[Libav-user] During screencast problems with audio when duration set

alessio matiz muec at virgilio.it
Wed Feb 26 20:49:06 CET 2014


Hello,
I'm recording a desktop session (video and audio) with command

"avconv -f alsa -i pulse -f x11grab -r 30 -s 1366x768 -i :0.0 -vcodec
libx264 -preset ultrafast -ab 320k -threads 8 screen.mkv"

And everything goes fine.
When I add duration for the recording with command -t 10, no sound is
recorded:

"avconv -f alsa -i pulse -f x11grab -r 30 -s 1366x768 -i :0.0 -t 10 -vcodec
libx264 -preset ultrafast -ab 320k -threads 8 screen.mkv"

Any suggestion?
Thanx!

Output for command:
avconv version 0.8.10-4:0.8.10-0ubuntu0.12.04.1, Copyright (c) 2000-2013 the
Libav developers
  built on Feb  6 2014 20:56:59 with gcc 4.6.3
[alsa @ 0xd2ca60] capture with some ALSA plugins, especially dsnoop, may
hang.
[alsa @ 0xd2ca60] Estimating duration from bitrate, this may be inaccurate
Input #0, alsa, from 'pulse':
  Duration: N/A, start: 1393444085.087724, bitrate: N/A
    Stream #0.0: Audio: pcm_s16le, 48000 Hz, 2 channels, s16, 1536 kb/s
[x11grab @ 0xd2d280] device: :0.0 -> display: :0.0 x: 0 y: 0 width: 1366
height: 768
[x11grab @ 0xd2d280] shared memory extension  found
[x11grab @ 0xd2d280] Estimating duration from bitrate, this may be
inaccurate
Input #1, x11grab, from ':0.0':
  Duration: N/A, start: 1393444085.131106, bitrate: 1007124 kb/s
    Stream #1.0: Video: rawvideo, bgra, 1366x768, 1007124 kb/s, 30 tbr,
1000k tbn, 30 tbc
File 'screen.mkv' already exists. Overwrite ? [y/N] y
Incompatible pixel format 'bgra' for codec 'libx264', auto-selecting format
'yuv420p'
[buffer @ 0xd2e7e0] w:1366 h:768 pixfmt:bgra
[avsink @ 0xd2c140] auto-inserting filter 'auto-inserted scaler 0' between
the filter 'src' and the filter 'out'
[scale @ 0xd2c8a0] w:1366 h:768 fmt:bgra -> w:1366 h:768 fmt:yuv420p
flags:0x4
[libx264 @ 0xd2bca0] lookaheadless mb-tree requires intra refresh or
infinite keyint
[libx264 @ 0xd2bca0] using cpu capabilities: MMX2 SSE2Fast FastShuffle LZCNT
[libx264 @ 0xd2bca0] profile Constrained Baseline, level 3.2
[libx264 @ 0xd2bca0] 264 - 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=1 psy_rd=1.00:0.00
mixed_ref=0 me_range=16 chroma_me=1 trellis=0 8x8dct=0 cqm=0 deadzone=21,11
fast_pskip=1 chroma_qp_offset=0 threads=8 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=crf mbtree=0 crf=23.0
qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.25 aq=0
Output #0, matroska, to 'screen.mkv':
  Metadata:
    encoder         : Lavf53.21.1
    Stream #0.0: Video: libx264, yuv420p, 1366x768, q=-1--1, 1k tbn, 30 tbc
    Stream #0.1: Audio: libvorbis, 48000 Hz, 2 channels, s16, 320 kb/s
Stream mapping:
  Stream #1:0 -> #0:0 (rawvideo -> libx264)
  Stream #0:0 -> #0:1 (pcm_s16le -> libvorbis)
Press ctrl-c to stop encoding
^Cframe=   56 fps= 21 q=-1.0 Lsize=    1130kB time=5.39
bitrate=1718.2kbits/s    
video:959kB audio:164kB global headers:4kB muxing overhead 0.246981%
[libx264 @ 0xd2bca0] frame I:1     Avg QP:21.00  size:238383
[libx264 @ 0xd2bca0] frame P:55    Avg QP:14.80  size: 13518
[libx264 @ 0xd2bca0] mb I  I16..4: 100.0%  0.0%  0.0%
[libx264 @ 0xd2bca0] mb P  I16..4:  1.7%  0.0%  0.0%  P16..4:  5.8%  0.0% 
0.0%  0.0%  0.0%    skip:92.4%
[libx264 @ 0xd2bca0] coded y,uvDC,uvAC intra: 47.3% 46.1% 45.2% inter: 3.6%
4.6% 3.9%
[libx264 @ 0xd2bca0] i16 v,h,dc,p: 62% 34%  2%  1%
[libx264 @ 0xd2bca0] i8c dc,h,v,p: 51% 25% 23%  2%
[libx264 @ 0xd2bca0] kb/s:1370.03
Received signal 2: terminating.




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