Re: [Traverso-devel] How's it going?

[Remon Sijrier]

Hi,

> Tell me about and I can take a look.

The whole idea about AudioWave drawing is detecting the highest/smallest value 
within a certain range.
By making the range powers of 2, it's easy to calculate level 2^n by the 
highest values of the 2 values of 2^(n-1)

From 1:64 and above, we store all values to hard disk, this takes ~ 1.5 % of 
the real audio size.
So if we want to display a certain waveform at level 1:1024, we seek to the 
correct position, and read in n pixels of information.

But for all other zoomlevels, there needs to be another way of calculating the 
levels.
For all levels smaller then 1:64, we read directly all the samples in from 
hard disk, and calculate the the peaks.

My idea for say all zoom levels > 1:200 we can use a sufficiently low _cached_ 
zoomlevel, and interpolate the peaks from there, by for example only 
interpolate from at max 5 other peak values for each new one.

So, in case of level 1:325, we calculate the highest level from 5 peak values 
from the cached peaks 1:64
For level 1:320, there will be a little offset which should be accounted for 
in a sensible way.

Peak::calculate_peaks() has both the < 1:64 (MicroView) and > 1:64 with powers 
of 2 (MacroView), so the third option as explained above is what needs to be 
added.
I hope I made my idea clear.

> I've tried to compile the CVS version but didn't succeed, I think it was
> the missing lv2. But lv2 isn't released yet, and I can't find the source
> to download. Why not include it in traverso?

slv2 is needed, it's easier to compile it yourself then that I include it in 
Traverso at this time.
Use svn to checkout from:
http://codeson.net/svn/libslv2/

> Another thing that is very important for me is to have it work with
> 44.1KHz mode on 48KHz fixed cards, letting ALSA do the samplerate
> conversion. Since aplay (alsa player) can do it, so should traverso.
> It's all about setting the right parameters in the right way, I believe...

The only thing to get this working would be using plughw, and nothing else.
But I remember something about the buffer size too.
Can you detect somehow what your audiocards prefered buffers size is ?

I'll reread your mails about this, and see what I can do.
If plughw didn't work for you, then there is more then just samplerate 
conversion.
If you compile traverso with debug on (look for this setting in src/base.pri) 
and run with --d2 , does it say something about the reason it fails to create 
the alsa driver ?

You can also jump in to #traverso if you need quick reply for something!

Remon