[mythtv] [mythtv-commits] Ticket #1104: multichannelaudio support

Paul Catchpole paul at paulcatchpole.co.uk
Sat Jan 12 20:57:19 UTC 2008


Paul Catchpole wrote:
> Paul Catchpole wrote:
>   
>> Paul Catchpole wrote:
>>   
>>     
>>> Ed Wildgoose wrote:
>>>   
>>>     
>>>       
>>>>> It works fine with the audio device for the frontend changed to a 
>>>>> 2-channel one. It's only when using the real 6-channel device and hence 
>>>>> the upmixer where the clipping occurs.
>>>>>   
>>>>>     
>>>>>       
>>>>>         
>>>>>           
>>>> #Often you have multiple volume controls for multichannel versus two 
>>>> channel - perhaps the multichannel mixer is too loud and causing the 
>>>> clipping?
>>>>
>>>> Ed
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>>>>   
>>>>     
>>>>       
>>>>         
>>> The 2-channel device used for testing is a simple ALSA upmixer with an 
>>> additional soft-volume added on top. I set the relative mixer levels a 
>>> long while ago and they've not changed since. I don't have a master on 
>>> this card, hence the softvol. I don't change the levels to test the 5.1 
>>> direct output, just move to another device which is the surround51 with 
>>> a softvol on top.
>>>
>>> For the previous testing I did of patch-38 [I think], where I had 
>>> clipping problems, I tried reducing mixer levels to no avail - the 
>>> 'clipped' output just happily scaled with the rest of the sound.
>>>
>>> I think Mark is probably correct in thinking it's a mathematical issue 
>>> with the new upmixer code, which seems to use lots of floating-point 
>>> maths...
>>>
>>> PC
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>>>   
>>>     
>>>       
>> Cheers for the patch, Mark.
>>
>> Recompiling with patch-42 now.
>>
>> Ta,
>>
>> Paul
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>>     
> Initially, I'd say 'top banana' - mythmusic is now working really well. 
> The upmixer sounds excellent with the few tracks I've tried...
>
> I'll try a few TV channels and some recordings then report back.
>
> I did notice that with -v audio set, I get a lot of the following 
> messages in the log:
>
> 2008-01-12 20:53:34.313 AO: Needs upmix
> 2008-01-12 20:53:34.313 AO: no change exiting
> 2008-01-12 20:53:34.313 AO: Needs upmix
> 2008-01-12 20:53:34.313 AO: no change exiting
> 2008-01-12 20:53:34.314 AO: Needs upmix
> 2008-01-12 20:53:34.314 AO: no change exiting
> 2008-01-12 20:53:34.314 AO: Needs upmix
>
>
> Thanks for the work, Mark.
>
> PC
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>   
PS: That error in the log is only with Mythmusic, not with a TV recording.

PC


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