On Thu, Jan 14, 2010 at 07:08:26PM +0100, fons@xxxxxxxxxxxxxxx wrote:
> On Thu, Jan 14, 2010 at 09:48:08AM -0800, Ken Restivo wrote:
>
> > Fons' code is like a finely-crafted jewel, and it is written
> > in a terse style that looks to me like hand-optimised ASM code
> > (i.e., variable names that are more like register names:
> > "_s1", "gy", "dx"), but I'm starting to understand it a little bit.
>
> It's not ASM style, it's mathematical notation.
>
> > It looks like he's windowing through the frames, and if the
> > frame is > 80 bytes, he windows through it in 64-byte
> > increments.
>
> That's something you'll find in many of my plugins.
> Its purpose is to normally have a block size of 64 frames,
> but avoid a very short (e.g. one frame) final block when
> 'nframes' can take arbitrary values, as could happen when
> parameters are automated and a host wants to update them
> in the middle of a period.
>
> while (nframes)
> {
> k = (nframes < 80) ? nframes : 64;
>
> // Process k frames, 16 <= k <= 64
>
> nframes -= k;
> }
>
> With your Jack settings the result will normally be two
> blocks of 64 frrames. Filter paramters are updated at
> block rate, with linear interpolation in between.
>
OK I tried a hack to check at the beginning of each process callback whether all the bytes in the buffer add up to 0, and then just return instead of going through the rest of your filter algorithm. And...
Your code is so efficient that after I added my little two-line hack, it made the problem WORSE! 10% CPU instead of 6%.
I'm just shaking my head over here. I have no idea what is going on.
Oh, and on a different topic, I did get my FastTrack Pro to run at 24bits. I just had to add the following to /etc/modprobe.d/sound: options snd-usb-audio device_setup=0x9 enable=1 The parameters did NOT get 24-bit mode going when given on the modprobe command line, but they DID work when added to modprobe.d. I suspect some kind of weird udev or hal magic going on.
Recording a band tomorrow. Alas, the tracking will be on ProTools, but the editing, overdubbing, and mixing will now be in Ardour. Yay!
-ken
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