[xine-user] Re: Can't decode LFE in stereo downmix?

[Gilles S. <gi...@vo...>]

> If there's a way to enable the LFE channel, please tell me.
Okay, I've found a way to get LFE mixed down in the stereo mix. But it
involves some asoundrc hacking. I created a virtual surround51 device whose
6 channels are then mixed down to two stereo channels which are in turn fed
to the dmix device. Of course, this solution applies to any media player,
you'll just have to configure it for 6 channel output.

Here's my current ~/.asoundrc:

pcm.!default
{
        type plug
        slave.pcm "dmixer"
}

# direct access to the soundcard
pcm.es1370
{
        type plug
        slave.pcm "hw:0"
}

pcm.dsp0
{
        type plug
        slave.pcm "dmixer"
}

pcm.dmixer
{
        type dmix
        ipc_key 6789  # Any unique number
        slave
        {
                pcm "hw:0,0"
                period_time 0
                period_size 1024
                buffer_size 8192
                periods 128
                rate 44100
        }
        bindings
        {
                0 0
                1 1
        }
}

ctl.mixer0
{
        type hw
        card 0
}


pcm.!surround51 {
        type route
        slave.pcm dmixer
        slave.channels 2
        ttable.0.0 0.8
        ttable.1.1 0.8
        ttable.2.0 0.2
        ttable.2.1 0.05
        ttable.3.0 0.05
        ttable.3.1 0.2
        ttable.4.0 0.4
        ttable.4.1 0.4
        ttable.5.0 0.7
        ttable.5.1 0.7
}

pcm.lfetest {
        type route
        slave.pcm dmixer
        slave.channels 2
        ttable.0.0 0
        ttable.1.1 0
        ttable.2.0 0
        ttable.2.1 0
        ttable.3.0 0
        ttable.3.1 0
        ttable.4.0 0
        ttable.4.1 0
        ttable.5.0 1
        ttable.5.1 1
}

I'm not yet sure about the routing values. But for the limited testing that
I did they are quite ok. The lfetest device is just for fun :-)

A nice reference for some of that alsa magic is
http://ALSA-project.org/alsa-doc/alsa-lib/pcm_plugins.html
And the more I read about alsa, the more I like it.

Gilles