Introduction to Wi-Fi radios

BBC would show its extreme bias towards DAB if it nobbles the live Internet streams

The BBC is considering using lower bit rate levels for the live radio station streams than for the on-demand (i.e. Listen Again) radio streams, and if it does this it would show how extremely biased the BBC is against the live Internet radio streams. The reason why it would do this is because the BBC is massively biased in favour of DAB, and it doesn't want the live Internet streams to outclass DAB in terms of audio quality. This would amount to the BBC deliberately degrading the quality of the live Internet streams, and it would also amount to the BBC deliberately mismanaging BBC resources that you and I pay for.

BBC's plans for the Internet radio streams

Earlier this year the BBC laid out its plans for improving the quality of its Internet radio streams:

1. The on-demand streams would start using higher bit rates with MP3 — this was implemented in July when radio was integrated into the BBC iPlayer
2. The live streams were meant to start using higher bit rates with MP3 soon afterwards, but the BBC said that they might use lower bit rates than for the on-demand streams (i.e. this is the subject of this article) — the bit rate increases for the live streams were then delayed in July until "after the Olympics", but they still haven't been increased at the time of writing
3. New encoders/servers would start to be used that are located in Broadcasting House, which would solve one of the problems that has contibuted to the quality of the Internet streams being so diabolical in recent years — these servers aren't in use yet either
4. The live and on-demand streams will switch from using MP3 to AAC/AAC+ later this year, and the BBC said they would reduce the bit rate levels compared to those used with MP3, but they said that the quality wouldn't be worse than it is on the MP3 streams (AAC/AAC+ is a bit more efficient than MP3, so the bit rates could be reduced a little without reducing the quality)

Bandwidth for the iPlayer TV vs Internet radio streams

The following graph shows the amount of bandwidth the iPlayer TV streams and the radio streams (live and on-demand combined) have been using up to now:

Data for the above graph was obtained from the BBC under the Freedom of Information Act

People in the TV industry are also predicting that on-demand viewing will account for 40% of all TV viewing by 2013, and using this 40% figure along with a couple of other assumptions, I estimate that the iPlayer TV streams bandwidth could be 120 times higher in 2013 than it is today. That would mean that the iPlayer TV streams bandwidth would be over 500 times higher than the radio streams are using today. Clearly, it would be nonsensical for the BBC to suggest that they couldn't use higher bit rates for the live streams due to the amount of bandwidth (or cost, because the cost is proportional to bandwidth) they require.

Quality of AAC/AAC+ versus MP3

The bit rates the BBC began using for the on-demand radio streams in July are as follows:

As the BBC has said that when the streams switch from using MP3 to AAC/AAC+ the audio quality wouldn't be reduced, this implies that the BBC would have to use a bit rate level of at least 96 kbps AAC for the streams that are currently using 128 kbps MP3, because the following blind listening test results (which are from tests carried out by audio coding enthusiasts on the well-respected Hydrogen Audio forums) show that 96 kbps AAC provides the same level of audio quality as 128 kbps MP3:

The above test results were for audio samples that were encoded using VBR (variable bit rate coding), whereas the BBC Internet radio streams use CBR (constant bit rate coding), so the quality of the BBC's streams will be slightly lower than those results suggest.

The table above also shows that the quality descends rapidly when the AAC/AAC+ bit rates are reduced to levels below 96 kbps — because the performance of 64 kbps AAC+ is a lot worse than that of 96 kbps AAC. Therefore, if they did use lower bit rates for the live compared to the on-demand streams, you still wouldn't expect them to use bit rate levels that were much lower because of the rapid reduction in quality as the bit rates fall below 96 kbps. But if they're going to use bit rate levels that are only slightly lower than 96 kbps for the stereo stations (apart from Radio 3), why don't they just use the same bit rate levels?? This is especially the case when you consider the justifications the BBC has come out with for why they think it would be acceptable to use lower bit rates for the live streams.

The BBC's "justifications" for using lower bit rates for the live streams

Excuse #1: Reliability

Firstly, I listen to 128 kbps Internet radio streams every day, and the streams are rock solid, so I dispute that this is even a problem. But I'll assume that there is a problem here just to demonstrate how ridiculous this excuse is anyway.

The BBC says that lower bit rate streams are "more reliable". But if we're talking about them using a bit rate of say 96 kbps for the on-demand streams and the bit rates of the live streams would only be slightly lower, the difference in reliability would be negligible. We're talking about bit rates that only broadband users can receive, and it's just plain nonsense to suggest that someone with an X Mbps broadband connection would see a significant difference in reliability between one sub-100 kbps stream and another at slightly lower bit rate. 

Then of course there's the fact that the iPlayer TV streams are using bit rates of 500 and 800 kbps for the normal and higher quality streams respectively. So if the radio streams wouldn't be reliable at bit rate levels below 100 kbps, the iPlayer TV streams shouldn't really work at all, and yet they do work. How odd.

The BBC's hyocrisy doesn't end there, though, because the on-demand radio streams would of course be using a higher bit rate than the live streams, which implies that the BBC would be in favour of the on-demand streams being "unreliable". And if you look elsewhere, GCap Media, which was the largest UK commercial radio group before it was taken over by Global Radio, has been using 128 kbps WMA Internet streams for all of its radio stations since the beginning of 2007, so they clearly don't think reliability is an issue, or they wouldn't use 128 kbps. Virgin Radio also uses 128 kbps streams for its stations, and James Cridland, who's the person in charge of the BBC's Internet radio streams, was the person who launched these streams when he used to work at Virgin. Then there's the few thousand Internet radio stations on Internet radio portals such as shoutcast.com that are using bit rates of 128 kbps or higher, none of which feel the need to use lower bit rates due to "reliability" problems either.

The reality is of course that there is no difference in reliability between two sub-100 kbps streams that are using slightly different bit rate levels.

Excuse #2: System administrators might block access to BBC streams

The other excuse the BBC has come up with is that they claim that the large majority of Internet radio listening takes place at work, and they claim they're concerned that system administrators might block access to BBC streams if the bit rate levels of the live radio streams were increased, because it would increase the bandwidth that office networks would have to deal with.

Firstly, I would dispute the BBC's suggestion that most Internet radio listening takes place in the workplace, because a recent market research survey into Internet radio listening showed that 89% of Internet radio listeners listen at home whereas only 24% listen while at work. Also, the exact same thing applies to this as applied to the point about reliability: if the BBC really is concerned about this issue, why are they using bit rates as high as 500 and 800 kbps for the iPlayer TV streams in the daytime; why isn't the BBC concerned about the bit rates being higher on the on-demand streams; and why are so many other Internet radio streams still using 128 kbps? If system administrators don't block access to these other streams, why would they block access to the BBC's live radio streams all of a sudden?

Also, office networks don't exist in a bubble separate from the telecoms world around them. Bandwidth for office networks goes up and becomes cheaper over time just like it does everywhere else. The live streams bit rates are using the same 64 kbps bit rate back in 2002 as they're using today (the kind souls at the BBC actually reduced the bit rates of the Internet streams in 2003, despite the cost of Internet bandwidth halving every 18 months), and I simply find it very difficult to believe that any system admin would have a problem with a few sub-100 kbps streams entering his/her network.

And even if this really were a legitimate cause for concern, there are a number of measures that the BBC could take to deliver higher quality streams wherever possible, which I'll discuss below. If the BBC isn't prepared to take the measures I've described, which I've already informed the BBC about (so they can't play dumb about this at a later date), that would speak volumes about whether they really want to provide higher quality, or whether it's really just an excuse to provide them at lower quality because they're so biased in favour of DAB.

Measures the BBC could take to deliver higher quality wherever possible

There's no need to use lower bit rates for stations with smaller audiences anyway

The following pie chart shows the proportion of live listening hours for the BBC's national stations:

The above figure clearly shows that the vast majority — 86.3% to be precise — of all listening to the BBC's live streams is accounted for by Radios 1, 2, 4 and 5. That implies that as the other stations only account for 13.7% between them then there's absolutely no reason to limit the bit rates of those stations anyway.

In addition, Radio 5 is a mono speech station, and mono stations only require about half of the bit rate of stereo stations, so using the same 64 kbps bit rate it's using at the moment, but with the AAC/AAC+ codec, it would provide good audio quality anyway, so there's no issue with the bit rate for Radio 5 either.

So even given the BBC's own excuses, it still has no justification for using bit rates that are lower than in the following table.

1 - I think they should use AAC rather than AAC+; to read why see here

Higher bit rates could be used in the evening

The vast majority of people work in the daytime, so the BBC could use higher bit rate levels in the evening when people aren't at work. Dynamic bit rate allocation is a feature you'd expect to find on modern audio encoders, and the BBC will have just purchased new AAC/AAC+ encoders for its iPlayer TV and radio streams, so they should be able to do this.

The BBC could deliver higher quality streams to people at home

Each computer that's connected to the Internet is assigned an IP address by an ISP or the organisation whose network the computer is connected to. Associated with each IP address is a 'hostname', i.e. a name given to that computer by the ISP or organisation. These IP address-hostname pairs are stored in the DNS (Domain Name System) database, and ISPs and organisations typically include their name in the hostname so you can tell from looking at the hostname which ISP or organisation the computer is connected to. For example, my ISP is Virgin.net ADSL, and my hostname is of the form:

client-xxx-xxx-xxx-xxx.glfd.adsl.virgin.net

where the 'xxx-xxx-xxx-xxx' consists of the IP address Virgin.net allocates to me. The 'adsl.virgin.net' part of the hostname string makes it obvious that I'm a Virgin.net ADSL user. To find out your IP address and hostname visit this web page, which automatically enters your IP address into the edit box, and if you click 'Lookup' it will perform a reverse DNS query to find the hostname associated with that IP address.

In the vast majority of cases you can tell which ISP or organisation a computer is connected to from the hostname, and in the case of consumer ISPs it also shows that the user is at home rather than at work. So the BBC could maintain a database that stores the ISP or organisation associated with each IP address, and the BBC could then deliver higher bit rate streams to people at home and lower bit rate streams to people at work.

Although there are over 4 billion IP addresses, ISPs and organisations are allocated ranges (sometimes very large ranges) of IP addresses, so the database would only need to hold a few million entries, if that — and it would only require a short program to be written that could be run to update the database automatically. The BBC already checks the IP addresses of people who're trying to access its streams anyway, because it performs a 'Geo-IP' check to determine which country a user is from, and the BBC delivers lower bit rate radio streams to non-UK users, and non-UK users aren't allowed to view the iPlayer TV streams at all.

For ISPs that provide Internet connectivity to both consumers and businesses, the BBC can always contact the ISP to find out which range of IP addresses are used for consumers and which are used for businesses.

At the end of the day, someone sitting at home and wanting to listen to a BBC live Internet radio stream should not receive a lower bit rate stream just in case they're at work when the BBC could easily determine that they're at home.

The BBC's gross mismanagement of the Internet streams over the last few years

It's easy to forget just how diabolical the quality was like over the last few years on the BBC's Internet radio streams before the bit rates were increased to slightly more reasonable levels last year, so I've uploaded a short sample of Radio 1's Internet radio stream recorded in October 2006 when the BBC was using the spectacularly high bit rate of 32 kbps:

FLAC lossless version

320 kbps MP3 version

The quality was diabolical on all of the BBC's streams over the period from 2003 to 2007, and the sad thing is that there was never actually any need for the quality to be anywhere near as bad as it was, for the following reasons:

• The BBC has had the opportunity to use the AAC+ audio codec to vastly improve the audio quality of its Internet streams (at no additional licensing cost to the BBC) at the very low bit rates it was using ever since January 2004, which was when Real added support for AAC+ to Real Player. Yet today, over four and a half years later, the BBC is still using the dire Real G2 codec for its live Internet streams.
• The live Internet streams for Radios 1, 2 and 4 were using a bit rate level of just 32 kbps until last year, even though the cost of Internet bandwidth for the BBC had been halving every 18 months since the mid 1980s due to Moore's Law. And in the same year as when R1, R2 and R4's Internet streams were still using 32 kbps, the BBC iPlayer TV streams were launched using a bit rate of 500 kbps — 16 times higher than the bit rate used for the radio streams.
• Not content with the above two factors that hugely degraded the quality, the BBC additionally butchered the audio for the Internet radio streams just for good measure. For the last six years, the BBC has been receiving its national radio stations off-air via satellite (i.e. the same BBC radio streams people receive on Sky) at Maidenhead, where the BBC's website servers are located, and the audio from the satellite streams are then recompressed to the Real audio format at the very low bit rates the BBC was using. This practice of decoding audio from one format and encoding to another is called 'transcoding', and it is terrible audio engineering practice, because it is guaranteed to reduce the audio quality. Furthermore, the lower the bit rates being encoded to the more important it is to avoid transcoding — yet the BBC was encoding to bit rate levels of 32 kbps, and you don't get much lower than that! The reason why they've been transcoding the audio for six years is to save the £5,000 - £10,000 per year needed for a dedicated direct data link to carry the audio from the BBC's studios to Maidenhead. And whilst they've been saving this paltry sum they've been spending between £6 million and £9 million per annum on transmitting their beloved DAB national multiplex. They're still doing this even today, but they are thankfully about to start using new encoders and servers that are located in Broadcasting House, which will finally solve the problem.   
• Also, there was actually absolutely no reason to transcode the audio for the BBC Listen Again streams anyway, because the audio for the Listen Again streams doesn't need to be encoded in real-time (live streams must be encoded in real-time, because the delay between the live broadcast on FM and that on the Internet, DAB etc can't be too long, whereas with on-demand streams even a few minutes delay in encoding the programme files and uploading them to the servers wouldn't matter), so the audio streams could have been sent to Maidenhead via the Internet. But this obviously never occurred to them, and they're still transcoding the audio for the on-demand streams.

There are only two possible explanations for why the above things were allowed to take place:

• It was deliberate, and the BBC wanted the live streams to be at appalling quality to put people off listening via the Internet so that people would be more likely to listen via DAB; or
• It was simply down to gross incompetence.

If it wasn't for the fact that I know that the person in charge of the technical side of the BBC Internet radio streams doesn't have an engineering background, I wouldn't hesitate to say that what has happened over the last few years was done deliberately, because I find it impossible to believe that anybody with a reasonable understanding of the technologies involved could possibly implement the Internet streams in such a diabolical manner as they have been over the last few years.

However, there is one thing that I definitely consider to be deliberate, which is the bit rate levels that the streams were using, because you don't need to have a technical background to know that higher bit rates provide higher audio quality and vice versa. But until last year the streams for Radios 1, 2 and 4 were using a bit rate of 32 kbps, and the people in charge must have deemed these bit rate levels to be adequate, which speaks volumes about how they regarded the Internet streams. Whether the bit rates were deliberately kept as low as possible in order to favour DAB is impossible to tell, though, and the BBC would never admit to this. But when you consider that Simon Nelson, the BBC Controller in charge of digital radio at the time, candidly admitted on Radio 4's Feedback programme in around 2004 that:

and also taking into consideration that the BBC reduced the bit rates of the Internet streams from 64 kbps in 2003, it certainly makes you wonder whether the bit rates were kept very low deliberately. And from my experience of following the goings on with the BBC and digital radio over the last few years, I definitely wouldn't put it past them doing this on purpose. The other points mentioned above could be down to gross incompetence, but they could equally have been done deliberately as well. I doubt we'll ever know.

I will say one thing though: if the BBC does use lower bit rate levels for the live streams than for the on-demand streams, I think that would prove once and for all that the BBC is extremely biased against the live Internet streams, and to my mind it would also show that the goings on over the last few years were no accident either.

I'm definitely going to complain to the BBC Trust if they do use lower bit rates for the live streams, because there's absolutely no justification for them doing this, and I'd urge others to do so as well. At best, the BBC has incompetently managed the Internet streams for years, and at worst they've deliberately provided low quality in order to deter people from listening via the Internet. If they go on to use lower bit rates for the live streams you can add deliberate mismanagement of BBC resources to the list of things to complain about. This needs to stop.

AAC versus AAC+

The following table shows the AAC profile that is chosen to be used by default on the Nero AAC/AAC+ encoder when different bit rate levels are used:

From reading the BBC Internet blogs about the Internet streams over the last few months, I've got the distinct impression that the BBC is going to use AAC+ for the Internet radio streams, but I think it would be better to use AAC.

There's a common misconception that AAC+ is better than AAC, which seems to be due to the fact that AAC+ is newer and the '+' sign seems to suggest that it's better as well. This is not the case, and AAC+ is merely better than AAC when very low bit rates are being used -- AAC is inherently better once the bit rate is above a certain threshold, as shown in the table above.

The reason why this is the case is down to the way AAC+ works. AAC+ uses the AAC codec to encode the bottom half of the audio spectrum, and it uses SBR (spectral band replication) to encode the top half of the audio spectrum very efficiently. SBR only uses a bit rate of between 1 - 3 kbps per channel, and the very high efficiency of AAC+ is purely down to the fact that SBR uses such an incredibly low bit rate.

However, SBR encodes the top half of the audio spectrum artificially (see this for an explanation of how SBR works -- note, however, that that article is written by Coding Technologies, which is the company that invented SBR, and they're prone to exaggerating how well it performs), so although SBR is extremely efficient, SBR isn't able to encode the top half of the audio spectrum as naturally or in as high a level of quality as AAC can, and that's basically why it's better to use AAC once the bit rate is above a certain threshold.

For example, if AAC and AAC+ were being used to encode at a bit rate of 128 kbps (with a 44.1 kHz sampling rate), and assuming that 15% of the bit rate is allocated to encoding the top half of the audio spectrum on AAC (which is roughly what you'd see in practice), the bit rate allocation for the two audio bands would be as follows:

At such higher bit rate levels it would be better to encode using AAC on its own, so that the encoder can choose how best to allocate the bits to the different frequency bands rather than the situation with AAC+ where the bit rate allocation between the high and low audio bands is imposed upon the encoder by the fact that SBR uses such a low bit rate level.
 
 

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