[FFmpeg-devel] [PATCH] avfilter/f_realtime: add option to scale speed

[Moritz Barsnick]

Signed-off-by: Moritz Barsnick <barsnick at gmx.net>
---
This adds two double precision divisions per frame, which seems acceptable.

I'm not sure scaling the limit by the factor is the correct idea.  It feels
right regarding the discontinuities, but not according to the limit option's
description.


 doc/filters.texi         | 4 ++++
 libavfilter/f_realtime.c | 7 +++++--
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/doc/filters.texi b/doc/filters.texi
index 65ce25bc18..60ebf2aa99 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -20829,6 +20829,10 @@ They accept the following options:
 @item limit
 Time limit for the pauses. Any pause longer than that will be considered
 a timestamp discontinuity and reset the timer. Default is 2 seconds.
+ at item speed
+Speed factor for processing. The value must be a float larger than zero.
+Values larger than 1.0 will speed up processing, smaller will slow it down.
+The @var{limit} is automatically adapted accordingly. Default is 1.0.
 @end table
 
 @anchor{select}
diff --git a/libavfilter/f_realtime.c b/libavfilter/f_realtime.c
index 171c16aaaa..8d4fbf642b 100644
--- a/libavfilter/f_realtime.c
+++ b/libavfilter/f_realtime.c
@@ -22,11 +22,13 @@
 #include "libavutil/time.h"
 #include "avfilter.h"
 #include "internal.h"
+#include <float.h>
 
 typedef struct RealtimeContext {
     const AVClass *class;
     int64_t delta;
     int64_t limit;
+    double speed;
     unsigned inited;
 } RealtimeContext;
 
@@ -36,7 +38,7 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
     RealtimeContext *s = ctx->priv;
 
     if (frame->pts != AV_NOPTS_VALUE) {
-        int64_t pts = av_rescale_q(frame->pts, inlink->time_base, AV_TIME_BASE_Q);
+        int64_t pts = av_rescale_q(frame->pts, inlink->time_base, AV_TIME_BASE_Q) / s->speed;
         int64_t now = av_gettime_relative();
         int64_t sleep = pts - now + s->delta;
         if (!s->inited) {
@@ -44,7 +46,7 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
             sleep = 0;
             s->delta = now - pts;
         }
-        if (sleep > s->limit || sleep < -s->limit) {
+        if (sleep > s->limit / s->speed || sleep < -s->limit / s->speed) {
             av_log(ctx, AV_LOG_WARNING,
                    "time discontinuity detected: %"PRIi64" us, resetting\n",
                    sleep);
@@ -65,6 +67,7 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
 #define FLAGS AV_OPT_FLAG_VIDEO_PARAM | AV_OPT_FLAG_AUDIO_PARAM | AV_OPT_FLAG_FILTERING_PARAM
 static const AVOption options[] = {
     { "limit", "sleep time limit", OFFSET(limit), AV_OPT_TYPE_DURATION, { .i64 = 2000000 }, 0, INT64_MAX, FLAGS },
+    { "speed", "speed factor", OFFSET(speed), AV_OPT_TYPE_DOUBLE, { .dbl = 1.0 }, DBL_MIN, DBL_MAX, FLAGS },
     { NULL }
 };
 
-- 
2.14.5