[LAU] [LAD] Screencasting with JACK [SOLVED!]

[J. Liles]

On Mon, Aug 12, 2013 at 5:17 AM, Diego Simak <diego.simak at gmail.com> wrote:

> 2013/8/12 Peder Hedlund <peder at musikhuset.org>:
> > Quoting Diego Simak <diego.simak at gmail.com>:
> >
> >> - Audio and video are not in sync, I can see the following message
> >> after executing the ffmpeg command:
> >>
> >> [swscaler @ 0x1ac5080] Warning: data is not aligned! This can lead to
> >> a speedloss
> >>
> >> diego at ruidosa:~$ ffmpeg -fflags +genpts+igndts -f x11grab -vsync 0 -r
> >> 30 -s 1366x768 -i :0.0+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 aaa.mkv
> >
> >
> >>   Duration: N/A, start: 1376226919.464630, bitrate: 1007124 kb/s
> >>     Stream #0:0: Video: rawvideo (BGR[0] / 0x524742), bgr0, 1366x768,
> >> 1007124 kb/s, 30 tbr, 1000k tbn, 30 tbc
> >> jack_port_get_latency_range called with an incorrect port 0
> >> [jack @ 0x1afbce0] JACK client registered and activated (rate=48000Hz,
> >> buffer_size=1024 frames)
> >> Guessed Channel Layout for  Input Stream #1.0 : stereo
> >> Input #1, jack, from 'screencast':
> >>   Duration: N/A, start: 1376226919.619355, bitrate: 3072 kb/s
> >>     Stream #1:0: Audio: pcm_f32le, 48000 Hz, stereo, flt, 3072 kb/s
> >> [swscaler @ 0x1ac5080] Warning: data is not aligned! This can lead to
> >> a speedloss
> >> frame=  122 fps= 23 q=-1.0 Lsize=    2774kB time=00:00:04.06
> >> bitrate=5588.3kbits/s
> >> video:2040kB audio:732kB subtitle:0 global headers:0kB muxing  overhead
> >> 0.097703%
> >
> >
> > A couple of things :
> >
> > * 1366 isn't a multiple of 8 which is probably why you get the "data is
> not
> > aligned! This can lead to a speedloss" warning. Set it to 1360 instead.
> >
>
> Ok, changing to 1360 and now no speedloss message is observerd.
>
> > * You've set ffmpeg to record at 30 fps but it seems your computer can
> only
> > manage to do 23 fps. That might be the cause of the A/V being out of
> sync.
> > Either decrease the capture area, change "-r:v 30" to something like
> "-r:v
> > 20" or try doing an uncompressed recording (replace "-vcodec h264 -preset
> > ultrafast -qp 0" with something like "-vcodec huffyuv"). In the latter
> case
> > you'll end up with a really big capture file which you might want/need to
> > demux, compress and remux afterwards.
> >
>
> I've tried both and still the audio is not in sync with the video:
>
> with -r:v 20
>
> ffmpeg -fflags +genpts+igndts -f x11grab -vsync 0 -r 30 -s 1360x768 -i
> :0.0+0,0 -vcodec h264 -f jack -ac 2 -r:a 48000  -i screencast -acodec
> pcm_s16le -r:v 20 -vsync 2 -async 1 -map 0:0,1,0 -map 1:0 -preset
> ultrafast -qp 0 toto.mkv
>
> I get this message every second:
>
> [libx264 @ 0x2832a00] non-strictly-monotonic PTS
>     Last message repeated 2 times
> frame=   11 fps=0.0 q=0.0 size=     587kB time=00:00:00.25
> bitrate=19235.5kbits/[libx264 @ 0x2832a00] non-strictly-monotonic PTS
>     Last message repeated 3 times
> frame=   23 fps= 21 q=0.0 size=     804kB time=00:00:00.65
> bitrate=10137.9kbits/[libx264 @ 0x2832a00] non-strictly-monotonic PTS
>     Last message repeated 3 times
> frame=   33 fps= 21 q=0.0 size=    1125kB time=00:00:01.00
> bitrate=9220.1kbits/s[libx264 @ 0x2832a00] non-strictly-monotonic PTS
>     Last message repeated 2 times
> frame=   44 fps= 21 q=0.0 size=    1461kB time=00:00:01.35
> bitrate=8866.4kbits/s
>
>
>
>
> without -r:v 20 and with -vcodec huffyuv
>
> I get as you said an enormeous file and this message, but this option
> seems to be better; e.g: audio is not in sync but better than h264
>
> Too many video packets in the buffer: (27 in 33747576 bytes).
> Maybe you are playing a non-interleaved stream/file or the codec failed?
> For AVI files, try to force non-interleaved mode with the -ni option.
> A:   8.2 V:   7.8 A-V:  0.461 ct:  0.074   0/  0 97%  3% 69.7% 71 0
>
>
>            ************************************************
>            **** Your system is too SLOW to play this!  ****
>            ************************************************
>
>
> It's a Core 2 Duo 2.27 GHz CPUs, don't know if its slow or not, seems it
> is...
>
> I still have to try what happens with J.Liles suggestion to use Xephyr
> but it seems that it will be the same.
>
> Thanks for your help, really appreciated!
>
>
> >  - Peder
> > _______________________________________________
> > Linux-audio-user mailing list
> > Linux-audio-user at lists.linuxaudio.org
> > http://lists.linuxaudio.org/listinfo/linux-audio-user
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>

Your system may indeed be too slow to play back the resulting video. You
should first transcode it to a more highly compressed format:

e.g. ffmpeg -i foo.mkv -acodec libvorbis -vcodec h264 bar.mkv
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