Re: [Csnd-dev] long-standing diskin/diskin2 issue

I think option 1 is the best, even though there is a chance that this will
break existing instruments.

On Fri, 11 Apr 2025 at 10:58, Victor Lazzarini <
[email protected]> wrote:

> Hi everyone,
>
> some advice needed here.
> While marking some student work, I came across an issue in diskin/diskin2
> that seems to be long standing
> and maybe someone might have come across this and dismissed it.
>
> The code I was looking at was reading a stereo file peaking near 0dbfs,
> but the output from diskin was
> double that (and so causing samples out of range). After several checks, I
> figured the problem was
> with diskin. Then I noticed the code was using the same variable for left
> and right
>
> asig, asig diskin …
>
> so I went to look at the sources and saw that diskin does some summing to
> these variables as
> part of its process. Normally, you would think that it would just
> overwrite them, but it is
> actually using them for some internal buffering. The result is that if the
> same variable is used,
> we get the strange effect of the two file channels being mixed up (and
> possibly other effects depending
> on diskin/diskin2 parameters).
>
> So I am in two minds about this:
>
> 1 - it is user error: we should throw an init error.
>
> 2 - it is not user error and diskin is not behaving properly.
>
> I don’t actually like the fact the opcode uses the output variable for
> buffering, but we probably have
> similar cases elsewhere. The simplest thing is to treat it as 1 and
> document it in the manual.
> Interestingly it is a similar issue I have encountered with
> pass-by-reference UDOs
> (see https://github.com/csound/csound/issues/2061)
>
> What do you think?
> ========================
> Prof. Victor Lazzarini
> Maynooth University
> Ireland
>
>