[FFmpeg-devel] [PATCH] avformat/rmdec.c: fix left shift of negative value in rm_sync()

[Andreas Rheinhardt]

James Almer:
> Fixes ticket 8143.
> 
> Signed-off-by: James Almer <jamrial at gmail.com>
> ---
>  libavformat/rmdec.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/libavformat/rmdec.c b/libavformat/rmdec.c
> index c9abd38d33..ccdc38f98a 100644
> --- a/libavformat/rmdec.c
> +++ b/libavformat/rmdec.c
> @@ -724,8 +724,7 @@ static int rm_sync(AVFormatContext *s, int64_t *timestamp, int *flags, int *stre
>  
>              num = avio_rb16(pb);
>              *timestamp = avio_rb32(pb);
> -            mlti_id = (avio_r8(pb)>>1)-1<<16;
> -            mlti_id = FFMAX(mlti_id, 0);
> +            mlti_id = FFMAX((avio_r8(pb) >> 1) - 1, 0) << 16;
>              *flags = avio_r8(pb); /* flags */
>          }
>          for(i=0;i<s->nb_streams;i++) {
> 
This will evaluate avio_r8(pb) twice when it is >= 4. I doubt that's
intended.

- Andreas