[Mesa-dev] [PATCH v2] vl/rbsp: add a check for emulation prevention three byte

[Christian König]

Am 09.08.2016 um 15:56 schrieb Leo Liu:
> This is the case when the "00 00 03" is very close to the beginning of
> nal unit header
>
> v2: move the check to rbsp init
>
> Signed-off-by: Leo Liu <leo.liu at amd.com>
> ---
>   src/gallium/auxiliary/vl/vl_rbsp.h | 11 +++++++++++
>   1 file changed, 11 insertions(+)
>
> diff --git a/src/gallium/auxiliary/vl/vl_rbsp.h b/src/gallium/auxiliary/vl/vl_rbsp.h
> index 7867238..c175e23 100644
> --- a/src/gallium/auxiliary/vl/vl_rbsp.h
> +++ b/src/gallium/auxiliary/vl/vl_rbsp.h
> @@ -61,7 +61,18 @@ static inline void vl_rbsp_init(struct vl_rbsp *rbsp, struct vl_vlc *nal, unsign
>      while (vl_vlc_search_byte(nal, num_bits, 0x00)) {
>         if (vl_vlc_peekbits(nal, 24) == 0x000001 ||
>             vl_vlc_peekbits(nal, 32) == 0x00000001) {
> +         unsigned valid;
> +         int i;
> +
>            vl_vlc_limit(&rbsp->nal, bits_left - vl_vlc_bits_left(nal));
> +         valid = vl_vlc_valid_bits(&rbsp->nal);
> +         /* search for the emulation prevention three byte */
> +         for (i = 24; i <= valid; i += 8) {
> +            if ((vl_vlc_peekbits(&rbsp->nal, i) & 0xffffff) == 0x3) {
> +               vl_vlc_removebits(&rbsp->nal, i - 8, 8);
> +               i += 8;
> +            }
> +         }

Mhm, I think that isn't 100% correct either.

We return inside the loop only when we find the next NAL unit after the 
current one, but if this is the last one that isn't the case.

>            return;

I think that just replacing thing return with a break and moving the 
code after the while should do the trick.

Regards,
Christian.

>         }
>         vl_vlc_eatbits(nal, 8);