Well, wow. After nearly forgetting to actually submit it and only writing the entry a few hours before the deadline, it turns out that the system I made while at Insanity Radio 1287AM has been nominated for the Best Technical Achievement award at the Student Radio Awards. So, I figured it would be worth actually writing up a little bit about what it is and what it does. And why you can use it, too, if you’re involved with a student radio station.
IRIS was written to replace MACIS, a system I bodged up out of necessity. At Insanity, we had a computer failure weeks before we went on air at the start of the first term, and lost all the data- including the entire playout system. Lessons have been learned (I made sure we replaced that machine with a box that had RAID, for starters) since, but we had the unenviable challenge of repopulating a student radio playout system from scratch with little to no staff. Enter MACIS!
MACIS was dumb. It talked to our playout system (PSquared’s Myriad 3.5) via the not-very-documented TCP/IP interface, had a web interface and drop box, and some background processing magic. It was implemented as a Ruby on Rails web application, since we already used Rails and Ruby for various tasks around the station (the website is all Rails, and Ruby was chosen for most scripting tasks because of its user friendliness to people not too familiar with programming. You passed it files, it converted them (the main purpose- Myriad doesn’t support AAC, MP4 or many other formats we were using for ingest), did a basic stab at normalization, and then imported the files. Myriad is slow at importing files- 1-2 minutes per file on average, so we let MACIS distribute workload across all four of our Myriad machines, speeding things up massively.
This was good and got us running, but then term started. We’re a student station and have specialist music shows, who upload their own content to the playout system every week, and new content for new music and chart shows came in regularly. MACIS was used for this, as it did the conversion automatically, saving our presenters loads of time. It also did batch imports quickly and efficiently, which sped things up. However, after a while, we stopped using it, and just provided a simple Ruby dropbox on a shared file server for conversion. MACIS was useful, but too buggy and inflexible. In addition, while it did a better job of getting metadata into Myriad than Myriad managed on its own, it had issues with some formats and material.
What was needed was a system that would let presenters upload content in any format, would sort out the metadata, handle conversion, and fire it off to the playout system for usage.
So, while presenters got back to using Myriad directly, I went back to the drawing board and scrapped MACIS. At this stage we were considering transitioning to the Rivendell open source playout system to replace Myriad, so I decided whatever I was going to make had to support both Myriad and Rivendell, and any other system you could imagine.
I also wanted to solve the loudness problem. Even doing normalization to every track imported, we had huge loudness level differences between some tracks, making life quite tricky for presenters and impacting our on-air sound. Especially given our lack of transmitter processing (we only have a limiter and preemphasis box on the AM system- no AGC or multiband comps), I wanted to do all I could to get everything as perceptually loud as everything else. Enter EBU Recommendation 128 for loudness measurement- with the help of some great libraries (libebur128 in particular), I implemented a simple version of the recommended processing system for loudness normalization, including LRA correction using a compressor. Thus, everything you run through IRIS comes out sounding about the same as everything else in terms of perceptual levels – as much as is possible without impacting the sound. Wish You Were Here is still going to have a quiet bit at the beginning- but IRIS will gently compress the track to make the difference less severe, and will then use R128′s standards to normalize to -23 LUFS.
Next up, user authentication. This was almost an afterthought, but added after talking to people about security. You register an account, and that account is either able to upload content only, upload and review (more on that in a sec), or administrate the system (ie modify users etc). This is done by user groups, which are pretty flexible, and easily adapted for your own usage via a simple permissions file. Uploads are linked to users- users can only see their uploads (unless they have permission to see more than that) and admins can see who owns a specific upload. You can also have emails sent on error conditions being met- so presenters know if a file they uploaded failed to make it to the playout system before they turn up to do their show and wonder where it is.
Metadata was one of the big issues I wanted to solve. Let’s say I have a track from a CD- I’ve ripped it and the ripper has embedded title/artist, maybe album metadata from Gracenote. For a playout system for radio this isn’t perfect- really we want to know the record label, copyright info, and so on. Enter MusicBrainz- a huge collaborative open database of music metadata. With some clever tools, IRIS matches up the track’s metadata to a MusicBrainz identifier and fills in the blanks. For most tracks, it can get everything- including ISRCs, year of release, and so on. This is great for music librarians and makes copyright reconciliation for PRS/PPL much simpler, since you’ve now got all this in a database.
Of course, if we know what the track is, we can do another useful step- especially so for student stations. Using the MusixMatch API service (commercial but free for nonprofits at present), we can get the lyrics to a track. This means we can do a quick once-over for words we don’t want on air (swearing). Of course, this assumes the track isn’t a radio edit. We do a quick check and skip the lyric pass for tracks that look like a radio edit, but if not, the track will be flagged for review.
Additionally, and this is intended specifically for situations where you have no control over the ingest quality that presenters are using to rip CDs or vinyl, tracks are flagged for review if they fail to meet quality restrictions. This can be specified as a function of sample rate and bit rate. This stops people trying to upload 96kbps MP3 at 32k sample rate. We don’t want that in the system. Not now, not ever. All of these parameters can be changed easily and simply by changing a single configuration file and restarting the app.
Once an upload is flagged for review an administrator or music librarian can review the track and either permanently reject it or approve it (in case of false positive lyric matches or odd uploads where quality restrictions aren’t able to be met).
Everything in IRIS is done through a web interface- uploads, management and monitoring. Every track has its own log of events, allowing administrators to debug and diagnose problems with ease, and giving clear and simple feedback to users. There are convenience functions such as automatic display of R128 loudness graphs pre/post normalization and compression, and display of all metadata available for tracks, plus lyrics if they were found.
The backend to IRIS is all Ruby and Rails, using a simple database server (PostgreSQL recommended) to store everything. Background processing is distributable over multiple computers with shared storage, allowing for CPU-intensive tasks to be spread across multiple machines. Given the R128 metering process includes a fourfold upsampling, this is particularly useful. You can run workers without running the whole web application, allowing you to install copies of the app onto lots of low-cost general purpose machines and have your own distributed ingest processing cluster on even a tight bugdet.
Of course, now you’ve got a track with lots of metadata and some normalized audio in WAV format (archived to FLAC pre-normalization, just in case you need the original audio). Now you need to get it into your playout system. Rivendell is supported, Myriad 3.6 now has dropbox support so you can just tell IRIS to export files to that dropbox in a Myriad-supported format, and you can also just do an export in any format you choose to an arbitrary folder. Export formats supported include FLAC, MP3, WAV, BWF (Broadcast WAVE Format) and AAC. Most of these flavours come with embedded metadata.
IRIS isn’t a perfect system, and it’s not an instant drop-in system; I don’t have the time to maintain it as such. What it is, though, is a flexible and powerful system that any average Linux user can install and have running in hours, and which can be used by any station looking to improve their import process. The entire project is open source, and can be obtained here- there’s also a bugtracker and wiki with some documentation (unfinished) on it. If you’d like to contribute, feel free- as I’ve stepped out from student radio to work on student television, I’ve not got a huge amount of time to work on it at the moment.