[vlc] VLC audio problem with bttv/V4L

[Ian B. MacDonald]

Hi all,

I am having trouble with VLC streaming using my bttv/v4l drivers in
conjunction with ALSA.

The box I am streaming from uses a bttv card, where the audio is patched
via an internal cable to the sound card.  MOTV/XawTV correctly displays
images, and outputs sound to the sound card.  VLC however does not
initiate the sound when it grabs the bttv stream. i.e. Nothing is being
output from the bttv card when VLC initiates the hardware to tune into a
terrestrial TV signal.

The tvaudio module controls the TV card's (STB TV PCI) audio demuxer
(TDA9850) however VLC does not initialize it the way my other bttv apps
do, and hence when VLC runs, the audio stream is silent (though the
encoding and decoding appear to be fine).

Many TV tuners work this way (send output to the sound card rather than
becoming a second soundcard themselves) so I am assuming this might be a
common problem with bttv TV card VLC users who use their soundcard as
the audio input source.

My VLC init line without line break characters is as follows:

vlc -vvv
v4l:/dev/video:norm=ntsc:frequency=361250:size=320x240:channel=0:adev=/dev/dsp:audio=1 --sout '#transcode{vcodec=mp4v,acodec=a52,vb=250,ab=48,deinterlace}:std{access=http,mux=ts,url=192.168.77.20:8000}' --ttl 12

This is cable 47 @ 320x240 with audio from /dev/dsp in stereo.  The
outputs are not final, but this does deliver a nice small clear picture
to other PCs on this LAN (Both Linux and Windows).  I have a v4l2 Linux
2.6.2 implementation and a Linux 2.4.24 implementation of the kernel
that works with this hardware and configuration. Both function exactly
the same (appear to).  I have tested streaming audio CDs to check the
encode and decode of the audio. 

To summarize:
XAWTV initiates sound which can be heard through my soundcard
VLC does not initiate any sound that can be heard through my soundcard
Sound output is controlled by a TDA9850(tvaudio) like many other
bttv/v4l devices.
VLC seems to encode and decode just fine


Any help appreciated,
Ian.

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