DVB-t Users - Utility to check reception

[Chris.Day]

ScanChannelsBDA EZ166

Description:
- Derived from Nate's Australian ScanChannelsBDA utility
- Modified for UK users and simplified so it just creates a log file
- Will check base frequencies and 166kHz offset

Usage:
- Download and run
- Read ScanChannelsBDA.log file that is created

Note 1: Not all BDA drivers are equal. Some will give nonsense figures. Most are good enough though.
Note 2: This utility is no longer suitable for Australian users (although I do have a version which includes both UK and Aus support). Other countries sharing the same frequencies as the UK should also work (UHF C21-68, 8MHz bandwidth). If you want support for Australia, download the original ScanChannelsBDA utility.

[sub]

Sounds useful. Just for my future reference (since we have no DVB-T), can you show me what the output of a typicaly run would look like?

Next time I get a user with one of the oddball brands of device, not normally tested with GB-PVR, that fails to find any channels - I'll send them here as a first stop. I'll eventually integrate some 166kHz logic into the GB-PVR channel scan...

[bgowland]

ScanChannelsBDA UK EZ166

The link returns an 'HTTP 404 - File not found' error.

Cheers,
Brian

[daza67]

Chris, is this derived from Nate's digitalwatch bits and pieces?

Daza

[Chris.Day]

Sounds useful. Just for my future reference (since we have no DVB-T), can you show me what the output of a typicaly run would look like?

Next time I get a user with one of the oddball brands of device, not normally tested with GB-PVR, that fails to find any channels - I'll send them here as a first stop. I'll eventually integrate some 166kHz logic into the GB-PVR channel scan...

Yes, please see the attachment. In the zip there are two log files. ScanChannelsBDA.log is from this version (166kHz offset search) and shows the kind of thing you'll see under ideal conditions (100% Quality, and all channel names, and transmitter name listed). The other log file is from the version I created for Hauppauge cards (no need to search 166kHz) but was created yesterday when I was able to receive additional channels from a distant transmitter. This shows what you will see with a poor quality signal (some of the muxes from Waltham are pretty poor in this log file), with very low quality numbers, and those numbers vary from reading to reading.

The main things that you can get from the log are:
- Which frequencies contain a signal on them (most drivers should report strength/quality even if they're unable to lock)
- What channels are on those frequencies (pending >9% quality)
- The name of the transmitter (in this example, "Belmont")
- The exact frequency including offsets (in this example, 762000 is actually on 762166kHz)
- Whether there are any "alternative" frequencies. Some transmitters will give the frequency of their relay transmitters. Belmont doesn't but Waltham does, for 514000kHz (it tells you that there is an alternative, which is the Nottingham transmitter, on 730000kHz).
- BDA filter names, right at the start of the log file

The link returns an 'HTTP 404 - File not found' error.

Fixed link.

Chris, is this derived from Nate's digitalwatch bits and pieces?

Yes, I believe that the original version is from Digital Watch and also from other's contributions on the DVB Owners forum. Source code (for GPL compliance) is available through the Hauppauge Forum.


Some Notes

Strength/Quality readings are entirely dependent upon how good your TV card's drivers are.

For example, none of Hauppauge's 88x-based cards (Conexant) can report signal strength per-se. They report a figure based upon the AGC RF level of the tuner (in a range of -41000 to +3000 at intervals of 2000). I suspect other manufacturer's Conexant-based cards will report similar figures. Hauppauge have done some trickery with Strength with 88x/CX22702 cards though in that Strength is calculated on-the-fly based upon levels that have already been "seen" by the tuner. In other words, if you were to jump straight to 690MHz, you will see a different figure than if you have gone up progressively through all frequencies up to 690MHz.

DiBcom based devices will give what appears to be Signal-to-Noise Ratio for Strength (or something that is made to look like SNR) and will typically be in double figures (e.g. 25 probably relates to 25dB). eMPIA based devices appear to give some kind of strength reading for Strength, typically 5-figure numbers. All of the Hauppauge devices using these chipsets behave in this way and it seems to be consistent (muxes which I know are weaker give lower numbers).

Most drivers base the Quality figure directly upon BER (sometimes there may be a Quality reading accessible directly from the demod; other times it will be something like the inverse of the BER reading). There may be some differences between different devices here. Hauppauge, on the CX22702 based cards, chose to scale just the "meaningful" numbers (as values of 1-100 are valid for Quality). So, on a Hauppauge CX22702-based card, values over 50% are generally OK, but you will see the number increase even for small increases in "real" signal quality. On standard CX22702 drivers, you will probably see something like 90% (for what is 50% with Hauppauge), and probably very little value increase. (I hope that makes sense - on the standard driver you get maybe 10 discrete values for useable quality, compared to 50 values on the Hauppauge driver). Other things that may affect Quality are whether BER is taken pre-Viterbi or post-Viterbi. Pre-Viterbi figures will show a lower quality, because it is before the error correction has been performed (pre-Viterbi is actually much more useful).

In Summary - No two devices will give comparable numbers

[SWK]

Hi Chris

I ran ScanChannelsBDA_EZ166.exe on my AF9005 DVB-T tuner, which GB-PVR is unable to find any channels.

When it attempts to tune the frequency -166kHz, my PC 'Blue Screens'. This is the same behaviour experienced in GB-PVR when using the Crystal Palace transmitter configuration. Please see "AfaTech AF9005 BDA Device" for more info.

Is it possible to disable this feature ?

Sean

[Chris.Day]

The only way to "disable" it is to use this version:
http://www.dayc.vispa.com/files/ScanChannelsBDA_EZ.exe

But ideally the manufacturer shouldn't provide such a crap driver. There's no excuse for it blue screening on a 166kHz offset search - a lot of software will do this.

[SWK]

Hi Chris

Thanks for the quick response. That works now, but does not find any channels, but does on my other DVB-T cards.

I will have a word with the manufacturer about thier crappy drivers :->

BTW, didn't you used to run http://www.decforum.com ?

Sean