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BBC Radio Drops WMA For MPEG-DASH
gbjbaanb writes: The BBC has converted its legacy WMA (Windows Media Audio) streams to the "industry-wide and open source" MPEG-DASH format. While this has left some users of old devices unable to receive the broadcasts, the BBC claims the use of WMA was "prohibitively expensive to operate"when existing licence agreements ran out. The BBC says that they are working with "radio industry and manufacturers towards using just one standard."
Yay.
BBC claims the use of WMA was "prohibitively expensive to operate"when existing licence agreements ran out.
ha ha ha ( said with a sarcastic tone )
MP3 is a compression codec. OGG is a container format. MPEG-DASH is a standard for how to do bitrate-adaptive streaming over HTTP. They're all completely different things.
MPEG-DASH is codec-agnostic, and does not require or imply any specific codec. However, since it's intended for audiovisual streaming (rather than just audio), and since it's done under the auspices of the MPEG, h.264/AAC are the obvious codec pair to choose. There is nothing stopping MPEG-DASH from being used to stream something like VP8/Vorbis or VP9/Opus... and in fact the WebM project has documentation detailing exactly that.
Missing from most of the articles on this, including the ones on their web site, is that they used to employ a senior Microsoft media guy who, unsurprisingly, set about converting everything to Microsoft Media formats - Ashley Highfield. Here's a 2007 article with a section of the controversy
BBC used to have one of the more progressive approaches to media with early mp3 streams, Dirac codec research...it then just stopped. Nice to see them get back towards the rest of the world - next step, please go HTML 5 video on the site as well and then we can avoid Flash.
I'm surprised you expect to hear about it here. Most people here seem to care about the codecs and whether they're free. DASH doesn't really care about codecs and really just defines how you create and use adaptive streams and is based on existing codecs/formats. It only standardised relatively recently and it's going to be big (but hopefully transparent), for example: http://www.dash-player.com/blo.... Expect to see it as a vendor neutral alternative to things like MS SmoothStreaming and even Apple's HLS, although the later requires you to have a player with your own decoders if you're sending more than a certain size to iOS devices.
That said, most implementors are doing AVC or HEVC with AAC in a fragmented MP4 container. VOD content is probably one file per stream and live is multiple files fragments) per stream.
This was really badly publicized. We listen to BBC Radio 3 over the internet in the mornings; our house is situated in a dead zone for over-the-air signals, so we're pretty much stuck with streaming. One morning last week, with no warning, came a repetitive announcement saying that the BBC had discontinued WMA and to "contact your device manufacturer". Our radio is manufactured by Pure, and we have been using Radio 3's direct streaming URL because Radio 3 repeatedly drops off Pure's database for days on end and consequently becomes unavailable. The direct URL, on the other hand, has been very reliable up to now.
The BBC say that they make MP3 streams available for all their channels. I couldn't find one anywhere on any of their websites, so I wrote to them and asked them what it was. Here's what they told me: "We are currently only sharing links to our new streams with aggregators and device manufacturers. We are not currently making the links for the new Shoutcast and HLS streams publicly available. Whilst it was previously our policy to share these we found that we could not assure quality this way.". So not only have they discontinued the old streams, they are deliberately hiding the new ones! This is nonsense. The BBC apparently doesn't want anyone to actually listen to their broadcasts! (I did eventually find a viable MP3 feed from radiofeeds.co.uk).
Now we get to bit rate... It was much ballyhooed a year or so ago that BBC Radio 3 was broadcasting the highest quality classical music available because they supplied a 256 kbps stream. It now seems that the maximum available is 128 kbps. Fine for portable radios, but I really don't think this is step in the right direction.
Looking at Dashif.org, I notice the following:
MPEG-DASH Highlighted Features
Advertisements can be inserted as a period between periods or segment between segments in both on-demand and live cases.
I'm a cynic, and I'm getting very suspicious about the suitability to this tech to the BBC.
"AAC is by far the best audio codec that I have come across...Too bad its proprietary"
Proprietary in what way? It's an ISO standard, among other things:
https://en.wikipedia.org/wiki/...
A.
...bringing you cynical quips since 1998
Due to Auntie Beeb's rampant xenophobia, those of you outside of the UK may have to use a proxy or VPN to spoof a UK IP address.
It's not xenophobia, you silly twit. The BBC is funded by UK licence payers, who have no obligation whatsoever to provide free content to people in other countries.
To have a right to do a thing is not at all the same as to be right in doing it
Flash is a security nightmare that we recently suggested deserves to rot in an unmarked grave.
No, you'd better mark that grave prominently. Don't want anyone to unearth it again by accident.
Someone had to do it.
Too bad [AAC is] proprietary
Proprietary in what way? It's an ISO standard
Probably "proprietary" as the antonym of "free software". ISO standards can be encumbered by patents, and these patents can be licensed under either royalty-free or uniform-royalty terms. AAC and other MPEG codecs tend to carry a uniform royalty, and free software cannot implement any process with a nonzero royalty. Opus, on the other hand, is royalty-free.
Why don't they just offer different streams at different bitrates?
Because the user doesn't know in advance which bitrate to choose. For one thing, non-technical users don't know what a bitrate is. For another, the throughput and latency of a particular user's connection to the Internet change over time, and interrupting the stream when the connection quality declines causes a poor user experience.
Based on this post, it looks like the BBC radio audio stream is encoded at a constant rate of 320 kbps using AAC-LC, delivered in the MPEG DASH container, and implemented in HTML5 using Media Source Extensions (MSE).
It is not clear to me if the BBC radio audio is being carried in MPEG DASH as MPEG-4 file format fragments or as an MPEG-2 Transport Stream, but I would suspect for audio-only it is MPEG-4 file format fragments.