I am using ffmpeg built from source at this revision in Fedora 20.
I am able to record audio perfectly fine with the command:
FFmpeg/ffmpeg -f alsa -ac 2 -i pulse -- output.wav
However, when I try both screen capture and audio, like this:
FFmpeg/ffmpeg -video_size 800x600 -framerate 25 -ac 2 -f x11grab -i :0.0+0,0 -ac 2 -f alsa -i pulse -ac 2 -acodec copy output.mpeg -ac 2
I'm getting a video with 0 audio channels, which I can check running FFmpeg/ffplay output.mpeg
Input #0, mpeg, from 'output.mpeg':
Duration: 00:00:09.44, start: 0.540000, bitrate: 2743 kb/s
Stream #0:0[0x1e0]: Video: mpeg1video, yuv420p(tv), 800x600 [SAR 1:1 DAR 4:3], 104857 kb/s, 25 fps, 25 tbr, 90k tbn, 25 tbc
Stream #0:1[0x1c0]: Audio: mp2, 0 channels, s16p
7.26 M-V: 0.000 fd= 0 aq= 0KB vq= 33KB sq= 0B f=0/0
and no audible sound is played. The position of -ac 2
doesn't change the behaviour, nor does repeating it only once. This is despite ffmpeg claims to record the audio with 2 channels, here is the input:
ffmpeg version N-71312-ga66dcfe Copyright (c) 2000-2015 the FFmpeg developers
built with gcc 4.8.3 (GCC) 20140911 (Red Hat 4.8.3-7)
configuration:
libavutil 54. 22.100 / 54. 22.100
libavcodec 56. 34.100 / 56. 34.100
libavformat 56. 29.100 / 56. 29.100
libavdevice 56. 4.100 / 56. 4.100
libavfilter 5. 13.101 / 5. 13.101
libswscale 3. 1.101 / 3. 1.101
libswresample 1. 1.100 / 1. 1.100
Trailing options were found on the commandline.
Input #0, x11grab, from ':0.0+0,0':
Duration: N/A, start: 1428348285.201679, bitrate: N/A
Stream #0:0: Video: rawvideo (BGR[0] / 0x524742), bgr0, 800x600, 25 fps, 25 tbr, 1000k tbn, 25 tbc
Guessed Channel Layout for Input Stream #1.0 : stereo
Input #1, alsa, from 'pulse':
Duration: N/A, start: 1428348285.225901, bitrate: 1536 kb/s
Stream #1:0: Audio: pcm_s16le, 48000 Hz, 2 channels, s16, 1536 kb/s
File 'output.mpeg' already exists. Overwrite ? [y/N] y
[mpeg @ 0x2d079a0] VBV buffer size not set, using default size of 130KB
If you want the mpeg file to be compliant to some specification
Like DVD, VCD or others, make sure you set the correct buffer size
Output #0, mpeg, to 'output.mpeg':
Metadata:
encoder : Lavf56.29.100
Stream #0:0: Video: mpeg1video, yuv420p, 800x600, q=2-31, 200 kb/s, 25 fps, 90k tbn, 25 tbc
Metadata:
encoder : Lavc56.34.100 mpeg1video
Stream #0:1: Audio: pcm_s16le, 48000 Hz, stereo, 1536 kb/s
Stream mapping:
Stream #0:0 -> #0:0 (rawvideo (native) -> mpeg1video (native))
Stream #1:0 -> #0:1 (copy)
I'm clueless. If anybody can tell me how to get this to work by either:
- fixing my mistakes in the command line flags
- if it's a regression, which revision to build from.
- any other way
I'll buy him/her a pint.