Re: [FFmpeg-devel] [PATCH 1/6] swscale/utils: Factor initializing single slice context out

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

Andreas Rheinhardt:
> Initializing slice threads currently uses the function
> (sws_init_context()) that is also used for initializing
> user-facing contexts with the only difference being that
> nb_threads is set to one before initializing the slice contexts.
> 
> Yet sws_init_context() also initializes lots of stuff
> that is not slice-dependent, i.e. (src|dst)Range. This
> currently only works because the code sets these fields
> to the same values for all slice contexts. This is not
> nice; even worse, it entails that log messages are printed
> once per slice context (and therefore fill the screen).
> 
> This commit lays the groundwork to fix this.
> 
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
> ---
>  libswscale/utils.c | 31 +++++++++++++++++++++----------
>  1 file changed, 21 insertions(+), 10 deletions(-)
> 
> diff --git a/libswscale/utils.c b/libswscale/utils.c
> index 85640a143f..c6fa07f752 100644
> --- a/libswscale/utils.c
> +++ b/libswscale/utils.c
> @@ -1268,6 +1268,9 @@ static enum AVPixelFormat alphaless_fmt(enum AVPixelFormat fmt)
>      }
>  }
>  
> +static int sws_init_single_context(SwsContext *c, SwsFilter *srcFilter,
> +                                   SwsFilter *dstFilter);
> +
>  static int context_init_threaded(SwsContext *c,
>                                   SwsFilter *src_filter, SwsFilter *dst_filter)
>  {
> @@ -1301,7 +1304,7 @@ static int context_init_threaded(SwsContext *c,
>  
>          c->slice_ctx[i]->nb_threads = 1;
>  
> -        ret = sws_init_context(c->slice_ctx[i], src_filter, dst_filter);
> +        ret = sws_init_single_context(c->slice_ctx[i], src_filter, dst_filter);
>          if (ret < 0)
>              return ret;
>  
> @@ -1322,8 +1325,8 @@ static int context_init_threaded(SwsContext *c,
>      return 0;
>  }
>  
> -av_cold int sws_init_context(SwsContext *c, SwsFilter *srcFilter,
> -                             SwsFilter *dstFilter)
> +static av_cold int sws_init_single_context(SwsContext *c, SwsFilter *srcFilter,
> +                                           SwsFilter *dstFilter)
>  {
>      int i;
>      int usesVFilter, usesHFilter;
> @@ -1344,13 +1347,6 @@ av_cold int sws_init_context(SwsContext *c, SwsFilter *srcFilter,
>      static const float float_mult = 1.0f / 255.0f;
>      static AVOnce rgb2rgb_once = AV_ONCE_INIT;
>  
> -    if (c->nb_threads != 1) {
> -        ret = context_init_threaded(c, srcFilter, dstFilter);
> -        if (ret < 0 || c->nb_threads > 1)
> -            return ret;
> -        // threading disabled in this build, init as single-threaded
> -    }
> -
>      cpu_flags = av_get_cpu_flags();
>      flags     = c->flags;
>      emms_c();
> @@ -2054,6 +2050,21 @@ fail: // FIXME replace things by appropriate error codes
>      return ret;
>  }
>  
> +av_cold int sws_init_context(SwsContext *c, SwsFilter *srcFilter,
> +                             SwsFilter *dstFilter)
> +{
> +    int ret;
> +
> +    if (c->nb_threads != 1) {
> +        ret = context_init_threaded(c, srcFilter, dstFilter);
> +        if (ret < 0 || c->nb_threads > 1)
> +            return ret;
> +        // threading disabled in this build, init as single-threaded
> +    }
> +
> +    return sws_init_single_context(c, srcFilter, dstFilter);
> +}
> +
>  SwsContext *sws_alloc_set_opts(int srcW, int srcH, enum AVPixelFormat srcFormat,
>                                 int dstW, int dstH, enum AVPixelFormat dstFormat,
>                                 int flags, const double *param)

Will apply this patchset tomorrow unless there are objections.

- Andreas

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