Re: [FFmpeg-devel] [PATCH] lavfi/vsrc_ddagrab: add an option to avoid duplicating frames

[Timo Rothenpieler <timo@rothenpieler.org>]

On 29.01.2024 20:03, Anton Khirnov wrote:
> Tested-by: Jiří Eliášek, Misha Aizatulin
> ---
>   doc/filters.texi           | 15 +++++++++++----
>   libavfilter/vsrc_ddagrab.c |  7 ++++++-
>   2 files changed, 17 insertions(+), 5 deletions(-)
> 
> diff --git a/doc/filters.texi b/doc/filters.texi
> index 1d70f4d934..b9b539acee 100644
> --- a/doc/filters.texi
> +++ b/doc/filters.texi
> @@ -28713,10 +28713,10 @@ it'll always be captured.
>   @item framerate
>   Maximum framerate at which the desktop will be captured - the interval between
>   successive frames will not be smaller than the inverse of the framerate. When
> -the desktop is not being updated often enough, the filter will duplicate
> -a previous frame. Note that there is no background buffering going on, so when
> -the filter is not polled often enough then the actual inter-frame interval may
> -be significantly larger.
> +@var{dup_frames} is true (the default) and the desktop is not being updated
> +often enough, the filter will duplicate a previous frame. Note that there is no
> +background buffering going on, so when the filter is not polled often enough
> +then the actual inter-frame interval may be significantly larger.
>   
>   Defaults to 30 FPS.
>   
> @@ -28749,6 +28749,13 @@ Passes all supported output formats to DDA and returns what DDA decides to use.
>   Filter initialization will fail if 10 bit format is requested but unavailable.
>   @end table
>   
> +@item dup_frames
> +When this option is set to true (the default), the filter will duplicate frames
> +when the desktop has not been updated in order to maintain approximately
> +constant target framerate. When this option is set to false, the filter will
> +wait for the desktop to be updated (inter-frame intervals may vary significantly
> +in this case).
> +
>   @end table
>   
>   @subsection Examples
> diff --git a/libavfilter/vsrc_ddagrab.c b/libavfilter/vsrc_ddagrab.c
> index 9c59faf53e..51e928d785 100644
> --- a/libavfilter/vsrc_ddagrab.c
> +++ b/libavfilter/vsrc_ddagrab.c
> @@ -101,6 +101,7 @@ typedef struct DdagrabContext {
>       int        out_fmt;
>       int        allow_fallback;
>       int        force_fmt;
> +    int        dup_frames;
>   } DdagrabContext;
>   
>   #define OFFSET(x) offsetof(DdagrabContext, x)
> @@ -124,6 +125,8 @@ static const AVOption ddagrab_options[] = {
>                                                      OFFSET(allow_fallback), AV_OPT_TYPE_BOOL,   { .i64 = 0    },       0,       1, FLAGS },
>       { "force_fmt",  "exclude BGRA from format list (experimental, discouraged by Microsoft)",
>                                                      OFFSET(force_fmt),  AV_OPT_TYPE_BOOL,       { .i64 = 0    },       0,       1, FLAGS },
> +    { "dup_frames", "duplicate frames to maintain framerate",
> +                                                   OFFSET(dup_frames), AV_OPT_TYPE_BOOL,       { .i64 = 1    },       0,       1, FLAGS },
>       { NULL }
>   };
>   
> @@ -1067,7 +1070,9 @@ static int ddagrab_request_frame(AVFilterLink *outlink)
>       now -= dda->first_pts;
>   
>       if (!dda->probed_texture) {
> -        ret = next_frame_internal(avctx, &cur_texture, 0);
> +        do {
> +            ret = next_frame_internal(avctx, &cur_texture, 0);
> +        } while (ret == AVERROR(EAGAIN) && !dda->dup_frames);
>       } else {
>           cur_texture = dda->probed_texture;
>           dda->probed_texture = NULL;

looks good to me
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