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

Thomas Guillem thomas at gllm.fr
Sat Jul 7 08:54:54 EEST 2018



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.

> 
> 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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> > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> >
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