[FFmpeg-devel] [PATCH] avfilter/f_cue: add cue and acue filters

[Bodecs Bela]

Hi Balint,


2018.09.06. 22:20 keltezéssel, Marton Balint írta:
>
> 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 <cus at 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
>>>
>>> + at 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
>>>
>>> + at anchor{cue}
>>> + at 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
>>> + at 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)" &
>
Thank you.

what about to create a new parameter for the filters: relcue/arelcue ?

relcue would be a relative value to current timestamp. This way the 
shell variable will be unneeded.

usage of cue and relcue would be mutally esclusive parameters.

> We are doing something similar to drive 16 TVs in a studio set 
> simultaneously.
>
> Regards,
> Marton
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bb