annotate examples/01-Basics/passthrough/render.cpp @ 507:1cec96845a23 prerelease

Explanted explantation

/*
 ____  _____ _        _    
| __ )| ____| |      / \   
|  _ \|  _| | |     / _ \  
| |_) | |___| |___ / ___ \ 
|____/|_____|_____/_/   \_\

The platform for ultra-low latency audio and sensor processing

http://bela.io

A project of the Augmented Instruments Laboratory within the
Centre for Digital Music at Queen Mary University of London.
http://www.eecs.qmul.ac.uk/~andrewm

(c) 2016 Augmented Instruments Laboratory: Andrew McPherson,
	Astrid Bin, Liam Donovan, Christian Heinrichs, Robert Jack,
	Giulio Moro, Laurel Pardue, Victor Zappi. All rights reserved.

The Bela software is distributed under the GNU Lesser General Public License
(LGPL 3.0), available here: https://www.gnu.org/licenses/lgpl-3.0.txt
*/

#include <Bela.h>
#include <rtdk.h>

bool setup(BelaContext *context, void *userData)
{
	// Nothing to do here...
	return true;
}

void render(BelaContext *context, void *userData)
{
	// Simplest possible case: pass inputs through to outputs
	for(unsigned int n = 0; n < context->audioFrames; n++) {
		for(unsigned int ch = 0; ch < context->audioChannels; ch++){
			// Two equivalent ways to write this code

			// The long way, using the buffers directly:
			// context->audioOut[n * context->audioChannels + ch] =
			// 		context->audioIn[n * context->audioChannels + ch];

			// Or using the macros:
			audioWrite(context, n, ch, audioRead(context, n, ch));
		}
	}

	// Same with analog channelss
	for(unsigned int n = 0; n < context->analogFrames; n++) {
		for(unsigned int ch = 0; ch < context->analogChannels; ch++) {
			// Two equivalent ways to write this code

			// The long way, using the buffers directly:
			// context->analogOut[n * context->analogChannels + ch] = context->analogIn[n * context->analogChannels + ch];

			// Or using the macros:
			analogWrite(context, n, ch, analogRead(context, n, ch));
		}
	}
}

void cleanup(BelaContext *context, void *userData)
{

}


/**
\example passthrough/render.cpp

Audio and analog passthrough: input to output
-----------------------------------------

This sketch demonstrates how to read from and write to the audio and analog input and output buffers.

In `render()` you'll see a nested for loop structure. You'll see this in all Bela projects. 
The first for loop cycles through `audioFrames`, the second through 
`audioChannels` (in this case left 0 and right 1).

You can access any information about current audio and sensor settings you can do the following: 
`context->name_of_item`. For example `context->audioChannels` returns current number of channels,
`context->audioFrames` returns the current number of audio frames, 
`context->audioSampleRate` returns the audio sample rate.

You can look at all the information you can access in ::BelaContext.

Reading and writing from the audio buffers
------------------------------------------

The simplest way to read samples from the audio input buffer is with
`audioRead()` which we pass three arguments: context, current audio 
frame and current channel. In this example we have 
`audioRead(context, n, ch)` where both `n` and `ch` are provided by 
the nested for loop structure.

We can write samples to the audio output buffer in a similar way using 
`audioWrite()`. This has a fourth argument which is the value of the output.
For example `audioWrite(context, n, ch, value_to_output)`.

Reading and writing from the analog buffers
-------------------------------------------

The same is true for `analogRead()` and `analogWrite()`.

Note that for the analog channels we write to and read from the buffers in a separate set 
of nested for loops. This is because the they are sampled at half audio rate by default. 
The first of these for loops cycles through `analogFrames`, the second through
`analogChannels`.

By setting `audioWriteFrame(context, n, ch, audioReadFrame(context, n, ch))` and
`analogWrite(context, n, ch, analogReadFrame(context, n, ch))` we have a simple 
passthrough of audio input to output and analog input to output.


It is also possible to address the buffers directly, for example: 
`context->audioOut[n * context->audioChannels + ch]`.
*/