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IDProjectCategoryView StatusDate SubmittedLast Update
0000248KdenliveUser Interfacepublic2008-10-21 23:422008-11-12 22:22
Reporterjmpoure 
Assigned To 
PriorityhighSeverityfeatureReproducibilityhave not tried
StatusclosedResolutionfixed 
PlatformDebianOSGNU/LinuxOS VersionSID
Product Version 
Target Version0.7.0Fixed in Version0.7.0 
Summary0000248: Aoss choppy sound during screen capture -> shoulb be using sox + alsa
DescriptionDear JB and friends,

AOSS provides choppy sound during screen capture.

I tested successfully this screen capture command:
Don't know why, but Aoss never proved to be reliable.

Therefore we should pipe sound using sox and Alsa.

sox -t alsa "default:CARD=Audio" -q -c1 -r48000 -t raw - | \
ffmpeg -f s16le -ab 128k -ar 48000 -ac 1 -i - -acodec mp2 \
-f x11grab -r 10 -s 1400x1050 -i :0.0 -vcodec mpeg4 \
-t 3 \
capture.avi

Thank you Dan for the input.

Advantages:
* Supports ALSA and OSS
* sox available under various platforms

In next stages, it should possible to capture sound from Kdenlive and display a vu-meter for sound level. Maybe directly in which case we do not need sox?

Would it be possible to integrate this pipe into Kdenlive?
This would be great to release tutorials.

Cheers,
Jean-Michel
TagsNo tags attached.
Build/Install Method
Attached Files? file icon aoos-bug.avi [^] (1,200,508 bytes) 2008-10-26 12:03

- Relationships

-  Notes
(0000549)
madsdyd (administrator)
2008-10-22 10:15

I am a bit confused about this, because it is my understanding, that capturing from alsa devices should work, using e.g. the oss emulation of the kernel.

Please have a look at e.g. this link: http://www.nabble.com/Capture-audio-from-alsa-td15819836.html [^]

It wont work for you?
(0000579)
ddennedy (developer)
2008-10-22 19:01

From the brief reading, it does seem that using a different program to capture the audio and piping it into ffmpeg is proving to be more reliable.

Hey, does that MPEG-4 edit well and not look too compressed? Ever tried using "-pix_fmt yuv422p -vcodec huffyuv capture.avi" or "-vcodec flashsv capture.flv?"
(0000699)
jmpoure (developer)
2008-10-26 11:58
edited on: 2008-10-26 12:24

Changing this issue to Confirmed bug:

1) I did a 5 minutes tutorial about screen capture using AOSS and the sound was terribly poor. Some words are cut or simply lost. AOSS is not reliable at all, so we should defenitely pipe from another program. See attached file for example.

2) Also, I agree with Dan that we should use yuv422p capture and then decide afterwards what we want for export.

3) Same ussue for sound capture using sox: we should keep the least compressed sound and decide afterwards what we want for export.

This works very well for me (10 second test):

sox -t alsa "default" -q -c1 -r48000 -t raw - | \
ffmpeg -f s16le -i - -acodec copy \
-f x11grab -r 10 -s 1280x768 -i :0.0 \
-pix_fmt yuv422p -vcodec huffyuv \
-t 10 \
capture.avi

This results in:

Input #0, s16le, from 'pipe:':
  Duration: N/A, start: 0.000000, bitrate: N/A
    Stream #0.0: Audio: pcm_s16le, 44100 Hz, mono, 705 kb/s
[x11grab @ 0x7f6362d3a5c0]device: :0.0 -> display: :0.0 x: 0 y: 0 width: 1280 height: 768
[x11grab @ 0x7f6362d3a5c0]shared memory extension found
Input #1, x11grab, from ':0.0':
  Duration: N/A, start: 1225023762.348554, bitrate: 314572 kb/s
    Stream #1.0: Video: rawvideo, rgb32, 1280x768, 314572 kb/s, 10.00 tb(r)
Output #0, avi, to 'capture.avi':
    Stream #0.0: Video: huffyuv, yuv422p, 1280x768, q=2-31, 200 kb/s, 10.00 tb(c)
    Stream #0.1: Audio: pcm_s16le, 44100 Hz, mono, 705 kb/s
Stream mapping:
  Stream #1.0 -> #0.0
  Stream #0.0 -> #0.1
[huffyuv @ 0x7f63628625a0]using huffyuv 2.2.0 or newer interlacing flag
frame= 30 fps= 10 q=0.0 Lsize= 27474kB time=3.00 bitrate=75021.3kbits/s
video:24108kB audio:259kB global headers:0kB muxing overhead 12.748274%

This seems like the ultimate tool to make quality screen captures.

(0000701)
madsdyd (administrator)
2008-10-26 21:14

A patch to enable alsa recording from kdenlive has been commited for svn rev. 2570.

jmpoure could you please test this, and close this issue, if it works to your satisfaction?

Thanks.

- Issue History
Date Modified Username Field Change
2008-10-21 23:42 jmpoure New Issue
2008-10-22 10:15 madsdyd Note Added: 0000549
2008-10-22 10:15 madsdyd Status new => feedback
2008-10-22 10:20 jmpoure Note Added: 0000550
2008-10-22 10:21 jmpoure Note Edited: 0000550
2008-10-22 10:25 jmpoure Note Edited: 0000550
2008-10-22 10:26 jmpoure Note Edited: 0000550
2008-10-22 19:01 ddennedy Note Added: 0000579
2008-10-26 11:58 jmpoure Note Added: 0000699
2008-10-26 11:58 jmpoure Status feedback => confirmed
2008-10-26 11:59 jmpoure Note Edited: 0000699
2008-10-26 12:02 jmpoure Summary Proposal to use sox + ffmpeg for screen capture => Aoss not reliable for sound : using sox + ffmpeg for screen capture
2008-10-26 12:03 jmpoure File Added: aoos-bug.avi
2008-10-26 12:04 jmpoure Status confirmed => acknowledged
2008-10-26 12:05 jmpoure Note Edited: 0000699
2008-10-26 12:15 jmpoure Note Edited: 0000699
2008-10-26 12:15 jmpoure Note Edited: 0000699
2008-10-26 12:17 jmpoure Note Edited: 0000699
2008-10-26 12:24 jmpoure Note Edited: 0000699
2008-10-26 12:24 jmpoure Note Edited: 0000699
2008-10-26 14:29 jmpoure Summary Aoss not reliable for sound : using sox + ffmpeg for screen capture => Aoss choppy sound during screen capture -> shoulb be using sox + alsa
2008-10-26 14:29 jmpoure Note Deleted: 0000550
2008-10-26 14:31 jmpoure Description Updated
2008-10-26 21:14 madsdyd Note Added: 0000701
2008-10-26 21:34 madsdyd Target Version => 0.7.0
2008-10-27 21:15 jmpoure Status acknowledged => closed
2008-10-27 21:15 jmpoure Resolution open => fixed
2008-11-12 22:22 madsdyd Fixed in Version => 0.7.0


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