[FFmpeg-devel] [PATCH] avcodec/vvc decode: ALF filtering without CC-ALF

[Nuo Mi]

On Fri, Jan 3, 2025 at 1:56 AM Frank Plowman <post at frankplowman.com> wrote:

> Hi both,
>
> Can we push either of these?  Someone else has reported the same issue
> on Trac (#11325).  The difference between the two proposed
> implementations seems rather superficial to me.
>
Seems my suggestion would complicate ff_vvc_alf_filter, so I pushed Chris's
instead.
Thank you patch and ping.

>
> Thanks and happy new year,
> Frank
>
> On 03/12/2024 02:17, Nuo Mi wrote:
> > Hi Chris and Frank,
> > Thank you for the patch and review.
> >
> > On Mon, Dec 2, 2024 at 10:27 PM Chris Warrington via ffmpeg-devel <
> > ffmpeg-devel at ffmpeg.org> wrote:
> >
> >> When a stream has ALF filtering enabled but not CC-ALF, the CC-ALF set
> >> indexes alf->ctb_cc_idc are being read uninitialized during ALF
> filtering.
> >>
> >> This change initializes alf->ctb_cc_idc whenever ALF is enabled.
> >>
> >> Ref. https://trac.ffmpeg.org/ticket/11325
> >>
> >> ---
> >>  libavcodec/vvc/ctu.c | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/libavcodec/vvc/ctu.c b/libavcodec/vvc/ctu.c
> >> index a32abdeb62..c972dcc33e 100644
> >> --- a/libavcodec/vvc/ctu.c
> >> +++ b/libavcodec/vvc/ctu.c
> >> @@ -2288,6 +2288,7 @@ static void alf_params(VVCLocalContext *lc, const
> >> int rx, const int ry)
> >>      ALFParams *alf                = &CTB(fc->tab.alf, rx, ry);
> >>
> >>      alf->ctb_flag[LUMA] = alf->ctb_flag[CB] = alf->ctb_flag[CR] = 0;
> >> +    alf->ctb_cc_idc[0] = alf->ctb_cc_idc[1] = 0;
> >>
> > This will introduce two writes for all blocks, even if there is no CC
> ALF.
> > How about checking the sps_ccalf_enabled_flag in ff_vvc_alf_filter?
> >
> >>      if (sh->sh_alf_enabled_flag) {
> >>          alf->ctb_flag[LUMA] = ff_vvc_alf_ctb_flag(lc, rx, ry, LUMA);
> >>          if (alf->ctb_flag[LUMA]) {
> >> @@ -2318,7 +2319,6 @@ static void alf_params(VVCLocalContext *lc, const
> >> int rx, const int ry)
> >>          const uint8_t cc_enabled[] = { sh->sh_alf_cc_cb_enabled_flag,
> >> sh->sh_alf_cc_cr_enabled_flag };
> >>          const uint8_t cc_aps_id[]  = { sh->sh_alf_cc_cb_aps_id,
> >> sh->sh_alf_cc_cr_aps_id };
> >>          for (int i = 0; i < 2; i++) {
> >> -            alf->ctb_cc_idc[i] = 0;
> >>              if (cc_enabled[i]) {
> >>                  const VVCALF *aps = fc->ps.alf_list[cc_aps_id[i]];
> >>                  alf->ctb_cc_idc[i] = ff_vvc_alf_ctb_cc_idc(lc, rx, ry,
> i,
> >> aps->num_cc_filters[i]);
> >> --
>