Vision Plus Vs Technotrend, an interesting little comparison Options

[DrP]

Firstly, this has hardly been a scientific test, but the results are still interesting enough. I've had the opportunity today to play with a technotrend based card again and as a last bit of interest, decided to see how the cards handle impulse noise.

For testing, each card was put into an identical PC (same motherboard, same hard disks, same etc etc). The cards were then fed from the same antenna via a simple splitter. Two leads were made up from the same batch of coax so false results from crappy vcr-type fly leads could be eliminated.

Both cards were tuned to the ABC (centre 212.5MHz) using the free version of tsreader (both showed 100% quality and > 80% signal strength in their native apps). Simple impulse noise was generated by turning a desk fan on and off randomly and the number of continuity errors logged by tsreader noted.

The VP generated over twice the number of continuity errors that the TT did. At times the TT generated no errors while the VP scored over 15. To see if the TT was really doing an apparently better job, the video was extracted from captures from both cards (short capture, the free tsreader is time limited). Considerably more corruption was noticed on the video from the VP.

Now this might be due to the way that tsreader runs each card, or it might be due to the rather unspectacular VP drivers themselves or it may be that the tuner module on the TT is more tollerant, but from the above it seems that if you have marginal reception, perhaps a VP isn't for you.

[ocujos]

DrP,

Do you know if tsreader works with Nebula cards?
I suspect that Nebula card would perform about the same as VP, very poor.
I remember when I had a Teac STB plugged in my antenna socket it could receive ch 10 whilst Nebula couldn't.
It appears that even cheap STB's like Teac have a far superior tuner then any DVB-T card.
We'll have to wait and see how DVICO performs. According to Renura, DVICO cards use the same tuner as found in many STB's, so in theory this should give DVICO cards the same reception quality.

[murrayt]

Ocujos

I am not sure that Renura said that at all.

Yes the post indicated that it is the same tuner as used in some STB's not necessarily many. But the analog tuner is just one part of the reception chain. Other components inc software are just as important. Remember the tuner modules are analog not 'digital'. The digital bit comes after the tuner mostly

I would like to see a test comparing a number of cards in the same way.
My Nebula generates 100% perfect recordings each day of the week, and if I use <CRTL I> to view the frame error/frame dropped stats it is usually one or two not many. I live in a Sydney location that is considered marginal to poor for reception. So I wonder about what factors contribut to good vs poor reception for others.

Are there some well heeled testers out there that have each of the cards that can be compared in these circumstances ?

I only have one (as above) and don't see the point in buying more at this time until the STB/Media player market starts to hum and we see what is on offer

PCI/USB cards will be in demand for enthusiasts like us, but the real money is in network players that are just around the corner

[DrP]

tsreader doesn't support the nebula card. I think I've seen it mentioned that the nebula uses the same tuner as the VP, if its a tuner issue, the nebula probably performs roughly the same.

[bpanther]

DrP,
Thanks for the interesting comparison.

I tried both the VisionPlus and the Avermedia cards using the same antenna. The VisionPlus appears to be more immune to noise and level issues than the Avermedia.
I'll try to do a better comparison (same recording on both) later.
In the case of the Avermedia it is probably not just the tuner, but also the software (people using Linux reported good results, different software revs from Avermedia performed differently).
I wish somebody had access to a fully equipped lab, which could simulate DVB-T under controlled conditions with various signal corruption mechanisms and produce an unbiased professional comparison between various cards.
Had a similar experience here with a stand-alone set-top-Box (the old SD Thomson unit), which performed better with an indoor dipole than the PC based DVB-T cards with an external Yagi...

Cheers,
Bpanther

[rumpole]

I've always used a TechnoTrend card and have been very happy with it.

It was rock solid in Linux with a hardware mpeg2 decoder which makes me think this is also one of the advantages an STB has - they all have dedicated hardware mpeg2 decoders.

I now run the Technotrend in windows with showshifter for the good HTPC interface and, now, dynamic ratio management and HD which I didn't have under Linux.

[renura]

tsreader doesn't support the nebula card. I think I've seen it mentioned that the nebula uses the same tuner as the VP, if its a tuner issue, the nebula probably performs roughly the same.

DrP,

The Nebula does not use the same tuner as the VP, I am not sure where this came from?

VP uses a Comtech, Nebula use Alps.


I have tested the VP (with three different tuners), the Nebula, the Technotrend (Nova-T), the DVICO and others. Including Comtech, LG, Thompson, Alps, Philips, etc tuners.

While again, there was no scientific proper process followed my general findings were as follows:

Using exactly the same environment, same antenna, aerial, PC hardware, cables, etc - Tuner A would behave better than tuner B, tuning in all channels, etc.

Change the aerial, while everythig else remain the same and now tuner B behaves better than tuner A, and so on.

We have tried this with numerous aerial/antennas and various locations with similar results.

The above related to both the ability to tune in weak signals as well as interference from other devices, such as fans nearby. I have not tested the recordings for errors as such, in any case there are many more "parties" in the delivery of that particular output than just a tuner.

You can draw your own conclusion from this. Our current thinking is that when we are pretty sure about this, we may very well recommend particular aerials with each card or even better, may be provide an aerial in the package.

It would be good to hear from other people who have more than one DVB-t card, as to their experiences.

Cheers


Renura

[DrP]

The latest build of tsreader supports the nebula.

I'd like to see some more posts from people who can more or less do what I did, if for nothing more than curiosity. That is, cards in identical hardware (at a pinch, in the same PC simultaenously) being fed from the same antenna via a splitter, essentially making everything as equal as possible and then generating some form of noise and watching what TSRreader says about continuity errors (there is a 4 bit counter field on each TS packet, continuity just means that the number wasnt received sequentially, who knows how many packets were actually dropped). Then do a capture using the program's native apps of the same PIDs and generate the noise and observe the video from the capture file directly using virtualdubmod.

I plan to redo my tests when all the broadcasts here (Mackay QLD) are available in digital as I will relocate my antenna for best digital reception.

[renura]

I plan to redo my tests when all the broadcasts here (Mackay QLD) are available in digital as I will relocate my antenna for best digital reception.

DrP,

Try and use different aerials/antennas, under the same circumstances, see if your results vary. Also test the tuners for scanning ability.

Also, I suggest use two exact set ups if you can, else use one card a time in the same set up and test them on the same channels within minutes from each other.

Cheers

Renura

[DrP]

With what I'm testing for, both cards would have to be active at the same time, otherwise its not really all that fair a test since I can't reproduce the exact same noise each time I press the buttons on the fan.

From a tuning POV, I've only used the complete scan on any DVB-t card once (the TT when it was new before it left my hands). From then on in, I've keyed the RF channel directly since I know what they are in advance.

[14all]

With what I'm testing for, both cards would have to be active at the same time, otherwise its not really all that fair a test since I can't reproduce the exact same noise each time I press the buttons on the fan.

What if one card is interfering on the other?

[DrP]

Thats a possibility, which is why I said do it at a pinch. If you check my original post, you'll see that I had two identical PCs to test with, so one card in each machine.

[renura]

What if one card is interfering on the other?

I have had the Nova-t and the VisionPlus in the same PC, working at the same time, without any detectable interference.

Cheers

Renura

[rumpole]

Renura, which program supports running the Nova-T and VisionPlus at the same time ?

[renura]

Renura, which program supports running the Nova-T and VisionPlus at the same time ?

Hi rumpole,

I was using two different applications, not the same program for both, although it may very well be possible to do that.

Cheers

Renura