Re: [FFmpeg-devel] [PATCH v3] avfilter/setpts: add option to preserve framerate

[Marton Balint <cus@passwd.hu>]

On Thu, 23 Jan 2025, Gyan Doshi wrote:

> In f121d95, the outlink framerate was unconditionally unset.
> This breaks/bloats outputs from CFR muxers unless the user explicitly
> set a sane framerate. And the most common invocation for setpts seen in
> workflows, our docs and across the web is `PTS-STARTPTS` or others of the
> form `PTS+constant` which preserve the input framerate.
>
> Fixes #11428
> ---
> Corrected failing FATES
>
> doc/filters.texi          | 6 ++++++
> libavfilter/setpts.c      | 6 +++++-
> tests/fate/hevc.mak       | 2 +-
> tests/fate/mov.mak        | 2 +-
> tests/filtergraphs/setpts | 2 +-
> 5 files changed, 14 insertions(+), 4 deletions(-)
>
> diff --git a/doc/filters.texi b/doc/filters.texi
> index b926b865ae..fc352ed34a 100644
> --- a/doc/filters.texi
> +++ b/doc/filters.texi
> @@ -31478,6 +31478,12 @@ This filter accepts the following options:
> @item expr
> The expression which is evaluated for each frame to construct its timestamp.
>
> +@item keep_fps (@emph{video only})
> +Boolean option which determines if the original framerate is preserved.
> +If set to false, be advised that a sane frame rate should be explicitly
> +specified if output is sent to a constant frame rate muxer.
> +Default is @code{true}.
> +

Maybe it is more intuitive if the option is negated and is called "vfr" 
instead, as it actually makes the output Variable Frame Rate by resetting 
the frame rate?

> @end table
>
> The expression is evaluated through the eval API and can contain the following
> diff --git a/libavfilter/setpts.c b/libavfilter/setpts.c
> index 75d96247af..6609fe86aa 100644
> --- a/libavfilter/setpts.c
> +++ b/libavfilter/setpts.c
> @@ -98,6 +98,7 @@ typedef struct SetPTSContext {
>     const AVClass *class;
>     char *expr_str;
>     AVExpr *expr;
> +    int keep_fps;
>     double var_values[VAR_VARS_NB];
>     enum AVMediaType type;
> } SetPTSContext;
> @@ -153,8 +154,10 @@ static int config_input(AVFilterLink *inlink)
> static int config_output_video(AVFilterLink *outlink)
> {
>     FilterLink *l = ff_filter_link(outlink);
> +    SetPTSContext *s = outlink->src->priv;
>
> -    l->frame_rate = (AVRational){ 1, 0 };
> +    if (!s->keep_fps)
> +        l->frame_rate = (AVRational){ 1, 0 };
>
>     return 0;
> }
> @@ -320,6 +323,7 @@ static int process_command(AVFilterContext *ctx, const char *cmd, const char *ar
> #if CONFIG_SETPTS_FILTER
> static const AVOption setpts_options[] = {
>     { "expr", "Expression determining the frame timestamp", OFFSET(expr_str), AV_OPT_TYPE_STRING, { .str = "PTS" }, .flags = V|F|R },
> +    { "keep_fps", "Preserve input framerate", OFFSET(keep_fps), AV_OPT_TYPE_INT, { .i64 = 1 }, 0, 1, .flags = V|F },

AV_OPT_TYPE_BOOL.

>     { NULL }
> };
> AVFILTER_DEFINE_CLASS(setpts);
> diff --git a/tests/fate/hevc.mak b/tests/fate/hevc.mak
> index 9e6fd72618..7797df786d 100644
> --- a/tests/fate/hevc.mak
> +++ b/tests/fate/hevc.mak
> @@ -210,7 +210,7 @@ $(HEVC_TESTS_444_12BIT): SCALE_OPTS := -pix_fmt yuv444p12le -vf scale
> fate-hevc-conformance-%: CMD = framecrc -i $(TARGET_SAMPLES)/hevc-conformance/$(subst fate-hevc-conformance-,,$(@)).bit $(SCALE_OPTS)
> $(HEVC_TESTS_422_10BIN): CMD = framecrc -i $(TARGET_SAMPLES)/hevc-conformance/$(subst fate-hevc-conformance-,,$(@)).bin $(SCALE_OPTS)
> $(HEVC_TESTS_MULTIVIEW): CMD = framecrc -i $(TARGET_SAMPLES)/hevc-conformance/$(subst fate-hevc-conformance-,,$(@)).bit \
> -	-pix_fmt yuv420p -map "0:view:0" -map "0:view:1" -vf setpts=N
> +	-pix_fmt yuv420p -map "0:view:0" -map "0:view:1" -vf setpts=N:keep_fps=0
>
> FATE_HEVC-$(call FRAMECRC, HEVC, HEVC, HEVC_PARSER) += $(HEVC_TESTS_8BIT) $(HEVC_TESTS_444_8BIT)
> FATE_HEVC-$(call FRAMECRC, HEVC, HEVC, HEVC_PARSER SCALE_FILTER) +=         \
> diff --git a/tests/fate/mov.mak b/tests/fate/mov.mak
> index ca13ebfd44..e0e95d3af0 100644
> --- a/tests/fate/mov.mak
> +++ b/tests/fate/mov.mak
> @@ -225,7 +225,7 @@ fate-mov-pcm-remux: CMP = oneline
> fate-mov-pcm-remux: REF = e76115bc392d702da38f523216bba165
>
> FATE_MOV_FFMPEG-$(call TRANSCODE, RAWVIDEO, MOV, TESTSRC_FILTER SETPTS_FILTER) += fate-mov-vfr
> -fate-mov-vfr: CMD = md5 -filter_complex testsrc=size=2x2:duration=1,setpts=N*N -c rawvideo -fflags +bitexact -f mov
> +fate-mov-vfr: CMD = md5 -filter_complex testsrc=size=2x2:duration=1,setpts=N*N:keep_fps=0 -c rawvideo -fflags +bitexact -f mov
> fate-mov-vfr: CMP = oneline
> fate-mov-vfr: REF = 1558b4a9398d8635783c93f84eb5a60d
>
> diff --git a/tests/filtergraphs/setpts b/tests/filtergraphs/setpts
> index 79037d1b65..c217778bb4 100644
> --- a/tests/filtergraphs/setpts
> +++ b/tests/filtergraphs/setpts
> @@ -1,2 +1,2 @@
> settb=1/1000,
> -setpts=1/(35*TB) * (N + 0.05 * sin(N*2*PI/25))
> +setpts=1/(35*TB) * (N + 0.05 * sin(N*2*PI/25)):keep_fps=0
> -- 
> 2.46.1
>

Thanks,
Marton
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