[FFmpeg-devel] [PATCH 1/3] avcodec/ass: Faster ff_ass_add_rect()

[James Almer]

On 12/19/2021 8:56 PM, Michael Niedermayer wrote:
> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> ---
>   libavcodec/ass.c | 33 +++++++++++++++++++++++++++------
>   libavcodec/ass.h |  7 +++++++
>   2 files changed, 34 insertions(+), 6 deletions(-)
> 
> diff --git a/libavcodec/ass.c b/libavcodec/ass.c
> index 725e4d42ba1..06714678722 100644
> --- a/libavcodec/ass.c
> +++ b/libavcodec/ass.c
> @@ -114,17 +114,31 @@ char *ff_ass_get_dialog(int readorder, int layer, const char *style,
>                          speaker ? speaker : "", text);
>   }
>   
> -int ff_ass_add_rect(AVSubtitle *sub, const char *dialog,
> +int ff_ass_add_rect2(AVSubtitle *sub, const char *dialog,
>                       int readorder, int layer, const char *style,
> -                    const char *speaker)
> +                    const char *speaker, unsigned *nb_rect_allocated)
>   {
> -    AVSubtitleRect **rects, *rect;
> +    AVSubtitleRect **rects = sub->rects, *rect;
>       char *ass_str;
> +    uint64_t new_nb = 0;
>   
> -    rects = av_realloc_array(sub->rects, sub->num_rects+1, sizeof(*sub->rects));
> -    if (!rects)
> +    if (sub->num_rects >= UINT_MAX)
>           return AVERROR(ENOMEM);
> -    sub->rects = rects;
> +
> +    if (nb_rect_allocated && *nb_rect_allocated <= sub->num_rects) {
> +        new_nb = FFMIN(sub->num_rects + sub->num_rects/16LL + 1, UINT_MAX);

Isn't this what av_fast_realloc() is for?

> +    } else if (!nb_rect_allocated)
> +        new_nb = sub->num_rects + 1LL;
> +
> +    if (new_nb) {
> +        rects = av_realloc_array(rects, new_nb, sizeof(*sub->rects));
> +        if (!rects)
> +            return AVERROR(ENOMEM);
> +        if (nb_rect_allocated)
> +            *nb_rect_allocated = new_nb;
> +        sub->rects = rects;
> +    }
> +
>       rect       = av_mallocz(sizeof(*rect));
>       if (!rect)
>           return AVERROR(ENOMEM);
> @@ -137,6 +151,13 @@ int ff_ass_add_rect(AVSubtitle *sub, const char *dialog,
>       return 0;
>   }
>   
> +int ff_ass_add_rect(AVSubtitle *sub, const char *dialog,
> +                    int readorder, int layer, const char *style,
> +                    const char *speaker)
> +{
> +    return ff_ass_add_rect2(sub, dialog, readorder, layer, style, speaker, NULL);
> +}
> +
>   void ff_ass_decoder_flush(AVCodecContext *avctx)
>   {
>       FFASSDecoderContext *s = avctx->priv_data;
> diff --git a/libavcodec/ass.h b/libavcodec/ass.h
> index 2c260e4e785..4dffe923d9f 100644
> --- a/libavcodec/ass.h
> +++ b/libavcodec/ass.h
> @@ -118,6 +118,13 @@ int ff_ass_add_rect(AVSubtitle *sub, const char *dialog,
>                       int readorder, int layer, const char *style,
>                       const char *speaker);
>   
> +/**
> + * Add an ASS dialog to a subtitle.
> + */
> +int ff_ass_add_rect2(AVSubtitle *sub, const char *dialog,
> +                     int readorder, int layer, const char *style,
> +                     const char *speaker, unsigned *nb_rect_allocated);
> +
>   /**
>    * Helper to flush a text subtitles decoder making use of the
>    * FFASSDecoderContext.