[FFmpeg-devel] [PATCH] avcodec/mpeg12dec: report error when picture type is unknown and err_detect is EXPLODE

[James Almer]

On 7/31/2021 10:54 PM, Marton Balint wrote:
> Signed-off-by: Marton Balint <cus at passwd.hu>
> ---
>   libavcodec/mpeg12dec.c | 10 ++++++++--
>   1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/libavcodec/mpeg12dec.c b/libavcodec/mpeg12dec.c
> index 858dca660c..129dc1c2aa 100644
> --- a/libavcodec/mpeg12dec.c
> +++ b/libavcodec/mpeg12dec.c
> @@ -1529,7 +1529,7 @@ static void mpeg_decode_quant_matrix_extension(MpegEncContext *s)
>           load_matrix(s, s->chroma_inter_matrix, NULL, 0);
>   }
>   
> -static void mpeg_decode_picture_coding_extension(Mpeg1Context *s1)
> +static int mpeg_decode_picture_coding_extension(Mpeg1Context *s1)
>   {
>       MpegEncContext *s = &s1->mpeg_enc_ctx;
>   
> @@ -1541,6 +1541,8 @@ static void mpeg_decode_picture_coding_extension(Mpeg1Context *s1)
>       if (!s->pict_type && s1->mpeg_enc_ctx_allocated) {
>           av_log(s->avctx, AV_LOG_ERROR,
>                  "Missing picture start code, guessing missing values\n");

The guessing part will no longer be true when explode is set.

> +        if (s->avctx->err_recognition & AV_EF_EXPLODE)
> +            return AVERROR_INVALIDDATA;
>           if (s->mpeg_f_code[1][0] == 15 && s->mpeg_f_code[1][1] == 15) {
>               if (s->mpeg_f_code[0][0] == 15 && s->mpeg_f_code[0][1] == 15)
>                   s->pict_type = AV_PICTURE_TYPE_I;
> @@ -1586,6 +1588,8 @@ static void mpeg_decode_picture_coding_extension(Mpeg1Context *s1)
>       ff_dlog(s->avctx, "alternate_scan=%d\n", s->alternate_scan);
>       ff_dlog(s->avctx, "frame_pred_frame_dct=%d\n", s->frame_pred_frame_dct);
>       ff_dlog(s->avctx, "progressive_frame=%d\n", s->progressive_frame);
> +
> +    return 0;
>   }
>   
>   static int mpeg_field_start(MpegEncContext *s, const uint8_t *buf, int buf_size)
> @@ -2599,7 +2603,9 @@ static int decode_chunks(AVCodecContext *avctx, AVFrame *picture,
>                   break;
>               case 0x8:
>                   if (last_code == PICTURE_START_CODE) {
> -                    mpeg_decode_picture_coding_extension(s);
> +                    int ret = mpeg_decode_picture_coding_extension(s);
> +                    if (ret < 0)
> +                       return ret;
>                   } else {
>                       av_log(avctx, AV_LOG_ERROR,
>                              "ignoring pic cod ext after %X\n", last_code);
>