[PD] 64 channel audio output with RME HDSP-Madi

[J. Schmidt]

zmoelnig at iem.at wrote:

> Quoting "J. Schmidt" <schmidje at idmt.fraunhofer.de>:
>
>> Hi,
>>
>> i have a problem with audio output on Linux with the RME Madi-card.
>> I use Alsa and it seems ok, but i get only one input and output channel.
>> My pdsettings are set up for 64 input and output channels.
>>
>> PD says
>>
>> - requested channels=0 but used=1
>> - playback device with 1 channels and buffer_time 42666 us opened
>> - requested channels=0 but used=1
>>
>> when i turn the audio on.
>>
>> Any hint? Or has anybody ever got pd to run as many channels?
>
>
>
> yes, we (the iem) are using the MADI card with 64 channels.
>
> the problem is, that pd (0.39.2) seems to just ignores the channel# 
> when doing alsa (or is it some special thing like alsamm, dunno) and 
> defaults it to 0.
> when it comes to opening the device, pd queries the device about the 
> max. and min. number of channels the device supports. now the madi has 
> a minimum of 1 channels and a maximum of 64 channels.
> the requested number of channels (in our case 0! because the number of 
> channels you typed in ist just ignored!!) is clamped between these 2 
> values, which results in 1.
> that is why you only get 1 channel.
>
> i think this doesn't happen on other devices, because most of them 
> just support one fixed number of channels (min.chan==max.chan)
>
> now what to do against it?
> i have once patched the s_audio_alsa.c, so that if the requested 
> channel is 0, this value is not clamped between the min. and max. 
> #channels but rather set to the max. #channels.
> i will see if i can find it.

Would be glad to get it!

> wini (who - as you probably know - has written both the madi-drivers 
> and the original memory-mapped alsa support for pd) has done something 
> different to make it work, but i don't know what exactly.
>
> of course, the cleanest solution would be to not-ignore the number of 
> channels requested by the user.
>
> mfg.a.r
> IOhannes
>
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Mfg jerome