Re: [FFmpeg-devel] [PATCH v3] lavc/libvpx: remove thread limit

[James Zern <jzern-at-google.com@ffmpeg.org>]

On Tue, Jan 10, 2023 at 2:47 AM mypopy@gmail.com <mypopy@gmail.com> wrote:
>
> On Thu, Jan 5, 2023 at 6:42 PM Dmitrii Ovchinnikov
> <ovchinnikov.dmitrii@gmail.com> wrote:
> [...]
> > diff --git a/libavcodec/libvpxenc.c b/libavcodec/libvpxenc.c
> > index 9aa5510c28..0627e13973 100644
> > --- a/libavcodec/libvpxenc.c
> > +++ b/libavcodec/libvpxenc.c
> > @@ -942,7 +942,7 @@ static av_cold int vpx_init(AVCodecContext *avctx,
> >      enccfg.g_timebase.num = avctx->time_base.num;
> >      enccfg.g_timebase.den = avctx->time_base.den;
> >      enccfg.g_threads      =
> > -        FFMIN(avctx->thread_count ? avctx->thread_count : av_cpu_count(), 16);
> > +        avctx->thread_count ? avctx->thread_count : av_cpu_count();
> >      enccfg.g_lag_in_frames= ctx->lag_in_frames;
> >
> Do you check the change with the old version libvpx?  as I know, older
> versions libvpx setting the number of threads higher than 16 will
> cause a crash, so I think at least a version check needs to be added
>

Do you have a bug or version in mind? There were some performance
regressions [1] over the releases and some issues with changing the
number of tiles, but I don't remember a crash for a high thread count
(though there have been plenty of crashes related to threads in
general [2]). The range check predates 1.4.0, which is the minimum
required by ffmpeg.

[1] https://crbug.com/webm/1574
[2] https://crbug.com/webm/851
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