[Libav-user] Using 0 for AVPacket.duration

[Alex Agranovsky]

Running into a problem when using AVPacket.duration value of 0, and 
writing to MP4/MOV with av_write_frame(). Overall, the approach works. 
However there's a problem with the last packet written to the file, 
which ends up with AV_PKT_FLAG_DISCARD added by the muxer. This doesn't 
seem to happen when writing to other formats (verified .mkv/.ts work as 
expected), so it seems like MOV mux having some trouble with figuring 
out last packet's duration, and prefers to just chuck it.

The only two workarounds I've found is

1. write an actual discardable/empty packet at the end of the file 
(adding AV_PKT_FLAG_DISCARD and proper pts to it).
2. buffer at least one packet, and flush it on close

The first solution seems dirty (and we did run into some consumers that 
have problems with input having D-flagged packets), the second solution 
would require more code restructuring than desirable. Is there no other 
way to indicate last packet's duration to MOV mux when writing the 
trailer/closing the file?

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