On Sat, 1 Sep 2018, Bodecs Bela wrote:
Hi Balint,
2018.08.25. 20:35 keltezéssel, Marton Balint írta:
To delay filtering until a given wallclock timestamp.
Signed-off-by: Marton Balint <c...@passwd.hu>
---
doc/filters.texi | 36 ++++++++++
libavfilter/Makefile | 2 +
libavfilter/allfilters.c | 2 +
libavfilter/f_cue.c | 182 +++++++++++++++++++++++++++++++++++++++++++++++
libavfilter/version.h | 2 +-
5 files changed, 223 insertions(+), 1 deletion(-)
create mode 100644 libavfilter/f_cue.c
diff --git a/doc/filters.texi b/doc/filters.texi
index 32c95b591c..79eec0c808 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -551,6 +551,11 @@ Set LFO range.
Set LFO rate.
@end table
+@section acue
+
+Delay audio filtering until a given wallclock timestamp. See the @ref{cue}
+filter.
+
@section adeclick
Remove impulsive noise from input audio.
@@ -6987,6 +6992,37 @@ indicates 'never reset', and returns the largest area
encountered during
playback.
@end table
+@anchor{cue}
+@section cue
+
+Delay video filtering until a given wallclock timestamp. The filter first
+passes on @option{preroll} amount of frames, then it buffers at most
+@option{buffer} amount of frames and waits for the cue. After reaching the cue
+it forwards the buffered frames and also any subsequent frames coming in its
+input.
+
+The filter can be used synchronize the output of multiple ffmpeg processes for
+realtime output devices like decklink. By putting the delay in the filtering
+chain and pre-buffering frames the process can pass on data to output almost
+immediately after the target wallclock timestamp is reached.
+
+Perfect frame accuracy cannot be guaranteed, but the result is good enough for
+some use cases.
just for my curiousity, will you please give an example/use_case how to
use these filters?
Here is a shell script:
#!/bin/bash
UNIX_TIMESTAMP=`date +%s`
TS=$((UNIX_TIMESTAMP*1000000 + 2500000))
ffmpeg -nostdin -nostats -stream_loop -1 -i input1.mp4 \
-vf "format=uyvy422,cue=$TS:preroll=0.5:buffer=0.5" \
-af "acue=$TS:preroll=0.5:buffer=0.5" -f decklink "DeckLink Duo (1)" &
ffmpeg -nostdin -nostats -stream_loop -1 -i input2.mp4 \
-vf "format=uyvy422,cue=$TS:preroll=0.5:buffer=0.5" \
-af "acue=$TS:preroll=0.5:buffer=0.5" -f decklink "DeckLink Duo (2)" &
ffmpeg -nostdin -nostats -stream_loop -1 -i input3.mp4 \
-vf "format=uyvy422,cue=$TS:preroll=0.5:buffer=0.5" \
-af "acue=$TS:preroll=0.5:buffer=0.5" -f decklink "DeckLink Duo (3)" &
ffmpeg -nostdin -nostats -stream_loop -1 -i input4.mp4 \
-vf "format=uyvy422,cue=$TS:preroll=0.5:buffer=0.5" \
-af "acue=$TS:preroll=0.5:buffer=0.5" -f decklink "DeckLink Duo (4)" &
We are doing something similar to drive 16 TVs in a studio set
simultaneously.
Regards,
Marton
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