[FFmpeg-devel] [PATCH v2] lavu/avframe: add a time_base field

[Marton Balint]

On Thu, 25 Nov 2021, Lynne wrote:

> This adds a time_base field (currently unused), analogue to the
> AVPacket.time_base field.
> This allows for API clients to exchange AVFrames directly, without
> needing to plumb extra data from sources via side mechanisms.

The objections raised before still stand I believe, and again, the main 
concern is that the API user won't know when to use the packet or frame 
timebase and when to use the frame/packet source timebase.

You write this in the doxy:
> Time base for the timestamps in this frame. May be 0, in which case the
> time_base from the frame source should be used.

One could easily think - based on this text alone - that every user of 
avcodec_receive_frame should check if AVFrame->time_base is 0 to 
calculate real PTS...

I'd be a lot more willing to accept this if you could document explicitly 
that AVFrame->time_base (and AVPacket->time_base) is not used by the API 
right now, and is similar to e.g. *opaque field. And later, if by using 
some magic flag or new API or whatever it turns out to make sense to 
actually use AVPacket/AVFrame time base, the doxy text can be extended 
accordingly.

Regards,
Marton