The box set has become a way of not just collecting favourite series but watching lots of episodes in one sitting. This indulgence has primarily been for films and TV shows on DVD but has now extended to streaming and download services. Radio listeners have had cassettes and CDs to binge on in the past, but over Christmas and the New Year the BBC made streamed box sets a reality for the audio-only medium.
These included Prince Charles on the 1,000th edition of the programme Private Passions; the best of performances from the Live Lounge; a new series of festive short stories; and music mixes by Trevor Nelson, Matt Lucas and Rudimental. All of this was hosted on a new audio platform, BBC Sounds, which allows people to listen on computers, mobile phones and other devices to access live programmes and on-demand material.
The BBC Sounds app was officially launched at the end of October, with live broadcasts of national and radio programmes from the London Eye. The new platform replaces iPlayer Radio, adding to what was already available with more than 100 hours of ‘new’ comedy and drama from the BBC archives, podcasts, music mixes and live broadcasts.
The user interface of BBC Sounds and what the app can do differs considerably from that of iPlayer Radio.
“We wanted to make a product that was very focused on audio and more personalised,” explains the executive product manager for BBC Sounds, Chris Kimber. “The iPlayer Radio app was a good product if you knew and loved radio but if you weren’t familiar with the BBC brands it was quite confusing and not welcoming.”
Kimber says the primary aim behind the new app was to “reach out to more than hardcore BBC radio fans” and allow people to discover what material was available. Being able to do this means there are even more technical differences between the two systems.
“BBC Sounds has been built from a set of APIs and is more consistent than iPlayer Radio, which ended up with too much complexity,” he comments.
In a blog about designing the API structure for BBC Sounds, software engineering team lead Patrick Cunningham wrote that, in the past, API endpoints had been created for particular features requested by clients. Cunningham and his team began to look at an API that was independent of a specific platform to create a single integration point. This has resulted in the layout and content of BBC Sounds being defined in an API.
Kimber observes that this makes the app “more consistent” and allows it to be rolled out across different platforms. “Because we’ve built a core business logic, if we want to build it out in another direction, such as working with voice devices such as Google Home and Amazon Echo, we can,” he says. “We’re able to provide the underlying technology for those.”
Material that ends up on BBC Sounds can come from a number of different sources, including podcasts produced at a presenter’s home on a computer-based DAW or programmes made in a fully equipped BBC studio. Jim Simmons, executive product manager for BBC Platform, Media Services, comments that many of the live programmes are captured off-air and taken into the department’s control room.
The source feeds are distributed by the BBC’s streaming system, Audio Factory, and then sent up to the cloud for processing by a cloud-based encoder into one of four bit rates: 48, 96, 128 or 320kb/s.
“These cover the range of devices from mobile up to top end hi-fi for a station such as Radio 3,” Simmonds says. “These are then formed into chunked HTTP for on-demand delivery.”
Simmonds says this works well for live material. Pre-recorded programmes are taken from the playout system and then sent for encoding. The app is able to interrogate the target receiving device so the most appropriate quality is delivered.
“Metadata is very important in deciding what is offered,” he explains. Kimber adds that metadata also plays a role in searching for programmes and podcasts. “At a very basic level we rely on good metadata to aggregate everything and then sort between genres, such as comedy, history and music.”
Metadata is additionally used for personalisation and particularly for the play-queue feature. Currently available only on the web, this will cue subsequent episodes in a series.
“If you’re listening to a podcast like Michelle Obama’s Becoming, the system will line-up the following edition so the listener doesn’t have to keep reaching down to select something,” Kimber says. “When we’ve finessed the logic, we think this will become really useful.”
A major technical point that is still being ironed out, for radio in general as well as audio streaming, is loudness. Simmonds says that the BBC has been working with the AES, which produced the TD 1004 loudness recommendations for audio streaming and network file playback.
These have been adopted for podcasts, with the target set at -18 LUFS (loudness units relative to full scale). “In noisy environments, podcasts were considered too quiet and we were getting complaints,” Simmonds explains. “We’ve added a loudness component for filebased delivery and -18 is a nice compromise.” He adds that there are still some problems because the different smart speaker AI voices work to their own loudness targets, with Alexa at -14 and Home on -16.