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All posts by shaun

Below are all of shaun's postings, with the most recent are at the bottom of the page.

C47 (682.0MHz) after switchover
Saturday 6 August 2011 8:54PM

Select channel 36 before switchover and there appears a map of the gulf of guinea! Do any TV channels actually broadcast on channel 36 or was that one never used ?

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Reading the comments about Nicam and digital TV transmission months after they were posted, I honestly don't understand why Mr. Lunn's comments were deemed so wrong. Nicam encoding could have easily been added to a channel's digital data stream instead of adding the Mpeg audio stream as now used. It would have broken the DVB standard, but that doesn't mean it wasn't technically possible, or feasable, (it certainly was) or couldn't even become part of the standard as an option especially with the BBC behind it. Personally I'd say there are issues with both Nicam and Mpeg audio, with Mpeg audio the quality is diabolical at lower bit rates, or with poor signals causing errors, as in digital radio broadcasts. Because of the quantisation Nicam drops bits at high volumes and this is supposedly masked by the ear, but I believe quality is lost, in some circumstances for example a range of pure tones with dissimilar volume levels, but a similar form of masking which fools the ear, is what mpeg audio also relies on.

My main concern with Mpeg is that the broadcaster has too much control of the minimum audio bitrate on Mpeg audio and might be therefore tempted to save bandwidth by using a much lower bitrate than is appropriate. This isn't allowed AFAIK for Nicam, so the sound quality is consistent, always being at the upper limits of the design.

Mpeg audio needs at least 256kbits/sec to compare with Nicam, but Nicam uses more than that I think.

In all cases error correction has to be added after encoding as an extra, the question would be how much would be needed.

Sadly the best systems don't always win in any case.

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I don't know how Sky can justify wanting MILLIONS of pounds a year for providing a few bytes on an EPG guide. Some newspaper articles on this are not very clear at all. As poined out on here, Sky does NOT retransmit the BBC programs. They just enable their boxes to be able to easily receive them, and provide an EPG.

They should consider it an honour to be able to do this, for the benefit of their paying (heavily paying) customers, (of which I am one) and the benefits of being able to provide a "one stop" platform. which receives virtually all British channels.

Sky wouldn't be half as popular if folk had also to use other equipment to receive the BBC channels or switch over to other equipment when they wanted to watch the BBC or see what was on it.

Sky was only considered a "full" reception solution, when ITV finally joined its EPG.

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