[vlc-devel] Doubts on VLC audio handling

Kaarlo Räihä agent_007 at luukku.com
Fri Mar 20 15:39:37 CET 2009

Assim Deodia kirjoitti 20.03.2009 kello 10:29:
> Hi All,
> I making a panning module for VLC as my final year project. I am having
> following doubts regarding VLC audio handling.
> 1) In aout_filter_sys_t: I can see int's for every channel (i.e. i_left,
> i_right etc) but not for LFE. does VLC handle in different way? I tried
> adding i_lfe to the structure and also to output buffer, and played
>  a 6ch
> file. Still there was no sound in lfe. I have attached the code
>  which i was
> testing.
> 2) I wish to determine the number of channel my system support. I
>  have a 5.1
> system but
> aout_FormatNbChannels( &p_filter->output ) was giving the number of
>  channel
> in file. Nor the values p_filter->input.i_physical_channels,
> p_filter->input.i_original_channels,
>  p_filter->output.i_physical_channels,
> p_filter->output.i_original_channels are corresponding to number of
> channels.

output.i_physical_channels should be set by audio output module. So results might vary if you for example try both DirectSound and Waveout outputs (APIs aren't same nor the device driver stuff). 

> 3) I need to do is to upmix a stream manually to the max supported
>  channel.
> Vista seems to do it atomically but i produce a 6ch stream from a 2ch
> stream?

IIRC upmixing is done by device drivers. So it shouldn't be automatic from OS side.

> Looking forward to hear soon.
> -- 
> Regards
> Assim

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