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• How to preserve shadows in image using ffmpeg ? [closed]

  27 décembre 2023, par Heroic_IMA

  I'm attempting to reduce png image file sizes using ffmpeg with these commands. They work really well except for the problem with the shadows. Is there a way to modify these commands to produce a result that properly preserves the shadows ?

  


  ffmpeg -i original.png -q 0 -vf palettegen palette.png

  


  ffmpeg -i original.png -i palette.png -q 0 -filter_complex '[0]format=rgba,scale=8064:8064[x];[x][1]paletteuse' output.png

  


  original image

  


  result image with wrong shadows

  


  The full original image is over 50 MB and these commands shrink it down to 17 MB. Using the site iloveimg.com to compress the image also results in a decrease from 50 to 17 MB except it doesn't have the shadow problem. So I assume this is possible, but I don't know exactly how they make this happen. I've also tried other command line tools but they don't compress it anywhere near as much as this. The eventual purpose will be to use these commands in a script to process hundreds of files.

  


• How to change resolution without compromising video quality using ffmpeg ?

  20 mars 2024, par blake banker

  I'm trying to develop a simple video transcoding system.
When you upload a video,
After extracting the video and audio separately,
I want to encode them at 360, 720, and 1080p resolutions respectively and then merge them to create three final mp4 files.
At this time, I have two questions.

  


  


  1. Is there a big difference between encoding the video and audio separately in the original video file and encoding the original video file as is ? In a related book, it is said that a system is created by separating video and audio, and I am curious as to why.

     


  


  2. I want to change the resolution without compromising the original image quality. At this time, the resolution of the uploaded file can be known at the time of upload. As a test, I created files according to each resolution, and found that the image quality was damaged. If I want to change only the resolution while keeping the original image quality, I would like to know how to adjust each ffmpeg option. We plan to change it to 360, 720, and 1080p.

     


  


  


• FFMPEG convert MTS to MP4 without losing metadata ?

  19 octobre 2019, par user9375050

  I’ve tried using ffmpeg to convert an MTS file to an MP4 file, with the -map_metadata 0 option. I’ve also tried suggestions to write the metadata to a file and then read from the file. Neither seem to work. EXifTool certainly shows the tags are there in the original file, but not the converted file. I’m mainly interested in the Date / Time Original tag. I’m at a loss as to what I’m doing wrong. Any ideas ?