X-Y scope

[edyasia]

 Hi guys... im newbie in forum...

Anyone have or can build a x-y scope for ipod 5g... build in a theme or only a plugin or demo.


Thanks in advance

Sorry my english

[cool_walking_]

Assuming it's not already there, since I don't know what a x-y scope is... you can't add new functionality with a theme, it would have to be a plugin.  This should be in the Feature Ideas forum.

[markun]

I believe he is talking about an oscilloscope where the x-axis is represented by one audio channel and the y-axis by the other (in case of stereo sound). Our existing oscilloscope plugin would be a good starting point, I don't think it would be too much work to add it.

EDIT: here you can find a link to an interesting audio file for testing the plugin: http://www.youtube.com/watch?v=s1eNjUgaB-g

[insanepotato]

wat the? i have never in my life heard or seen anything like in that vid. is that real? its dam amazing.

[Spoonman]

the video is fu.... awsome...

i guess what the o.p. means is something like when you record in wavelab there is a x y scope, you can see it in this screenshot:
http://www.softpedia.com/screenshots/Wavelab_3.png

[TexasRockbox]

Here is illustration of an audio X-Y scope for those who have not see one (in this case a Marantz 2130):

[r00tb33r]

Here is illustration of an audio X-Y scope for those who have not see one (in this case a Marantz 2130):

What does it do?  Cool looking stuff.

[EDIT]
I have a lab oscilloscope which I have used to plot Right vs. Left output from my computer, if thats in fact what X-Y scope does.
Have a look here (pictures courtesy of me):
http://s180.photobucket.com/albums/x298/r00tb13r/2006-07-06/

[Chronon]

Yes it's the same.  In the standard mode a sawtooth ramp generator (equivalently the time-base generator) controls the beam deflection along the x-axis and the y-axis deflection is given by the voltage on a specific input channel.  X-Y mode uses the voltage on another input channel to control the deflection of the beam along the x-axis.

[insanepotato]

Ok, I hacked the Oscilloscope and have a "working" prototype; but have hit a wall.
What i have so far is a plugin which will map a single pixel every cycle, with the left channel as the X component (Cartesian co-ordinates) and the right for the Y.
To be blunt, its pretty boring watching a single pixel jump about.

What do I need to make it like that video?

I'm thinking that I should plot all the points within the space of say 50 milliseconds(?), then clear the screen and repeat; instead of one point then clear as current.

But i don't know what the ideal rate should be.

[bwaslo]

You need what is called "persistence".  That comes free with the technology with an old phosphor type scope.  For digital scopes, or for doing it in Rockbox, you need to do just what you said, keep the least N points -- keep a list of points that get shown, and at updates, add new ones at the end and delete old ones from the beginning.  If  you want to make it snazzy, make the persistence a user configurable variable.

[insanepotato]

Ok, I think I can do that 

Thanks

[Strife89]

When you get a patch up, do link it here, please.

[dreamlayers]

Plugins currently cannot access actual PCM data.  They can just get peak values.  If those were used, the result wouldn't quite be an X-Y scope.  Part of FS#10065 adds a pcm_get_peak_buffer function for plugins, which allows access to PCM data

[insanepotato]

I have still yet to use the code from the FS#10065, and know nothing about PCM data; but here's what I have thus far: FS#10135

It seemed to work in the simulator, but doesn't really on a real device. All the points appear in the lower right of the screen, which leads me to believe the peaks are always positive(?). If this is true, how do i get the negative peaks?

The code used in Oscillosope to get the peaks is (not exactly as appears in Oscilloscope):
        x = rb->mas_codec_readreg(0xC);
        y = rb->mas_codec_readreg(0xD);
        rb->pcm_calculate_peaks(&x, &y);
The following is later performed on x and y before they are drawn (not exactly as appears in Oscilloscope)
        x =  LCD_HEIGHT/2-1 - (((LCD_HEIGHT-2) * x) >> 16));
        y =  LCD_HEIGHT/2+1 + (((LCD_HEIGHT-2) * x) >> 16));

(Is the bit shifting to get only the positive peak? if so, do i just "<< 16" to get the negative?)

If someone could possibly give some explanations or link me up to some reading material, that would be great 

[edyasia]

Hi!!! i`m impressed for this thread...

For winamp users here is a post started for me about X-y scope.... for a example.   http://forums.winamp.com/showthread.php?threadid=249159

Thanks and waiting for x-y final plugin or demo release