Finish Phone / Lofi effect

[topisani]

We need dsp and graphics for a lofi/phone/radio type of effect.

[AlbertSmit]

I will see if i can come up with a cool idea for the graphics. :)

[jmidt]

So, since i can't find a good rundown of the effect on video: What is it? It seems like mostly some bitcrushing - perhaps with some granular elements. There's definitely some glitchyness going on...

[topisani]

the OP-1 has an effect that does i think a bit of analogue sounding distortion + definately some bit crushing and some "glitchyness", which seems a bit like a randomly/envelope triggered gate. But i dont think this is necessarilly what we have to do with it. I just think we need something to destroy sound, both analogue-like and digital (bit crushing)

[AlbertSmit]

@jmidt Short video of 'Phone' effect (starts at 3:20 if timestamp doesn't work).

[Hate9]

I don't know about the OP-1 effect, but in general, the reason phones sound the way they do is because of heavy signal filtering (e.g. hard low and high passing), so maybe it could be a combination of hard passing, noise modulation, and bitcrushing.

[AlbertSmit]

Current state of this effect's UI.

F E E D B A C K T I M E !

[nebularnoise]

@D-I-S-K-U-S That OP1 effect sounds like Linear Predictive Coding, as used in the Speak&Spell, or Bitspeek for instance. I have some material on that, I'll try and see what I can dig up.

As for the 'traditional' lofi phone sound, yeah, it's mostly highpassing at 300Hz and downsampling at 7kHz. Then, predistortion and bitcrushing can be added for good measure.

[nebularnoise]

LPC is far from trivial for me to implement from scratch, but there are a couple of open source DSP libraries that do it. We could either import it, or inspire from their code.

• Soundpipe lpc module (repo)
• SNDTools lpc
• VoiceCodec

Soundpipe looks the most interesting IMHO. The only downside is that Soundpipe's lpc is limited to a 10 pole filter lpc. Don't get me wrong, 10 pole is exactly the kinda sound we're looking for, since it's the rough model used in the S&S, but adjustable filter order could have been nice to have.

Either way, if anyone's interested in the maths that are involved, I found those slides to be reasonably exhaustive.

[topisani]

status on this? For me to really be enthusiastic about it, it would need to be not too similar to the OP-1 phone.

Also, @D-I-S-K-U-S We need to rework that UI for the new style. To be honest, I'm not too sure about it anyway, but lets see whats possible in a rework

Do we want to do this before v0.0.1? gives us about two months to have it in

[AlbertSmit]

Yeah, we/I should probably come up with a new UI concept for this thats a bit more abstract. On it!

[AlbertSmit]

I was just looking through the Faust documentation, and I found there's vocal synthesis.
Would that be anything we can work with @nebularnoise?
A similar effect at least, not necessarily the same.

[jmidt]

Updated. Added GFI flair.

We need to finish this effect. Most of the DSP has already been written, it just needs to be wrapped up in a proper effects engine struct. The code currently in this PR: #104 but should be moved to a proper feature/ branch.

Apart from the code, we also need new UI ideas in the new style.

[jmidt]

I have started work on this again. It is now in the feature/LPC branch