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I have a 1080p wmv video that I'd like to convert to a lower quality (preferably 720p) video. I would like to keep the audio intact. How can I accomplish this in Ubuntu?

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3 Answers 3

up vote 5 down vote accepted

Since you used an ffmpeg tag I will use that for the answer.

ffmpeg -i input.wmv -s hd720 -c:v libx264 -crf 23 -c:a aac -strict -2 output.mp4

Change the video quality by specifying a different CRF parameter. See the x264 encoding guide for more info.

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Option 'sameq' was removed. If you are looking for an option to preserve the quality (which is not what -sameq was for), use -qscale 0 or an equivalent quality factor option. –  juanmah Apr 4 '13 at 9:15

Newer versions of FFmpeg would perhaps use the scale video filter, I give an example below which also simply copies the audio track as you have requested:

ffmpeg -i input.wmv \
       -c:v libx264 -preset veryslow -tune film -crf 22 -vf scale=-1:720 \
       -c:a copy \
       output.mp4

The -tune option can be omitted or you could try -tune animation depending on the type of video clip you are using.

If you decided that you would like to transcode the audio you could do worse than to use the external library libfdk_aac as follows:

ffmpeg -i input.wmv \
       -c:v libx264 -preset veryslow -tune film -crf 22 -vf scale=-1:720 \
       -c:a libfdk_aac -b:a 128k \
       output.mp4

and this is certainly what I would do with a wmv file that I was scaling, you should find the results more than acceptable...

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If you want to keep intact all the audio tracks, subtitles and so on, you should use something like this:

ffmpeg -i input.mkv -map 0:0 -map 0:1 -map 0:2 -map 0:3 -map 0:4 -vf scale=-1:720 -c:v libx264 -crf 18 -preset veryslow -c:a:0 copy -c:a:1 copy -c:s copy  output.mkv

In this case, the input.mkv file has two audio tracks and two subtitles. You can specify all the audio tracks (or subtitles, or videos, etc.) one by one or as a single entity (as I specified for subtitles).

Hope it helps...

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