Re: [FFmpeg-devel] [PATCH 3/4] avutil/cuda_check: propagate AVERROR_UNRECOVERABLE when needed

[Soft Works <softworkz@hotmail.com>]

> -----Original Message-----
> From: ffmpeg-devel <ffmpeg-devel-bounces@ffmpeg.org> On Behalf Of
> Timo Rothenpieler
> Sent: Tuesday, November 22, 2022 4:16 PM
> To: ffmpeg-devel@ffmpeg.org
> Subject: Re: [FFmpeg-devel] [PATCH 3/4] avutil/cuda_check: propagate
> AVERROR_UNRECOVERABLE when needed
> 
> 
> 
> On 22/11/2022 14:31, James Almer wrote:
> > On 11/22/2022 10:21 AM, Timo Rothenpieler wrote:
> >> On 22/11/2022 14:07, James Almer wrote:
> >>> Based on a patch by Soft Works.
> >>>
> >>> Signed-off-by: James Almer <jamrial@gmail.com>
> >>> ---
> >>>   libavutil/cuda_check.h | 4 ++++
> >>>   1 file changed, 4 insertions(+)
> >>>
> >>> diff --git a/libavutil/cuda_check.h b/libavutil/cuda_check.h
> >>> index f5a9234eaf..33aaf9c098 100644
> >>> --- a/libavutil/cuda_check.h
> >>> +++ b/libavutil/cuda_check.h
> >>> @@ -49,6 +49,10 @@ static inline int ff_cuda_check(void *avctx,
> >>>           av_log(avctx, AV_LOG_ERROR, " -> %s: %s", err_name,
> >>> err_string);
> >>>       av_log(avctx, AV_LOG_ERROR, "\n");
> >>> +    // Not recoverable
> >>> +    if (err == CUDA_ERROR_UNKNOWN)
> >>> +        return AVERROR_UNRECOVERABLE;
> >>
> >> Why does specifically CUDA_ERROR_UNKNOWN get mapped to
> unrecoverable?
> >
> > It's the code that Soft Works found out was returned repeatedly no
> > matter how many packets you fed to the encoder, which meant it was
> stuck
> > in an unrecoverable state. See
> > http://ffmpeg.org/pipermail/ffmpeg-devel/2021-October/287153.html
> >
> > If you know of cases where this error could be returned in valid
> > recoverable scenarios that are not already handled in some other
> way,
> > what do you suggest could be done?
> 
> It's more that that very much depends on the context the function is
> used in.
> In the context of an active de/encoding loop, every non-success
> return
> would be unrecoverable. Or even during init.
> 
> While in other places a failure just breaks a single frame and if it
> somehow recovery, it can continue on. Though that's usually the
> exception.

Can you give an example for this in ffmpeg where CUDA returns an
error and ffmpeg continues?

At the time when I had submitted the patch, I had replied this to James
after he had argued that the behavior would be correct as is and
a user who would want ffmpeg to exit in such case, must specify 
the -xerror parameter.


softworkz:
> When there's an error in a filter => ffmpeg exits
> When there's an error in an encoder => ffmpeg exits
> When there's an error initializing a decoder or an encoder
> => ffmpeg exits
>
> So why shouldn't ffmpeg exit when there's an unrecoverable error 
> in a decoder?


AFAIR, in case of filtering and encoding, any "normal" CUDA 
error is already sufficient to cause ffmpeg to exit.


> In any case, this function does not seem the right place to map an
> arbitrary return code to such a result. 

That depends on whether you consider CUDA_ERROR_UNKNOWN as 
generally unrecoverable. When you do - like I did - then
it's the right place IMO.

If you doubt it, then yes - it wouldn't be the right place.

Best regards,
softworkz
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