[FFmpeg-devel] [PATCH 1/2] avfilter/vf_fps: add way to get CFR output without knowing input frame rate

[Paul B Mahol]

On 10/29/19, Gyan <ffmpeg at gyani.pro> wrote:
>
>
> On 29-10-2019 07:17 PM, Paul B Mahol wrote:
>> Signed-off-by: Paul B Mahol <onemda at gmail.com>
>> ---
>>   doc/filters.texi     |  3 +++
>>   libavfilter/vf_fps.c | 10 +++++++++-
>>   2 files changed, 12 insertions(+), 1 deletion(-)
>>
>> diff --git a/doc/filters.texi b/doc/filters.texi
>> index 11f715319a..1e815bf940 100644
>> --- a/doc/filters.texi
>> +++ b/doc/filters.texi
>> @@ -10737,6 +10737,9 @@ Pass through last frame if input duration has not
>> been reached yet.
>>   @end table
>>   The default is @code{round}.
>>
>> + at item input
>> +Pick output frame rate from input if it is available. The default is
>> disabled.
>> +Useful to change input to constant frame rate without needing to know
>> input frame rate.
>>   @end table
>>
>>   Alternatively, the options can be specified as a flat string:
>> diff --git a/libavfilter/vf_fps.c b/libavfilter/vf_fps.c
>> index cf1e36726a..3561332f0e 100644
>> --- a/libavfilter/vf_fps.c
>> +++ b/libavfilter/vf_fps.c
>> @@ -70,6 +70,7 @@ typedef struct FPSContext {
>>       int frames_out;            ///< number of frames on output
>>       int dup;                   ///< number of frames duplicated
>>       int drop;                  ///< number of framed dropped
>> +    int input;                 ///< should filter use input framerate if
>> one is set
>>   } FPSContext;
>>
>>   #define OFFSET(x) offsetof(FPSContext, x)
>> @@ -87,6 +88,7 @@ static const AVOption fps_options[] = {
>>       { "eof_action", "action performed for last frame",
>> OFFSET(eof_action), AV_OPT_TYPE_INT, { .i64 = EOF_ACTION_ROUND }, 0,
>> EOF_ACTION_NB-1, V|F, "eof_action" },
>>           { "round", "round similar to other frames",  0,
>> AV_OPT_TYPE_CONST, { .i64 = EOF_ACTION_ROUND }, 0, 0, V|F, "eof_action" },
>>           { "pass",  "pass through last frame",        0,
>> AV_OPT_TYPE_CONST, { .i64 = EOF_ACTION_PASS  }, 0, 0, V|F, "eof_action" },
>> +    { "input", "use input framerate is available", OFFSET(input),
>> AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, V|F },
>>       { NULL }
>>   };
>>
>> @@ -99,7 +101,8 @@ static av_cold int init(AVFilterContext *ctx)
>>       s->status_pts   = AV_NOPTS_VALUE;
>>       s->next_pts     = AV_NOPTS_VALUE;
>>
>> -    av_log(ctx, AV_LOG_VERBOSE, "fps=%d/%d\n", s->framerate.num,
>> s->framerate.den);
>> +    if (!s->input)
>> +        av_log(ctx, AV_LOG_VERBOSE, "fps=%d/%d\n", s->framerate.num,
>> s->framerate.den);
>>       return 0;
>>   }
>>
>> @@ -153,8 +156,13 @@ static int config_props(AVFilterLink* outlink)
>>       AVFilterLink    *inlink = ctx->inputs[0];
>>       FPSContext      *s      = ctx->priv;
>>
>> +    if (s->input && inlink->frame_rate.num > 0 && inlink->frame_rate.den
>> > 0) {
>> +        outlink->time_base  = av_inv_q(inlink->frame_rate);
>> +        outlink->frame_rate = inlink->frame_rate;
>
> Maybe add some sanity checks for very high frame rates e.g. some WebMs
> whose video fps is detected as 1000.

Not needed.

>
>> +    } else {
>>       outlink->time_base  = av_inv_q(s->framerate);
>>       outlink->frame_rate = s->framerate;
>> +    }
>>
>>       /* Calculate the input and output pts offsets for start_time */
>>       if (s->start_time != DBL_MAX && s->start_time != AV_NOPTS_VALUE) {
>
> Gyan
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