Hi, Thank you for your review.
It seems your mail did not reach the ML for whatever reason. I have ensured your comments are all left verbatim below so that others may read them. On 29/12/2024 03:44, Nuo Mi wrote: > Hi Frank, > Thank you for the patch. > > On Sun, Dec 22, 2024 at 9:40 PM Frank Plowman <p...@frankplowman.com > <mailto:p...@frankplowman.com>> wrote: >> >> When the current subpicture has sps_subpic_treated_as_pic_flag >> equal to >> 1, motion vectors are cropped such that they cannot point to >> other >> subpictures. This was accounted for in the prediction logic, but >> not >> in pred_get_y, which is used by the scheduling logic to determine >> which >> parts of the reference pictures must have been reconstructed >> before >> inter prediction of a subsequent frame may begin. Consequently, >> where a >> motion vector pointed to a location significantly above the >> current >> subpicture, there was the possibility of a race condition. Patch >> fixes >> this by cropping the motion vector to the current subpicture in >> pred_get_y. >> >> Signed-off-by: Frank Plowman <p...@frankplowman.com >> <mailto:p...@frankplowman.com>> >> --- >> You can reproduce this issue with the bitstream available here: >> https://chromium.googlesource.com/chromium/src/+/lkgr/media/test/ >> data/vvc_frames_with_ltr.vvc?format=TEXT <https:// >> chromium.googlesource.com/chromium/src/+/lkgr/media/test/data/ >> vvc_frames_with_ltr.vvc?format=TEXT> >> Note this link downloads the file in base 64 format rather than >> binary. >> You can use base64 -d <BASE 64 FILE> > <BINARY FILE> to convert >> it to >> binary. The issue does not reproduce very reliably with a normal >> number >> of threads. For better reproducibility, run ffmpeg with 100+ >> threads. >> --- >> libavcodec/vvc/ctu.c | 30 +++++++++++++++++++----------- >> 1 file changed, 19 insertions(+), 11 deletions(-) >> >> diff --git a/libavcodec/vvc/ctu.c b/libavcodec/vvc/ctu.c >> index f80bce637c..6857c79f2b 100644 >> --- a/libavcodec/vvc/ctu.c >> +++ b/libavcodec/vvc/ctu.c >> @@ -2393,23 +2393,30 @@ static int has_inter_luma(const >> CodingUnit *cu) >> return cu->pred_mode != MODE_INTRA && cu->pred_mode != >> MODE_PLT >> && cu->tree_type != DUAL_TREE_CHROMA; >> } >> >> -static int pred_get_y(const int y0, const Mv *mv, const int >> height) >> +static int pred_get_y(const VVCLocalContext *lc, const int y0, >> const Mv *mv, const int height, const VVCFrame *src_frame) >> { >> - return FFMAX(0, y0 + (mv->y >> 4) + height); >> + const VVCSPS *sps = src_frame->sps; >> + const VVCPPS *pps = src_frame->pps; >> + const int subpic_idx = lc->sc->sh.r->curr_subpic_idx; >> + const int subpic_t = pps->subpic_y[subpic_idx]; > > _t reserved by types, line int8_t Good catch! Could you rename this to subpic_top locally when you commit to avoid sending a v2? Alternatively, I have fixed it locally in the case a v2 is needed for other reasons. > >> + const int subpic_treated_as_pic = sps->r- >> >sps_subpic_treated_as_pic_flag[subpic_idx]; >> + return FFMAX(subpic_treated_as_pic ? subpic_t : 0, y0 + (mv->y >> >> 4) + height); > > Clipping to the subpicture bottom might be better, as y + (mv->y >> 4) + > height could be much smaller than the bottom boundary. The pathological case only occurs when the clipping causes the y-coordinate of the referenced area to increase. The MV is only clipped to the bottom boundary (specifically to subpic_bottom - height) in the case y + (mv->y >> 4) + height > subpic_bottom hence the clipped y is less than the unclipped y and the issue does not occur. Clipping to the subpicture bottom would result in reduced performance as it would add unnecessary dependencies, particularly for single-subpicture sequences which make up the majority of sequences. > >> } >> >> -static void cu_get_max_y(const CodingUnit *cu, int max_y[2] >> [VVC_MAX_REF_ENTRIES], const VVCFrameContext *fc) >> +static void cu_get_max_y(const VVCLocalContext *lc, const >> CodingUnit *cu, int max_y[2][VVC_MAX_REF_ENTRIES]) >> { >> + const VVCFrameContext *fc = lc->fc; >> const PredictionUnit *pu = &cu->pu; >> >> if (pu->merge_gpm_flag) { >> for (int i = 0; i < FF_ARRAY_ELEMS(pu->gpm_mv); i++) { >> - const MvField *mvf = pu->gpm_mv + i; >> - const int lx = mvf->pred_flag - PF_L0; >> - const int idx = mvf->ref_idx[lx]; >> - const int y = pred_get_y(cu->y0, mvf->mv + >> lx, >> cu->cb_height); >> + const MvField *mvf = pu->gpm_mv + i; >> + const int lx = mvf->pred_flag - PF_L0; >> + const int idx = mvf->ref_idx[lx]; >> + const VVCRefPic *refp = lc->sc->rpl[lx].refs + idx; >> + const int y = pred_get_y(lc, cu->y0, mvf->> >mv >> + lx, cu->cb_height, refp->ref); >> >> - max_y[lx][idx] = FFMAX(max_y[lx][idx], y); >> + max_y[lx][idx] = FFMAX(max_y[lx][idx], y); >> >> } >> } else { >> const MotionInfo *mi = &pu->mi; >> @@ -2424,8 +2431,9 @@ static void cu_get_max_y(const CodingUnit >> *cu, >> int max_y[2][VVC_MAX_REF_ENTRIES] >> for (int lx = 0; lx < 2; lx++) { >> const PredFlag mask = 1 << lx; >> if (mvf->pred_flag & mask) { >> - const int idx = mvf->ref_idx[lx]; >> - const int y = pred_get_y(y0, mvf->mv >> + >> lx, sbh); >> + const int idx = mvf- >> >ref_idx[lx]; >> + const VVCRefPic *refp = lc->sc- >> >rpl[lx].refs + idx; >> + int y = pred_get_y(lc, >> y0, >> mvf->mv + lx, sbh, refp->ref); >> >> max_y[lx][idx] = FFMAX(max_y[lx][idx], >> y + >> max_dmvr_off); >> } >> @@ -2452,7 +2460,7 @@ static void ctu_get_pred(VVCLocalContext >> *lc, >> const int rs) >> >> while (cu) { >> if (has_inter_luma(cu)) { >> - cu_get_max_y(cu, ctu->max_y, fc); >> + cu_get_max_y(lc, cu, ctu->max_y); >> ctu->has_dmvr |= cu->pu.dmvr_flag; >> } >> cu = cu->next; >> -- >> 2.47.0 >> -- Frank _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
