Sparklines For JUCE AudioBlocks
MIT License

Read my blog article on audio sparklines!

Melatonin Audio Sparklines

This is a C++ JUCE module that summarizes and visualizes what's in an AudioBlock.

It's nice to get a quick idea of what's happening to your JUCE audio buffers during development or tests.


Set up a git submodule in your project tracking the main branch. I usually stick mine in a modules directory.

git submodule add -b main modules/melatonin_audio_sparklines
git commit -m "Added melatonin_audio_sparklines submodule."

To update melatonin_audio_sparklines, you can:

git submodule update --remote --merge modules/melatonin_audio_sparklines

If you use CMake (my condolences (jk jk)), inform JUCE about the module in your CMakeLists.txt:


Include the header where needed:

#include "melatonin_audio_sparklines/melatonin_audio_sparklines.h"

JUCE Usage: printSparkline

Call melatonin::printSparkline(myAudioBlock); and under the hood, DBG will be called.

If you are lucky, you'll see a healthy looking wave (like this cutie little square wave) spat out into your console:

Block is 1 channel, 441 samples, min -0.999994, max 0.999994, 100% filled

Or a sine:

Block is 1 channel, 441 samples, min -0.999994, max 0.999994, 100% filled

You can output the sparkline in full sample-by-sample uncompressed glory with melatonin::printSparkline(myAudioBlock, false) or display it without normalization with melatonin::printSparkline(myAudioBlock, true, false).

lldb installation

Thanks to Jim Credland's existing lldb formatters I felt bold enough to jump in and figure out how to get sparklines in your lldb-driven IDE.

Put this line in a file named ~/.lldbinit (create it if necessary), pointing to

command script import ~/path/to/melatonin_audio_sparklines/

On hover you'll get a summary:

Screenshot 2021-06-22 SineMachine – CycleNote cpp - CLion

On click you'll get sparklines and the ability to browse samples:

Screenshot 2021-06-22 SineMachine – CycleNote cpp - CLion

If you'd like to read more about this, read my post on creating lldb type summaries and children.

Feature key

Here are what the symbols mean that will show up in the sparkline

0 = true 0
x = zero crossing
E = out of bounds (below -1.0 or above 1.0)
I = Inf (Infinity, meaning you've divided by zero)
N = NaN (undefined calculation that's not INF)
S = Subnormal detected


printSparklines was tested on VS2019 on Windows, Xcode on MacOS and CLion on Windows and MacOS.

The lldb python script was tested on MacOS CLion and Xcode only.

Xcode gotcha

If you are using Xcode exclusively, you might want to plop this somewhere


MacOS native font rendering seems to flip the height of two of the characters (⎺ vs. ‾) but it's fine in MacOS CLion, etc.

Don't like how they look?

I'm not a fan of VS2019 with the default Consolas font. Everywhere else it seems to look good! Open an issue if you can make it nicer!

Reminder: Don't leave a printSparkline call in your audio path

Not only does DBG itself allocate, but the whole name of the game is string manipulation here, so if you are sticking a printSparkline in your audio callback, expect those sweet sweet dropouts.