dshow issue with virtual audio cable number of channels

Questions involving a Windows version of FFmpeg.
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pkv
Posts: 2
Joined: Sun May 21, 2017 11:59 pm

dshow issue with virtual audio cable number of channels

Post by pkv » Mon May 22, 2017 12:47 am

hello

I have set up virtual audio cable (v4.15) to work in 8 channel mode. Windows does recognize the 8 channels as can be seen from the captures (see attachments, vue-meters moving for more than 2 channels in VAC Control Panel).
Capture1.JPG
Capture1.JPG (92.93 KiB) Viewed 639 times
Capture.JPG
Capture.JPG (38.01 KiB) Viewed 639 times
However ffmpeg seems to recognize only a single mode (stereo). This seems related to ffmpeg since the virtual audio cable filter does allow for 8 channels.

Code: Select all

ffmpeg -list_options 1 -f dshow -i audio="Line 1 (Virtual Audio Cable)"
ffmpeg version N-86040-g3d55e4883c Copyright (c) 2000-2017 the FFmpeg developers
  built with gcc 6.3.0 (Rev2, Built by MSYS2 project)
  configuration:  --enable-avisynth --enable-libmp3lame --enable-libopus --enable-libvorbis --enable-libx264 --enable-schannel --enable-decklink --enable-librtmp --enable-libfdk-aac --enable-sdl2 --enable-openssl --enable-gpl --enable-nonfree --disable-debug
  libavutil      55. 62.100 / 55. 62.100
  libavcodec     57. 95.101 / 57. 95.101
  libavformat    57. 72.101 / 57. 72.101
  libavdevice    57.  7.100 / 57.  7.100
  libavfilter     6. 89.100 /  6. 89.100
  libswscale      4.  7.101 /  4.  7.101
  libswresample   2.  8.100 /  2.  8.100
  libpostproc    54.  6.100 / 54.  6.100
[dshow @ 0000024e72f36e60] DirectShow audio only device options (from audio devices)
[dshow @ 0000024e72f36e60]  Pin "Capture" (alternative pin name "Capture")
[dshow @ 0000024e72f36e60]   min ch=1 bits=8 rate= 11025 max ch=2 bits=16 rate= 44100
    Last message repeated 22 times
And of course calling 8 channels therefore fails :

Code: Select all

ffmpeg -channels 8 -f dshow -i audio="Line 1 (Virtual Audio Cable)" -vn -acodec
 copy -f null -
ffmpeg version N-86040-g3d55e4883c Copyright (c) 2000-2017 the FFmpeg developers
  built with gcc 6.3.0 (Rev2, Built by MSYS2 project)
  configuration:  --enable-avisynth --enable-libmp3lame --enable-libopus --enable-libvorbis --enable-libx264 --enable-schannel --enable-decklink --enable-librtmp --enable-libfdk-aac --enable-sdl2 --enable-openssl --enable-gpl --enable-nonfree --disable-debug
  libavutil      55. 62.100 / 55. 62.100
  libavcodec     57. 95.101 / 57. 95.101
  libavformat    57. 72.101 / 57. 72.101
  libavdevice    57.  7.100 / 57.  7.100
  libavfilter     6. 89.100 /  6. 89.100
  libswscale      4.  7.101 /  4.  7.101
  libswresample   2.  8.100 /  2.  8.100
  libpostproc    54.  6.100 / 54.  6.100
[dshow @ 000001d8f25a7200] Could not set audio only options
[dshow @ 000001d8f25a7200] Searching for audio device within video devices for Line 1 (Virtual Audio Cable)
[dshow @ 000001d8f25a7200] Could not find audio only device with name [Line 1 (Virtual Audio Cable)] among source devices of type video.
audio=Line 1 (Virtual Audio Cable): I/O error
while with 2 channels this is working fine:

Code: Select all

ffmpeg -channels 2 -f dshow -i audio="Line 1 (Virtual Audio Cable)" -vn -acodec
 copy -f null -
ffmpeg version N-86040-g3d55e4883c Copyright (c) 2000-2017 the FFmpeg developers
  built with gcc 6.3.0 (Rev2, Built by MSYS2 project)
  configuration:  --enable-avisynth --enable-libmp3lame --enable-libopus --enable-libvorbis --enable-libx264 --enable-schannel --enable-decklink --enable-librtmp --enable-libfdk-aac --enable-sdl2 --enable-openssl --enable-gpl --enable-nonfree --disable-debug
  libavutil      55. 62.100 / 55. 62.100
  libavcodec     57. 95.101 / 57. 95.101
  libavformat    57. 72.101 / 57. 72.101
  libavdevice    57.  7.100 / 57.  7.100
  libavfilter     6. 89.100 /  6. 89.100
  libswscale      4.  7.101 /  4.  7.101
  libswresample   2.  8.100 /  2.  8.100
  libpostproc    54.  6.100 / 54.  6.100
Guessed Channel Layout for Input Stream #0.0 : stereo
Input #0, dshow, from 'audio=Line 1 (Virtual Audio Cable)':
  Duration: N/A, start: 13173.334000, bitrate: 1411 kb/s
    Stream #0:0: Audio: pcm_s16le, 44100 Hz, stereo, s16, 1411 kb/s
Output #0, null, to 'pipe:':
  Metadata:
    encoder         : Lavf57.72.101
    Stream #0:0: Audio: pcm_s16le, 44100 Hz, stereo, s16, 1411 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
Press [q] to stop, [?] for help
size=N/A time=00:00:01.52 bitrate=N/A speed=0.758x
video:0kB audio:345kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
Exiting normally, received signal 2.
Any pointers ? the build was compiled a few days ago with alvarado script derived from that of rogerdpack.
Should I post a ticket on ffmpeg.org ? or is there something I missed ...
Thanks for any help.

rogerdpack
Posts: 1872
Joined: Fri Aug 05, 2011 9:56 pm

Re: dshow issue with virtual audio cable number of channels

Post by rogerdpack » Wed May 24, 2017 11:48 am

It's possibly some limitation of the driver since in essence, ffmpeg is just showing you "what directshow advertises" it's probably not a problem on the ffmpeg side anyway. GL!

pkv
Posts: 2
Joined: Sun May 21, 2017 11:59 pm

Re: dshow issue with virtual audio cable number of channels

Post by pkv » Sat May 27, 2017 11:00 am

Thanks Roger for offering your valuable opinion. :)
I have submitted the issue to Eugene Muzychenko who is having a look at it. Hope he'll find what's wrong !
(I take advantage of this occasion for thanking you for all your work here and elsewhere, I've learned a lot by reading your posts)

NicolasNablaware
Posts: 1
Joined: Mon Nov 13, 2017 5:38 pm

Re: dshow issue with virtual audio cable number of channels

Post by NicolasNablaware » Mon Nov 13, 2017 5:39 pm

Hello man,

I'm having the same exact problem, did you fix yours ?

Thank you.


Nicolas
Team Nablaware

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