[FFmpeg-user] Thumbnail tile slow on big video files

[trash at skrilnetz.net]

  Thanks Gyan! The file is exactly 3600 seconds long and I take 4  
frames (20%,40%,60% and 80%).
Adding /-t 2900 -skip_frame nokey/ would be the right thing to do?  
Will that be fast even with a 10Gig video file?

Quoting Gyan <gyandoshi at gmail.com>:

> On Thu, May 18, 2017 at 5:53 PM, <trash at skrilnetz.net> wrote:
>
>> Hi,
>>
>> I run the code below to produce a tile thumnail from video files. That
>> seems to be very slow on big video files. Anything that I do wrong, or I
>> could improve to speed up processing?
>>
>> ffmpeg -ss 720 -i $input_path -f image2 -vframes 1 -aspect 4:3 -filter:vf
>> select='isnan(prev_selected_t)+gte(t-prev_selected_t\,720)',
>> scale="'if(gt(a,4/3),128,-1)\':'if(gt(a,4/3),-1,96)\'",pad="
>> w=128:h=97:x=(ow-iw)/2:y=(oh-ih)/2:color=black",tile=4x1 -y
>> $output_filename
>>  
>
> Since your command produces exactly (or upto) 4 frames at an interval of
> 720 seconds, you can add    -t 2900 -skip_frame nokey    before  -i
> $input_path. Only keyframes are passed to the filters, so that should hurry
> things up. Also, there's no need to keep the command running after 4 frames
> have been found.
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