I've been driving around assuming that the poor reception on my motorhome was due to the aerial being mounted on fibreglass bodywork, but reading recent forums, particularly lemmy's request for a new release, I could well be subject to bugs: could someone kindly outline what the problems are? What I'm calling poor reception could well, for instance, be the AF feature malfunctioning.

Currently AF works in a fairly pants fashion; it waits until the signal is totally gone before it polls frequencies in the AF list to locate the new frequency.

Obviously, it needs to background poll the alternative frequencies and switch to the strongest one when the signal strength exceeds that of the current frequency for a certain period.

This is on the wishlist, but I can't give dates I'm afraid. I'm fairly sure it will get done, because I want it (worst case, I'll do it myself )

Hugo

Send me a patch if you do, the wife goes bananas if she can't get Jonathan Ross on a saturday morning - I can't wait for a beta, my marriage won't last!

Thanks for the prompt reply.

I have to warn you that it's not going to happen in the near future, I'm rather busy... AF is only used if you're moving about though. The way I handle this at the moment is just to have lots of presets of adjacent stations and flick through them when reception starts to go down the toilet - manual AF

Hugo

I got the motorhome to move about: Sandringham tomorrow; Cirencester last week ; Scotland before that - I'm as well off re-tuning. Hey-Ho, what's one small minus in a sea of plusses, I'm just annoyed that I won't be able to load the new beta 'till I get back on Monday.

YAY!


do it, then email me the phone number of your favourite food-by-phone service!


bye,
[L]

Greetings!

email me the phone number of your favourite food-by-phone service

The Wrestler's. +44 01223 566553. Ask for Tom.

In reply to:

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Obviously, it needs to background poll the alternative frequencies and switch to the strongest one when the signal strength exceeds that of the current frequency for a certain period.

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I've been thinking about how to implement this, over the last few weeks. The scheme I have in mind is maintaining a record of all the AF frequencies, and for each one, remember when it was last checked and its signal strength at that time. Now, we can compare the strength of the current reception with each of the other stations adjusted by some uncertainty factor based on how long since the candidate was last measured. If any of the adjusted strengths appears greater than the current signal, sample it again, and consider switching. The RDS decoder has a silence detector to help with choosing sample times, doesn't it?

The advantage of this scheme is that the stronger a station is, the more often it's sampled. Conversely, weak stations get only a small proportion of the available sampling opportunities, until they get stronger.

You don't actually have to remember the time of the last check for each frequency - you can adjust the remembered strength as you go. And probably bias the measurement to give slightly more strength to the current signal (for hysteresis, preventing the tuner switching back and forth repeatedly).

I've probably already said I'm looking forward to better AF switching (it will improve TA, for one thing). But I acknowledge it could be a long wait, so I'm not going to get agitated about it.

The way I handle this at the moment is just to have lots of presets of adjacent stations and flick through them when reception starts to go down the toilet - manual AF

If/when you do implement it Hugo could you add the following feature. My head unit allows you to manually trigger a rescan, which means that when the reception is going to hell in a hand cart, but the head unit hasn't spotted that it is bad I can press one button to force it to rescan for a better signal.

Yes, there are lots of schemes that have been thought of to help with quick polling of stations; in theory we can use the silence detector, but in practice we probably won't as it can be a bit of a pain due to the way the tuner is connected and userspace/kernel space latency issues.

Basically it'll probably interleave polls, with weaker AFs being polled less frequently. If it has a good candidate, it'll do a longer poll - long enough to pick up the 16-bit station ID from the RDS stream on the other frequency so it can check that the polled station is actually the same one the user is listening to. If the station being polled is the same, the switch is almost totally inaudible.

The tuner is very fast too, which means that even polls to weak stations are hard to hear.

Hugo

In reply to:

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The tuner is very fast too, which means that even polls to weak stations are hard to hear.

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That's very true. I sometimes demonstrate this to passengers by saying, "Listen to this," as I switch between two frequencies of the same station. The usual response is, "Listen to what? I can't hear anything different." Which is exactly the point.

One question - does the AF processing need to be in the (user-mode) player? Because if it were in the kernel (rds.c?), it could benefit from geurilla development.

In fact, I'm tempted to start some kernel hacking myself if I can get one of Patrick's tuner kits soon enough.

Could be in the kernel, I suspect. We put the RDS stream checking into the device driver, so you can just interpret the packets and take note of the commands from the player.

A very large amount of the work is already done in the player, though, it just needs finishing.

Hugo

then please pull some coders from the goodie department into it, will you?


/me silently agrees to sacrifice a year's worth of new features in exchange for a working RDS

I mean, how often do I need new gimmicks? and how often do I need a working RDS?

bye,
[L]