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Unbalanced volume (channels) on headset audio


I use a headset to make phone calls and when they are mono the great awesomeness of the Linux audio stack seems to change volume only on the active channel (e.g. the right channel). So when I listen to some music (stereo) afterwards the channels are not balanced anymore and one side is louder than the other. And this persists thanks to saving the preferences across reboots. Duh.

As usually checking Pulseaudio (pavucontrol) is useless, it shows balanced channels.

But checking Alsa (alsamixer) revealed the issue and alsamixer can fix this, too:

Step 1: run alsamixer in a terminal and select your headset after pressing [F6]:

Alsamixer: Select sound card

Step 2: Select the headset audio output with [<-] and [->] cursor keys:

Alsamixer: Unbalanced channels on the headset (left / right channel loudness are different)

Step 3: Press [b] to balance the left and right channels:

Alsamixer: Balanced channels (left / right channel loudness) again

Step 4: Press [Esc] to exit alsamixer which will keep the changed settings (... great choice of key, [q] raises the left channel's loundness ...).

Step 5: Save this setting by running sudo alsactl store which should update /var/lib/alsa/asound.state with the fixed settings so they persist across reboots.

Step 6: Enjoy music again :-).

If you need to script this, amixer is the tool to use, e.g. amixer -c 1 set "Headset" 36.
1 is the card number which you see in alsamixer, "Headset" is the channel name, also from alsamixer (which can contain blanks, hence the quotes around the name) and 36 is the desired loundness level for both channels. See the screenshots above where to find the data or run aplay -l to see the cards on your PC and amixer -c 1 (with your card id) to see the channels that (virtual, USB) sound card has.

Converting a DVD film (mpeg2) to DV


There are a gazillion web pages telling you how to convert DV to MPEG2 for DVD use. But I got a DVD from a corporate event and needed to convert it to DV to be cut in kdenlive. So just the other way around. Try to find a web page about that direction (needle in haystack, anyone?).

Giving up on google, I tried unsuccessfully with the swiss army knife that comes to mind first (ffmeg).

While something like ffmpeg -i vts_01_1.vob -i vts_01_2.vob -i vts_01_3.vob -sameq -target dv ../Raum_Video.avi creates a nice .avi, even mplayer complains about it violating the dv and avi standards.

So back to digging around in tutorials and forums and trial and error with other tools. Finally I found Avidemux to be the tool of choice. It encapsulates ffmpeg and other tools nicely to make them produce the expected results. Set video to DV (lavc), Audio to WAV PCM and the container format to AVI and go grab a coffee meal. It creates a nice DV file that you can easily work with in your favorite video editor.

Screenshot of Avidemux in action