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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

DVD

dvd://1 -dvd-device PATH -sid 31 (where PATH is the path to the DVD image)

cd $DVD_DIR/VIDEO_TS && ffmpeg -i "concat:$(echo *.VOB|tr ' ' '|')" -map 0:1 -map 0:3

or cat $DVD_DIR/VIDEO_TS/*.VOB | ffmpeg -i - -map 0:1 -map 0:3

where for a multi-title DVD you’ll need to figure out the correct set of VOB files, and -map 0:1 and -map 0:3 might need to be refined according to ffmpeg’s output of the language list; you’ll also need to add some ffmpeg *output* options, e.g. -vcodec mpeg4 -b:v 600k -strict -2 -g 50 -vf yadif -c:a aac -b:a 160k output.mp4

These commands do *not* handle subtitles.

Some discs work better with mencoder, while other discs work better with ffmpeg, so *both* commands are useful to keep.

.flv and other video files

rtmp streams embedded in complex Javascript etc

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

iptables -t nat -A OUTPUT -p tcp --dport 1935 -m owner \! --uid-owner root -j REDIRECT

rtmpsuck

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.) This method was last tested in 2017 and is unlikely to work in the latest non-Flash browsers.

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:

ffmpeg -i videoS.mp4 -i videoP.mp4 -map 0:a:0 -map 1:v:0 -map 1:s:0 -c copy -c:s mov_text output.mp4

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

mplayer -udp- m\!x61s\x74\x65r' -udp-ip (second device’s IP) video1.mp4

mplayer -udp- \x73\x6c\x61\x76e' -udp-seek-threshold 0.1 -udp-ip (second device’s IP) video2.mp4

(press v to toggle subtitles or f to toggle full-screen; I’ve obfuscated the options that use technical terms which some viewers might misunderstand as a racist insult)

To play the two videos on the same machine, one with sound only and sent to HDMI, the other with full-screen picture, and sound sent to Bluetooth, set the system to use PulseAudio (not PipeWire: Raspberry Pi OS 12 needs sudo raspi-config / Advanced / Audio to set it back to PulseAudio) and do:

mplayer -noconsolecontrols -vo null -udp- \x73\x6c\x61\x76e' -udp-seek-threshold 0.1 -ao pulse::alsa_output.platform-(value from pacmd list-sinks).hdmi.hdmi-stereo video2.mp4 & mplayer -fs -nosub -udp- m\!x61s\x74\x65r' -ao pulse::bluez_sink.(MAC address).a2dp_sink video1.mp4

(also works with URLs instead of saved video files, in which case I suggest adding -cache-min 1 -cache 1048576 to each command if you have 4GB+ of RAM)

To have the two languages in two stereo channels on the same player, first create a WAV file:

ffmpeg -i input1.mp4 -i input2.mp4 -filter_complex '[0:a]aconvert=s16:mono[l]; [1:a]aconvert=s16:mono[r]; [l][r]amerge[snd]' -map '[snd]' audio.wav

ffmpeg -i input1.mp4 -i input2.mp4 -filter_complex '[0:a]aformat=sample_fmts=s16:channel_layouts=mono[l]; [1:a]aformat=sample_fmts=s16:channel_layouts=mono[r]; [l][r]amerge[snd]' -map '[snd]' audio.wav

Then, to keep the picture from the first file, do:

ffmpeg -i input1.mp4 -i audio.wav -map 0:v -map 1:a -vcodec copy output.mkv

and proceed with output.mkv (if it lacks sound, it’s probably an ffmpeg version issue: try -b:v 10000k output.mp4 instead of -vcodec copy output.mkv).

Or if the pictures differ as well (for example on-screen text has been translated) then you might wish to show both pictures at once. The following command will do that, positioning them diagonally to reduce peripheral-motion annoyance when trying to watch only one; it works only if both videos are the same size.

ffmpeg -i input1.mp4 -i input2.mp4 -i audio.wav -filter_complex '[0:v]pad=iw*2:ih*2:0:ih[tmp]; [tmp][1:v]overlay=W/2:0[pic]' -map '[pic]' -map 2:a -b:v 3000k output.mp4

If the videos are additionally of different sizes, you’ll need a longer version of this command:

W1=$(ffprobe -show_entries stream=width input1.mp4 |grep ^width=|head -1|cut -d= -f2); W2=$(ffprobe -show_entries stream=width input2.mp4 |grep ^width=|head -1|cut -d= -f2); H1=$(ffprobe -show_entries stream=height input1.mp4 |grep ^height=|head -1|cut -d= -f2); H2=$(ffprobe -show_entries stream=height input2.mp4 |grep ^height=|head -1|cut -d= -f2); ffmpeg -i input1.mp4 -i input2.mp4 -i $Audio -filter_complex "[0:v]pad=$[$W1+$W2]:$[$H1+$H2]:0:$H2[tmp]; [tmp][1:v]overlay=$W1:0[pic]" -map '[pic]' -map 2:a -b:v 3000k output.mp4

Recording the desktop

Linux/X11 region around mouse, audio from microphone:

ffmpeg -f alsa -i pulse -f x11grab -follow_mouse 100 -show_region 1 -r 25 -i "$DISPLAY" output.mkv

ffmpeg -f alsa -i pulse -f x11grab -s 480:480 -follow_mouse 100 -show_region 1 -r 25 -i "$DISPLAY" -f video4linux2 -i /dev/video0 -filter_complex '[2:v]crop=160:480:240:0,split=2[d][D];[d]pad=640:480:480:0[c];[c][1:v]overlay=0:0[o]' -map '[o]' -map 0:a -t 60 -y output.mkv -map '[D]' -f matroska -t 60 - | ffplay -autoexit -noborder -left 0 -

ffmpeg -f alsa -i pulse -f video4linux2 -i /dev/video0 -filter_complex '[1:v]split=2[d][D]' -map '[d]' -map 0:a -y output.mkv -map '[D]' -f matroska - | ffplay -autoexit -noborder -left 0 -

(press q on the original command terminal to stop the recording)

ffmpeg -i output.mkv -codec copy output.mp4

(but for some applications you might also need to recode h264)

DOSBox (audio from programs): in dosbox.conf (or ~/Library/Preferences/DOSBox* on Mac) set the captures= directory to something (e.g. /tmp) and the default start/stop keybinding Ctrl-Alt-F5 (or Ctrl-F6 for audio only). Beware at least some versions of DOSBox can partially lose videos in some circumstances.

Mac OS X: “QuickTime Player” despite its name is not just a player. Its File menu contains options to record the screen with optional microphone narration, or to record from camera. Results are placed in ~/Movies and I think version 10.9+ of OS X also lets you record *part* of the screen (otherwise you have to post-process with mencoder’s -vf crop=w:h:x:y if you don’t want the whole screen).

Series of pictures

You *could* just do (for example) mencoder 'mf://*.jpg' -mf fps=0.2 but it’s sometimes possible for mencoder to crash on signal 11 as it tries to scale pictures, so it might be worth pre-scaling, for example for PAL DVD: for N in *.jpg ; do jpegtopnm "$N" | pnmscale -xysize 720 576 | pnmpad -black -width 720 -height 576 | pnmtopng > "$(echo "$N"|sed -e s/jpg$/png/)";done (followed by the mencoder command on *.png, or on @listfile to ensure it processes them in the correct order)

Output options

Android, iPhone or Mac

-of lavf -lavfopts format=mp4 -vf dsize=480:352:2,scale=0:0,harddup -ovc x264 -sws 9 -x264encopts bitrate=512:bframes=0:chroma_me:me=umh:frameref=6:global_header:level_idc=30:nocabac:partitions=all:subq=5:threads=auto:trellis=1 -oac faac -faacopts mpeg=4:object=2:raw:br=128 -o output.mp4

Nokia S60, S40 etc

-ofps 24 -of lavf -lavfopts format=mp4 -vf dsize=320:240:2,scale=0:0 -oac lavc -ovc lavc -lavcopts aglobal=1:vglobal=1:acodec=libfaac:abitrate=96:vcodec=mpeg4 -o output.mp4

Windows 10 or Mac with large screen

Playable on *recent* versions of Windows Media Player (Windows 10 should work), and also playable on Mac QuickTime:

-of lavf -lavfopts format=mp4 -ovc x264 -sws 9 -x264encopts bframes=0:chroma_me:me=umh:frameref=6:global_header:level_idc=30:nocabac:partitions=all:subq=5:threads=auto:trellis=1 -oac faac -faacopts mpeg=4:object=2:raw:br=128 -o output.mp4

Zoom Cloud Meetings

Zoom added a built-in video-share function to version 5.4.3 but only on Windows and Mac (use Share Screen / Advanced / Video and choose a file), but on GNU/Linux the method below is still needed (and might also work for other video-conferencing software that has “screen sharing” but no option to feed a video to it directly).

echo pause | mplayer -as\x73' -\x73\x6c\x61\x76e' -noborder video.mp4

(I’ve obfuscated the options for enabling subtitle fonts and waiting on standard input, because some might misunderstand these technical terms as a racist insult if accidentally shown on a conference screen—beware they might still show up if you’re using a terminal that shows the currently-executing command on its title bar.) Optionally add -ss start-second and/or -endpos length before the video.

Mplayer then starts paused so you can set up the screen-share on that window.

mpv --geometry=1280x720 --video-unscaled=yes --pause video.mp4

(needs adjusting for the video size)—and the first use of Share Screen is likely to require a restart of the video-conferencing software after you’ve been prompted to change the Mac’s security settings, so I’d advise running a test meeting first.

vlc -f --start-paused video.mp4 vlc://quit

(with optional --start-time and --stop-time after the --start-paused)—VLC starts paused so you can set up the screen-share on that window before pressing Space to play, and VLC quits at the end so the screen-share stops automatically.

If your PulseAudio distorts the video’s sound on the remote side due to bad resampling, you can correct this in .config/pulse/daemon.conf—Charles Z Henry suggests:

resample-method = speex-fixed-7

default-sample-rate = 48000

alternate-sample-rate = 44100

—this might need a restart of your desktop session.

“Share computer audio” can silently fail on some Fedora 34 setups, reportedly because Fedora changed from PulseAudio to PipeWire and PipeWire’s PulseAudio plugin is not supported as well as real PulseAudio (it seems it works on some machines but not others). It may be necessary to unmute, set “Suppress background noise” as low as possible, be quiet, hope the fan doesn’t spin up, and accept degraded audio going from the speaker to the microphone.

To show static pictures (e.g. slides) : VLC can take multiple images on the command line (and can set “minimal interface” on the menus + not full-screen); by default each image is played for 10 seconds, but Space pauses, then on each slide advance, press n and Space to advance to the next slide and re-pause.

Patching one Zoom meeting into another Zoom meeting

The Mac version of Zoom lets you run a second instance if you launch it via a /j/ URL, and this second instance can be set to share the screen of the first instance of Zoom (tested on Zoom 5.9.1 on macOS 12.2.1). This might be useful if a group wants to watch a presentation and then break off for separate discussion without needing control of the main meeting’s breakout-room facility. The “share computer audio” option does *not* work when sharing the screen of another Zoom instance: you must use speaker to microphone. But if you’ve installed BlackHole (or SoundFlower on older Macs) you can set one Zoom instance to output sound to a Multi-Output Device (created in the “Audio/MIDI Setup” application) and the other instance to take microphone input from the BlackHole device (you’ll then need to change this setting if you want to speak later).

Old Windows or Windows Mobile

-ovc lavc -lavcopts vcodec=wmv2 -oac lavc -lavcopts acodec=wmav2 -of lavf -vf dsize=320:240:2,scale=0:0 -o output.wmv

MP3 audio

(any picture will be discarded)

-ovc copy -of rawaudio -oac mp3lame -lameopts vbr=2:q=9:aq=0 -o output.mp3

“Play All” bookmarklet

If you are on a (probably RedHat) setup where the only working audio player is the browser, you can drag this link to your bookmarks bar: Play All then press it after loading a file:// directory listing containing sound files. (Alternatively, serve that directory to a mobile device with headphones and arrange for the script to be injected into the directory listing. Or install mocp.)

DVDs and VCDs

(based on mencoder documentation with some changes)

-oac lavc -ovc lavc -of mpeg -mpegopts format=dvd:tsaf -vf expand=:::::16/9,scale=720:576,harddup -srate 48000 -af lavcresample=48000 -lavcopts vcodec=mpeg2video:vrc_buf_size=1835:vrc_maxrate=9800:keyint=15:vstrict=0:acodec=mp2:aspect=16/9 -ofps 25 -o output.mpg

Check the size of the .mpg (note DVD-5’s “4.7G” is 4.38GiB and allow for overheads); if too big, add :vbitrate=4000 or whatever to the -lavcopts list

(Ffmpeg’s concatenation is more complex than mencoder’s: it’s best done *after* all files are converted, and you’d need to do something like ffmpeg -i file1.mpg -i file2.mpg -i file3.mpg -filter_complex '[0:0][0:1] [1:0][1:1] [2:0][2:1] concat=n=3:v=1:a=1[v][a]' -map '[v]' -map '[a]' -target pal-dvd output.mpg which requires ffmpeg 1.1+; the 0..2 and the =3 need changing according to the number of input files, and any bitrate limit might need to be added again. Such concatenation might not be necessary if the dvdauthor command below takes multiple mpgs, but it doesn’t always.)

mkdir DVD/ && export VIDEO_FORMAT=PAL && dvdauthor -o DVD/ -t -v 16:9 output.mpg && dvdauthor -o DVD/ -T && rm output.mpg && mkisofs -dvd-video -v -o DVD.iso DVD && rm -r DVD

-oac lavc -ovc lavc -of mpeg -mpegopts format=xvcd -vf dsize=352:288:2,harddup -srate 44100 -af lavcresample=44100 -lavcopts acodec=mp2:abitrate=224:vcodec=mpeg1video:keyint=15:vrc_buf_size=327:vrc_minrate=1152:vrc_maxrate=1152:vbitrate=1152:aspect=16/9 -ofps 25 -o output.mpg

Then run vcdimager output.mpg and write with cdrdao write videocd.cue or convert to ISO with bchunk videocd.bin videocd.cue videocd.iso

-oac lavc -ovc lavc -of mpeg -mpegopts format=xsvcd -vf dsize=480:576:2,harddup -srate 44100 -af lavcresample=44100 -lavcopts vcodec=mpeg2video:mbd=2:keyint=15:vrc_buf_size=917:vrc_minrate=600:vbitrate=2500:vrc_maxrate=2500:acodec=mp2:abitrate=224:aspect=16/9 -ofps 25 -o output.mpg

then run vcdimager -t svcd output.mpg and burn with cdrdao write videocd.cue.

See also spaced-out audio tracks with cdrdao

Legal

All material © Silas S. Brown unless otherwise stated. Android is a trademark of Google LLC. Apple is a trademark of Apple Inc. Bluetooth is a registered trademark held by the Bluetooth Special Interest Group. Google is a trademark of Google LLC. HDMI is a trademark or registered trademark of HDMI Licensing LLC in the United States and other countries. iPhone is a trademark of Apple in some countries. Javascript is a trademark of Oracle Corporation in the US. Linux is the registered trademark of Linus Torvalds in the U.S. and other countries. Mac is a trademark of Apple Inc. MP3 is a trademark that was registered in Europe to Hypermedia GmbH Webcasting but I was unable to confirm its current holder. Raspberry Pi is a trademark of the Raspberry Pi Foundation. WeChat is a trademark of Tencent Holdings Limited. Windows is a registered trademark of Microsoft Corp. Zoom is a trademark of Zoom Video Communications, Inc. Any other trademarks I mentioned without realising are trademarks of their respective holders.