[libav-devel] [PATCH] avfilter: allow setpts filter to use wallclock time for calculations

[Vladimir Pantelic]

I have a webcam that outputs raw MJPEG over HTTP and for which I need
to create timestamps in order to properly avplay or avconv the stream.
Thus I extended vf_setpts to allow to get the current wallclock time and
use that as a timestamp with:

        setpts='(GETTIME - STARTTIME) / (TB * 1000000)"

>From 7adfbdff0cb1d529364254ec4b242e89cfa753ec Mon Sep 17 00:00:00 2001
From: Vladimir Pantelic <vlado...@gmail.com>
Date: Wed, 23 Jan 2013 13:54:08 +0100
Subject: [PATCH] avfilter: allow setpts filter to use wallclock time for
 calculations

Signed-off-by: Vladimir Pantelic <vlado...@gmail.com>
---
 doc/filters.texi        |    9 +++++++++
 libavfilter/vf_setpts.c |    7 +++++++
 2 files changed, 16 insertions(+), 0 deletions(-)

diff --git a/doc/filters.texi b/doc/filters.texi
index 34db2f4..ff9764c 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -1864,6 +1864,12 @@ previous input PTS
 @item PREV_OUTPTS
 previous output PTS
 
+@item GETTIME
+current time in us
+
+@item STARTTIME
+current time at the start of the movie in us
+
 @end table
 
 Some examples follow:
@@ -1883,6 +1889,9 @@ setpts=N/(25*TB)
 
 # fixed rate 25 fps with some jitter
 setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))'
+
+# generate timestamps from a "live source" and rebase onto the current timebase
+setpts='(GETTIME - STARTTIME) / (TB * 1000000)"
 @end example
 
 @anchor{setsar}
diff --git a/libavfilter/vf_setpts.c b/libavfilter/vf_setpts.c
index 0c4881e..74dc583 100644
--- a/libavfilter/vf_setpts.c
+++ b/libavfilter/vf_setpts.c
@@ -29,6 +29,7 @@
 #include "libavutil/eval.h"
 #include "libavutil/internal.h"
 #include "libavutil/mathematics.h"
+#include "libavutil/time.h"
 #include "avfilter.h"
 #include "internal.h"
 #include "video.h"
@@ -45,6 +46,8 @@ static const char *const var_names[] = {
     "PTS",         ///< original pts in the file of the frame
     "STARTPTS",   ///< PTS at start of movie
     "TB",          ///< timebase
+    "GETTIME",     ///< current time in us
+    "STARTTIME",   ///< current time at the start of the movie in us
     NULL
 };
 
@@ -60,6 +63,8 @@ enum var_name {
     VAR_PTS,
     VAR_STARTPTS,
     VAR_TB,
+    VAR_GETTIME,
+    VAR_STARTTIME,
     VAR_VARS_NB
 };
 
@@ -94,6 +99,7 @@ static int config_input(AVFilterLink *inlink)
     SetPTSContext *setpts = inlink->dst->priv;
 
     setpts->var_values[VAR_TB] = av_q2d(inlink->time_base);
+    setpts->var_values[VAR_STARTTIME] = av_gettime();
 
     av_log(inlink->src, AV_LOG_VERBOSE, "TB:%f\n", setpts->var_values[VAR_TB]);
     return 0;
@@ -114,6 +120,7 @@ static int filter_frame(AVFilterLink *inlink, AVFilterBufferRef *frame)
     setpts->var_values[VAR_INTERLACED] = frame->video->interlaced;
     setpts->var_values[VAR_PTS       ] = TS2D(frame->pts);
     setpts->var_values[VAR_POS       ] = frame->pos == -1 ? NAN : frame->pos;
+    setpts->var_values[VAR_GETTIME   ] = av_gettime();
 
     d = av_expr_eval(setpts->expr, setpts->var_values, NULL);
     frame->pts = D2TS(d);
-- 
1.7.6.rc1.1.g2c162b


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