FFmpeg to the Rescue
So with Cinelerra not working for desktop recordings, I needed an alternate way to record my desktop screen as well as the audio from the person being interviewed. After some searching a good deal of trial and error, I found from the link in the reference section at the bottom of the page, a very nice ffmpeg command. You can save to any format you want. The example below shows how to save the microphone audio (hw:0,0) in PCM format. The desktop video is brought in via the xllgrab format specifier :
ffmpeg -f alsa -i hw:0,0 -ac 2 -ar 48000 -acodec pcm_s16le -f x11grab -r 24 -s 1280x720 -i :0.0 -aspect 16:9 -vcodec libx264 -vpre lossless_ultrafast -threads 8 -y output.mov
I later tweaked the command to do a bit more, using pulse audio as input as well as saving out to an iPod compatible format:
ffmpeg -f alsa -i pulse -f x11grab -s 1280x720 -r 23.98 -i :0.0 -vcodec libx264 -acodec pcm_s16le -ab 128k -ar 48000 -ac 1 -b 2000k -bt 750k -refs 1 -deblockalpha 0 -deblockbeta 0 -subq 1 -me_range 21 -bf 0 -level 30 -g 300 -keyint_min 30 -sc_threshold 40 -rc_eq 'blurCplx^(1-qComp)' -qcomp 0.7 -qmax 51 -qdiff 4 -i_qfactor 0.71428572 -maxrate 2000k -bufsize 2M -cmp 1 -threads 8 output.mov
Errors
Not sure how yet to resolve these ffmpeg errors:
[alsa @ 0x16512a0] Estimating duration from bitrate, this may be inaccurate
Input #0, alsa, from 'hw:0,0':
Duration: N/A, start: 17479.447401, bitrate: N/A
Stream #0.0: Audio: pcm_s16le, 32000 Hz, 2 channels, s16, 1024 kb/s
[x11grab @ 0x1650240] device: :0.0 -> display: :0.0 x: 0 y: 0 width: 1280 height: 720
[x11grab @ 0x1650240] shared memory extension found
[x11grab @ 0x1650240] Estimating duration from bitrate, this may be inaccurate
Input #1, x11grab, from ':0.0':
Duration: N/A, start: 1327197224.425685, bitrate: 707788 kb/s
Stream #1.0: Video: rawvideo, bgra, 1280x720, 707788 kb/s, 24 tbr, 1000k tbn, 24 tbc
Incompatible pixel format 'bgra' for codec 'libx264', auto-selecting format 'yuv420p'
Along the way, I received an error:
"unknown field slave"
Finding a bit more about ALSA
This ended up being because I had edited my /etc/asound.conf file from the default. This corrupted my sound card settings. I was reacquainted with some debugging commands and places where "sound stuff" lives:
[sodo@computer etc]$ arecord -l
**** List of CAPTURE Hardware Devices ****
card 0: U0x46d0x821 [USB Device 0x46d:0x821], device 0: USB Audio [USB Audio]
Subdevices: 0/1
Subdevice #0: subdevice #0
card 2: MobilePre [MobilePre], device 0: USB Audio [USB Audio]
Subdevices: 0/1
Subdevice #0: subdevice #0
[sodo@computer etc]$ amixer -c 2
Simple mixer control 'Speaker',0
Capabilities: pvolume pswitch pswitch-joined penum
Playback channels: Front Left - Front Right
Limits: Playback 0 - 31
Mono:
Front Left: Playback 31 [100%] [0.00dB] [on]
Front Right: Playback 31 [100%] [0.00dB] [on]
Simple mixer control 'PCM',0
Capabilities: pvolume pswitch pswitch-joined penum
Playback channels: Front Left - Front Right
Limits: Playback 0 - 31
Mono:
Front Left: Playback 25 [81%] [0.00dB] [on]
Front Right: Playback 25 [81%] [0.00dB] [on]
Simple mixer control 'PCM',1
Capabilities: volume volume-joined penum
Playback channels: Mono
Capture channels: Mono
Limits: 0 - 2
Mono: 2 [100%]
Simple mixer control 'Analog In',0
Capabilities: pvolume cvolume pswitch pswitch-joined cswitch cswitch-joined penum
Playback channels: Front Left - Front Right
Capture channels: Front Left - Front Right
Limits: Playback 0 - 31 Capture 0 - 31
Front Left: Playback 28 [90%] [6.00dB] [off] Capture 31 [100%] [12.00dB] [on]
Front Right: Playback 28 [90%] [6.00dB] [off] Capture 31 [100%] [12.00dB] [on]
[sodo@computer ~]$ cat /proc/asound/cards
0 [U0x46d0x821 ]: USB-Audio - USB Device 0x46d:0x821
USB Device 0x46d:0x821 at usb-0000:00:1d.7-6, high speed
1 [MobilePre ]: USB-Audio - MobilePre
M Audio MobilePre at usb-0000:00:1d.0-1, full speed
[sodo@computer etc]$ ls /dev/snd
by-id by-path controlC0 controlC2 pcmC0D0c pcmC2D0c pcmC2D0p seq timer
[sodo@computer etc]$ cat /etc/asound.conf
#
# Place your global alsa-lib configuration here...
#
@hooks [
{
func load
files [
"/etc/alsa/pulse-default.conf"
]
errors false
}
]
Also, I learned about xwininfo, a cool command that shows you your desktop settings:
[sodo@computer videoConfTest]$ xwininfo
xwininfo: Window id: 0x320003b "Hak5 - Linux Screen Recording, Boxee Python Development and Qnext - YouTube - Google Chrome"
Absolute upper-left X: 0
Absolute upper-left Y: 53
Relative upper-left X: 0
Relative upper-left Y: 22
Width: 1280
Height: 971
Depth: 24
Visual: 0x21
Visual Class: TrueColor
Border width: 0
Class: InputOutput
Colormap: 0x20 (installed)
Bit Gravity State: NorthWestGravity
Window Gravity State: NorthWestGravity
Backing Store State: NotUseful
Save Under State: no
Map State: IsViewable
Override Redirect State: no
Corners: +0+53 -1280+53 -1280-0 +0-0
-geometry 1280x971+0-0
Finally, I installed Skype and dealt with resolving a bunch of dependency problems (as usual):
VideoCamming
And a simple way to trigger mplayer to open up your videocam:
mplayer tv:// -tv driver=v4l2 device=/dev/video0
Another simple way to capture the output:
ffmpeg -f alsa -i hw:0 -f video4linux2 -s 320x240 -i /dev/video0 out.mpg
Or a more complex example, saving the video into an iPod friendly format:
ffmpeg -f alsa -i pulse -f video4linux2 -i /dev/video0 -aspect 16:9 -s 1280x720 -r 23.98 -vcodec libx264 -acodec libfaac -ab 128k -ar 48000 -ac 1 -b 2000k -bt 750k -refs 1 -deblockalpha 0 -deblockbeta 0 -subq 1 -me_range 21 -bf 0 -level 30 -g 300 -keyint_min 30 -sc_threshold 40 -rc_eq 'blurCplx^(1-qComp)' -qcomp 0.7 -qmax 51 -qdiff 4 -i_qfactor 0.71428572 -maxrate 2000k -bufsize 2M -cmp 1 -threads 8 output.mov
Finally, guvcview is a very nice program to control one's videocam:
Reference
http://www.linuxquestions.org/questions/linux-newbie-8/recording-desktop-with-ffmpeg-877580/
http://www.youtube.com/watch?v=mNz5Lrc06_s
http://forums.fedoraforum.org/showthread.php?t=256681
http://ffmpeg.org/ffprobe.html#pulse
http://alien.slackbook.org/blog/adding-an-alsa-software-pre-amp-to-fix-low-sound-levels/
http://forums.opensuse.org/english/get-technical-help-here/multimedia/471522-record-my-desktop-using-ffmpeg-post2433494.html
http://superuser.com/questions/251338/mencoder-capture-from-camera-and-microphone
http://ubuntuforums.org/showthread.php?t=1556038 (using jack)
http://wiki.linuxaudio.org/wiki/screencasttutorial (jack_capture)
https://help.ubuntu.com/community/Webcam (webcam)
http://howto-pages.org/ffmpeg/ (a nice, human readable version of the FFmpeg doc)
http://www.tldp.org/HOWTO/Alsa-sound-6.html (amixer settings)
