VOB conversion quality in FFmpeg

Question

I am trying to convert a VOB file to mpeg like this:

./ffmpeg.exe -i VTS_01_2.VOB -r 24  out1.mpeg

However, the quality is very poor.

I tried ./ffmpeg.exe -i VTS_01_2.VOB -vcodec copy out1.mpeg

But the file size is too large (90% of original – 300 MB for 4 minute video), and Windows Movie Maker hangs on trying to import it.

How can I get a decent quality MPEG from my VOB?

Answer 1

ffmpeg -i input.vob -c:v copy -c:a copy output.mpg  

This command does not reduce the size or alter quality. This merely demuxes the VOB and repackages it as an MPEG. You should be left with exact same quality. The size changes minimally due to losing the overhead of the VOB container.

If you want to maintain quality and reduce size you are going to have to convert it with another encoder like x264 or XviD to an MKV or MP4 container, for example:

ffmpeg -i input.vob -c:v libx264 -c:a aac -strict experimental output.mp4

This will give you H.264 video and AAC audio. Set -crf 23 for the video quality, where less means better quality (sane values are from 18–28). The audio quality can be changed with -b:a 192k for fixed bitrate, or if you want to use another encoder such as -c:a libfaac, you can choose VBR with -q:a 100 (100% default quality).

Answer 2

The syntax in the previous answer doesn't work on my Mac OS. This one seemed to work fine, with slightly different options (-sameq to match the input quantizer, -ss for the start time offset and -t for the duration):

ffmpeg -i VTS_01_1.VOB -sameq -strict experimental -ss 1612 -t 28 test.mpg