Maxim max_pole
Fri Sep 11 15:14:15 CEST 2009

Hi guys,

I'm about to submit an updated patch for indeo3 replacement. My last
technical question is about how to handle the following frame types:

- NULL or SYNC frames don't contain any picture. Those are needed for
the synchronization purposes because the .AVI container doesn't support
variable frame rate. The decoder usually sends the previous picture
again if such a frame is encountered.

- NONREF or DROPPABLE INTER frames act just like the normal INTER frames
with exception those can be discarded easily without damaging the whole
video sequence. Thus a video can be displayed at reduced frame rate if
there no enough decoding resources available...

Now my questions:
- which action should be taken in order to inform the ffmpeg about the
above mentioned frames (setting a flag, send the previously decoded
frame, do nothing)?
- what should the decoder do in the case there it must hurry up: check a
special flag and skip decoding of the NONREF frames, decode fewer planes?
- how ffmpeg reacts on such frames (discard them if needed, ignore)?

Thanks in advance
Best regards

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