[FFmpeg-devel] [PATCH 1/2] avcodec/videotoolboxenc: fix undefined behavior with rc_max_rate=0

[Aman Gupta]

On Fri, Jul 6, 2018 at 10:55 PM Thomas Guillem <thomas at gllm.fr> wrote:

>
>
> On Thu, Jul 5, 2018, at 20:49, Aman Gupta wrote:
> > On Wed, Jul 4, 2018 at 3:05 AM Thomas Guillem <thomas at gllm.fr> wrote:
> >
> > > On macOS, a zero rc_max_rate cause an error from
> > > VTSessionSetProperty(kVTCompressionPropertyKey_DataRateLimits).
> > >
> > > on iOS (depending on device/version), a zero rc_max_rate cause invalid
> > > arguments from the vtenc_output_callback after few frames and then a
> crash
> > > within the VideoToolbox library.
> > > ---
> > >  libavcodec/videotoolboxenc.c | 2 ++
> > >  1 file changed, 2 insertions(+)
> > >
> > > diff --git a/libavcodec/videotoolboxenc.c
> b/libavcodec/videotoolboxenc.c
> > > index ac847358ab..aa9aae7e05 100644
> > > --- a/libavcodec/videotoolboxenc.c
> > > +++ b/libavcodec/videotoolboxenc.c
> > > @@ -1019,6 +1019,7 @@ static int vtenc_create_encoder(AVCodecContext
> > >  *avctx,
> > >
> > >      if (vtctx->codec_id == AV_CODEC_ID_H264) {
> > >          // kVTCompressionPropertyKey_DataRateLimits is not available
> for
> > > HEVC
> > > +        if (max_rate > 0) {
> >
> >
> > I think it would be better to add this condition to the existing if block
> > above so we can avoid another level of indentation.
>
> That's what I first wanted to do but there is a also a profile level in
> this code block.
>

I split the profile block into another conditional, and added max_rate to
this one. Applied to master and release/4.0

Aman


>
> >
> > Patch looks fine to me otherwise. I can make this change and commit this
> > week.
> >
> > Aman
> >
> >
> > >          bytes_per_second_value = max_rate >> 3;
> > >          bytes_per_second = CFNumberCreate(kCFAllocatorDefault,
> > >                                            kCFNumberSInt64Type,
> > > @@ -1058,6 +1059,7 @@ static int vtenc_create_encoder(AVCodecContext
> > >  *avctx,
> > >              av_log(avctx, AV_LOG_ERROR, "Error setting max bitrate
> > > property: %d\n", status);
> > >              return AVERROR_EXTERNAL;
> > >          }
> > > +        }
> > >
> > >          if (profile_level) {
> > >              status = VTSessionSetProperty(vtctx->session,
> > > --
> > > 2.18.0
> > >
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