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I'm upscaling a 200x200 video to 400x400 using the -sws_flags scaling option to set the scaling algorithm. Now, I can't tell by the console output if some algorithm was used, neither by the looks of the output video when resized. And also the video remains the same size after trying different scaling algorithms. I now can't tell if some algorithm was used or not. How can I found out or see in the console or even afterwards what scaling algorithm was used?

Command-line looks like this:

ffmpeg -i old_vid_200x200.mkv -vf scale=400:400 -sws_flags lanczos new_vid_400x400.mkv

Thanks

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    Could you please provide the console output as well?
    – Rajib
    Aug 8, 2014 at 13:20
  • You can just try the command above on some random video. Anyway, I think my attempt to resize a video smoothly failed. Quality of the result Video is way to bad to be considerable. I have tried all of the algorithms now. You can try out the algorithms with ffplay also.
    – k t
    Aug 9, 2014 at 9:52

1 Answer 1

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I've read that -vf scale=400:400 -sws_flags lanczos can be buggy so it is better to use -vf scale=400:400:flags=lanczos instead. (source)

To see the scaling algorithm you can use -loglevel verbose and/or add print_info flag to the scaler (example: -vf scale=400:400:flags=lanczos+print_info). (source)

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