[FFmpeg-devel] Re: [PATCH v4] avfilter/vf_blackframe: add slice threading

[Michael Niedermayer via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

[-- Attachment #1.1: Type: text/plain, Size: 3447 bytes --]

Hi Raja

On Tue, Dec 23, 2025 at 10:14:41PM +0530, Raja Rathour via ffmpeg-devel wrote:
> ---
>  libavfilter/vf_blackframe.c | 80 ++++++++++++++++++++++++++++++++-----
>  1 file changed, 71 insertions(+), 9 deletions(-)
> 
> diff --git a/libavfilter/vf_blackframe.c b/libavfilter/vf_blackframe.c
> index f0aa53e133..f09d564bf7 100644
> --- a/libavfilter/vf_blackframe.c
> +++ b/libavfilter/vf_blackframe.c
> @@ -32,6 +32,7 @@
>  
>  #include "libavutil/internal.h"
>  #include "libavutil/opt.h"
> +#include "libavutil/mem.h"
>  #include "avfilter.h"
>  #include "filters.h"
>  #include "video.h"
> @@ -45,6 +46,14 @@ typedef struct BlackFrameContext {
>      unsigned int last_keyframe; ///< frame number of the last received key-frame
>  } BlackFrameContext;
>  
> +typedef struct ThreadData {
> +    const uint8_t *data; // Pointer to the image data
> +    int linesize;        // How wide is the memory line
> +    int bthresh;         // The black threshold
> +    int width;           // Image width
> +    unsigned int *counts; // POINTER to the array where threads write results
> +} ThreadData;
> +
>  static const enum AVPixelFormat pix_fmts[] = {
>      AV_PIX_FMT_YUV410P, AV_PIX_FMT_YUV420P, AV_PIX_FMT_GRAY8, AV_PIX_FMT_NV12,
>      AV_PIX_FMT_NV21, AV_PIX_FMT_YUV444P, AV_PIX_FMT_YUV422P, AV_PIX_FMT_YUV411P,
> @@ -55,22 +64,72 @@ static const enum AVPixelFormat pix_fmts[] = {
>      snprintf(buf, sizeof(buf), format, value);  \
>      av_dict_set(metadata, key, buf, 0)
>  
> +static int blackframe_slice(AVFilterContext *ctx, void *arg, int jobnr, int nb_jobs)
> +{
> +    ThreadData *td = arg;

> +    // --- C90 HARD FIX: ALL DECLARATIONS AT THE VERY TOP ---

remove useless comments, like this


> +    int slice_start, slice_end, x, y;
> +    const uint8_t *p;
> +    unsigned int local_nblack = 0;
> +    // ------------------------------------------------------
> +

> +    // Safety check
> +    if (!td || !td->data || !td->counts) return 0;

explain how these are possible conditions


> +
> +    slice_start = (ctx->inputs[0]->h * jobnr) / nb_jobs;
> +    slice_end   = (ctx->inputs[0]->h * (jobnr+1)) / nb_jobs;
> +    
> +    p = td->data + slice_start * td->linesize;
> +
> +    for (y = slice_start; y < slice_end; y++) {
> +        for (x = 0; x < td->width; x++)
> +            local_nblack += p[x] < td->bthresh;
> +        p += td->linesize;
> +    }
> +
> +    // Save my private count
> +    td->counts[jobnr] = local_nblack;
> +    return 0;
> +}
> +
>  static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
>  {
>      AVFilterContext *ctx = inlink->dst;
>      BlackFrameContext *s = ctx->priv;
> -    int x, i;
> +    // --- C90 HARD FIX: ALL DECLARATIONS AT THE VERY TOP ---
>      int pblack = 0;
> -    uint8_t *p = frame->data[0];
>      AVDictionary **metadata;
>      char buf[32];
> -
> -    for (i = 0; i < frame->height; i++) {
> -        for (x = 0; x < inlink->w; x++)
> -            s->nblack += p[x] < s->bthresh;
> -        p += frame->linesize[0];
> +    ThreadData td;
> +    int nb_threads;

> +    unsigned int *thread_counts;

please use a descriptive name that describes whats in the array

thx

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Republics decline into democracies and democracies degenerate into
despotisms. -- Aristotle

[-- Attachment #1.2: signature.asc --]
[-- Type: application/pgp-signature, Size: 195 bytes --]

[-- Attachment #2: Type: text/plain, Size: 163 bytes --]

_______________________________________________
ffmpeg-devel mailing list -- ffmpeg-devel@ffmpeg.org
To unsubscribe send an email to ffmpeg-devel-leave@ffmpeg.org