Liquidsoap – A scripting language for multimedia streaming | Hacker News Reader

Liquidsoap – A scripting language for multimedia streaming

liquidsoap.info

110 pointsselvan19 comments

Why are the 'examples' on a programming language website text explanations, rather than code examples? This project could benefit from following the writers' rule of thumb: "show, don't tell".

On the first page they have only two lines of pretty trivial code which makes it hard to tell if I want to spend more time looking into this project. To make matters worse, the first place I'm exposed to actual code is on the second page of their documentation. Until then, it's all wall-o-text style pages.

I found documentation > cookbook (https://www.liquidsoap.info/doc-1.4.4/cookbook.html) a better place to scratch this itch :)

This should be on the first page! Exactly what would get me into the project.

Liquidsoap is great! It's hugely flexible, I can hardly imagine a broadcast-like use-case that wouldn't be covered by it.

Strange timing though; according to the liquidsoap slack channel, the "hopefully last beta" of 2.0.0 was released just two weeks ago, and it has some great improvements, like "first-class support of video" (which is huge, it's not just video multiplexing or these 24/7 YouTube streams, but some advanced real-time stuff[1] was already possible), and "Enhanced language features making the script language a fully-featured language" which sort of was a headache in my experience - it was in this "Greenspun's moratorium"[2] where you could do a lot of things, but some of it was really awkward, and there were walls in unexpected places.

So, when I saw this post, I thought 2.0.0 was out, but it seems it's right around the corner still? Anyway, I'm really looking forward to it, and I recommend anyone interested to follow the project!

[1]: https://www.liquidsoap.info/doc-1.4.4/video.html#detailed-ex... [2]: https://en.wikipedia.org/wiki/Greenspun%27s_tenth_rule

LiquidSoap is great - literally once you get a hang of it, it's very powerful at what it does - scripting a possibly dynamic and interactive program list for a digital radio for example.

But its documentation is difficult to parse, examples are too advanced and the learning curve steeper than it should be.

It took me a week to have something going, even if it was "take this bunch of MP3s and randomise them with jingles here and there", nothing more complex than that.

Why is this a new programming language, instead of just a library for existing languages?

Maybe people who want to program radio shows mostly don’t know a general-purpose programming language, and making them learn one would be overkill?

I would argue that the learning curve for learning a programming language and a well-written purpose-built library versus a domain specific language is virtually the same. If the target is someone that has zero experience programming, their process will likely involve a lot of cookbook copy-paste at first, then tweaking the recipes, and then once they have some confidence of how the steps fit together and some inferences about the causal model behind it, they may start to piece together their own recipes.

A lot of complex domain specific libraries are practically languages all their own even though they are just sets of APIs inside a general purpose language (think OpenGL, CV libraries, ML and scientific Python libs, etc.). Knowing Python doesn't put you at too much of an advantage over someone who doesn't when it comes to applying PyTorch. The advantage of a library is that the learner can eventually expand beyond its capabilities and compound some of their investment and capability versus a DSL that puts you at the mercy of what the author is willing to add / implement.

DSLs seem to come from a mindset that someone won't have to learn much in order to be dangerous, which is almost never the case. The bigger leap seems to be between things like:

- GUIs that are fully guided / wizard type setups

- GUIs that are somewhat drag and drop (can have similar challenges to free-form text, but at least you know what tools are available to you)

- Text that is guided (e.g. a configuration file that is completely filled in, but has a lot of comments and can be tweaked

- Free-form text wherein you are starting from a blank canvas and need to have some ideas in your head about what is possible and what tools you have at your disposal (programming)

I notice it's written in OCaml, so maybe you can use it as a library from OCaml?

I'm working on an [very basic] audio streaming project.

Still looking at the examples and docs and cases, but this might be just what I need to fill some gaps—at least in future iterations. Particularly a simple encoder/transcoder interface.

Are there any live examples viewable/listenable?

https://github.com/LibreTime/libretime

Check out this project called libretime, in the past they used liquid soap for their playback. Basically it's an online Foss radio streaming platform mainly used for radiostations to add in automation for their coverage

Thanks. I'm always keeping my eyes open for projects in the larger space.

LibreTime looks to be a lot larger than the domain I'm working to serve but it looks great and also looks like a good place to take notes on open sourcing an audio project.

https://github.com/UniversityRadioYork/jukebox is a pretty good example of lots of its capabilities glued together. It's also my go to tool for gluing live audio things together

Excellent! Thank you

I've been using Liquidsoap for over 5 years now, running radio stations with live DJs, automatic archiving, volume normalisation and whatever custom stuff you want to add to it. I've also experimented with the video side of it for a few years, including OBS live video ingest support.

I currently run 5 Liquidsoap radio + video streams off the one server. It's a very powerful tool for broadcasting in general. Liquidsoap powered radio https://nightride.fm Liquidsoap powered video https://www.youtube.com/watch?v=kgBcg4uBd9Q

Is there something similar for offline mixing and transcoding as fast as possible instead of live?

For video theres VapourSynth[0], not sure of an equivalent for audio outside of just scripting ffmpeg but that’s probably not as flexible as what you’re after.

[0] http://www.vapoursynth.com/

Thanks

Oh, nice, it's written in OCaml.

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