Changes between Version 15 and Version 16 of Creating multiple outputs


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Timestamp:
Jun 4, 2016, 1:15:59 AM (18 months ago)
Author:
rogerdpack
Comment:

add note about parallel delay

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  • Creating multiple outputs

    v15 v16  
    1515ffmpeg -i input -acodec … -vcodec … output1 
    1616}}} 
    17 but either iteration will work in a sane shell. 
     17but either version will work in a sane shell. 
    1818 
    1919== Different parallel outputs == 
     
    2222[[Image(creating_multiple_outputs2.png)]] 
    2323 
    24 `ffmpeg` supports multiple outputs created out of the same input(s). The usual way to accomplish this is: 
     24`ffmpeg` supports multiple outputs created out of the same input(s) in the same process. The usual way to accomplish this is: 
    2525{{{ 
    2626ffmpeg -i input1 -i input2 \ 
     
    106106                -c copy -f mpegts local.ts 
    107107}}} 
     108 
     109=== Parallel encoding === 
     110 
     111Outputting and re encoding multiple times in the same FFmpeg process will typically slow down to the "slowest encoder" in your list.  Some encoders (like libx264) perform their encoding "threaded and in the background" so they will effectively allow for parallel encodings, however audio encoding may be serial and become the bottleneck, etc.  It seems that if you do have any encodings that are serial, it will be treated as "real serial" by FFmpeg and thus your FFmpeg may not use all available cores.  One work around to this is to use multiple ffmpeg instances running in parallel, or possible piping from one ffmpeg to another to "do the second encoding" etc.