[FFmpeg-devel] [PATCH] ffv1enc: reduce stack usage.

[wm4]

On Tue,  2 Sep 2014 20:32:57 +0200
Reimar Döffinger <Reimar.Doeffinger at gmx.de> wrote:

> A bit more complex than e.g. adding it to the context, but
> using the context for something that will be used only during
> initialization seemed a bit wasteful.
> 
> Signed-off-by: Reimar Döffinger <Reimar.Doeffinger at gmx.de>
> ---
>  libavcodec/ffv1enc.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/libavcodec/ffv1enc.c b/libavcodec/ffv1enc.c
> index b63ed42..4611f94 100644
> --- a/libavcodec/ffv1enc.c
> +++ b/libavcodec/ffv1enc.c
> @@ -862,9 +862,11 @@ static av_cold int encode_init(AVCodecContext *avctx)
>      }
>      if (avctx->stats_in) {
>          char *p = avctx->stats_in;
> -        uint8_t best_state[256][256];
> +        uint8_t (*best_state)[256] = av_malloc_array(256, 256);
>          int gob_count = 0;
>          char *next;
> +	if (!best_state)
> +            return AVERROR(ENOMEM);
>  
>          av_assert0(s->version >= 2);
>  
> @@ -875,6 +877,7 @@ static av_cold int encode_init(AVCodecContext *avctx)
>                      if (next == p) {
>                          av_log(avctx, AV_LOG_ERROR,
>                                 "2Pass file invalid at %d %d [%s]\n", j, i, p);
> +                        av_freep(&best_state);
>                          return AVERROR_INVALIDDATA;
>                      }
>                      p = next;
> @@ -888,6 +891,7 @@ static av_cold int encode_init(AVCodecContext *avctx)
>                                  av_log(avctx, AV_LOG_ERROR,
>                                         "2Pass file invalid at %d %d %d %d [%s]\n",
>                                         i, j, k, m, p);
> +                                av_freep(&best_state);
>                                  return AVERROR_INVALIDDATA;
>                              }
>                              p = next;
> @@ -896,6 +900,7 @@ static av_cold int encode_init(AVCodecContext *avctx)
>              gob_count = strtol(p, &next, 0);
>              if (next == p || gob_count <= 0) {
>                  av_log(avctx, AV_LOG_ERROR, "2Pass file invalid\n");
> +                av_freep(&best_state);
>                  return AVERROR_INVALIDDATA;
>              }
>              p = next;
> @@ -933,6 +938,7 @@ static av_cold int encode_init(AVCodecContext *avctx)
>                  }
>              }
>          }
> +        av_freep(&best_state);
>      }
>  
>      if (s->version > 1) {

Is there any specific purpose to these changes? Sure, 64KB stack is
pushing a bit, but it should be fine on all normal systems.