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I am running the below command, to reduce the size of a mp4 video

ffmpeg -i input.mp4 -acodec mp2 output.mp4

After the output is created, I run the command again on the output and so on, because the reduction size is only around 0.1 Mb with each command execution, so I need to reduce around 2-3 Mb, that"s why I need to run the command iteratively.

I want to write a bash script to do this automatically, instead of I keep running the command again and again. And if there is an option to stop running the command, if the files size reached the size I want ?

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    Instead of re-encoding the video 30 times, which sounds like a terrible idea to me, you should rather try and change the quality settings in ffmpeg and just convert it once, I believe. See man ffmpeg for supported arguments. – Byte Commander Jul 14 '18 at 10:27
  • @ByteCommander hey, yes I know it is a terrible idea, but unfortunately, I searched a lot online, and I didn't find a good alternative solution – Mostafa Hussein Jul 14 '18 at 10:29
  • I believe the suggestions given are valid iterations would be a bad idea but in any case, this should help although not tested: for i in ./*; do for y in $(seq 1 <END>); do ffmpeg -i "$i" -acodec mp2 output.mp4; done; done – George Udosen Jul 14 '18 at 11:43
  • Some hints here for targeting a specific size: askubuntu.com/q/1027340/57576 – andrew.46 Jul 15 '18 at 23:15
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Really dont do this -- you damage the quality each time.

Try an ffmpeg command like this:

ffmpeg -i input.mp4 -c:v libx265 -crf 30 -c:a copy output.mp4

So (in this example) I use the h265 codec for video and set a factor of 30. A smaller number will give a larger file with better quality and a higher number a smaller file and poorer quality. The audio is just copied. I don't know whats in your source file, but usually the biggest saving come from re compressing the video

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