[FFmpeg-devel] [PATCH] avcodec/cbs_h266: Fix regression in DVB clip introduced by 93281630a71c06642adfebebb0d4b105a4e02e91

[Frank Plowman]

On 10/11/2024 12:13, Nuo Mi wrote:
> This commit introduced a regression to VVC_HDR_UHDTV1_OpenGOP_3840x2160_50fps_HLG10_mosaic.ts.
> 
> Root Cause:
> The AV_CEIL_RSHIFT(a, b) macro uses bit tricks that work only when -a is a negative value.
> However, due to integer promotion rules, this behavior does not extend to the unsigned int type.
> 
> See "6.3.1.1 Boolean, characters, and integers" in the "ISO/IEC 9899" for details.
> 
> Reported-by: Frank Plowman <post at frankplowman.com>
> ---
>  libavcodec/cbs_h266_syntax_template.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/libavcodec/cbs_h266_syntax_template.c b/libavcodec/cbs_h266_syntax_template.c
> index b21d07491b..6b2d6534ef 100644
> --- a/libavcodec/cbs_h266_syntax_template.c
> +++ b/libavcodec/cbs_h266_syntax_template.c
> @@ -1162,7 +1162,7 @@ static int FUNC(sps)(CodedBitstreamContext *ctx, RWContext *rw,
>              for (i = 1; i <= current->sps_num_subpics_minus1; i++) {
>                  if (!current->sps_subpic_same_size_flag) {
>                      if (current->sps_pic_width_max_in_luma_samples > ctb_size_y) {
> -                        const unsigned int win_right_edge =
> +                        const int win_right_edge =
>                              current->sps_pic_width_max_in_luma_samples
>                            - current->sps_conf_win_right_offset * sub_width_c;
>                          us(wlen, sps_subpic_ctu_top_left_x[i], 0,
> @@ -1172,7 +1172,7 @@ static int FUNC(sps)(CodedBitstreamContext *ctx, RWContext *rw,
>                          infer(sps_subpic_ctu_top_left_x[i], 0);
>                      if (current->sps_pic_height_max_in_luma_samples >
>                          ctb_size_y) {
> -                        const unsigned int win_bottom_edge =
> +                        const int win_bottom_edge =
>                              current->sps_pic_height_max_in_luma_samples
>                            - current->sps_conf_win_bottom_offset * sub_height_c;
>                          us(hlen, sps_subpic_ctu_top_left_y[i], 0,
> @@ -1183,9 +1183,9 @@ static int FUNC(sps)(CodedBitstreamContext *ctx, RWContext *rw,
>                      if (i < current->sps_num_subpics_minus1 &&
>                          current->sps_pic_width_max_in_luma_samples >
>                          ctb_size_y) {
> -                        const unsigned int win_left_edge =
> +                        const int win_left_edge =
>                              current->sps_conf_win_left_offset * sub_width_c;
> -                        const unsigned int win_left_edge_ctus =
> +                        const int win_left_edge_ctus =
>                              AV_CEIL_RSHIFT(win_left_edge, ctb_log2_size_y);
>                          us(wlen, sps_subpic_width_minus1[i],
>                             win_left_edge_ctus > current->sps_subpic_ctu_top_left_x[i]
> @@ -1200,9 +1200,9 @@ static int FUNC(sps)(CodedBitstreamContext *ctx, RWContext *rw,
>                      if (i < current->sps_num_subpics_minus1 &&
>                          current->sps_pic_height_max_in_luma_samples >
>                          ctb_size_y) {
> -                        const unsigned int win_top_edge =
> +                        const int win_top_edge =
>                              current->sps_conf_win_top_offset * sub_height_c;
> -                        const unsigned int win_top_edge_ctus =
> +                        const int win_top_edge_ctus =
>                              AV_CEIL_RSHIFT(win_top_edge, ctb_log2_size_y);
>                          us(hlen, sps_subpic_height_minus1[i],
>                             win_top_edge_ctus > current->sps_subpic_ctu_top_left_y[i]

LGTM!