# Meridel

> Mid/side mixer: set the centre and the sides separately, spread or narrow the image, and turn the whole image left or right without losing energy. Decode mode takes a mid/side recording in; encode mode sends mid/side out.

- Engine id: `org.sournd.utility.meridel`
- Category: Utility
- Licence: paid: £2.99 an effect or £4.99 a synth, once (owned for good, with updates), or included in the Everything plan (£14.99 a month)
- Version: 1.0.0
- Latency: 0 samples
- Tail: 0 s
- Sidechain input: no
- Channels: mono or stereo
- Audio demo: https://sournd.com/static/preview/demos/meridel.mp3 (plucked chords, default settings)

## Parameters

The id is the C ABI parameter id and the JUCE parameter id (as a decimal string).

| Id | Key | Name | Min | Max | Default | Unit | Taper |
|---|---|---|---|---|---|---|---|
| 0 | `mode` | Mode (stereo, decode M/S, encode M/S) | 0 | 2 | 0 | - | linear |
| 1 | `mid_db` | Mid | -24 | 12 | 0 | dB | linear |
| 2 | `side_db` | Side | -24 | 12 | 0 | dB | linear |
| 3 | `width_pct` | Spread | 0 | 200 | 100 | % | linear |
| 4 | `direction_deg` | Direction | -45 | 45 | 0 | deg | linear |

## Use it in JUCE

CMake ([quick start](/docs/juce/index.md)):

```cmake
juce_add_module(path/to/sournd_engine)
target_include_directories(MyPlugin PRIVATE path/to/include)
target_link_libraries(MyPlugin PRIVATE sournd_engine path/to/libsournd_cabi.a)
```

C++:

```cpp
#include <sournd_engine/sournd_engine.h>

sournd::SourndEngine engine { "org.sournd.utility.meridel" };
juce::AudioProcessorValueTreeState parameters { *this, nullptr, "Parameters",
    sournd::SourndEngineParameters::createLayout (engine) };
sournd::SourndEngineParameters bridge { engine, parameters };

// prepareToPlay
engine.prepare ({ sampleRate, (juce::uint32) maximumBlock, 2 });
bridge.prepare (sampleRate);
setLatencySamples ((int) engine.latency());

// processBlock
bridge.apply ((uint32_t) buffer.getNumSamples());
juce::dsp::AudioBlock<float> block { buffer };
engine.process (juce::dsp::ProcessContextReplacing<float> { block });

// get/setStateInformation: hold getCallbackLock() around saveState / loadState,
// so state work never overlaps processBlock (full example: /docs/juce/)
```

Plain C:

```c
sournd_engine *e = NULL;
if (sournd_engine_create("org.sournd.utility.meridel", &e) == SOURND_OK) {
    sournd_engine_prepare(e, 48000.0, 512);
    sournd_engine_set_param(e, 0, 0); /* Mode (stereo, decode M/S, encode M/S) */
    sournd_engine_process(e, in, out, 2, frames);
    sournd_engine_destroy(e);
}
```

## How it is made

Original sOURnd utility blending general techniques: sum/difference mid/side matrixing, independent mid and side gains, side scaling for width, and an energy-preserving rotation of the left/right vector.

## Ask your AI

Paste this into your coding assistant:

```text
Add the sournd engine org.sournd.utility.meridel to my JUCE plugin. Follow https://sournd.com/docs/juce/index.md
and the engine reference at https://sournd.com/engines/meridel/index.md. Expose every parameter through APVTS.
```