[FFmpeg-devel] [PATCH 3/4] avcodec/mpegutils: consolidate single byte av_log()

[James Almer]

On 9/3/2021 3:39 PM, Michael Niedermayer wrote:
> Fixes: Timeout (56sec -> 15sec)
> Fixes: 37141/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MPEG4_fuzzer-6192122867875840
> 
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> ---
>   libavcodec/mpegutils.c | 56 ++++++++++++++++++++++++------------------
>   1 file changed, 32 insertions(+), 24 deletions(-)
> 
> diff --git a/libavcodec/mpegutils.c b/libavcodec/mpegutils.c
> index e5105ecc58..e91c554781 100644
> --- a/libavcodec/mpegutils.c
> +++ b/libavcodec/mpegutils.c
> @@ -187,7 +187,6 @@ void ff_print_debug_info2(AVCodecContext *avctx, AVFrame *pict, uint8_t *mbskip_
>   
>           av_freep(&mvs);
>       }
> -

Stray change.

>       /* TODO: export all the following to make them accessible for users (and filters) */
>       if (avctx->hwaccel || !mbtype_table)
>           return;
> @@ -195,71 +194,80 @@ void ff_print_debug_info2(AVCodecContext *avctx, AVFrame *pict, uint8_t *mbskip_
>   
>       if (avctx->debug & (FF_DEBUG_SKIP | FF_DEBUG_QP | FF_DEBUG_MB_TYPE)) {
>           int x,y;
> +#define MB_STRING_SIZE 6
> +        char *mbstring = av_malloc(MB_STRING_SIZE * mb_width + 1);
> +        if (!mbstring)
> +            return;
>   
>           av_log(avctx, AV_LOG_DEBUG, "New frame, type: %c\n",
>                  av_get_picture_type_char(pict->pict_type));
>           for (y = 0; y < mb_height; y++) {
> +            char *mbs = mbstring;
>               for (x = 0; x < mb_width; x++) {
> +                av_assert0(mbs - mbstring <= MB_STRING_SIZE * x);
>                   if (avctx->debug & FF_DEBUG_SKIP) {
>                       int count = mbskip_table ? mbskip_table[x + y * mb_stride] : 0;
>                       if (count > 9)
>                           count = 9;
> -                    av_log(avctx, AV_LOG_DEBUG, "%1d", count);
> +                    *mbs++ = '0' + count;

This is ugly and not very obvious at first glance. Can you use lavu's 
bprint or something like that instead?

>                   }
>                   if (avctx->debug & FF_DEBUG_QP) {
> -                    av_log(avctx, AV_LOG_DEBUG, "%2d",
> -                           qscale_table[x + y * mb_stride]);
> +                    int q = qscale_table[x + y * mb_stride];
> +                    *mbs++ = '0' + q/10;
> +                    *mbs++ = '0' + q%10;
>                   }
>                   if (avctx->debug & FF_DEBUG_MB_TYPE) {
>                       int mb_type = mbtype_table[x + y * mb_stride];
>                       // Type & MV direction
>                       if (IS_PCM(mb_type))
> -                        av_log(avctx, AV_LOG_DEBUG, "P");
> +                        *mbs++ = 'P';
>                       else if (IS_INTRA(mb_type) && IS_ACPRED(mb_type))
> -                        av_log(avctx, AV_LOG_DEBUG, "A");
> +                        *mbs++ = 'A';
>                       else if (IS_INTRA4x4(mb_type))
> -                        av_log(avctx, AV_LOG_DEBUG, "i");
> +                        *mbs++ = 'i';
>                       else if (IS_INTRA16x16(mb_type))
> -                        av_log(avctx, AV_LOG_DEBUG, "I");
> +                        *mbs++ = 'I';
>                       else if (IS_DIRECT(mb_type) && IS_SKIP(mb_type))
> -                        av_log(avctx, AV_LOG_DEBUG, "d");
> +                        *mbs++ = 'd';
>                       else if (IS_DIRECT(mb_type))
> -                        av_log(avctx, AV_LOG_DEBUG, "D");
> +                        *mbs++ = 'D';
>                       else if (IS_GMC(mb_type) && IS_SKIP(mb_type))
> -                        av_log(avctx, AV_LOG_DEBUG, "g");
> +                        *mbs++ = 'g';
>                       else if (IS_GMC(mb_type))
> -                        av_log(avctx, AV_LOG_DEBUG, "G");
> +                        *mbs++ = 'G';
>                       else if (IS_SKIP(mb_type))
> -                        av_log(avctx, AV_LOG_DEBUG, "S");
> +                        *mbs++ = 'S';
>                       else if (!USES_LIST(mb_type, 1))
> -                        av_log(avctx, AV_LOG_DEBUG, ">");
> +                        *mbs++ = '>';
>                       else if (!USES_LIST(mb_type, 0))
> -                        av_log(avctx, AV_LOG_DEBUG, "<");
> +                        *mbs++ = '<';
>                       else {
>                           av_assert2(USES_LIST(mb_type, 0) && USES_LIST(mb_type, 1));
> -                        av_log(avctx, AV_LOG_DEBUG, "X");
> +                        *mbs++ = 'X';
>                       }
>   
>                       // segmentation
>                       if (IS_8X8(mb_type))
> -                        av_log(avctx, AV_LOG_DEBUG, "+");
> +                        *mbs++ = '+';
>                       else if (IS_16X8(mb_type))
> -                        av_log(avctx, AV_LOG_DEBUG, "-");
> +                        *mbs++ = '-';
>                       else if (IS_8X16(mb_type))
> -                        av_log(avctx, AV_LOG_DEBUG, "|");
> +                        *mbs++ = '|';
>                       else if (IS_INTRA(mb_type) || IS_16X16(mb_type))
> -                        av_log(avctx, AV_LOG_DEBUG, " ");
> +                        *mbs++ = ' ';
>                       else
> -                        av_log(avctx, AV_LOG_DEBUG, "?");
> +                        *mbs++ = '?';
>   
>   
>                       if (IS_INTERLACED(mb_type))
> -                        av_log(avctx, AV_LOG_DEBUG, "=");
> +                        *mbs++ = '=';
>                       else
> -                        av_log(avctx, AV_LOG_DEBUG, " ");
> +                        *mbs++ = ' ';
>                   }
>               }
> -            av_log(avctx, AV_LOG_DEBUG, "\n");
> +            *mbs++ = 0;
> +            av_log(avctx, AV_LOG_DEBUG, "%s\n", mbstring);
>           }
> +        av_freep(&mbstring);
>       }
>   }
>