Rockbox

OK, Now I've cleaned up the code a little bit.
Should be more readable now; no functional changes.

Looks nice and simple. However, it violates quite a few of our coding guidelines, so it needs some more cleaning.
Furthermore, it uses quite a lot of floating point arithmetics, which we aren't too fond of. But I think we can let that pass, since it's only a plugin.

Good work!

Which coding guidelines does it violate?

It mainly violates the guidelines regarding identifiers. From docs/CONTRIBUTING:

Identifiers
-----
We do not want mixed case identifiers.
Variables and function names should be all lower case.
Struct and enum names should be all lower case.
Preprocessor symbols and enum constants should be all upper case.

New version that does not violate any coding guidelines:

Really nice, many people will love this :)

Another nitpick from CONTRIBUTING though,

"Keep lines below 80 columns length."

OK, if this version violates the coding guidelines again, I'll start crying.

Better start crying then... :-)

schmittTriggered=0;

:-)

*cry*

Well, I added a little bar that shows how 'wrong' your pitch is.
I also corrected that guideline violation, and if I find another one, I'll simply give up ;)

If the played note is loud enough, the tuner is now quite usable.
I'd be very grateful if someone actually tried my plugin and tell me any bugs/suggestions...

Desowin tried it for me on his e200, and for some unexplainable reason it didn't even start recording !?!
Could anyone else with an player with a built-in mic try this for me?

This really needs to have recording used as the example plugins and core use it so that it operates with a periodic callback (ie. not constantly stopping and restarting recording). There's not much room to vary from those formulas and expect it to operate properly. No parts are optional.

The sample buffer should be 32-bit aligned BTW.

I tried a periodic callback that provides a new buffer for recording, but even after several days I couldn't get it to work properly: it always crashed after 0-10 seconds with some buffer overflow error, no matter how much buffer I gave it... It didn't help that there's no documentation at all, and the few plugins that use it are so complicated that I don't understand what I have to do...

32-bit aligned would be a signed int, right?

Also, the reason for the plugin not working on sansas has to do with the fact that they cannot record with a 44,1K sample rate - I'm working on it.

I made an intrument tuner myself using the "proper" method of recording. I'll see if I can apply my recording code to your pitch detection algorithm.

Surely, why not?

New version, much better gui. Still doesn't work on Sansas though..

I uncommented
print_int_xy(0,160,(int) *rb->rec_freq_sampr);
print_int_xy(0,200,(int) SAMPLE_RATE);

and both are reported as 22050 on the sansa e280 not 88200 as mentioned in the comments?

Really? I could only test this in the simulator since I don't own a sansa...
Does the actual tuning work too? Does the GUI display correctly on the sansa's screen?

@MikeS: The sample buffer is now 32-bit aligned -> int32_t.

The tuning doesnt work on the sansa - but its not down to the samplerate
The GUI does display correctly - and looks good

Strange... Could you put a "rb->splash(0, "callback!");" into recording_callback() for testing purposes?
If recording works, it should display "callback" every second or so. If not, recording does not work at all.

The callbacks are working- the splash pops up every sec or so

some observations 9on the sansa):
tc is always 0 hence freq is 0

If I exit pitch and go to recording, the mic is not responsive. If I then exit
recording and restart it, the mic responds.

This suggests something in the code is preventing the mc responding to input

My main problem is that there's no documentation at all, nowhere!
There are some plugins that use recording, but they just use some functions and do not explain what they do exactly...
I know for sure that I'm doing several things wrong, but nobody actually helps me fixing those problems.
So until I get some more information, I'm afraid I can't help you.
It seems to be working on most targets, and I don't own a sansa to "reverse engineer" the recording api.
Thanks for testing it nevertheless!

I know I promised to help you with the recording code, I just haven't had time yet. Sorry about that. Regarding the documentation, it's a sad fact that we lack plenty of documentation on the Rockbox internals. We try to keep up as weel as we can, but it is hard enough to find the time for the coding itself, and the documentation always has lower priority.

I got recording working on the sansa by changing the gain values from 100 to 39 (the range is given in as3514.c as 0 to 39 with 23 default)

rb->sound_set(SOUND_MIC_GAIN, 39);
rb->audio_set_recording_gain(39,39, AUDIO_GAIN_MIC);

Im not convinced that the sound_set()ine is actually doing anything. I think the gain
is being set by the audio_set_recording_gain()

recording now works although the pitch indication jumps around a bit. maybe some averaging would help.

Good to hear! I only added sound_set() because some other plugin used it...
I can't work on the plugin right now because cygwin doesn't work anymore and I can't get the toolchain installed on AndLinux.
The 'jumpiness' of the tuner is due to the fact that the Schmitt trigger algorithm only works reliably when the tone is quite loud.
So if you play a loud note, it shouldn't jump so much. I intend to fix that when I can compile again.

Tested on iaudio X5.
Detection doesn't work too well using built-in microphone though;
[either that or my guitar is way off-tune ;-) ]

here is a version that works with sansa

I have removed rb->sound_set(SOUND_MIC_GAIN, 39);

gain is set at 39 instead of 100 as per as3514.c
rb->audio_set_recording_gain(39,39, AUDIO_GAIN_MIC);

I added some code in display_freq() that prevents the red bar set at -32 cents when freq=0 (no signal)

if ((int)freq == 0) /* prevents red bar at -32 cents when freq= 0*/
{ ldf = 0;
}

It wouldn't compile unless I change line 500 to

enum plugin_status plugin_start(const struct plugin_api* api, const void* parameter)

I added and changed a couple things to get this to compile for my iHP-120, it has a grayscale lcd. Hope I didn't mess anything up.