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I've got an .mp4 file that's currently 830x1100 (it's a screencast) that I need to resize down to 114x150. I've been experimenting for hours with ffmpeg settings and nothing comes out looking nice and sharp. The original file looks decent, and I can't figure out why the downscaling makes it look so blurry.

Unfortunately I can't share the video because it contains a walkthrough for software that hasn't yet been released.

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2 Answers 2

up vote 3 down vote accepted

114x150 is incredibly small considering the size of the source and I'm not sure if any scaling method will give you a satisfactory result. That being said you can experiment with the -sws_flags option in ffmpeg.

ffmpeg -i input -filter:v scale=114:-1 -sws_flags lanczos output

This is just an example: I'm not suggesting that lanczos is going to be your best bet. Default is bicubic. See the full list at ffmpeg -h full.

Also remember to provide a high enough quality that compression artifacts don't interfere. See the FFmpeg and x264 Encoding Guide for examples.

Another option, although probably not a great suggestion, is to try the unsharp filter.

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One of the most dirty DSP tricks is to slowly scale up and then scale down the final result.

The first step is called "Incremental Upsampling". And they appear to teach it in University level photoshop (?) See http://library.albany.edu/imc/pdf/upsampling.pdf

The second step is to resize to your original output.

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