[FFmpeg-user] Screencast produces only gray output

Tue Nov 20 13:18:54 CET 2012

On 2012-11-20 02:54, Carl Eugen Hoyos wrote:
> <look <at> ebookring.net> writes:
>
>> $ ffmpeg -f alsa -ac 2 -i pulse -f x11grab -r 10 -s 1280x800
>> -i :0.0 -acodec pcm_s16le -vcodec libx264 -pix_fmt yuv420p
>> -preset ultrafast -crf 0 -threads 0 output.mkv
>
>> frame=  230 fps=7.1 q=0.0 Lsize=   10363kB time=00:00:23.00
>                  _^_
>
> This looks very suspicious, please try with a significantly
> lower resolution or -r 5.
>
> Carl Eugen
>


Here's the result; (no audio is captured but the video is acceptable 
and will play with FFplay, VLC & Totem


$ ffmpeg -f alsa -ac 2 -i pulse -f x11grab -r 5 -s 1280x800 -i :0.0 
-acodec pcm_s16le -vcodec libx264 -pix_fmt yuv420p -preset ultrafast 
-crf 0 -threads 0 output.mkv
ffmpeg version N-42139-g7693543 Copyright (c) 2000-2012 the FFmpeg 
developers
   built on Nov  8 2012 22:15:12 with gcc 4.4.3 (Ubuntu 
4.4.3-4ubuntu5.1)
   configuration: --enable-gpl --enable-libfaac --enable-libmp3lame 
--enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora 
--enable-libvorbis --enable-libvpx --enable-libx264 --enable-nonfree 
--enable-version3 --enable-x11grab
   libavutil      52.  5.100 / 52.  5.100
   libavcodec     54. 71.100 / 54. 71.100
   libavformat    54. 36.100 / 54. 36.100
   libavdevice    54.  3.100 / 54.  3.100
   libavfilter     3. 21.106 /  3. 21.106
   libswscale      2.  1.102 /  2.  1.102
   libswresample   0. 16.100 /  0. 16.100
   libpostproc    52.  1.100 / 52.  1.100
[alsa @ 0xae5d580] Estimating duration from bitrate, this may be 
inaccurate
Guessed Channel Layout for  Input Stream #0.0 : stereo
Input #0, alsa, from 'pulse':
   Duration: N/A, start: 1353413584.631743, bitrate: 1536 kb/s
     Stream #0:0: Audio: pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s
[x11grab @ 0xae5abc0] device: :0.0 -> display: :0.0 x: 0 y: 0 width: 
1280 height: 800
[x11grab @ 0xae5abc0] shared memory extension found
[x11grab @ 0xae5abc0] Estimating duration from bitrate, this may be 
inaccurate
Input #1, x11grab, from ':0.0':
   Duration: N/A, start: 1353413584.845664, bitrate: 163840 kb/s
     Stream #1:0: Video: rawvideo (BGR[0] / 0x524742), bgr0, 1280x800, 
163840 kb/s, 5 tbr, 1000k tbn, 5 tbc
File 'output.mkv' already exists. Overwrite ? [y/N] y
using cpu capabilities: MMX2 SSE2Slow SlowCTZ
[libx264 @ 0xae55820] profile High 4:4:4 Predictive, level 3.2, 4:2:0 
8-bit
[libx264 @ 0xae55820] 264 - core 129 r16 1cffe9f - H.264/MPEG-4 AVC 
codec - Copyleft 2003-2012 - 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=1 
lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 
bluray_compat=0 constrained_intra=0 bframes=0 weightp=0 keyint=250 
keyint_min=5 scenecut=0 intra_refresh=0 rc=cqp mbtree=0 qp=0
Output #0, matroska, to 'output.mkv':
   Metadata:
     encoder         : Lavf54.36.100
     Stream #0:0: Video: h264, yuv420p, 1280x800, q=-1--1, 1k tbn, 5 tbc
     Stream #0:1: Audio: pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s
Stream mapping:
   Stream #1:0 -> #0:0 (rawvideo -> libx264)
   Stream #0:0 -> #0:1 (pcm_s16le -> pcm_s16le)
Press [q] to stop, [?] for help
frame=  345 fps=5.1 q=0.0 Lsize=   55203kB time=00:01:09.82 
bitrate=6477.0kbits/s
video:41749kB audio:13091kB subtitle:0 global headers:0kB muxing 
overhead 0.663149%
[libx264 @ 0xae55820] frame I:2     Avg QP: 0.00  size:408454
[libx264 @ 0xae55820] frame P:343   Avg QP: 0.00  size:122254
[libx264 @ 0xae55820] mb I  I16..4: 100.0%  0.0%  0.0%
[libx264 @ 0xae55820] mb P  I16..4: 15.1%  0.0%  0.0%  P16..4: 20.6%  
0.0%  0.0%  0.0%  0.0%    skip:64.2%
[libx264 @ 0xae55820] coded y,uvDC,uvAC intra: 91.4% 90.8% 90.7% inter: 
17.5% 23.5% 23.3%
[libx264 @ 0xae55820] i16 v,h,dc,p: 40% 59%  0%  0%
[libx264 @ 0xae55820] i8c dc,h,v,p: 11% 57% 31%  0%
[libx264 @ 0xae55820] kb/s:4956.54


Here also is the result of the FFplay command;

$ ffplay output.mkv
ffplay version N-42139-g7693543 Copyright (c) 2003-2012 the FFmpeg 
developers
   built on Nov  8 2012 22:15:12 with gcc 4.4.3 (Ubuntu 
4.4.3-4ubuntu5.1)
   configuration: --enable-gpl --enable-libfaac --enable-libmp3lame 
--enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora 
--enable-libvorbis --enable-libvpx --enable-libx264 --enable-nonfree 
--enable-version3 --enable-x11grab
   libavutil      52.  5.100 / 52.  5.100
   libavcodec     54. 71.100 / 54. 71.100
   libavformat    54. 36.100 / 54. 36.100
   libavdevice    54.  3.100 / 54.  3.100
   libavfilter     3. 21.106 /  3. 21.106
   libswscale      2.  1.102 /  2.  1.102
   libswresample   0. 16.100 /  0. 16.100
   libpostproc    52.  1.100 / 52.  1.100
Input #0, matroska,webm, from 'output.mkv':
   Metadata:
     ENCODER         : Lavf54.36.100
   Duration: 00:01:09.82, start: 0.000000, bitrate: 6477 kb/s
     Stream #0:0: Video: h264 (High 4:4:4 Predictive), yuv420p, 
1280x800, SAR 1:1 DAR 8:5, 5 fps, 5 tbr, 1k tbn, 10 tbc (default)
     Stream #0:1: Audio: pcm_s16le, 48000 Hz, 2 channels, s16, 1536 kb/s 
(default)
Frame changed from size:0x0 to size:1280x800632KB sq=    0B f=0/0
   23.42 A-V: -0.185 fd=   1 aq=  429KB vq=  845KB sq=    0B f=0/0


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