[FFmpeg-user] mpeg2 filesize reduction: reduce video, enhance audio, codec selection

Beeblebrox zaphod at berentweb.com
Mon May 5 16:14:53 CEST 2014


I have several large videos ranging in size 5G - 9G. These videos are from
a training seminar recorded on an amateur camera and only consist of human
speech (no microphone).

* I would like to reduce file size, and reduction in image quality is not a
* I don't want to reduce audio quality; in fact the sound is not good so I
need to increase the volume and maybe even augment by frequency (?)
* Encoding is: $ file video1.mpg > MPEG sequence, v2, program multiplex
* My questions concerning this problem:

1. VIDEO: Does x264_high yield the tightest-packed, best quality video
image? The tighter it's packed the less frame reduction that is necessary?
(from here http://keyj.emphy.de/video-encoder-comparison/)
2. AUDIO: I should copy the source as is, and use "output_volume = 2" or is
there some "preamp" toggle which will give better results?
3. I don't know what audio codec was used in the MPEG-2 file, but
considering there are better codecs now, which one (should be a lossless
one I imagine) should I use for better audio compression?
4. There were many *.mpg files from the camera dump, and I wanted each
seminar day to be a single file. So I already ran "$ cat M2U00210.MPG
M2U00211.MPG M2U00212.MPG (etc...) > video1.mpg". Did that operation
degrade any of the audio?

The final command is perhaps something like below?
ffmpeg -i video1.mpg -acodec copy 'volume=2' -vcodec libx264
* Not sure what format out-file should be (mp4?),
* Not sure if & how I should specify size (-s), bitrate (-b) and framerate,
* Not sure whether the audio should be "copy" or a lossless codec (smaller
file size),
* Not sure whether frequency-level audio correction & enhancement is
possible in ffmpeg

Thanks for your time & Regards.

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