[CM] adding an extra channel

[Kjetil S. Matheussen]

On Tue, 12 Jun 2007, Kjetil S. Matheussen wrote:

>
>
> On Tue, 12 Jun 2007, e deleflie wrote:
>
>>  All,
>>
>>  I've got a situation where I read eiether 3 or 4 channel files, then
>>  pump the channels through a LADSPA plugin.
>>
>>  the LADSPA plugin requires 4 channels. So when I read a 3 channel
>>  file, I need to create a fourth, empty (no signal) channel.
>>
>>  I cant seem to find the command for creating a new channel.
>>
>>  something like this:
>>
>>  (let ((index (open-sound name)))
>>                ((if (= (channels 0) 3) (add-channel 0) ))
>> 
>
>
> This is a work-around, but you can use new-sound instead of open-sound, and 
> then use insert-sound to insert channels from your file into the sound:
>
>
> (open-sound name)
> (if (= (channels) 3)
>   (let ((snd (new-sound (string-append name ".4-channels") (header-type) (data-format) (srate) 2)))
>     (let loop ((ch 0))
>       (insert-sound name 0 ch snd)
>       (if (< ch 3)
> 	   (loop (1+ ch)))))


(Oops, warning, I didn't actually test that code.)

http://ccrma.stanford.edu/software/snd/snd/extsnd.html#newsound
http://ccrma.stanford.edu/software/snd/snd/extsnd.html#insertsound