11 Aug
2013
11 Aug
'13
3:18 p.m.
2013/8/8 J. Liles <malnourite(a)gmail.com>
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/d02509d04d396a98646ca81e9ba3…
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.
Enjoy!
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My result:
- I had to change screen size to 1366x768 according to my laptop display
- 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
This is the full log.
Thank you very much!
diego@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
ffmpeg version N-55422-gb37ff48 Copyright (c) 2000-2013 the FFmpeg developers
built on Aug 10 2013 10:54:00 with gcc 4.6 (Ubuntu/Linaro 4.6.3-1ubuntu5)
configuration: --enable-libx264 --enable-x11grab --enable-gpl
--enable-libvorbis --disable-yasm
libavutil 52. 41.100 / 52. 41.100
libavcodec 55. 24.100 / 55. 24.100
libavformat 55. 13.102 / 55. 13.102
libavdevice 55. 3.100 / 55. 3.100
libavfilter 3. 82.100 / 3. 82.100
libswscale 2. 4.100 / 2. 4.100
libswresample 0. 17.103 / 0. 17.103
libpostproc 52. 3.100 / 52. 3.100
[x11grab @ 0x1ae3700] device: :0.0+0,0 -> display: :0.0 x: 0 y: 0
width: 1366 height: 768
[x11grab @ 0x1ae3700] shared memory extension found
Input #0, x11grab, from ':0.0+0,0':
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] deprecated pixel format used, make sure you did
set range correctly
No pixel format specified, yuv444p for H.264 encoding chosen.
Use -pix_fmt yuv420p for compatibility with outdated media players.
-async is forwarded to lavfi similarly to -af
aresample=async=1:min_hard_comp=0.100000:first_pts=0.
[libx264 @ 0x2b6e520] using cpu capabilities: MMX2 SSE2Fast SSSE3
FastShuffle SSE4.1 Cache64
[libx264 @ 0x2b6e520] profile High 4:4:4 Predictive, level 3.2, 4:4:4 8-bit
[libx264 @ 0x2b6e520] 64 - core 120 r2151 a3f4407 - H.264/MPEG-4 AVC
codec - Copyleft 2003-2011 - http://www.videolan.org/x264.html -
options: cabac=0 ref=1 deblock=0:0:0 analyse=0:0 me=dia subme=0 psy=0
mixed_ref=0 me_range=16 chroma_me=1 trellis=0 8x8dct=0 cqm=0
deadzone=21,11 fast_pskip=0 chroma_qp_offset=0 threads=3
sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0
constrained_intra=0 bframes=0 weightp=0 keyint=250 keyint_min=25
scenecut=0 intra_refresh=0 rc=cqp mbtree=0 qp=0
Output #0, matroska, to 'aaa.mkv':
Metadata:
encoder : Lavf55.13.102
Stream #0:0: Video: h264 (libx264) (H264 / 0x34363248), yuv444p,
1366x768, q=-1--1, 1k tbn, 30 tbc
Stream #0:1: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 48000 Hz,
stereo, s16, 1536 kb/s
Stream mapping:
Stream #0:0 -> #0:0 (rawvideo -> libx264)
Stream #1:0 -> #0:1 (pcm_f32le -> pcm_s16le)
Press [q] to stop, [?] for help
[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%
[libx264 @ 0x2b6e520] frame I:1 Avg QP: 0.00 size:596863
[libx264 @ 0x2b6e520] frame P:121 Avg QP: 0.00 size: 12324
[libx264 @ 0x2b6e520] mb I I16..4: 100.0% 0.0% 0.0%
[libx264 @ 0x2b6e520] mb P I16..4: 7.6% 0.0% 0.0% P16..4: 0.3%
0.0% 0.0% 0.0% 0.0% skip:92.1%
[libx264 @ 0x2b6e520] coded y,u,v intra: 11.9% 37.1% 37.5% inter: 0.2% 0.2% 0.2%
[libx264 @ 0x2b6e520] i16 v,h,dc,p: 91% 8% 0% 0%
[libx264 @ 0x2b6e520] kb/s:4107.72
Received signal 2: terminating.
diego@ruidosa:~$
diego@ruidosa:~$
diego@ruidosa:~$