[FFmpeg-devel] [FFmpeg-cvslog] avcodec/mpeg12dec: do not discard older a53 captions

[James Almer]

> ffmpeg | branch: master | Paul B Mahol <onemda at gmail.com <https://ffmpeg.org/mailman/listinfo/ffmpeg-cvslog>> | Sat Jun 20 15:02:48 2020 +0200| [29ea4e1b3c511de0a406722bcfffa11604745451] | committer: Paul B Mahol
>
> avcodec/mpeg12dec: do not discard older a53 captions
>
> Fixes #6105.
>
> >/http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=29ea4e1b3c511de0a406722bcfffa11604745451
> /---
>
>  libavcodec/mpeg12dec.c | 22 +++++++++++++++++-----
>  1 file changed, 17 insertions(+), 5 deletions(-)
>
> diff --git a/libavcodec/mpeg12dec.c b/libavcodec/mpeg12dec.c
> index a12857d358..1253bde66e 100644
> --- a/libavcodec/mpeg12dec.c
> +++ b/libavcodec/mpeg12dec.c
> @@ -2242,13 +2242,25 @@ static int mpeg_decode_a53_cc(AVCodecContext *avctx,
>          /* extract A53 Part 4 CC data */
>          int cc_count = p[5] & 0x1f;
>          if (cc_count > 0 && buf_size >= 7 + cc_count * 3) {
> -            av_freep(&s1->a53_caption);
> -            s1->a53_caption_size = cc_count * 3;
> -            s1->a53_caption      = av_malloc(s1->a53_caption_size);
> +            if (s1->a53_caption && s1->a53_caption_size > 0) {
> +                uint8_t *old_a53_caption = s1->a53_caption;
> +                int old_a53_caption_size = s1->a53_caption_size;
> +
> +                s1->a53_caption_size = old_a53_caption_size + cc_count * 3;
> +                s1->a53_caption      = av_malloc(s1->a53_caption_size);
> +                if (s1->a53_caption) {
> +                    memcpy(s1->a53_caption, old_a53_caption, old_a53_caption_size);
> +                    memcpy(s1->a53_caption + old_a53_caption_size, p + 7, cc_count * 3);
> +                }
> +                av_freep(&old_a53_caption);
> +            } else {
> +                s1->a53_caption_size = cc_count * 3;
> +                s1->a53_caption      = av_malloc(s1->a53_caption_size);
> +                if (s1->a53_caption)
> +                    memcpy(s1->a53_caption, p + 7, s1->a53_caption_size);
> +            }
>              if (!s1->a53_caption) {
>                  s1->a53_caption_size = 0;
> -            } else {
> -                memcpy(s1->a53_caption, p + 7, s1->a53_caption_size);
>              }
>              avctx->properties |= FF_CODEC_PROPERTY_CLOSED_CAPTIONS;
>          }

You should have used av_realloc() instead (And you should have sent a
patch to the mailing list as well).
See h264_sei.c and hevc_sei.c