Cable box questions

[jackwanders]

I have Comcast's "Expanded Basic" cable, along with their standard cable box for OnDemand and the on-screen guide. I run the composite video to my TV and the analog audio to my AV receiver.

Lately some of my channels have been coming in a bit crappy. The video gets blocky and the audio cuts in and out. Sometimes i'll lose the video completely. I was just wondering if there was any way to help alleviate this through the cable box, or whether Comcast is just f'ing things up on their end.

Also, in the 'audio setup' screen, there are three output options under 'advanced'. Mono, Stereo, and Matrix. What exactly does Matrix mean? I have a feeling it has something to do with faking multi-channel audio, but I'm not sure.

[bangbang023 Veteran]

The connectivity problems are most likely stemming from Comcast's end of things ,though you may want to call them and ask.

As for Matrix sound, it is emulated surround sound.

[jackwanders]

Another audio question. There's an option for audio compression, with three options: None, Light and Heavy.

I'm having a tough time figuring any difference between the three, other than that 'Heavy' is a good bit louder than the other options at any given volume.

Is there any benefit to compressing the audio for my situation (audio straight from cable box to receiver)? Is there a situation where it would be beneficial? How and why is the audio being compressed?

[bangbang023 Veteran]

The "compression" may refer to the "width" of the audio, similar to what SA boxes offer. Narrow, which would equal high compression on your box, is louder too as it basically keeps both stereo signals sounding closer together.

(This is what I believe. I just woke up and can't think any more in depth)

[jackwanders]

yeah. i wasn't able to find anything out conclusively, but a handful of google searches make me think it has to do with the dynamic range of the audio. the heavier the compression, the narrower the range.

this pretty much jives with what you just said, so I'm gonna go w/ it. all i know is that when i dropped the coaxial cable from the box to the TV in favor of the composite video to the tv and rca audio straight to the receiver, the audio got much richer and the receiver's pro logic II really went to work.

Edited April 21, 2006 by Jack31081

[bangbang023 Veteran]

Of course the audio got better lol. There's much more breathing room for it now when each channel has it's own signal and cable.

[jackwanders]

but the signal's coming from the street through coax...

just because the road went from one lane to two doesn't mean the pinto turns into a hummer...

[bangbang023 Veteran]

but the signal's coming from the street through coax...

just because the road went from one lane to two doesn't mean the pinto turns into a hummer...

It's the output you are supposed to be looking at, not the input. The information coming in is VERY different than the information going out.

[SeaClearly]

Your video breakups could also be caused by some line issues if your area has started to offer advanced digital simulcasting. This means that with a digital box your analog channels (channels below 100) will be digital instead of analog. Sometimes a splitter or a bad cable could cause this once they make the switch as the digital feed in most cases is stored at a higher frequency. My Comcast area has our digital channel feeds for our analog channels between 700-750Mhz and my splitter just didn't like these channels being in this frequency even though it supported it. So a Comcast tech came out and installed a new splitter and also tested all my wiring and one of the cable caps needed to be replaced and that fixed all the breakup problems and I now have even better picture quality. Thank god my area as techs that are union techs so stuff gets done the right way on the first try. You can find out if your area has switched to ADS by tuning into an analog channel like SciFi for example. Once tuned to this channel press the Info button and if you see the Dolby logo (double D logo) your area has ADS. If you don't see this double D logo your area hasn't yet gone ADS so your problem would most likely be elsewhere.

[jackwanders]

Interesting. Well, here's the thing.

I got my cable set up in October. I live in an apartment building, and my apartment has one cable outlet in the living room. The tech installed a splitter and ran one end to the cable box in the living room and another to the cable modem in my bedroom. After the installation was complete, I picked up another splitter and split the line in my bedroom to go to both the cable modem and a smaller TV (no cable box).

For the first few months, I distinctly remember some of the channels having static, a sign of regular old analog cable. Some snow here and there, or the wavy lines, stuff like that. But over the past month or two, the static is gone, and the picture quality is really good (as good as you can get w/ regular cable i imagine). Unless, of course, I'm getting the video/audio breakups (blocky video, audio cutting in and out).

Now, I'll have to check when I get home, but I would think that what you said is right, SeaClearly. That Comcast has switched to ADS and the analog channels have been converted to digital. However, like I said, the TV in my bedroom has no cable box, but I can watch TV just fine on that set too. The picture quality is better on some channels than others, and some channels don't come in at all, but most of the channels that do come in are fine. Would an older TV (~5 years old) be able to handle a digital signal w/o a cable box? Could a cable line carry both analog and digital signals?

Also, I don't know if the splitter is the problem. Some days, reception will be great. No problems on any channel. Then on some days, a few channels will be pretty much unwatchable, to the point where the video cuts out altogether. And it's always the same channels (CNN, Headline News, Discovery, Comedy Central, VH1, a few others). Broadcast channels are always fine, and most of the cable channels aren't affected either.

If the splitter is the problem, would the video problems be consistent, or could they come and go as I've described?

[zerolimit]

I had cable before now I have sat. but anyways I had the same problem. If you have a new box then it should be the cable. Alot of people dont understand that the cable running through your home could be the problem or the cable running from the pole. call your cable companie and they should come out and fix it for you. You are paying for their service and you expect good service. Just give them a call.

[SeaClearly]

Interesting. Well, here's the thing.

I got my cable set up in October. I live in an apartment building, and my apartment has one cable outlet in the living room. The tech installed a splitter and ran one end to the cable box in the living room and another to the cable modem in my bedroom. After the installation was complete, I picked up another splitter and split the line in my bedroom to go to both the cable modem and a smaller TV (no cable box).

For the first few months, I distinctly remember some of the channels having static, a sign of regular old analog cable. Some snow here and there, or the wavy lines, stuff like that. But over the past month or two, the static is gone, and the picture quality is really good (as good as you can get w/ regular cable i imagine). Unless, of course, I'm getting the video/audio breakups (blocky video, audio cutting in and out).

Now, I'll have to check when I get home, but I would think that what you said is right, SeaClearly. That Comcast has switched to ADS and the analog channels have been converted to digital. However, like I said, the TV in my bedroom has no cable box, but I can watch TV just fine on that set too. The picture quality is better on some channels than others, and some channels don't come in at all, but most of the channels that do come in are fine. Would an older TV (~5 years old) be able to handle a digital signal w/o a cable box? Could a cable line carry both analog and digital signals?

Also, I don't know if the splitter is the problem. Some days, reception will be great. No problems on any channel. Then on some days, a few channels will be pretty much unwatchable, to the point where the video cuts out altogether. And it's always the same channels (CNN, Headline News, Discovery, Comedy Central, VH1, a few others). Broadcast channels are always fine, and most of the cable channels aren't affected either.

If the splitter is the problem, would the video problems be consistent, or could they come and go as I've described?

If you noticed better picture quality lately than before I would say your area has gone ADS and that is most likely causing your problems. Also advanced digital simulcast should give you a hint with the word simulcast. So if your using a normal TV without a box it will still work as normal. In simple terms Comcast is offering seperate digital feeds of all your existing analog channels while still having the existing analog channels going like normal. So if you have a digital box your box will get a firmware update with new mapping software so when you tune into your existing analog channels with your digital box the mapping software would be updated to tune into the digital feed instead of the analog feed. Without mapping software getting updated you would need to tune into another channel which is confusing for customers which is why they update the mapping software so you can get the digital feed without having to do anything different than before. If you have been with Comcast for a while if you remembered seeing say 10+ new channels in high numbers like in the 800s for example that would be a clue that your area went ADS as this is what they did the test them and if you tuned these channels in they most likely said not authorized. They also could have said Test or something like that.

Also ADS could cause only specific channels at specific times to have problems as each of these channels are at specific frequencies. So a cable system has for example a total bandwidth of 750Mhz and these are split up in chunks of 6Mhz spaces. This 750Mhz system handles all services including phone, cable, vod and internet. So for example in each 6Mhz space Comcast will hold about 5-8 digital channels, one analog channel or 2-3 HD channels using compression. So your splitter for example could be having a very very hard time dealing with the frequency range of 700-710 for example so all channels that are between 700-706Mhz would have problems. So if your having 10 or so channels for example having problems that seem random they might not be random at all. Again these are brand new channel put into unused bandwidth or unused frequencies which most likely are higher frequencies and the higher the frequency the more likely a bad cable or splitter would have problems. For example I just recently had a brand new splitter that was defective that couldn't handle anything over 450Mhz just on one of the three outputs which caused all my HD channels to breakup like crazy and for my VOD to error out time and time again. Plus about 40 total digital channels including a few music choice channels refused to work. This would be and off and on issue as a bad splitter or cable could work one minute and not work the next minute.

I hope this gives you a better idea what is going on. You should look at all splitters and cables that are placed inbetween the wall jack and your box. Also if you can try unplugging everything else including the splitter and feeding the digital box with just the coax cable from the wall. If things work correctly than you must look at both the cable used from the splitter to your box and the splitter itself. So if the cable that was going into the input of the splitter into the box works than try using the cable that went from the output of the splitter into the box and use that directly from the wall jack instead. If things will work than its not the cable so at that point try a different output on the splitter for the digital box and if it works than that specific output jack on the splitter was bad and it might very well work fine with your cable modem. It can't hurt to try these things out first because it may fix all your problems without a tech being needed or anything being replaced.

[jackwanders]

Great post, SeaClearly. After work today I'll definitely play around with the cables and splitters. Very informative. Thanks.

[jackwanders]

Ok. So first, a review of my current setup:

The first spliter is a 'Regal', supplied by Comcast with a range of 5-1000Mhz. The second splitter (PC/TV) is an Acoustic Research splitter from BestBuy w/ a range of 5-1500Mhz.

First, I disconnected the first splitter and connected the cable box directly to the wall. Problems gone. Good picture & audio. No breakups or cut outs.

Next, I swapped the two splitters and reconnected everything. Problems came back. Choppy picture & audio on fixed set of channels.

Then, I disconnected the cable that runs to the second splitter from the first splitter (still swapped) and the problems cleared up. When I so much as touched the second cable to the splitter, the picture would cut out for a bit, then come back, with the same choppiness. It was here where I noticed something else odd. With just the cable box cable attached to the AR spliter, things seemed ok. But if I so much as nudged the splitter (or more specifically, the cable attached to the wall outlet, the picture would cut out. Leave it alone, picture would come back.

So. My first inclination is to assume that the 8" of cable from the wall to the first splitter is bad. Unfortunately, I have no spare cable to test against, and I can't swap cables around since they are mostly well nailed into place along my walls and baseboards. So, tomorrow I'm gonna hit radioshack or bestbuy and pick up a foot or two of high quality cable and see if that works. I'm also gonna take a look at their splitters to see if there are any amplifying splitters I can try, because another possibility it seems is that the signal strength weakens when both cables are attached to the splitter and that causes the degraded picture & audio.

[majortom1981]

You have a bad splitter.

Simple as that.

Also shouldnt the tv and computer be conencted to the back of the cablebox?

[bangbang023 Veteran]

I'm assuming the cable box is connected to a different tv than the one shown on the right.

You should replace the first splitter with one like the AR you have on the other end.

[jackwanders]

I'm assuming the cable box is connected to a different tv than the one shown on the right.

You should replace the first splitter with one like the AR you have on the other end.

Correct. The cable box is hooked to my tv in my living room while the second splitter, pc and tv are in my bedroom.

As for switching the first splitter for an AR splitter, I tried that. At one point I had the following setup:

wall -> AR splitter -> cable box

This seemed to work OK, but when I attached the other cable (the one that runs to my bedroom) the picture degraded. Even when that cable wasn't hooked up to anything on the other end.

After a bit more reading this morning, I think it has something to do with signal loss. When only the cable box cable is connected, there's no signal loss as the signal passes straight through. As soon as the other cable is connected, the signal is split and there is some signal loss.

So I'm gonna pick up one of these after work today:

It's got a wider range, and boasts the lowest signal loss. So I'll give it a shot.

Also, what is a "power pass"...does this mean that the output with the arrow is amplified somehow?

[jackwanders]

Ugh. So picked up the monster splitter seen above.

There was ZERO difference between that and the other splitters.

I ran two different cables from the cable box to the wall. Each worked fine and the problems went away. So the cables are fine.

I used those two cables to go wall -> splitter -> cable box. Problems came right back.

Unless anyone's got any ideas, I think it's time to throw in the towel and cal Comcast.

[SeaClearly]

Ugh. So picked up the monster splitter seen above.

There was ZERO difference between that and the other splitters.

I ran two different cables from the cable box to the wall. Each worked fine and the problems went away. So the cables are fine.

I used those two cables to go wall -> splitter -> cable box. Problems came right back.

Unless anyone's got any ideas, I think it's time to throw in the towel and cal Comcast.

Call Comcast and tell them that when you use their splitter the picture on several channels breaks in and out but if you connect the cable box without the splitter it works perfectly. This should prompt them to have a tech come out and test the splitter itself but when the tech comes out just tell him to check the signal strength coming into your house. Also keep in mind that having the signal being amplified too much could cause this problem along with too little. Also the signal coming into your house from outside might be too little or too high so they should at least try and adjust this. I can say now that your problem is most likely the signal coming into your house and I think the signal is too high so when you amplify it even more its killing the signal once it reaches your box. Also the signal coming into your house cannot be altered by you but has to be done by a tech outside your house. Sometimes they need to increase the signal if you have multiple services with multiple boxes that require a few more splitters. But a tech is indeed needed now so I would give them a call and have them come out in the evening after you get off work or on the weekend.

[bangbang023 Veteran]

Yeah, it's going to be an outside line issue. I know when I added my 4th box (on top of the previous 3 and internet), they had to run a second main line to my house to support it properly (we had a lot of drop outs with the internet for a week).