[PD] how to iterate over left and right channel separately in one Pd class?

[katja]

Ok so I did the ugly thing with the right channel input and output pointers:

memcpy(outR, inR, vectorsize * sizeof(t_float));
inR = outR;

Works like a charm, thanks again.

Katja



On Fri, Jan 11, 2013 at 10:05 PM, Miller Puckette <msp at ucsd.edu> wrote:
> copy_perform assumes the data is 4-byte aligned so might save a test
> or two compared to memcopy() - but I really don't know.  I never
> benchmarked the two against each other :)
>
> M
>
> On Fri, Jan 11, 2013 at 09:36:41PM +0100, katja wrote:
>> Hi Miller,
>>
>> Thanks for the solution. The routines are in place so copying the
>> right channel input to output should do it. Is there any reason to
>> prefer copy_perform() over memcpy()? I'm trying to make the most
>> efficient reverb for RPi & Co.
>>
>> Katja
>>
>>
>>
>> On Fri, Jan 11, 2013 at 7:57 PM, Miller Puckette <msp at ucsd.edu> wrote:
>> > Hi Katja -
>> >
>> > There's one example of this in sigfft_dspx() - a complex FFT that 'natively'
>> > works on 2 signals in-place but has to deal with various cases in which
>> > buffers get re-used.  It's ugly but the basic idea is first to get the
>> > inputs copied to the outputs (unless they're already there in the correct
>> > order in which case nothing needs to be done) and then run the in-place
>> > algorithm.
>> >
>> > If the algo only works out-of-place (i.e. you need 4 distinct buffers, 2
>> > in and 2 out) the only way out is (at least conditionally) allocate temporary
>> > copies of the inputs before writing to any outputs.
>> >
>> > I may be able to add an optional way tilde objects can request that output
>> > buffers be distinct from input ones sometime in the future - but this is a
>> > couple of steps away for me right now :)
>> >
>> > M
>> >
>> > On Fri, Jan 11, 2013 at 03:32:09PM +0100, katja wrote:
>> >> Hello,
>> >>
>> >> I'm working on a Pd class with stereo channels (reverb), and the
>> >> routine happens to be most efficient when iterating over the samples
>> >> per channel, instead of left and right together in the perform loop.
>> >> However, when doing two while loops in one object, one for left and
>> >> one for right, the right channel samples get overwritten because of
>> >> sample-wise in-place computation. Is this an inescapable truth? I
>> >> mean, I could write a left channel class and a right channel class
>> >> (actually did that to verify that it works), but it's inconvenient to
>> >> use. What could be an efficient way to get them in one object?
>> >>
>> >> Thanks,
>> >> Katja
>> >>
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