Anyone using Portaudio?

[Andrej Mitrovic]

This is interesting. It appears the callback function is not called
frequently enough. Really weird.. it must be some bug in my code.

You see, I have a sample rate of 44100hz per second, and a buffer size
of 64. This basically means that for 1 second of audio I need to fill
~680buffers per second in my callback (the callback is called ~680
times per second, and each buffer is 64 frames in size), so ~680 * 64
= ~44100. The C code gets its callback called around 680 times, but
interestingly the D code gets its callback called only 29 times. This
is why I hear the sound stuttering, its because my callback isn't
getting called frequently enough and the audio card is filling the
missing buffers with zeros.

Now I have to figure out why it's not getting called often enough.

On 10/18/10, Andrej Mitrovic <andrej.mitrovich at gmail.com> wrote:
> Yeah, that's what I would usually do. The trouble is there's a library
> in DLL format, and there's only a couple of calls to it and that's it.
> But somehow the C client code performs better. I've just tried a D1
> sample, with the same result. I'll have to investigate..
>
> On 10/17/10, Denis Koroskin <2korden at gmail.com> wrote:
>> On Mon, 18 Oct 2010 01:10:31 +0400, Andrej Mitrovic
>> <andrej.mitrovich at none.com> wrote:
>>
>>> There's a .d header file in the Bindings project on dsource which I'm
>>> using with the Portaudio DLL v19, and I'm implicitly loading the DLL.
>>> There's a  sine playback example, and I'm comparing the usage of
>>> Portaudio from the C sine example (patest_sine.c) compared to the D one
>>> (patest_sine_hello.d). The C and D code are almost identical, however
>>> there seems to be a pretty big overhead when using D.
>>>
>>> I can safely use a buffer size of 64 frames in the C example, but in the
>>> D one the minimum I could get was around 1800 frames.
>>>
>>> I've tried compiling with-O -release -inline, and issuing a call to
>>> GC.disable() before the call to Pa_StartStream(). I've also tried
>>> compiling the portaudio DLL in Release mode. But none of this had any
>>> effect. Anything lower than 1800 for the buffer size gives me choppy
>>> sound in D.
>>>
>>> There shouldn't be a problem with such a small buffer size, all the data
>>> is preallocated and the buffers are prefilled with data, so it can't be
>>> a CPU bottleneck issue. Since D uses C functions directly, I just don't
>>> see where the overhead could be.
>>>
>>> Has anyone used Portaudio with D2 (or D1 for that matter) with
>>> close-to-equal performance as when using C?
>>
>>  From my experience, starting with D that purely calls C code and then
>> slowly porting it to D (one piece of code at a time) usually helps
>> revealing the problem. Just try to keep it the same (i.e.
>> interchangeable). You can do that by marking functions as extern (C) and
>> optionally having some of the variables as extern (C) __gshared.
>>
>