Under the iPlayer hood for radio
The quick answer is "they're different per station, they're different whether live or on-demand, and they'll change at least another two times this year". If that satisfies you, you have no requirement to read on. If you want more information, however, I'm happy to help. Note that I'm only talking about national radio, and only for listeners in the UK.
First, you'll notice that for "live" we're currently using Windows Media Player rather than Real Player (for most of you - we still give Real to some operating systems). We're doing this because we know online radio is particularly useful in the office, and chances are that Windows Media is automatically installed on most computers, and most corporates won't let you install other software. It should, therefore, 'just work'. I should though say that if you need RealPlayer for your internet radio or your fridge, those streams continue; we've no plans to remove them.
The future for "live" is firstly to significantly improve the bitrate (which we'll do in July). In parallel with that we're working on a way of delivering higher-quality still, using a Flash-based player and an AAC-family stream. We're working with our distribution partners to enable this; the upshot is that it should sound even better but use less bandwidth.
For "on-demand", you'll have spotted that we're using Flash, within the lovely embedded media player that you're familiar with for TV in the iPlayer. Under the hood is a protected MP3 stream for now: again, we're shifting over to AAC-family later in the year. The real difference here is the quality - we've significantly improved the bitrates we can offer.
For on-demand content, we're launching iPlayer with four MP3 profiles based on the content of the programme: and we're using four different bitrates for these profiles.
- Pop music (eg Radio 1 or Asian Network) is 128k stereo.
- Classical music (Radio 3) is 192k stereo.
- Stereo speech (Radio 4) is 128k stereo.
- Mono speech (Radio 5live) is 80k mono.
These are the launch bitrates; we'll tweak things, and moving to the AAC family will reduce the bitrates we use (to make your listening more reliable, whilst maintaining audio quality). Again, the Real listen-again streams that your internet radio uses will still work.
Finally, perhaps I might be able to let you into a bit of a dirty secret. For the last six years, the online streams from BBC national radio have been taken from satellite: the same feeds you get on Freesat or Sky. So we've been taking a lossy MP2 audio feed, and then encoding it further into even lower bitrates. As we move into higher quality audio online, clearly this has to stop. So, from July, it will - we'll be encoding everything within Broadcasting House, plugged in to the studio feeds. So better bitrate is only part of the story - it's also better sound.
If you've got feedback about radio within iPlayer beta, we're watching your blogs; or if you're blogless, please do comment here.