[FFmpeg-devel] [PATCH 05/10] lavc/libopenh264enc: prompt slice number changing according to cpus

[Fu, Linjie]

> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of
> Anton Khirnov
> Sent: Friday, April 10, 2020 18:23
> To: FFmpeg development discussions and patches <ffmpeg-
> devel at ffmpeg.org>
> Subject: Re: [FFmpeg-devel] [PATCH 05/10] lavc/libopenh264enc: prompt
> slice number changing according to cpus
> 
> Quoting Linjie Fu (2020-04-06 13:14:48)
> > Libopenh264enc would set the slice according to the number of cpu cores
> > if uiSliceNum equals to 0 (auto) in SM_FIXEDSLCNUM_SLICE mode.
> >
> > Prompt a warning for user to catch this.
> >
> > Signed-off-by: Linjie Fu <linjie.fu at intel.com>
> > ---
> >  libavcodec/libopenh264enc.c | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/libavcodec/libopenh264enc.c b/libavcodec/libopenh264enc.c
> > index dab8244..01a85fb 100644
> > --- a/libavcodec/libopenh264enc.c
> > +++ b/libavcodec/libopenh264enc.c
> > @@ -237,6 +237,9 @@ FF_ENABLE_DEPRECATION_WARNINGS
> >      param.sSpatialLayers[0].sSliceCfg.uiSliceMode               = s->slice_mode;
> >      param.sSpatialLayers[0].sSliceCfg.sSliceArgument.uiSliceNum = avctx-
> >slices;
> >  #endif
> > +    if (avctx->slices == 0 && s->slice_mode == SM_FIXEDSLCNUM_SLICE)
> > +        av_log(avctx, AV_LOG_WARNING, "Auto slice number, "
> > +               "default to use the number of CPU cores: %d\n", av_cpu_count());
> 
> Generally makes sense, but I'd avoid the call to av_cpu_count() since we
> don't know what method precisely will libopenh264 use to set the slice
> count. So IMO just say something like "slice count will be set
> automatically".

There is a statement in the API definition[1] for uiSliceNum which says:
 	when uiSliceNum=0 means auto design it with cpu core number.
So IMHO it seems clear enough if I got it correctly.

I'm good with this suggestion and will update, since the detailed slice number
would also be dumped in debug level as well (however a little bit mixed up with
all the debug info), thx.

- Linjie

[1] https://github.com/cisco/openh264/blob/master/codec/api/svc/codec_app_def.h#L351