Stellar Labs ATSC HD Modulator - Page 2 - AVS Forum | Home Theater Discussions And Reviews
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post #31 of 195 Old 02-20-2017, 10:05 AM - Thread Starter
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Quote:
Originally Posted by Erik Garci View Post
To clarify, the cable was disconnected from the tuner's input but still connected to the modulator's output, so the cable itself was spilling signal into the air. However, when I disconnected the cable from the modulator's output as well, the tuner could not receive the signal via antenna.
Interesting. Lol I wonder if you put an actual antenna on the output how far across a room you could send the signal?
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post #32 of 195 Old 02-20-2017, 10:39 AM
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Erik Garci;
That's a completely different story. If that wasn't the case, that would of never passed FCC certification for RF emission testing. Anyway, I surely wouldn't feed that into a system before any DA's (distribution amps).

.
.
Recording free OTA TV for 'time shifting' has been here since 1975. Will there be DVR's to do the same when ATSC3 obsoletes existing DVR's??
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post #33 of 195 Old 02-20-2017, 06:58 PM
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Quote:
Originally Posted by Erik Garci View Post
To clarify, the cable was disconnected from the tuner's input but still connected to the modulator's output, so the cable itself was spilling signal into the air. However, when I disconnected the cable from the modulator's output as well, the tuner could not receive the signal via antenna.
Coax cable, to work properly, is designed to be terminated at each end, with a load equal to the rating of the cable (in this case 75 ohms). The cable will keep the signals it is carrying within the cable, and prevent outside signals from getting in.

However, if left unterminated at one end, the cable becomes a moderately effective antenna.
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post #34 of 195 Old 02-22-2017, 03:27 PM
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Quote:
Originally Posted by cpalmer2k View Post
Interesting. Lol I wonder if you put an actual antenna on the output how far across a room you could send the signal?
I ordered one of these (I have wanted to play with an ATSC modulator for a decade or more) and it arrived today.

Feeding a mag mount HAM 70cm antenna and tuned to channel 14 (free and clear in my area) in my basement, the signal was strong enough to be picked up on my roof mount TV antenna. This is interesting considering the mag mount is vertical polarization and the roof mount is horizontal. I checked SWR and it was decent about 1.7:1

Plugged in a chromecast since it was an easy source. One of my TVs receives the signal with no issues, video and audio is fine. However the other TV receives the signal with video mostly being okay but audio has chirps and glitches constantly. Also the on screen displays on the TV are very glitchy basically twitching across the screen. Interesting fact is, they're both Westinghouse TVs although different sizes and way different software.

Both TVs showed 3/4 signal strength which, like I said is impressive considering I am feeding a 1/4 wave ham mag mount in my basement mispolarized and traveling through 2 floors the roof and across the house.

PSIP clock is obviously not accurate with no way to set it.
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post #35 of 195 Old 02-22-2017, 03:54 PM
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Quote:
Originally Posted by sgarringer View Post
PSIP clock is obviously not accurate with no way to set it.
Does the modulator even send PSIP time? I basically expected it to send no PSIP at all, so your receiver would lock to another station's PSIP when tuned to that station and then either keep time itself or just freeze when tuned to the modulator's channel.
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post #36 of 195 Old 02-22-2017, 04:56 PM - Thread Starter
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I got mine today as well but won't have a chance to play with it in depth until the weekend. Do some of the menu options only become available when you've fed a source into it? I see others here referencing audio settings. The only menu option I can get by playing with the front panel buttons is the option to set the channel.
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post #37 of 195 Old 02-22-2017, 05:00 PM - Thread Starter
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Quote:
Originally Posted by sgarringer View Post
I ordered one of these (I have wanted to play with an ATSC modulator for a decade or more) and it arrived today.

Feeding a mag mount HAM 70cm antenna and tuned to channel 14 (free and clear in my area) in my basement, the signal was strong enough to be picked up on my roof mount TV antenna. This is interesting considering the mag mount is vertical polarization and the roof mount is horizontal. I checked SWR and it was decent about 1.7:1

Plugged in a chromecast since it was an easy source. One of my TVs receives the signal with no issues, video and audio is fine. However the other TV receives the signal with video mostly being okay but audio has chirps and glitches constantly. Also the on screen displays on the TV are very glitchy basically twitching across the screen. Interesting fact is, they're both Westinghouse TVs although different sizes and way different software.

Both TVs showed 3/4 signal strength which, like I said is impressive considering I am feeding a 1/4 wave ham mag mount in my basement mispolarized and traveling through 2 floors the roof and across the house.

PSIP clock is obviously not accurate with no way to set it.
So... what type of cheap antenna would everybody suggest for this thing? My plan was to cut my existing antenna cable in the attic and terminate everything in my bonus room where these and their source will be located, mix in the modulator feeds, and then send it back out from there. But considering the bonus room is about ~10 feet away from the antenna I could practically broadcast the signal from these to it directly with the right small antenna.
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post #38 of 195 Old 02-22-2017, 06:33 PM
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Quote:
Originally Posted by JHBrandt View Post
Does the modulator even send PSIP time? I basically expected it to send no PSIP at all, so your receiver would lock to another station's PSIP when tuned to that station and then either keep time itself or just freeze when tuned to the modulator's channel.
Believe it or not.. it does send most of the ATSC tables..including an STT (system time table)....seems to be set to:
1980/01/06 ..This is a bit impressive IMHO, having set up countless ATSC muxes myself.

I have not looked at this directly on an analyzer yet..this capture is from a friend, Thanks to Steve.
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post #39 of 195 Old 02-22-2017, 06:41 PM
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Quote:
Originally Posted by cpalmer2k View Post
So... what type of cheap antenna would everybody suggest for this thing? My plan was to cut my existing antenna cable in the attic and terminate everything in my bonus room where these and their source will be located, mix in the modulator feeds, and then send it back out from there. But considering the bonus room is about ~10 feet away from the antenna I could practically broadcast the signal from these to it directly with the right small antenna.
I'd strongly recommend keeping the output confined to coax (except maybe for a bit of experimenting, as above). I doubt the signal is "clean" enough to be used legally as a white-space device, so if you broadcast it, you're likely to cause interference.
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post #40 of 195 Old 02-22-2017, 07:04 PM
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Quote:
Originally Posted by cpalmer2k View Post
I got mine today as well but won't have a chance to play with it in depth until the weekend. Do some of the menu options only become available when you've fed a source into it? I see others here referencing audio settings. The only menu option I can get by playing with the front panel buttons is the option to set the channel.
I find no additional settings besides the menu option to set the channel. I will connect it to a device which will give me some flexibility to select audio output on the HDMI connector tomorrow/this weekend.

It shows the station name as Stellar and frustratingly since it sends time/date my TV clock changes when I change the channel to the device.

I will also hit it with a spectrum analyzer to see how clean the output is, although it would have to be fairly clean if it's expected to be mixed in with other signals on a wire and not interfere.
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post #41 of 195 Old 02-22-2017, 07:30 PM
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Quote:
Originally Posted by sgarringer View Post
It shows the station name as Stellar and frustratingly since it sends time/date my TV clock changes when I change the channel to the device.
Uh-oh; sounds like bad news for MStar tuners/DVRs (HomeWorX, iView, etc.). They may still work, but with the date/time thrown off, you won't be able to do timed recordings from this modulator.

They really need to put in a menu option to correctly set the date/time - or, if the thing doesn't have any way to keep time internally, just totally remove the STT from the signal. No date/time is better than consistently wrong date/time.
Quote:
Originally Posted by sgarringer View Post
I will also hit it with a spectrum analyzer to see how clean the output is, although it would have to be fairly clean if it's expected to be mixed in with other signals on a wire and not interfere.
We await your results. I did see in the very brief manual that they recommend you set the modulator at least 3-4 channels away from any in-use channels, which implies the output spreads quite a ways from the selected channel. (Consumer-grade analog NTSC modulators have the same problem, so it wouldn't be surprising.)

Last edited by JHBrandt; 02-26-2017 at 03:49 PM.
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post #42 of 195 Old 02-23-2017, 03:15 AM
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Quote:
Originally Posted by JHBrandt View Post
I doubt the signal is "clean" enough to be used legally as a white-space device
If it doesn't talk to a white space device database, then it can't be used legally as a white space device at all.

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post #43 of 195 Old 02-23-2017, 04:25 PM
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Quote:
Originally Posted by bdfox18doe View Post
Believe it or not.. it does send most of the ATSC tables..including an STT (system time table)....seems to be set to:
1980/01/06 ..This is a bit impressive IMHO, having set up countless ATSC muxes myself.

I have not looked at this directly on an analyzer yet..this capture is from a friend, Thanks to Steve.
Is it really 720p30 (aka 720p at 30fps)?
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post #44 of 195 Old 02-24-2017, 09:18 AM
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I'll check on the frame rate, it wouldn't surprise me if it is 30 fps. The audio issues may be related to the mpeg audio being utilized instead of AC-3. I am planning on using these multiplexed onto a house system RF feed. It ain't a cable quality modulator, but for the price it ain't bad. I have three set up on adjacent channels, and the receivers seem to lock with no problems.
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post #45 of 195 Old 02-24-2017, 03:40 PM
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Originally Posted by Mizzou! View Post
I have three set up on adjacent channels, and the receivers seem to lock with no problems.
That's good news; it means they don't interfere with each other, at least as long as they're all roughly equally strong.

So if the top station in your area is RF 51, you'd need to skip up to RF 55 or so for the lowest one, but then you could use 56, 57, etc. all the way up to 69 without skipping any more channels.

Of course that would be super expensive, but at least you don't have to skip 3-4 channels for each additional modulator, so you don't end up with a fairly low limit of 4 to 6 channels above RF 51. (Of course there will be more free space after repacking.)

That may not apply if you mix modulators of different models though. It'll be interesting to see if the Stellar and PVI modulators can be used on adjacent channels.
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post #46 of 195 Old 02-25-2017, 09:27 AM
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Has anyone had any luck getting a firmware update that might fix the audio glitches? Tried to use it last night to watch a movie and the gltiches made it unwatchable. I've only tried one source so far, is the problem with the source or the device or do we know yet?
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post #47 of 195 Old 02-25-2017, 02:27 PM
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The glitches do seem to come from the modulator. But oddly, not every receiver experiences them. So far we know the Channel Master DVR+ does experience audio glitches but some TVs don't. What receiver are you getting them with? Probably need to let MCM Electronics know, so if it can be fixed they can get Stellar Labs working on it.

No firmware update yet. Right now the MCM Electronics page only has a .pdf of the manual available for download.
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post #48 of 195 Old 02-25-2017, 03:48 PM
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Got mine last night and just now got a chance to hook it up and try it out. I'm using a DVR+ as input to the modulator for testing. Seems to work fine, even on "Channel Master TV" Internet channels.

Good news: no audio glitches on an old iView, although as previously noted, the time is stuck at midnight (precluding timed recordings on said iView). However, the HDMI source does need to be set to PCM; otherwise there's no audio at all. Apparently the modulator isn't smart enough to pass through Dolby Digital. Too bad - that would've been an easy workaround for the audio glitches.

Edit: I don't know if this is common or just an iView oddity (there are a lot of those), but my iView shows it as channel 16-4, not 16-1. I haven't been able to get Windows Media Center to recognize the signal on either 16-1 or 16-4 though, even though my PC's tuners see a strong signal on RF 16. As CPalmer2K suggests in the next post, there may be something funky about its channel map. I've had similar WMC problems with broadcast stations that don't have their channel map configured correctly.

I made a test recording of a minute or so of RT on the iView. It is indeed 720p30. According to MediaInfo it's true 30 f/s, not 29.97. Audio is MPEG version 1 layer 2, not Dolby Digital. Those oddities may explain why some receivers experience audio glitches.

More good news: When tuned to RF 16, I can receive KERA on RF 14 and KTVT on RF 19 just fine, so the signal doesn't seem to spread too far from the selected channel. Its high signal level does seem to overload the iView's tuner enough to interfere with most LPTVs in my area, even ones far from RF 16, so it looks like I'll need to attenuate its output.

HDMI pass-through seems to work fine. The only wrinkle is, when the HDMI input is turned off, a floating "no signal" banner is sent not only to the RF output, but also to the HDMI output! Not a big deal but something to be aware of.

That's all for now - more to come though.

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post #49 of 195 Old 02-25-2017, 04:57 PM - Thread Starter
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It looks like this is going to be a return for me too. I've tried it with several sources, and get the same audio glitches others have described. Even more troubling to me is the fact that the audio/video seems WAY out of sync. Not to mention that the quality is much worse than the PVI mod I had used previously.

For testing purposes I've fed it several ways

First I tried feeding 1080i video thinking that because it is already 30fps it might eliminate some of the glitches. No dice using either "Dolby Digital" or "PCM". I did however get audio with Dolby Digital.

Next I tried feeding 720p with Dolby Digital and PCM. It actually seemed to function better in this mode, but it still has the awful audio glitches.

I think they need more of a *DELAY* on the input/output. I've seen some of the same issues on the older PVI modulator I had when I set the delay factor too low. I'd rather have the feed be delayed and be right than it be closer to real time with horrible sound.

Also the two TVs I have tried don't recognize the channel correctly. They see it is as 0-0

Last edited by cpalmer2k; 02-25-2017 at 05:02 PM.
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post #50 of 195 Old 02-25-2017, 05:59 PM
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Quote:
Originally Posted by cpalmer2k View Post
It looks like this is going to be a return for me too. I've tried it with several sources, and get the same audio glitches others have described. Even more troubling to me is the fact that the audio/video seems WAY out of sync.... I did however get audio with Dolby Digital.

...

Also the two TVs I have tried don't recognize the channel correctly.
So, glitchy audio with two different TVs ... What TVs were they? (If other readers have the same TVs they'll obviously need to avoid this modulator.)

Eric had better luck with his LG and Sony TVs. Hopefully it works with most/all of them. Edit: It does work with my LG TV, a model 32LK330-U8. I reset the modulator to RF 69; it came up as 69-4 on the LG. Here's a summary of what's been reported/found so far:

  • LG TVs: Works on some models (confirmed to work on model 55EC9300 and 32LK330-U8), not all
  • Panasonic TV: Works
  • Samsung TV: Works
  • Sony TV: Works (confirmed on model KDL-22BX300)
  • Visio TV: Works on some models, not all
  • Westinghouse TVs: Works on some models, not all
  • Dish DTVPal/Channel Master CM-7000Pal DVRs: Works, including recording*
  • Dish VIP722 (w/ ATSC tuner): Doesn't work
  • Channel Master DVR+: Doesn't work
  • MStar-based DVRs (iView, HomeWorX, etc.): Mostly works: tunes/plays channel OK; recordings are bad with some (older?) models but work with others
  • Philco CECB (probably Magnavox too): Works
  • RCA DTA800 CECB: Doesn't work
  • Windows Media Center: Doesn't work

*Found as channel 0-0, so the Pal assigns a channel number of 7n-0 (on mine it came up as 71-0)

Interesting you got audio (albeit glitchy) with DD pass-through while all I got was silence. Once I switched it to PCM, audio (on working devices listed above) was perfect: no glitches or sync issues.

At this point it looks like this modulator may work fine, or be totally unusable, depending on which receiver(s) you hook it to.

Edit: Sources I tried were a DVR+ and a Toshiba DVD recorder. Obviously quality on the Toshiba is limited to SD. The DVR+ was set to output 720p.

Last edited by JHBrandt; 03-14-2017 at 02:23 PM. Reason: Update list of working/non-working receivers
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post #51 of 195 Old 02-25-2017, 06:52 PM - Thread Starter
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Quote:
Originally Posted by JHBrandt View Post
So, glitchy audio with two different TVs ... What TVs were they? (If other readers have the same TVs they'll obviously need to avoid this modulator.)



Eric had better luck with his LG and Sony TVs, although he didn't mention the model numbers. I'm going to try it on my own LG TV in a few. Hopefully it works with most/all of them.



Interesting you got audio (albeit glitchy) with DD pass-through while all I got was silence. Once I switched it to PCM, audio on the iView was perfect: no glitches or sync issues.


I've tried a Vizio and an LG. My two sources so far were a Roku and a TiVo
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post #52 of 195 Old 02-25-2017, 06:57 PM
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Quote:
Originally Posted by JHBrandt View Post
The glitches do seem to come from the modulator. But oddly, not every receiver experiences them. So far we know the Channel Master DVR+ does experience audio glitches but some TVs don't. What receiver are you getting them with? Probably need to let MCM Electronics know, so if it can be fixed they can get Stellar Labs working on it.

No firmware update yet. Right now the MCM Electronics page only has a .pdf of the manual available for download.
I have three TVs, a westinghouse 32" circa 2008. This firmware was updated around 2010. This has no glitches.

A westinghouse 42" circa 2008 with factory original firmware (none available). This has audio glitches.

I also have one of the RCA DTV tuners from the original digital transition and haven't been able to get it to find the signal yet...

1/3 works

Really bummed. Had yuge hopes for this device.

Sources tried: Chromecast, Roku, and Popcorn Hour A100
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post #53 of 195 Old 02-25-2017, 07:03 PM
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I'm guessing that's an RCA DTA800 CECB that it doesn't work with?

I haven't tried any CECBs yet. I'll give it a shot with a couple I have and add them to the list above.
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post #54 of 195 Old 02-25-2017, 07:05 PM - Thread Starter
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Just as an experiment I did reduce the signal heavily, wondering if overload might be causing some of the issues. I had a small bag of 12db attenuators I got several years ago to help bring my cable modem into spec (our neighborhood's signal is VERY high). I tried running the output into the TV first with one of those and then two of those, and finally three of them. I still had good signal at that point but the glitches were consistently the same.
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post #55 of 195 Old 02-25-2017, 07:39 PM
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I didn't think attenuators would help with the audio glitches, but it was worth a try. Attenuating the signal did improve reception of my LPTV stations though.
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post #56 of 195 Old 02-25-2017, 08:23 PM - Thread Starter
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Quote:
Originally Posted by JHBrandt View Post
I didn't think attenuators would help with the audio glitches, but it was worth a try. Attenuating the signal did improve reception of my LPTV stations though.
Another trend I have noticed... the more motion, louder the volume, etc the worse the glitches. That's another reason I believe it has something to do with the delay factor the encoder uses. It just can't keep up (perhaps partially due to it having to cut down on the number of frames). I really would be curious to see how the PVI MiniMod measures up since it is full resolution.

I'm going to hook this up to my VHS/DVD Recorder tomorrow and see how it works with the lower resolution 480i signal coming in off the HDMI port on it. That might partially confirm/disprove my theory.
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post #57 of 195 Old 02-25-2017, 08:43 PM
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I just discovered something odd myself. If I watch the modulator's channel on my iView, it plays fine. But if I record the channel, the file plays back with some audio drop-outs, video freezes, and sync issues. I tried playing the recordings on both my iView and a PC, and had issues with both, so the problem is in the recording file itself. I also tried two different recording media: a spinning-platter HDD and a micro SD card, both of which can record the local Fox station without issue, so I know it isn't a problem with the media.

I wonder if the bit rate occasionally gets too high for the iView to handle when there's a lot of motion, causing some frames to get dropped from the recording?

Update: Tried again with a very similar HomeWorX HW-150. This one recorded the modulator just fine!

There are several minor differences between the two; what most likely made the difference, I think, is that the older iView has a 7816 SoC while the newer HomeWorX has a 7802. (Newer iViews also use a 7802 chip, so they may record OK as well.) The two chips and their firmware make recordings in slightly different, incompatible formats.

BTW, a DTVPal also records this modulator's output just fine - and unlike the iView and HomeWorX, the Pal's clock isn't thrown off by the modulator's bogus STT. (It discards outliers when it scans channels to calculate time.) So if you want to record from this thing, a good ol' DTVPal is worth considering.

Last edited by JHBrandt; 02-26-2017 at 05:06 PM.
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post #58 of 195 Old 02-26-2017, 01:22 PM
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Originally Posted by videobruce View Post
I never noticed the 720p is only 30fps. They really pinched pennies there all the way around.
I suspect its video compression isn't very efficient, so they had to go all the way down to 720p30 to make sure they could fit everything into 19Mb/s even when there's rapid motion. That may also explain why the iView couldn't record the modulator reliably, as well as why the audio glitches cpalmer2k is getting seem to depend on the amount of motion in the video; I suspect spikes in the video bit rate may be at play.
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Another trend I have noticed... the more motion, louder the volume, etc the worse the glitches.
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post #59 of 195 Old 02-27-2017, 08:37 AM - Thread Starter
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I played with it some more yesterday and can't find any combination that eliminates these issues we've all discussed. I got my RMA# and return label this morning. I'm just going to return mine. I might try the PVI model when it becomes available, but based on appearances I'm betting it is based on the same technology. Though the PVI is listed as full 1080p, so possibly it has a better encoder.
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post #60 of 195 Old 02-27-2017, 07:03 PM
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Sounds to me like too many folks are having too many problems with too many different receivers. I don't think the Stellar mod went through enough testing before they started selling it. I got lucky with mine, which works OK with most of my receivers (certainly well enough given the price), but a lot of folks like you will have to send theirs back due to incompatibilities.

I'm now starting to see the need for a more robust menu that can do more than just set the channel. It'd be nice to tell it how to upconvert a 4:3 480p signal, for instance (as it is, it just stretches the picture; an option to pillar-box or zoom instead would be nice; an option to partially zoom, a la the old CM-7000 converter boxes, would be really nice).

I'm sure some of the problems could be fixed in the firmware, but I don't even know if Stellar provided a way to update it! They do have a USB port intended for video to play; maybe there's a special combination of buttons that will load updated firmware from a USB stick.

Hopefully you'll have better luck with the PVI. I bet that one's not on the market yet because they're still testing and working out issues.
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