[FFmpeg-user] Help with Concatenating Please

Jim DeLaHunt list+ffmpeg-user at jdlh.com
Thu Apr 4 02:59:19 EEST 2019

Hello, Mark:

Welcome to the ffmpeg-user mailing list. I hope you are able to find out 
what you need, and get good use out of *ffmpeg*.

On 2019-04-03 14:01, Mark Scott wrote:
> …I need to add 2 seconds of black silent video to the head of
> the encoded file. Would this be accomplished by concatenating the original
> video file, with a separate video file that has the 2 seconds of black?

That is one way to do it.  A better way is to use the video source 
"color" <http://ffmpeg.org/ffmpeg-all.html#color> to generate 
solid-colour video of the form you need, at run time. Use the audio 
source "aevalsrc" <http://ffmpeg.org/ffmpeg-all.html#aevalsrc> to 
generate silence. Then use the video filter "concat" 
<http://ffmpeg.org/ffmpeg-all.html#concat-3> to concatenate the video 
streams together.

Here is the skeleton of "color" and "concat" in use. (I have not tested 
this, and I have discarded audio sources, and this should all be one line):

    ffmpeg -i in.mov -an -filter_complex 'color=black:duration=2.0 [black]; [black] [0:0] concat=n=2:v=1:a=0 [v]'
      -map '[v]' out.mov

On 2019-04-03 14:01, Mark Scott wrote:
> …I need to take an Apple ProRes 4444 file, 1920x1080, 23.98 fps, 16 bit
> integer stereo audio,
> and encode it to be Apple ProRes 422 HQ 1920X1080, 23.98fps 24bit integer
> stereo audio….

Obviously, my skeleton above doesn't do all this.  Have you worked out 
how to make *ffmpeg* do the conversion you need from ProRes 4444 to 
ProRes 422 HQ?  If so, maybe a good next step is to post the complete, 
uncut command line and output which does this conversion to this list. 
Maybe someone will be able to help you fold in the "color" and 
"aevalsrc" and "concat" filters to that.

On 2019-04-03 14:01, Mark Scott wrote:
> I'm very new to ffmpeg and I don't have much experience using command lines
> to encode video….

Ah. You are in for an adventure, then. *ffmpeg* can do many things, but 
"gently introduce people to use of command lines" is not usually one of 
them. :-)

I hope this helps!

     --Jim DeLaHunt, jdlh at jdlh.com     http://blog.jdlh.com/ (http://jdlh.com/)
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