Re: [Qtractor-devel] Repeated drum hits via drumkv1 sometimes sound different

[Rui N. C. <rn...@rn...>]

hi Frank

can you provide the sample file in particular or only the qtractor .atz 
session budle with just the interesting track or clip?

cheers
-- 
rncbc aka. Rui Nuno Capela
rn...@rn...


On 3/14/21 8:58 AM, Frank Neumann wrote:
> 
> Hi Rui and list,
> 
> I am observing an oddity with drumkv1 in Qtractor (actually, I believe this
> issue is independent of Qtractor, but since I am not aware of a drumkv1
> specific mailing list, I take the liberty of reporting it here).
> 
> In Qtractor, I created a new MIDI track with a drumkv1 instance, and in it I
> have created a tiny 2-bar sequence with a short drum sample played on every
> beat. Same note length, same velocity for every hit.
> 
> In drumkv1, I have turned off DCF, DCA, LFO and the limiter - so, there should
> be no (or not a lot) of operations going on in the signal path.
> 
> If I now play back this sample (it's attached, for reference) and repeat over
> the 2-bar sequence, I notice that every now and then the snare sounds
> "slightly differently". I had first noticed the effect in a multi-track
> session where I was thinking one of the other tracks is clipping somehow, but
> I could now nail this down to this drumkv1 instance.
> 
> I have recorded the Qtractor output via jack_capture, and analyzed the onset of
> every hit. I am attaching a screenshot of two hits which show significant
> differences in their onset.
> 
> One suspicion was that when samplerate of that sample and of my jackd do not
> match (say, 44100 <-> 48000), the problem could be within libsamplerate, but
> I converted the sample to match jackd's samplerate, and the issue is still
> there.
> 
> Any idea what could be causing this? My expectation would have been that
> repeated hits with the same input produce the same (or almost the same
> output) every time. Is there some additional processing going on in drumkv1
> I should be aware of?
> 
> Note, if I import that sample directly into an _audio_ track in Qtractor
> and copy&paste it a couple of times and play it back, the issue does not appear.
> So it must be something inside drumkv1. My version of drumkv1 is 0.9.21,
> to be precise Git commit 69224d.
> 
> This might sound harmless, but in the mentioned multi-track arrangement it is
> creating pretty obvious clicks that have become quite disturbing once I
> realized they are there.
> 
> If I should instrument my drumkv1 plugin somehow to sput debug information
> about played buffer position, I'll be glad to try out anything you suggest.
> 
> Thanks,
> Frank
>