[FFmpeg-user] Speed up overlaying process

[Dzung Nguyen]

On Aug 21, 2013, at 5:19 PM, Paul B Mahol <onemda at gmail.com> wrote:

> On 8/21/13, Dzung Nguyen <dzungng89 at gmail.com> wrote:
>> I'm overlaying two videos together:
>> 
>> ffmpeg -i video1.mpg -i video2.mpg -filter_complex
>> "color=c=black:size=1280x720[base]; [0:v] setpts=PTS_STARTPTS,
>> scale=856x642 [left]; [1:v] setpts=PTS_STARTPTS, scale=424x318
>> [right]; [base][left] overlay=shortest=1:y=39[tmp1]; [tmp1][right]
>> overlay=shortest=1:x=856:y=201" -q:v 0 output.mpg
>> 
>> This takes very long time, for a final output of 1hour. Which setting
>> should I change to make it faster? (remove scale filter)?
> 
> Usually one would inspect what part of filtering takes most of time.
> Encoding and not scaling is probably most costly operation that you are doing.
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Can you please elaborate on this? Two videos have the correct size already, but without scaling filter it is displayed at wrong position.