Re: Bitrate capability of DAB radios



On 10/01/2012 23:46, J G Miller wrote:
On Tue, 10 Jan 2012 22:09:10 +0000, Richard Evans wrote:

I don't find FM multipath to be all that bad.

Not in your location for reception from Wrotham.

Actually I mostly use FM in the car, and I don't often listen to the national stations.

At home if I listen to the radio, I tend to listen online. Except very first thing in the morning, when I tend to use the Scanner in my bedroom, since I discovered that it can just about pick up Radio Jackie But if I listen for any length of time, then I tend to switch to the web stream via my Squeezebox.

For most
people at home with a proper VHF Band II antenna (not a horrible
bit of pink plastic coated wire dangling from the wall) then
reception of the four BBC network services will not have this
problem.

I don't use a proper FM aerial any more, as it took up too much space in my flat, and since I can now use the internet instead, there doesn't seem to be much point.

Not using a proper aerial, I do get multipath distortion here. As the position of my flat tends to favor reflected signals from across the valley, and tends to attenuate the direct path signals from London. (BTW. In case you were wondering, I'm rather badly placed to receiver Wrotham). However the sort of multipath distortion I get here is usually only noticeable on my hi-fi system, it is to subtle to notice it on any slightly lower quality system.

In car I find the same is true. I don't notice loss of actual sound quality quality due to multipath. I do notice dropouts in signal, and I do sometimes notice my car stereo reducing the stereo image, due to poor signal levels, but that is because I tend to listen to stations from outside their normal coverage area. When however I tune into a stronger signal, I rarely hear any problems.

Basically, I find that loss of quality due to multipath, usually only makes a subtle difference, which is only noticeable on a hi-fi system. All other problems are due to loss of signal, but if signal levels are good enough, then FM is fine for every day listening.



Well previously you said "regardless of quality". But how can you ignore
quality, and not ignore hiss.

Because the hiss is a fundamental aspect of the method of transmission
whereas encoding artifacts are dependent on the bit rate allocated by
the multiplex operator.

I find hiss far less annoying, than the flatness of the DAB stereo image,
or the compression artifacts.

I did not suggest that other factors as you described were not more important
overall, my comments were purely in terms of what DAB reception can provide,
not the low quality which it is used to deliver in the UKofGB&NI.

OK fair enough. Although to me this point is academic. DAB is technically capable of providing better sound quality than FM, but I'm only interested in what is actually provided, and there are good reason why, in the real world, DAB is not providing what it could.

As things stand, I can't see any way that DAB is going to provide anything near FM sound quality. So if we want to listen to music radio in the car, then most people are better off listening to FM.


Well probably possible in theory, but I have never known my car stereo
to do that. So I reckon it must be rare for it to happen in the real
world.

You do not notice it because you probably only listen to BBC network
radio and not distant local stations in your automobile.

No, the station I listen to most often is Radio Jackie, when I'm driving too or from work. This is a fairly low power transmission, and I'm outside their normal coverage area. I get signal dropouts when I'm driving through Caterham Valley, but for most of the rest of my journey to work, the signal is perfectly acceptable. In some places my car stereo reduces the stereo image, due to weak signal. However I still don't notice the loss of quality due to multipath that pro DAB people talk about. The only problems I ever notice are due to a weak signal, and even being outside the normal coverage area, I only notice these problems in a few areas.

My main point, is that actual loss of sound quality, due to multipath distortion, is usually only noticeable on a hi-fi system. But if you are listening on a hi-fi, then you are probably at home, and so you probably have the option of listening online instead.

Richard E.
.



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