[FFmpeg-devel] [PATCH] libavfilter/vf_overlay_cuda: Pass the main frame to the output if secondary frame is not available. now filter fails if secondary frame is not available due to e.g secondary source delay.

[Nicolas George]

Alex Pokotilo (12020-08-21):
> I'm sorry. I'm a newbie. Am I right I just need to commit in following format:

No need to apologize.

> first line: short description......
> LF
> more details here

Exactly.

> Should I send a new patch as a separate email or reply to this one ?

It does not matter.

> I create a filter graph with vf_cuda_overlay in my application. I
> start sending frames into a "main" stream link using
> av_buffersrc_write_frame.
> I start sending frames into a "secondary" stream too almost
> immediately. I have one output sink in my filter graph.

What are the timestamps (and corresponding time bases) of the first
frame you send on each input?

> After each write I call av_buffersink_get_frame and get AVERROR_BUG
> from vf_overlay_cuda for some time initially but after several frames
> it starts returning mixed frame.
> I've checked vf_blend and other framesync filters. They do the same as
> I did in the fix.

The fix is probably right, but I would like to make 100% sure, and I do
not have a CUDA setup. Plus, it would help check the code of your
application is right.

> Maybe the problem In my application I cannot guarantee that both
> streams have the same timeline.
> Could you please point me to the place where framesync checks second
> stream availability before it calls it's filter(overlay_cuda_blend in
> my case).
> This topic is very complex to me now so any help from your side can
> really help me.

The code in framesync is rather complex because it is designed to handle
a wide variety of cases.

If you are willing to make a quick test, this would be interesting: in
libavfilter/framesync.c, in the function ff_framesync_init_dualinput,
replace fs->in[1].before = EXT_NULL; with EXT_INFINITY and see if it
changes something.

But most importantly, seeing the timestamps of the frames would let me
know if the issue is exactly what I think it is.

Regards,

-- 
  Nicolas George
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 833 bytes
Desc: not available
URL: <https://ffmpeg.org/pipermail/ffmpeg-devel/attachments/20200821/431b4508/attachment.sig>