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TVGOS conversion tests for DS 9950 and other cecbs

post #1 of 9
Thread Starter 
Hi - on one of the DTVPal threads, I was commenting on how TVGOS worked, and someone else cited a quotation from January that I had seen before, from a Gemstar guy who said that the RCA cecb passed the TVGOS data from a digital station to its converted output, and that most other cecbs would probably do so, too

I commented that I should try the DS9950 that my housemate just got.

Well, over the last three days, I hooked up my housemate's 9950 next to my high-def setup, which includes an LG3410a digital receiver/high-def recorder that gets its TVGOS data from analog PBS locally. I set the 9950 to channel 5-1, the local CBS station, which has been reported to be carrying the TVGOS data currently (cf. the Sony 250/500 thread, and the associated operational manual from spiffy http://www.spiffspace.com/sonydvr.html#Section2.

1 - For the first night, I joined the 9950's output with (another branch of) the signal from the antenna, and I turned off ALL the analog channels in the 3410a's setup AND in its TV Guide screen, but TURNED on channel 3 in both. In real life, channel 3 is the analog NBC station from Sacramento that isn't received at all in Berkeley (100 miles away and through hills...).

When I looked to see what I was receiving with this setup, on channel 3 I was getting a pretty clear analog version of CBS 5.1...it seemed slightly snowy, but I checked that cc (closed captioning) worked, which confirmed that the vbi data was coming through from the DS9950's conversion. I could, of course, also get all the local digital channels, and hmm...I am puzzled over what I checked about the normal analog channels at that time...

I left the 3410a on channel 3, turned it off, and checked the next AM to see what had happened. I found it had gotten TVGOS data, but when I checked the service screen that identifies the host channel for TVGOS, it still said it was channel 9, the local PBS station...

2 - for the second night, I removed the branch from the antenna from the 3410a's input, leaving only the rf from the 9950. This time, I checked what I could see via the 3410a more carefully, finding that I could still see very poor signal from the lower analog channels, except for channel 3 (the converted channel), which came in with a very nice picture, but for channel 9 (PBS) I was getting a snowy picture but good sound, and - as I went to the UHF channels - the picture got quite good. I also found I was still getting all the digital channels perfectly...I didn't try to figure out why this was. I did check the relatively poor channel 9 reception to see if cc was coming across, and it wasn't, indicating that vbi wasn't being received (or at least not well). I set the 3410a on channel 3 and left it on overnight again.

When I checked the next day, the 3410a had NOT received TVGOS listings overnight. I checked the service menu for the host channel, and is reported "0", which I take to mean it didn't find a TVGOS host overnight.

3 - I removed the antenna branch cable that HAD been joined into the 3410a for the first night's test, but that I had left lying behind the 3410a...I was worried the unit might be picking something up from it. I ran night 3 in the same configuration as 2, i.e., with input only from the 9950 and with the 3410a tuned to channel 3 before turning it off. This time I got PARTIAL listings, and the service menu now identified channel 9 (the PBS station) as the host channel.

Because I was still puzzled over the low quality reception of the analog channels, I did the test I should have done during the previous day: I removed the cable from the 9950 to the 3410a, and ALL reception disappeared, indicating that the low-quality analog and good digital was coming via this cable. With the cable connected, I then hit the analog pass-through button on the 9950's remote back and forth and found that I always received digital, but with pass-through off I received channel 3 (the conversion from 5.1) clearly, and the real analog channels poorly. With pass-through on, I did not receive channel 3, but received everything else well.

I concluded at first that this means that in the 9950's digital conversion mode, there is just a filter against the UHF channels, which is removed in pass-through mode.

But I just realized that another alternative is that it is the CABLE connecting the 9950 and the 3410a that is providing these puzzling signals. So I just tried the 3410a with just that piece of cable as the antenna, and found that I did receive some signal, but it was generally POORER for analog than I was receiving from the 9950 with pass-through OFF, and I was only receiving THREE digital channels with just the cable, rather than all of them. So the 9950 seems to be passing higher frequencies reasonably well even if pass-through is off. Of course, the fact that the cable has a device hanging on the other end of it may make it a better antenna....I don't know about that.

And I have to conclude that my test of TVGOS reception is inconclusive because the data from PBS analog was still available. UGH all around...I'll have to wait for my DTVPal; but even then, the availability of the PBS data may make any current test fruitless...hmm...seems like I need a sharp high-pass filter for the antenna signal going INTO the cecb...
post #2 of 9
Thread Starter 
Well, looks like frank70 has used a Sony digital receiver/high-def recorder to test whether a Tivax STB-T9 converts TVGOS data carried by a digital CBS station, and the answer is no - cf http://www.avsforum.com/avs-vb/showt...1#post14247641

This not really a big surprise, but takes a little air out of the inference from something someone from Gemstar said in January that most boxes would probably pass TVGOS data (along with the cc data).

The Gemstar person also said they has specifically TESTED the RCA cecb and it DID convert TVGOS.

...anybody tried that?
post #3 of 9
Has anyone been able to get the DTVPAL box to output TVG data on ANY LINES? First active line I see is 20, and that is just 'setup'. Data on line 21 is Closed Captioning.

Thanks Jan
post #4 of 9
Quote:
Originally Posted by avnstf View Post

Well, looks like frank70 has used a Sony digital receiver/high-def recorder to test whether a Tivax STB-T9 converts TVGOS data carried by a digital CBS station, and the answer is no - cf http://www.avsforum.com/avs-vb/showt...1#post14247641

This not really a big surprise, but takes a little air out of the inference from something someone from Gemstar said in January that most boxes would probably pass TVGOS data (along with the cc data).

He also said they has specifically TESTED the RCA cecb and it DID convert TVGOS.

...anybody tried that?

Woops, I just realized by "he" you meant the Gemstar tech rather than Frank70. I got confused by the "has" vs "had". I kept looking in Frank70's post but never saw any reference to RCA

You should start a thread that tests just TVGOS reinsertion for various units.

Do you have the link that mentions the RCA test? If the RCA does reinsert and the Tivax doesn't for the same channel at the same time then that is good evidence that Tivax doesn't reinsert TVGOS. However it doesn't tell you who or how many do or don't.

If the RCA did reinsert, then it is also clear that some units do reinsert even though they don't advertise it. It would confirm the claim that Gemstar tested the RCA unit and found it to reinsert so part of that statement would be true. The question then is the rest of the statement a subtle attempt to mislead or are they really expecting other CECBs to do resinsertion and have some basis for that belief.

To be absolutely sure what is going on it would be nice to know the actual mechanism of TVGOS VBI reinsertion. I've been trying to look for the specs for DVS706 but have been unsuccessful. I wanted to look at the data format to see if there is a flag in the DVS706 data that controls whether a particular line should be reinserted or not. For example (and I'm just posing a hypothetical here) if the DVS706 in the tested transmission had a flag that disabled reinsertion, then we wouldn't know whether a unit did the reinsertion or not, unless the unit ignored the flag.

In your research have you found any information or specs on DVS706?
post #5 of 9
Thread Starter 
Quote:
Originally Posted by sfhub View Post

Woops, I just realized by "he" you meant the Gemstar tech rather than Frank70. I got confused by the "has" vs "had". I kept looking in Frank70's post but never saw any reference to RCA

thanks - I edited that for clarity

Quote:
You should start a thread that tests just TVGOS reinsertion for various units.

actually, I already edited the name of this one to include other units, but I didn't go further than I did to avoid conflicting with the DTVPal and TVGOS thread - do you think I should just remove the reference in the thread title to DS9950?

Quote:
Do you have the link that mentions the RCA test? If the RCA does reinsert and the Tivax doesn't for the same channel at the same time then that is good evidence that Tivax doesn't reinsert TVGOS. However it doesn't tell you who or how many do or don't.

If the RCA did reinsert, then it is also clear that some units do reinsert even though they don't advertise it. It would confirm the claim that Gemstar tested the RCA unit and found it to reinsert so part of that statement would be true. The question then is the rest of the statement a subtle attempt to mislead or are they really expecting other CECBs to do resinsertion and have some basis for that belief.

Here's the original quotation from the Gemstar guy that appeared in the Sony 250 thread:
"Hello Michael - In reference to your inquiry, your customers utilizing both OTA and CATV will have no problems with FCC 03-273. As you are aware, the VBI signal carried by your station will cease and be picked up by your local CBS affiliate. VBI in its original form will no longer "natively" exist and all new EPG's and VBI 21's will be able to decode the digital format. As for legacy equipment, CATV operators will still transmit the VBI with their analog signal, mainly due to regulations regarding VBI 21. Additionally, NTIA requires all CECB's to decode legacy VBI", again, mainly due to VBI 21 (see fcc. gov/cgb/consumerfacts/CC_converters .html for more information.) We have tested extensively with the RCA DTA800B and found it to pass VBI 10-21 encoding perfectly.
Other units complying with NTIA should produce similar results. Please let me know if you need any further information." (http://www.avsforum.com/avs-vb/showt...9#post13064099)

There has been discussion of this in the LG3410a thread, e.g., http://www.avsforum.com/avs-vb/showt...2#post13067782

Quote:
To be absolutely sure what is going on it would be nice to know the actual mechanism of TVGOS VBI reinsertion. I've been trying to look for the specs for DVS706 but have been unsuccessful. I wanted to look at the data format to see if there is a flag in the DVS706 data that controls whether a particular line should be reinserted or not. For example (and I'm just posing a hypothetical here) if the DVS706 in the tested transmission had a flag that disabled reinsertion, then we wouldn't know whether a unit did the reinsertion or not, unless the unit ignored the flag.

In your research have you found any information or specs on DVS706?

I confess, I don't know what that is...
post #6 of 9
DVS706 is the standard to transmit VBI in MPG.

Gemstar referred to it as a way they were planning on delivering TVGOS that could be reinserted into the CECB output.

First question I had was whether the DVS706 standard is indeed what they ended up going with to deliver legacy VBI to be reinserted into analog output of boxes.

Another question I had was whether DVS706 was the single mechanism being used going forward to deliver TVGOS on digital transmissions. By "single" mechanism, I mean the same data would be used both by digital capable TVGOS receivers and also for converter boxes that need to reinsert TVGOS VBI into their analog output. One hypothetical possibility is they chose to split the true digital TVGOS and the legacy VBI TVGOS delivery into 2 separate mechanisms so digital TVGOS could evolve on its own. Another possbility is they use DVS706 for everything to keep everything simple and minimize any new development.

Personally I always like to understand the flow chart of how something is supposed to work before guessing as to why something isn't happening so that's why I wanted to read up on DVS706.
post #7 of 9
Thread Starter 
Quote:
Originally Posted by sfhub View Post

DVS706 is the standard to transmit VBI in MPG.

Gemstar referred to it as a way they were planning on delivering TVGOS that could be reinserted into the CECB output.

First question I had was whether the DVS706 standard is indeed what they ended up going with to deliver legacy VBI to be reinserted into analog output of boxes.

Another question I had was whether DVS706 was the single mechanism being used going forward to deliver TVGOS on digital transmissions. By "single" mechanism, I mean the same data would be used both by digital capable TVGOS receivers and also for converter boxes that need to reinsert TVGOS VBI into their analog output. One hypothetical possibility is they chose to split the true digital TVGOS and the legacy VBI TVGOS delivery into 2 separate mechanisms so digital TVGOS could evolve on its own. Another possbility is they use DVS706 for everything to keep everything simple and minimize any new development.

Personally I always like to understand the flow chart of how something is supposed to work before guessing as to why something isn't happening so that's why I wanted to read up on DVS706.

yes, I understand...actually Jan J in the thread on the LG 3410a seems to know more about this than anyone else I know, and he and Rammitinski have made unsuccessful first attempts to try the DTVPal conversion, and there's some additional commentary about that here: http://www.avsforum.com/avs-vb/showt...2#post14247252
post #8 of 9
I've been detailing my testing using the DTVPal with HDD/DVD recorders over in this thread mainly, if anybody wants to read and follow it:

http://www.avsforum.com/avs-vb/showthread.php?t=1044665

I won't get around to trying the Pal with the Sony DVR until after I'm done with those recorders.
post #9 of 9
Thread Starter 
I decided I would test the RCA cecb to see whether it converted TVGOS as was claimed months ago by someone from Gemstar, BUT - like others - I was not able to get one at Walmart...they come in in the AM and are no longer there when most people appear...and it doesn't look like it can be had from an online dealer...
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