Back to Silas S. Brown's home page

Notes on video conversion with mencoder

These are some quick notes I made to provide starting points for mencoder command lines. It is meant for conversions that are legal (own work, personal use of products without DRM, etc). I am not an mencoder expert but just collected some options that worked for me.

Input from: DVD | video file | rtmp stream | Flash audio | edits | audio file | FM | language merge | desktop | pictures
Output to: Android, iPhone or Mac | Nokia S60, S40 etc | Windows 10 | Zoom Cloud Meetings | Old Windows or Windows Mobile | MP3 audio | DVD, VCD or SVCD

Input options


.flv and other video files

rtmp streams embedded in complex Javascript etc

You need root access to a GNU/Linux machine with rtmpdump

Flash audio

On a GNU/Linux machine with ~/.asoundrc set to
pcm.teeraw { type empty
slave.pcm "tee:default,'/tmp/out.raw',raw" }

use FLASH_ALSA_DEVICE=teeraw firefox and (e.g.) sox -t raw -r 44100 -c 2 -b 16 -s /tmp/out.raw /tmp/out.wav then proceed with out.wav. (To reduce risk of /tmp/out.raw being overwritten, start sox before interacting with the browser to stop the stream.)

Edit decision lists

Use -edl filename, where each line of the file is start-second end-second 0 (use mplayer to find the seconds and to test the EDL). You can add up the total number of minutes you've cut by piping the EDL through python2 -c 'import sys;print sum(float(l.split()[1])-float(l.split()[0]) for l in sys.stdin)/60.0'

Audio file (static or blank picture)

This might be useful for porting audio to old DVD players that don't support MP3 etc. You need to first add the audio to blank video using ffmpeg: (command adapted from Stefano Sabatini's suggestion on ffmpeg-user)
ffmpeg -i input-audio.wav -s 640x480 -f rawvideo -pix_fmt rgb24 -r 25 -i /dev/zero -shortest -vcodec libx264 -preset medium -tune stillimage -crf 24 -acodec copy output.mkv
then proceed with output.mkv (convert it to .mpg as per DVD output below, etc) You can also use ffmpeg to attach audio to a still image:
ffmpeg -i audio.mp3 -loop 1 -i picture.jpg -shortest -vcodec mpeg4 -b:v 800k audio.avi
(then convert audio.avi into the required output format)
Or to replace the soundtrack of an existing video (for language dubbing etc),
ffmpeg -i video.mp4 -i sound.wav -map 0:v -map 1:a -vcodec copy output.mkv
then proceed with output.mkv

FM radio

As above, but if recording the audio to MP3 you might want to avoid wasting space encoding any frequencies above 15kHz. This is because FM stereo requires a 4kHz guard band around the 19kHz pilot signal, therefore any audio you get above 15kHz must be the result of equipment noise; therefore the option of a 32kHz sample rate (Nyquist cutoff 16kHz) makes sense, but your ADC circuitry might not do that well so it's probably best to convert in software:
rec --input-buffer=1048576 -t raw -r 44100 -c 2 -b 16 -e signed-integer - | sox -t raw -r 44100 -c 2 -b 16 -e signed-integer - -t raw -r 32000 -c 2 -b 16 -e signed-integer - | lame -h -s 32 -r - -o output.mp3
(older versions of sox might need -2 -s or -w -s instead of -b 16 -e signed-integer in three places of the above command)

Two language versions

If a video is available in two versions with different-language sound tracks:

To play the two videos on separate devices but time-synchronised over a local network: