# Artifacts / "Hot" Signal



## nycaudioman (Mar 17, 2015)

Hello fellow Tivo users. I have been a loyal customer since Series 2, and am experiencing an issue with my new Tivo Roamio (basic). When watching certain shows, I see what looks like MPEG artifacts or macroblocking, usually on dark colors.

For example, in the attached shot you can see Harvey's black jacket on the show Suits. On a friend's Tivo Premiere, the suit is smooth. On mine, it is blocky.

I e-mailed Tivo and they suggested attenuating the signal, so I now have a 9db attenator _and_ a 6db attenuator on the line. The problem did not improve at all.

Does anyone else have any thoughts on what could be causing this issue?

I know there were some older posts where FiOS users (I am on Optimum) with hot signals saw "pixelation", but I am not sure if these are the types of issues they were seeing, since I would consider this more as blockiness than pixelation.


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## JoeKustra (Dec 7, 2012)

What is your signal strength and SNR? If the signal is at 100 you might add more attenuation. I've see variable devices up to 45db.


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## L David Matheny (Jan 29, 2011)

nycaudioman said:


> Hello fellow Tivo users. I have been a loyal customer since Series 2, and am experiencing an issue with my new Tivo Roamio (basic). When watching certain shows, I see what looks like MPEG artifacts or macroblocking, usually on dark colors.
> 
> For example, in the attached shot you can see Harvey's black jacket on the show Suits. On a friend's Tivo Premiere, the suit is smooth. On mine, it is blocky.
> 
> ...


Could it be image degradation due to an overly compressed cable signal? If you and your friend record the same show, are his file sizes larger than yours? (If not, it could still be a signal problem.) Can you try recording with your Roamio at your friend's house?

If you can watch some shows using "chase play", check the count of uncorrected errors at the start of the show, then immediately check again when you see macroblocking. If the uncorrected error count didn't increase, the macroblocking must have been in the transmitted signal.


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## nycaudioman (Mar 17, 2015)

Thanks for the replies. My original signal strength was 92% with an SNR of 37 db.

After adding in a 9 db attenuator, 6db attenuator, and now also a splitter with a 3.5 db loss, I am seeing a signal strength of 85% and SNR of 34 db, but still getting the same artifacts on some channels (but almost always on black colors). I will definitely try some of the troubleshooting steps you have suggested.

I was honestly hoping more of you would have seen this, as I was hoping it was a common problem with an easy fix, but I guess it is going to require some more work! Thanks for your replies so far.


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## worachj (Oct 14, 2006)

If multiple devices are doing scaling it could lead to the macro-blocking (TiVo, AV, TV). I usually like one device to do the scaling, so I set my TiVo to the same resolution as my TV (1080p). Try playing around with the different resolutions in TiVo.


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## nycaudioman (Mar 17, 2015)

worachj said:


> If multiple devices are doing scaling it could lead to the macro-blocking (TiVo, AV, TV). I usually like one device to do the scaling, so I set my TiVo to the same resolution as my TV (1080p). Try playing around with the different resolutions in TiVo.


Thanks for your reply! I checked my Tivo and it is set to 1080i (well, it's set to automatic mode which is showing 1080i), which it says is the preferred setting for my TV (a 4k Samsung HU8550).

I spoke to Tivo and they were USELESS. Other than trying the attenuators (which from my earlier post you can see did not work), they suggested trying a different HDMI cable. That has been the extent of their support so far. (For the record, changing the HDMI cable does not help.)


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## Dan203 (Apr 17, 2000)

It's your cable company compressing the signal. TiVo records the digital signal directly. Having a "hot" signal will not cause these sorts of artifacts. If the signal strength/SNR was to high or low you'd get dropouts in the video, not macroblocking. Macroblocking is caused by the encoding. In a lot of areas cable companies will take the already compressed signal from OTA channels and recode it to an even lower bitrate to save space on their line. That process can introduce artifacts like this.


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## JoeKustra (Dec 7, 2012)

Question. Would it be possible to gauge the degree of compression from the file size? Given one hour of 1080i/dd5.1 that uses 7-8GB on the TiVo, would that be an indicator of good, bad, or can't tell?


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## sinanju (Jan 3, 2005)

Dan203 said:


> It's your cable company compressing the signal. TiVo records the digital signal directly. Having a "hot" signal will not cause these sorts of artifacts. If the signal strength/SNR was to high or low you'd get dropouts in the video, not macroblocking. Macroblocking is caused by the encoding. In a lot of areas cable companies will take the already compressed signal from OTA channels and recode it to an even lower bitrate to save space on their line. That process can introduce artifacts like this.


I would agree. This sort of problem first started showing up when Comcast started squishing 3 HD channels into a single QAM where there was supposed to be only 2. Whenever there was sufficient activity on the combined channels, pictures would degrade as you've shown. I don't know about Optimum, but I'd bet they're doing the same thing. FiOS is glass all the way to the house, so they don't have the bandwidth issues and don't have to play those games. Here's an article from back in the day with a picture to show the difference:

http://www.dailytech.com/Comcast+Trades+Quality+for+Quantity+with+HDTV+Offerings/article11312.htm



JoeKustra said:


> Question. Would it be possible to gauge the degree of compression from the file size? Given one hour of 1080i/dd5.1 that uses 7-8GB on the TiVo, would that be an indicator of good, bad, or can't tell?


On FiOS, an hour of 1080i HD is about that. My copy of the latest Broadchurch, for example, is 7.74GB

*Edit*:

If this was the sort of "hot signal" problem that FiOS folks saw back in the bad old days, you'd see RS Uncorrected errors.


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## Dan203 (Apr 17, 2000)

JoeKustra said:


> Question. Would it be possible to gauge the degree of compression from the file size? Given one hour of 1080i/dd5.1 that uses 7-8GB on the TiVo, would that be an indicator of good, bad, or can't tell?


That's actually quite high. Based on the file being 7.5GB that would put the video bitrate over 16Mbps, which should be plenty.

Typically we see this when they try to cram a 1080i signal into 10-11Mbps so they can fit 3 HD streams on a single QAM.

It could be the cable company getting a bad signal from their source. Or they could be doing some bad post processing. Bitrate is not everything. If the signal already looks like sh*t then it's going to continue to look like sh*t no matter how many bits you use to encode it.


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## JoeKustra (Dec 7, 2012)

Dan203 said:


> That's actually quite high. Based on the file being 7.5GB that would put the video bitrate over 16Mbps, which should be plenty.
> 
> Typically we see this when they try to cram a 1080i signal into 10-11Mbps so they can fit 3 HD streams on a single QAM.
> 
> It could be the cable company getting a bad signal from their source. Or they could be doing some bad post processing. Bitrate is not everything. If the signal already looks like sh*t then it's going to continue to look like sh*t no matter how many bits you use to encode it.


Thanks. I have, in the past, checked a recording with kmttg and seen a bit rate of about 18Mbps. My cable feed does combine a 1080i and a 720p broadcast channel into one 6MHz channel. I don't know what they do for the other networks, but I shudder to think since A&E, SyFy and others are usually under 7MB files. Thanks for the info.

As for the bad network feed, that has happened. We get "streaking" that is not HD or SD specific. Usually a call to the cable company fixes the issue in a few days. I guess I'm lucky to have a small cable company.

As for the OP's problem, I have seen it only when the content is 1080/p24 and it is being converted (poorly) to 1080i/p60. Movie trailers from a Sony server are the best example. On the Roamio the same trailer stays 1080/p24 and looks fine.


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## nycaudioman (Mar 17, 2015)

Thanks everyone for your feedback so far. As the OP, here is some additional information based on what you have been discussing...

- The show I first saw the blocking on was a Jay Mohr comedy show on Showtime. The show recorded just over an hour of time (about 71 minutes) and was about 4.5 GB.

- This week I was watching Justified on FX and saw what looked like pixelation in some of the backgrounds of the scenes, even though the characters themselves were crisp. I just checked the file size on that hour long show, and it is only 2.27 GB.

What's odd is that my friend has a nearly identical setup, also on Optimum, and in the next town over, and does NOT have the blocking issue I do. I've reached out to him to ask what his file sizes are.


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## sinanju (Jan 3, 2005)

nycaudioman said:


> Thanks everyone for your feedback so far. As the OP, here is some additional information based on what you have been discussing...
> 
> - The show I first saw the blocking on was a Jay Mohr comedy show on Showtime. The show recorded just over an hour of time (about 71 minutes) and was about 4.5 GB.
> 
> ...


Watch a channel with which you're having trouble live. If you see the problem, go to Account & System Info>DVR Diagnostics and find the channel in the list. If you see an RS Uncorrected count that is more than a couple hundred (sometimes happens on initial tuning) or, more importantly, incrementing, you have a signal issue.


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## Dan203 (Apr 17, 2000)

nycaudioman said:


> - The show I first saw the blocking on was a Jay Mohr comedy show on Showtime. The show recorded just over an hour of time (about 71 minutes) and was about 4.5 GB.


Now that's low! That's only about 8.5Mbps.


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## JoeKustra (Dec 7, 2012)

nycaudioman said:


> Thanks everyone for your feedback so far. As the OP, here is some additional information based on what you have been discussing...
> 
> - This week I was watching Justified on FX and saw what looked like pixelation in some of the backgrounds of the scenes, even though the characters themselves were crisp. I just checked the file size on that hour long show, and it is only 2.27 GB.
> 
> What's odd is that my friend has a nearly identical setup, also on Optimum, and in the next town over, and does NOT have the blocking issue I do. I've reached out to him to ask what his file sizes are.


Wow. I just checked Justified (66 minutes) and it's 6.29GB on my HD feed. Could your feed be sending you SD by accident? That could explain the quality issues. Even my feed for Forever takes 3.44GB, ABC being my worst HD channel. You may have something to explore.


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## Dan203 (Apr 17, 2000)

It's possible his cable company is using H.264 encoding. I don't think they could use bitrates that low with MPEG-2 and get anything usable. With H.264 it would still be on the low end for HD, which could explain the qualty issues.


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## nycaudioman (Mar 17, 2015)

Thanks everyone for your replies so far. As the original poster, I was wondering if any readers here are also on Optimum / Cablevision, and have similar small recording sizes? I am surprised to be having this issue, because they are known to be a relatively good cable provider.


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## telemark (Nov 12, 2013)

Dan203 made an important point. You need to figure out what codec is being used before comparing file sizes or bit rates.

VLC is good for this.


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## Jed1 (Jun 18, 2013)

nycaudioman said:


> Thanks everyone for your replies so far. As the original poster, I was wondering if any readers here are also on Optimum / Cablevision, and have similar small recording sizes? I am surprised to be having this issue, because they are known to be a relatively good cable provider.


I read your posts and your are watching a channel that is native 720p. You indicate that your unit is set to output 1080i. Try selecting multiple resolutions on your TiVo and send the native signal directly to your TV and let that do the conversion. Turn of any enhancement features on your TV and make sure the TV is not running in torch mode.

Set the TiVo to output 480i, 480p, 720p, and 1080i. If this is a Roamio unit do not use 1080p as there is no content produced in 1080p/60.
1080p/60 puts an enormous bandwidth load on your HDMI cable and can cause HDMI issues.


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## IrishTV99 (Dec 10, 2008)

I'm having this exact issue with FIOS channels on my Roamio, and I have the exact same Samsung TV. I wonder if it is the TV - I never noticed the issue before, and the TV is only a month old. I first noticed it on ABC, watching (the fairly dark) Agents of SHIELD. Agent Carter (same channel, also dark tones) was worse.


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## JoeKustra (Dec 7, 2012)

IrishTV99 said:


> I'm having this exact issue with FIOS channels on my Roamio, and I have the exact same Samsung TV. I wonder if it is the TV - I never noticed the issue before, and the TV is only a month old. I first noticed it on ABC, watching (the fairly dark) Agents of SHIELD. Agent Carter (same channel, also dark tones) was worse.


No conclusion, but I record and watch Forever every week. I have never seen such poor display quality. I have my Roamio set to 1080p output. File sizes posted above. I'll record SHIELD this week. If it's bad I'll post it.


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## nycaudioman (Mar 17, 2015)

IrishTV99 said:


> I'm having this exact issue with FIOS channels on my Roamio, and I have the exact same Samsung TV. I wonder if it is the TV - I never noticed the issue before, and the TV is only a month old. I first noticed it on ABC, watching (the fairly dark) Agents of SHIELD. Agent Carter (same channel, also dark tones) was worse.


Starting to get worried now that this is an issue between the Samsung HU8550 and the Tivo.


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## IrishTV99 (Dec 10, 2008)

I'm considering taking one of my non-Tivo HD boxes and seeing if it looks any better. My previous TV was a 7-8 year old slim projection Sony. I never saw the banding issues with that set using the same TiVo.

I also ordered a new cable card from Verizon...I've had other glitchy issues, and my card is super old.


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## Dixon Butz (Mar 28, 2003)

nycaudioman said:


> Starting to get worried now that this is an issue between the Samsung HU8550 and the Tivo.


Oh you have an 8550. So do I. 
The issue you are having is from your cable provider. It is just compression artifacts.
I just cut the cord from Dish which had the same artifacts in blacks. Now I am on over the air with a Tivo and I don't see those artifacts anymore. OTA is not re-compressed like on cable or satellite. 
I was able to compare Dish and OTA for a few days. And I have to say OTA looks stunning on my 8550. Never seen such a great PQ. The PQ looks the same on the Tivo as it does directly connected to the TV. 
What you need to do is tweak the black levels on your TV so they are not as noticeable.


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## Dan203 (Apr 17, 2000)

Could also be the TVs settings. Have you calibrated the TV at all? If it's too bright or the contrast is off then it may make things like this more obvious.


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## HarperVision (May 14, 2007)

Dixon Butz said:


> Oh you have an 8550. So do I. The issue you are having is from your cable provider. It is just compression artifacts. I just cut the cord from Dish which had the same artifacts in blacks. Now I am on over the air with a Tivo and I don't see those artifacts anymore. *OTA is not re-compressed like on cable or satellite.* I was able to compare Dish and OTA for a few days. And I have to say OTA looks stunning on my 8550. Never seen such a great PQ. The PQ looks the same on the Tivo as it does directly connected to the TV. What you need to do is tweak the black levels on your TV so they are not as noticeable.


It may not be "re-compressed", but it can certainly be "compressed", especially dependent on the number of sub-channels being broadcast within the same ATSC 8-VSB Channel bandwidth.


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## JoeKustra (Dec 7, 2012)

HarperVision said:


> It may not be "re-compressed", but it can certainly be "compressed", especially dependent on the number of sub-channels being broadcast within the same ATSC 8-VSB Channel bandwidth.


I guess we need to redefine channel. But anyhow, if someone was really bored they could use the DVR diagnostic to check the frequency of every channel. All "channels" are still 6MHz, be they NTSC, 8VSB or QAM. Like you said, sub-channels get squeezed into that bandwidth. Before my channels became encrypted the SD channels were 10 to 12 per 6MHZ, the HD were two (1080i and 720p) to a main channel, and 40+ for music. The TiVo shows the real frequency of the main channel even with a cable card. I'm not bored enough to do it though. Yet.


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## Dixon Butz (Mar 28, 2003)

HarperVision said:


> It may not be "re-compressed", but it can certainly be "compressed", especially dependent on the number of sub-channels being broadcast within the same ATSC 8-VSB Channel bandwidth.


Yeah that is what I meant. I know OTA is compressed. But cable and sat compresses it again. I could easily see the difference between OTA and Dish. 
The Comcast in my area had very bad PQ 2 years ago. 
The HD OTA looks amazing in DC and Baltimore. Only 2 HD channels that are slightly lower in PQ. 5 and 7.


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## nycaudioman (Mar 17, 2015)

Dan203 said:


> Could also be the TVs settings. Have you calibrated the TV at all? If it's too bright or the contrast is off then it may make things like this more obvious.


Dan, I wanted to get back to you on this post. The TV (Samsung 8550) was professionally ISF calibrated.

You are right that lowering the brightness setting (but keeping backlight up) does make the artifacts less obvious.

It is just hard for me to believe that Optimum / Cablevision is this poor a signal, since they are known as a good company, which makes me want to further investigate whether this is a Tivo or Samsung issue. But the posts on this forum are making me start to believe it really is the signal. Which is frustrating because it is one thing I can't do anything about.

Again, Tivo Support has been useless. Their latest suggestion was to try new coax cables, which did not help.


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## Dan203 (Apr 17, 2000)

The artifacts you show in the first post are not the type you get when the signal is too high/low. Those will typically be vertical strips of blocks from a partially decoded frame and will almost always be accompanied by an audio drop as well. What you're seeing is macro blocking caused by the encoding. Trust me I'm an expert in temporal encoding, and what you're seeing there is almost certainly caused by the bitrate being too low. Based on the file sizes you posted the bitrate is really low if they're using MPEG-2 and still not great even if they're using H.264. Areas of large solid colors and scenes with a lot of motion are the first to suffer when the bitrate is too low. There are techniques that some decoders use to hide these types of artifacts. Typically they soften the picture (i.e. blur it) to make the hard lines between the blocks less noticble. You're TV probably even has a setting somewhere called like "MPEG noise reduction" or something like that which does exactly that at the display level. TiVo doesn't have a setting like that, but if you want to force it you could se the TiVo to 720p mode and then when it plays 1080i content the deinterlace and resize will likely create the same effect. 

But one thing I will say for sure... You're barking up the wrong tree by swamping cables and trying to raise/lower your cable signal. What you're seeing there is in the encoding and the best you can do is try to kake it less obvious using the filters on your TV or by lowering the brightness.


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## Dixon Butz (Mar 28, 2003)

Also, with these Samsung VA panels, you have to sit almost dead center. Otherwise the contrast ratio greatly decreases and you will see every artifact in blacks.


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## Diana Collins (Aug 21, 2002)

nycaudioman said:


> ...It is just hard for me to believe that Optimum / Cablevision is this poor a signal, since they are known as a good company, which makes me want to further investigate whether this is a Tivo or Samsung issue. But the posts on this forum are making me start to believe it really is the signal. Which is frustrating because it is one thing I can't do anything about...


Where I live in NJ we have Cablevision/Optimum, Verizon FiOS, and of course DirecTV and Dish, available. DirecTV and FiOS have the best HD picture quality, with FiOS winning some channels, DirecTV winning others. Dish, which encodes 1080i HD as 1080x1440 (i.e they reduce the horizontal resolution) actually comes in second. Cablevision is, and always has been, dead last around here.


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## IrishTV99 (Dec 10, 2008)

Dixon Butz said:


> Also, with these Samsung VA panels, you have to sit almost dead center. Otherwise the contrast ratio greatly decreases and you will see every artifact in blacks.


Very true.

I was able to counter my issue (somewhat) by lowering the brightness and boosting the backlight. I'm otherwise using the CNET settings, which I've been very happy with.


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