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

[Lorenzo Sutton]

On 06/07/2013 11:07 PM, Len Ovens wrote:
>
> On Fri, June 7, 2013 1:14 pm, Lorenzo Sutton wrote:
>> 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]
>
> Now if libav would just stop shipping with links from ffmpeg, debian could
> ship both...

I agree, and I think for clarity they should call it with its proper 
name (libav or avconv or whatever) and not 'trick' user into installing 
it when they think they are installing ffmpeg.

>
>> 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)
>
> A script that runs xrandr could probably do that automatically. xrandr has
> the screen sizes (the size of each monitor with position as well as the
> size of combined screen size in the case of two monitors). I think there
> are tools that will give a window size and position as well and most of
> the screen capture tools allow "rubberbanding" a rectangle, so that should
> not be hard either... I am pretty sure I could figure that out in
> tk/tcl... my python is not that advanced yet.
>
>> 	 - you need to connect your jack output(s) to the ffmpeg jack input
>> after you've started recording
>
> jack.plumbing from the jack-tools package might make that less painful.
> Possibly some of the session managers too.

Yes.. Ideally someone (tm) could hack up a script to select the screen 
rectangle to capture, the jack outputs you want and then start ffmpeg 
with the correct parameters and same for jack.plumbing

>
>> 	- fairly big output file
>
> Most of us have fairly big hard drives these days  ;)  maybe I just don't
> do enough recording to make mine seem small.

True... what I meant here was mostly related to uploading as you usually 
want to share your screencast.
>
> There are enough scripting GUIs around (like tk/tcl and everything newer)
> it would not be hard to create a GUI to wrap around all that and the
> recoding below. The biggest stumbling block is a real ffmpeg. Did you have
> to remove libav?

I never installed it. Just went straight to the mentioned 'Compile for 
ubuntu' guide.

Lorenzo

>
>> 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
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>>
>
>