diff --git a/doc/filters.texi b/doc/filters.texi
index ad8b5daee9..583cc30cb0 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -5466,6 +5466,13 @@ previous output PTS
 
 @item PREV_OUTT
 previous output time in seconds
+
+@item RTCTIME
+wallclock (RTC) time in microseconds
+
+@item RTCSTART
+wallclock (RTC) time at the start of the movie in microseconds
+
 @end table
 
 @subsection Examples
@@ -5506,6 +5513,12 @@ Apply an offset of 10 seconds to the input PTS:
 @example
 setpts=PTS+10/TB
 @end example
+
+@item
+generate timestamps from a "live source" and rebase onto the current timebase
+@example
+setpts='(RTCTIME - RTCSTART) / (TB * 1000000)'
+@end example
 @end itemize
 
 @section ebur128
diff --git a/libavfilter/f_setpts.c b/libavfilter/f_setpts.c
index db1d91cf4e..1c2edb826b 100644
--- a/libavfilter/f_setpts.c
+++ b/libavfilter/f_setpts.c
@@ -27,6 +27,7 @@
 #include "libavutil/eval.h"
 #include "libavutil/internal.h"
 #include "libavutil/mathematics.h"
+#include "libavutil/time.h"
 #include "avfilter.h"
 #include "internal.h"
 #include "audio.h"
@@ -49,6 +50,8 @@ static const char *const var_names[] = {
     "STARTT",      ///< time at start of movie
     "T",           ///< original time in the file of the frame
     "TB",          ///< timebase
+    "RTCTIME",     ///< wallclock (RTC) time in micro seconds
+    "RTCSTART",    ///< wallclock (RTC) time at the start of the movie in micro seconds
     NULL
 };
 
@@ -69,6 +72,8 @@ enum var_name {
     VAR_STARTT,
     VAR_T,
     VAR_TB,
+    VAR_RTCTIME,
+    VAR_RTCSTART,
     VAR_VARS_NB
 };
 
@@ -103,6 +108,7 @@ static int config_input(AVFilterLink *inlink)
 
     setpts->type = inlink->type;
     setpts->var_values[VAR_TB] = av_q2d(inlink->time_base);
+    setpts->var_values[VAR_RTCSTART] = av_gettime();
 
     setpts->var_values[VAR_SAMPLE_RATE] =
         setpts->type == AVMEDIA_TYPE_AUDIO ? inlink->sample_rate : NAN;
@@ -145,6 +151,7 @@ static int filter_frame(AVFilterLink *inlink, AVFilterBufferRef *frame)
     setpts->var_values[VAR_PTS       ] = TS2D(frame->pts);
     setpts->var_values[VAR_T         ] = TS2T(frame->pts, inlink->time_base);
     setpts->var_values[VAR_POS       ] = frame->pos == -1 ? NAN : frame->pos;
+    setpts->var_values[VAR_RTCTIME   ] = av_gettime();
 
     switch (inlink->type) {
     case AVMEDIA_TYPE_VIDEO: