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

[Lynne]

25 Nov 2021, 23:49 by cus at passwd.hu:

>
>
> 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.
>

So you'd like for the field to either be fully opaque or fully working (by always
having the correct time_base value)?
That sounds fair, description changed:
"Time base for the timestamps in this frame. Currently unused by any API,
users can set this and use it as an opaque field. In the future, this field may
be set by the API for you, but its value will always be ignored."