doc/filters: document asetpts in single place

Signed-off-by: Paul B Mahol <onemda@gmail.com>

doc/filters.texi

@@ -933,75 +933,6 @@ disable padding for the last frame, use:
 asetnsamples=n=1234:p=0
 @end example
 
-@section asetpts
-
-Change the PTS (presentation timestamp) of the input audio frames.
-
-This filter accepts the following options:
-
-@table @option
-
-@item expr
-The expression which is evaluated for each frame to construct its timestamp.
-
-@end table
-
-The expression is evaluated through the eval API and can contain the following
-constants:
-
-@table @option
-@item PTS
-the presentation timestamp in input
-
-@item PI
-Greek PI
-
-@item PHI
-golden ratio
-
-@item E
-Euler number
-
-@item N
-Number of the audio samples pass through the filter so far, starting at 0.
-
-@item S
-Number of the audio samples in the current frame.
-
-@item SR
-Audio sample rate.
-
-@item STARTPTS
-the PTS of the first frame
-
-@item PREV_INPTS
-previous input PTS
-
-@item PREV_OUTPTS
-previous output PTS
-
-@item RTCTIME
-wallclock (RTC) time in microseconds
-
-@item RTCSTART
-wallclock (RTC) time at the start of the movie in microseconds
-
-@end table
-
-Some examples follow:
-
-@example
-# start counting PTS from zero
-asetpts=expr=PTS-STARTPTS
-
-#generate timestamps by counting samples
-asetpts=expr=N/SR/TB
-
-# generate timestamps from a "live source" and rebase onto the current timebase
-asetpts='(RTCTIME - RTCSTART) / (TB * 1000000)"
-@end example
-
-
 @section asetrate
 
 Set the sample rate without altering the PCM data.
@@ -7975,16 +7906,17 @@ frame rate, only defined for constant frame-rate video
 the presentation timestamp in input
 
 @item N
-the count of the input frame, starting from 0.
+the count of the input frame for video or the number of consumed samples,
+not including the current frame for audio, starting from 0.
 
 @item NB_CONSUMED_SAMPLES
 the number of consumed samples, not including the current frame (only
 audio)
 
-@item NB_SAMPLES
+@item NB_SAMPLES, S
 the number of samples in the current frame (only audio)
 
-@item SAMPLE_RATE
+@item SAMPLE_RATE, SR
 audio sample rate
 
 @item STARTPTS
@@ -8070,6 +8002,13 @@ Generate timestamps from a "live source" and rebase onto the current timebase:
 @example
 setpts='(RTCTIME - RTCSTART) / (TB * 1000000)'
 @end example
+
+@item
+Generate timestamps by counting samples:
+@example
+asetpts=N/SR/TB
+@end example
+
 @end itemize
 
 @section settb, asettb