[LAD] Screencasting with JACK [SOLVED!]

[Patrick Shirkey]

On Fri, August 9, 2013 12:58 pm, J. Liles wrote:
> On Thu, Aug 8, 2013 at 6:54 PM, J. Liles <malnourite at gmail.com> wrote:
>
>>
>> As some of you may recall, every time I've posted a demo video to LAD,
>> I've had to include a disclaimer excusing the poor quality due to a lack
>> of
>> functional screencasting tools.
>>
>> Well, it took a couple of weeks of hair pulling and many, many hours of
>> testing, but I finally arrived at a solution.
>>
>> Anyone who wants to create a screencast and record audio via JACK *in
>> perfect sync* must do the following:
>>
>> Get ffmpeg. Apply this patch to it:
>>
>>
>> https://github.com/original-male/FFmpeg/commit/d02509d04d396a98646ca81e9ba327a501486130.patch
>>
>> Build it with vorbis and h264 support.
>>
>> Then, start your favorite desktop environment. I use Xephyr for this.
>>
>> Have jack running (at -r 48000)
>>
>> Then run the following command:
>>
>> ffmpeg -fflags +genpts+igndts -f x11grab -vsync 0 -r 30 -s 1920x1080 -i
>> :${DISPLAY}.+0,0 -vcodec h264 -f jack -ac 2 -r:a 48000  -i screencast
>> -acodec pcm_s16le -r:v 30 -vsync 2 -async 1 -map 0:0,1,0 -map 1:0
>> -preset
>> ultrafast -qp 0 "$FILE"
>>
>> Where DISPLAY is the number of your X11 display and FILE is the filename
>> for the screencast. I use a .mkv extension for the matroska container.
>>
>> Remember to connect the streams you want recorded to the 'screencast'
>> JACK
>> inputs!
>>
>> With this setup I'm able to record a full 30 FPS @ 1080P with audio in
>> perfect sync. Please share your results too. With some more evidence I
>> might have a good case to get ffmpeg to accept my patch.
>>

They are pretty helpful folks and will give you useful feedback if you
submit the patch and they see any issues.




>> Enjoy!
>>
>>
>>
>>
>>
>>
>>
> Forgot to mention, use at least these options when configuring ffmpeg:
>
> ./configure --enable-libx264  --enable-x11grab --enable-gpl
> --enable-libvorbis


It would be interesting to have an app for this... Similar to Time
Machine. Just a big button that automatically saves the past x mins.

If you are interested let me know. I think I can find some time for that.



--
Patrick Shirkey
Boost Hardware Ltd