[LAU] Desktop recorders - was "Another Reality" LP

[Lorenzo Sutton]

On 06/05/2013 10:42 AM, Atte André Jensen wrote:
> On 05/28/2013 10:35 PM, Len Ovens wrote:
>
>> As a UbuntuStudio team member, I would be very interested in your
>> findings. We would like to include a desktop recorder, but would prefer
>> the best we can ship. The xvidcap page says that xvidcap is an OSS audio
>> application.
>
> I wanna join the choir.
>
> I tried the screen casters I know of xvidcap, kazam and recordmydesktop,
> and non of them are really working (terribly loose description, I know).

Recently, the only effective way I've found to  do screen recording with 
jack is using ffmpeg - yet this must be the 'original' ffmpeg not libav 
which is now packaged e.g. in Debian, which I couldn't get to work with 
jack - And this needs to be compiled by hand on debian [1]

This is the script I use (adapted from someone else (TM) I found online):

ffmpeg -f jack -ac 2 -i ffmpeg -f x11grab -r 30 -s 1280x800 -i :0.0 
-acodec pcm_s16le -vcodec libx264 -preset ultrafast -threads 0 output.avi

Advantages:
	- it works well (with jack)
	- very good quality
	- good audio/video sync
Disadvantages:
	- you have to manually calculate the screen size and rectangle (-s and 
-i switches)
	 - you need to connect your jack output(s) to the ffmpeg jack input 
after you've started recording
	- fairly big output file

For the last 'drawback' you can convert to a compressed video format 
such as webm. Recently I am use (again stolen, ehm, inspired from some 
online forum [2]):

ffmpeg -y -i "$INFILE" -threads 8 -f webm -vcodec libvpx -g 120 -level 
216 -profile 0 -qmax 42 -qmin 10 -rc_buf_aggressivity 0.95 -vb 2M 
-acodec libvorbis -aq 90 -ac 2 $OUTFILE

This will give a nice webm video which is about 20% the filesize of the 
original avi

Here is a quick short example of the final output:
http://gnufunk.org/~lorenzosu/temp/ffmpeg_grab_test.webm


Hope this helps
Lorenzo.
PS This (longer) was also created with the same technique:
http://vimeo.com/36609964

[1] I succeed on Debian wheezy amd64 following this: 
https://ffmpeg.org/trac/ffmpeg/wiki/UbuntuCompilationGuide
[2] I actually found the source for this: 
http://ubuntuforums.org/showthread.php?t=1522381&p=9539218#post9539218 - 
thanks demizer