[mythtv] [mythtv-commits] Ticket #1104: multi channel audio support

[Paul Catchpole]

Mark Spieth wrote:
>>  Sorry, again I have to correct myself. I now know what you mean with
>> "rumble". With FILTERED_LFE defined I do have rumble (only with watching
>> TV, mythvideo and mythmusic are fine). The problem I noticed before
>> (without FILTERED_LFE defined) is more like an echo in LFE or like LFE is
>> not playing the correct data. I don't know how to describe this further.
>> This is just happening while watching TV. mythvideo and mythmusic are
>> fine.
>>     
>
> the LFE delay can be played with by changing the starting value of k2.
> the latency is supposedly N/2 which is 4096 samples, however this may not be 
> correct.
> whilst it cant be more than N/2 it may be N/4.
> Without filtering some parts of male voices gets through into the LFE as 
> this simple
> method just uses all the input.
> somehow the sliding windowed add is adding the rumble in LFE_FILTERED mode, 
> and is so bad that it cant currently be used.
> I will do some research into this as I added it to pro_optimizer's code. 
> There is not much doco on this and the original code was for windows as a 
> foobar filter.
>
> mark
>
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>   
Hi Mark,

I've just compiled today's SVN with the v35 patch...

On gentoo, I had to emerge fftw-3.1.2 in order to provide a header file 
required to compile.

Source code version     : 15217M
SVN Branch              : trunk
Library API version     : 0.21.20071211-1
Network Protocol Version: 36
Options compiled in:
 linux debug using_oss using_alsa using_backend using_dvb using_frontend 
using_iptv using_lirc using_v4l using_x11 using_xrandr using_xv 
using_xvmcw using_bindings_perl using_opengl using_live

Using the ALSA:surround51 device, UK DVB-T, frontend CPU on playback: 55%.

I'm getting constantly broken audio, with a noticable echo, and the 
following in the logs:

2007-12-22 16:28:14.691 WriteAudio: buffer underrun
2007-12-22 16:28:14.875 WriteAudio: buffer underrun
2007-12-22 16:28:15.116 WriteAudio: buffer underrun
2007-12-22 16:28:15.330 WriteAudio: buffer underrun
2007-12-22 16:28:15.517 WriteAudio: buffer underrun
2007-12-22 16:28:15.728 WriteAudio: buffer underrun
2007-12-22 16:28:15.910 WriteAudio: buffer underrun
2007-12-22 16:28:16.169 WriteAudio: buffer underrun
2007-12-22 16:28:16.370 WriteAudio: buffer underrun
2007-12-22 16:28:16.686 WriteAudio: buffer underrun
2007-12-22 16:28:16.888 WriteAudio: buffer underrun
2007-12-22 16:28:17.087 WriteAudio: buffer underrun
2007-12-22 16:28:17.293 WriteAudio: buffer underrun
2007-12-22 16:28:17.477 WriteAudio: buffer underrun
2007-12-22 16:28:17.703 WriteAudio: buffer underrun
2007-12-22 16:28:17.904 WriteAudio: buffer underrun

I will try and record a clip of the sound!

Are there any parameters I can tune to try and help?

Paul