[FFmpeg-user] play only left/right channel from an audio input

Tue Mar 13 14:39:19 CET 2012

I have 2 steams, one video and one audio ( stereo ) and I want the output
to have 2 streams one video and one stereo with the left ( or right )
channel muted, what is the correct command.

This is my original command:

-f dshow -i video="screen-capture-recorder":audio="Stereo Mix (IDT High
Definition" -vcodec  libx264 -preset ultrafast -tune film -r 10 -async 1
-ab 32k -ar 22050  -f mpegts udp://192.168.5.230:48551

ffmpeg version N-38292-ga4c22e3 Copyright (c) 2000-2012 the FFmpeg
developers
  built on Feb 27 2012 14:50:39 with gcc 4.6.2
  configuration: --enable-gpl --enable-version3 --disable-w32threads
--enable-runtime-cpudetect --enable-avisynth --enable-bzlib --enable-frei0r
--enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libfreetype
--enable-libgsm --enable-libmp3lame --enable-libopenjpeg --enable-librtmp
--enable-libschroedinger --enable-libspeex --enable-libtheora
--enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis
--enable-libvpx --enable-libx264 --enable-libxavs --enable-libxvid
--enable-zlib
  libavutil      51. 41.100 / 51. 41.100
  libavcodec     54.  4.100 / 54.  4.100
  libavformat    54.  1.100 / 54.  1.100
  libavdevice    53.  4.100 / 53.  4.100
  libavfilter     2. 62.101 /  2. 62.101
  libswscale      2.  1.100 /  2.  1.100
  libswresample   0.  7.100 /  0.  7.100
  libpostproc    52.  0.100 / 52.  0.100
[dshow @ 01BE8AA0] Estimating duration from bitrate, this may be inaccurate
Input #0, dshow, from 'video=screen-capture-recorder:audio=Stereo Mix (IDT
High Definition':
  Duration: N/A, start: 20641.769000, bitrate: 1411 kb/s
    Stream #0:0: Video: rawvideo, bgr24, 1680x1050, 25 tbr, 10000k tbn, 25
tbc
    Stream #0:1: Audio: pcm_s16le, 44100 Hz, 2 channels, s16, 1411 kb/s
Incompatible pixel format 'bgr24' for codec 'libx264', auto-selecting
format 'yuv420p'
[buffer @ 01C509A0] w:1680 h:1050 pixfmt:bgr24 tb:1/1000000 sar:0/1
sws_param:
[buffersink @ 01C6E960] auto-inserting filter 'auto-inserted scale 0'
between the filter 'src' and the filter 'out'
[scale @ 01C6EBE0] w:1680 h:1050 fmt:bgr24 -> w:1680 h:1050 fmt:yuv420p
flags:0x4
[libx264 @ 01C51180] using cpu capabilities: MMX2 SSE2Fast SSSE3
FastShuffle SSE4.2
[libx264 @ 01C51180] profile Constrained Baseline, level 4.0
[mpegts @ 01C50A00] muxrate VBR, pcr every 1 pkts, sdt every 200, pat/pmt
every 40 pkts
Output #0, mpegts, to 'udp://192.168.5.230:48551':
  Metadata:
    encoder         : Lavf54.1.100
    Stream #0:0: Video: h264, yuv420p, 1680x1050, q=-1--1, 90k tbn, 10 tbc
    Stream #0:1: Audio: mp2, 22050 Hz, 2 channels, s16, 32 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo -> libx264)
  Stream #0:1 -> #0:1 (pcm_s16le -> mp2)
Press [q] to stop, [?] for help
frame=    8 fps=  0 q=0.0 size=       0kB time=00:00:00.00 bitrate=
0.0kbits/s dup=0 drop=7
frame=   13 fps= 12 q=0.0 size=       0kB time=00:00:00.00 bitrate=
0.0kbits/s dup=0 drop=15
frame=   18 fps= 11 q=10.0 size=     351kB time=00:00:00.50
bitrate=5751.3kbits/s dup=0 drop=23
frame=   23 fps= 11 q=0.0 size=     577kB time=00:00:01.00
bitrate=4728.6kbits/s dup=0 drop=31
frame=   28 fps= 11 q=8.0 size=     759kB time=00:00:01.50
bitrate=4144.0kbits/s dup=0 drop=39
frame=   34 fps= 11 q=0.0 size=     813kB time=00:00:02.10
bitrate=3169.9kbits/s dup=0 drop=46
frame=   34 fps= 10 q=-1.0 Lsize=     881kB time=00:00:03.03
bitrate=2382.4kbits/s dup=0 drop=48

video:801kB audio:12kB global headers:0kB muxing overhead 8.460626%
[libx264 @ 01C51180] frame I:1     Avg QP:20.00  size:332259
[libx264 @ 01C51180] frame P:33    Avg QP: 8.12  size: 14777
[libx264 @ 01C51180] mb I  I16..4: 100.0%  0.0%  0.0%
[libx264 @ 01C51180] mb P  I16..4:  1.2%  0.0%  0.0%  P16..4:  9.1%  0.0%
0.0%  0.0%  0.0%    skip:89.7%
[libx264 @ 01C51180] coded y,uvDC,uvAC intra: 34.1% 14.3% 9.9% inter: 4.4%
3.4% 3.4%
[libx264 @ 01C51180] i16 v,h,dc,p: 60% 38%  1%  1%
[libx264 @ 01C51180] i8c dc,h,v,p: 67% 22% 12%  0%
[libx264 @ 01C51180] kb/s:1929.15
[dshow @ 01BE8AA0] real-time buffer 348% full! frame dropped!
    Last message repeated 1 times
Received signal 2: terminating.

2012/3/13 Lou <lou at lrcd.com>

> On Tue, 13 Mar 2012 01:30:01 +0200
> jacob s <jacobhameiri at gmail.com> wrote:
>
> > 2012/3/13 Lou <lou at lrcd.com>
> >
> > > On Tue, 13 Mar 2012 00:56:28 +0200
> > > jacob s <jacobhameiri at gmail.com> wrote:
> > >
> > > > Hello,
> > > >
> > > > Given a stereo audio input, is it possible to filter only left/right
> > > > channel ?
> > > > For example if I have a file with 2 audio channels can I create a new
> > > file
> > > > that has the left channel audio only ?
> > >
> > > We need more information; "a new file that has the left channel audio
> > > only" can be interpreted as:
> > >
> > > * A mono output.
> > > * A stereo output with input left audio in both channels of the output.
> > > * A stereo output with input left audio in the left channel and silence
> > >  in the right channel of the output.
> >
> > - A stereo output with input left audio in the left channel and silence
> in
> > the right channel of the output.
>
> ffmpeg -i input.wav -map_channel 0.0.0 -map_channel -1 output.wav
>
> This will select the first channel, which I assume is your left
> channel. Adapted from http://ffmpeg.org/ffmpeg.html#Advanced-options
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