View Full Version : MPEG4 quality issues
In preparation for the upcoming OTA flood, I figured I would take this opportunity to post a few snapshots I took of my screen. I only spent about 15 minutes checking through one show, but these are representative of quality problems I have seen on many shows, and all exclusive to MPEG4-delivered programs.
Attachments to follow...
Coffey77
12-06-06, 11:32 PM
I'm guessing pixelated/blocky with sound drops? From what I've been overhearing, it's not D's fault so much as it is the feed from the Network to D*V. They could be trying to pass the buck, but why would they do that?:nono2:
Files are too large for attachment, so I'll host them externally....
Here is the title screen (http://xs.to/xs.php?h=xs110&d=06494&f=ToeTags1.jpg) in MyVOD. Only included for reference.
Here (http://xs.to/xs.php?h=xs110&d=06494&f=ToeTags2.jpg) we see what is bothering me most... lines of solid white blocks on large field transitions....
And it doesn't just last for a single field either. Here (http://xs.to/xs.php?h=xs110&d=06494&f=ToeTags3.jpg) is the next field... doesn't clear up in this (http://xs.to/xs.php?h=xs110&d=06494&f=ToeTags4.jpg) image either... it just "changes".
There's also a problem with 'temporal artifacting', motion vectors that get lost or misdefined.
This image (http://xs.to/xs.php?h=xs410&d=06494&f=ToeTags5.jpg) is the one right before the problem image. And here (http://xs.to/xs.php?h=xs410&d=06494&f=ToeTags6.jpg) is the offending image. Note how part of the moving image was misplaced by the encoder. Only lasts one frame, since the next frame (http://xs.to/xs.php?h=xs410&d=06494&f=ToeTags7.jpg) has gone back to normal placement.
A close up (http://xs.to/xs.php?h=xs410&d=06494&f=ToeTags8.jpg) shows that it is indeed a large series of blocks that were misplaced horizontally.
Coffey77
12-06-06, 11:48 PM
:new_puppy I see dead people... What type of input are you using? HDMI? Composite? Throw down some of the variables you've got, TV type, HR20 software version and all that good stuff and it'll help people help you. We want to help you help you so help us help you to help you...:scratchin Anyway, I usually get something like that once a show, give or take. Drives the wife nuts. I'm guessing it's just a problem on their end with the compression of the signal down to the MPEG4 format. It didn't happen when I used the OTA. There I'd just get a nice red line on the side of my screen or some garbled stuff near the top of the screen. I never notice it when I'm in the 70's (who didn't enjoy the Best Beaches of 2004 this afternoon??) but always get something when I'm watching the Network locals in HD.
The third set of problems revolves around inappropriately interlaced images.
Here is a series of three (http://xs.to/xs.php?h=xs410&d=06494&f=ToeTags9.jpg) successive (http://xs.to/xs.php?h=xs410&d=06494&f=ToeTags10.jpg) frames (http://xs.to/xs.php?h=xs410&d=06494&f=ToeTags11.jpg) showing how fast-moving images can confuse the encoder, causing it to interlace large portions of the fields before and after a large full-image change.
:new_puppy I see dead people... What type of input are you using? HDMI? Composite? Throw down some of the variables you've got, TV type, HR20 software version and all that good stuff and it'll help people help you. We want to help you help you so help us help you to help you...:scratchin Anyway, I usually get something like that once a show, give or take. Drives the wife nuts. I'm guessing it's just a problem on their end with the compression of the signal down to the MPEG4 format. It didn't happen when I used the OTA. There I'd just get a nice red line on the side of my screen or some garbled stuff near the top of the screen. I never notice it when I'm in the 70's (who didn't enjoy the Best Beaches of 2004 this afternoon??) but always get something when I'm watching the Network locals in HD.
These are captured from an HR20 hooked through a WB68 (via runs of less than 50 feet receiver to switch, approximately 15 feet switch to dish) to an AU9.
Not that it could cause this (since these are stills), but hookup is component to a Sony KP53HS10. And before anyone mentions it, yes I know there's a service issue with the chassis (which is why I didn't see this stuff as badly before - bonus points to whoever identifies the issue) and yes I know my mirror and lenses need a good cleaning. :D
The artifacts do not show up in any form when watching via OTA either through the H20 or direct into the Samsung slimfit tube upstairs. They do show up when watching the same show via MPEG4 on the Samsung slimfit (connected via HDMI).
It is the encoder. The blocky nature and the texturing on the blocks themselves shows that pretty clearly.
Signal levels:
On 101 (http://xs.to/xs.php?h=xs410&d=06494&f=Sigs101.jpg), 110 (http://xs.to/xs.php?h=xs410&d=06494&f=Sigs110.jpg), 119 (http://xs.to/xs.php?h=xs410&d=06494&f=Sigs119.jpg), 99 (http://xs.to/xs.php?h=xs410&d=06494&f=Sigs99b.jpg), and 103 (http://xs.to/xs.php?h=xs410&d=06494&f=Sigs103a.jpg).
Coffey77
12-07-06, 12:14 AM
I get 0 on my 101 number 4.
The main reason I'm posting this is twofold.
1) These artifacts make my viewing experience an effort in 'ignoring every time the encoder vomits' instead of 'watching the show'. If they happened twice a show, that might be one thing. But this happens a LOT in my DMA on the shows I watch, especially CSI (all the flashing).
2) OTA recording is coming "very soon", and D* knows it will really demonstrate the craptastic quality of their MPEG4 encoding process. All I have to do is record the same show via OTA and D*, take a few comparison shots from the same timeframes, and the artifacting will be apparent.
D* is pushing MPEG4 as their major... no, make that only way going forward for HD. It's pretty clear they're pushing to get rid of MPEG2, and the faster the better. But if their strategy is to grab the locals via OTA (instead of HD-SDI) and then decode/re-encode or direct transcode the MPEG2 to MPEG4, then their quality will never approach OTA levels. I really hope their plan is to place the MPEG4 encoders directly at the local station, feeding it with HD-SDI. If it isn't, maybe this series of images will push them a little further in that direction.
Tom Robertson
12-07-06, 12:35 AM
Some thoughts:
It is my understanding that in some locations D* is taking a feed via fibre from the local stations to their uplink center. In other locations, they grab OTA.
They are working with their transcoder manufacturer to improve the transcoding experience. Not all uplink centers are running the same version of the transcoding firmware (or were, things change daily as you know.)
At one of our local stations, the station engineers are going crazy keeping HD working. Most often they are having problems with DD these days, but they've had lots of problems with HD to SD transitions, switching, etc. Its a mess. And D* has to take that all in. (Having said that, your experience with OTA indicate your locals are likely fairly stable.)
How many of us have some OTA capability and can side-by-side already? I actually don't have a clue, but I know I can, you can, and others can. In some locations people indicate their MPEG4 experience is nearly as good as OTA. In my case, its clear that MPEG4 isn't as good as OTA, but for most shows, it might be "good enough", but not for sports. (Well, maybe chess...)
I am interested to see if HD nationals will improve with MPEG4 by virtual of being less bit starved (if D* so chooses) or if we'll continue to suffer HD-lite.
Lets hope for good things,
Tom
D* will get MPEG-4 right eventually, they have to, they have bet the farm on it. It is the future, ...the present is "shake down".
OTA is the Gold Standard, PQ will be measured against it for quite some time to come. (and soon, the vast majority of us will have the ability to compare MPEG-4 (as delivered by D*) and OTA-HD.
Coffey77
12-07-06, 08:25 AM
Let's not forget the vastly improved signal strength of HDTV OTA. Way out here in Bumble, it'd be like old times when you only got 3 channels... One was a show, the other was a simulcast of that show, and the third was QVC. At one point, I pulled down signal from an indoor non amped antenna (small little bugger) so I moved to the big rooftop mount and was doing well. Still needs tweeking and maybe a bigger booster but was getting most Chicago locals and sidebands.
LameLefty
12-07-06, 08:31 AM
Meklos - I'm in the same market as you and I haven't seen glitches like that except very, very occasionally, usually on recordings made during bad weather. In fact, that CSI was recorded last Thursday night, the night all that terrible wind and driving rain came blowing through the area, as I recall (I was out in it at my daughter's soccer practice in fact :( ). I think most of what you're seeing is weather-related. No question there are some MPEG4 problems but they don't seem to be very widespread in our experience over the last 7 weeks.
Meklos - I'm in the same market as you and I haven't seen glitches like that except very, very occasionally, usually on recordings made during bad weather. In fact, that CSI was recorded last Thursday night, the night all that terrible wind and driving rain came blowing through the area, as I recall (I was out in it at my daughter's soccer practice in fact :( ). I think most of what you're seeing is weather-related. No question there are some MPEG4 problems but they don't seem to be very widespread in our experience over the last 7 weeks.
That was spending 15 minutes going through one archived recording. I have others from various timeframes showing the same effects (been telling the wife not to delete anything). I'll try to get them posted tonight.
spolaski
12-07-06, 09:02 AM
For what it's worth I haven't seen the problems you have. What I do see is a large amount of macro-blocking during rapid scene changes to the point where I find it distracting at times.
It tends to vary from channel to channel, so it could be a feed issue or it could be a D* issue if they're turning down the bitrate to squeeze a few more channels into the same amount of bandwidth. It's not really something new, I've noticed this since first subscribing 10 years ago. It may just be more noticeable now with HD as there's no place to hide any imperfections.
upnorth
12-07-06, 09:05 AM
The main reason I'm posting this is twofold.
1) These artifacts make my viewing experience an effort in 'ignoring every time the encoder vomits' instead of 'watching the show'. If they happened twice a show, that might be one thing. But this happens a LOT in my DMA on the shows I watch, especially CSI (all the flashing).
2) OTA recording is coming "very soon", and D* knows it will really demonstrate the craptastic quality of their MPEG4 encoding process. All I have to do is record the same show via OTA and D*, take a few comparison shots from the same timeframes, and the artifacting will be apparent.
D* is pushing MPEG4 as their major... no, make that only way going forward for HD. It's pretty clear they're pushing to get rid of MPEG2, and the faster the better. But if their strategy is to grab the locals via OTA (instead of HD-SDI) and then decode/re-encode or direct transcode the MPEG2 to MPEG4, then their quality will never approach OTA levels. I really hope their plan is to place the MPEG4 encoders directly at the local station, feeding it with HD-SDI. If it isn't, maybe this series of images will push them a little further in that direction.
I have had MPEG-4 locals since May have not seen anything like your describing here.
As far as #2 above many have had the opportunity to view OTA along with MPEG-4 on there H20 for close to a year now many reports of good results and there are those that are not as fortunate but they are improving with encoder updates.
OTA is the Gold Standard, PQ will be measured against it for quite some time to come. (and soon, the vast majority of us will have the ability to compare MPEG-4 (as delivered by D*) and OTA-HD.
And yet to some of us, OTA is worthless. The Erie, PA market has HORRIBLE OTA with NO high-def programming. Heck, they've resisted even going DIGITAL!
I have a large bar-like powered Terk antenna that I bought a year and a half ago for indoor or outdoor mounting. I'm within five miles of just about every station here. Signal reception is poor and snowy.
OTA - big whoopty doo for people in Erie, PA.
Is it any wonder I "moved" to Pittsburgh a few years ago? :-P
Not sure if this will make you feel any better, but I had two main issues with the local MPEG4 feeds in Philadelphia. CBS and NBC had the horrible 8mm effect (a filmy, shiny quality that looked weird) and also a lot of sound and video dropouts. A couple of days ago, the 8mm effect magically disappeared on the 1080i feeds (CBS and NBC), and the ABC feed was unwatchable. All of a sudden, ABC was back, and it looks very good, sharp, and no sound/video glitches yet. Seems like they did something on the hardware side, not related to the HR20 (the H20 had the same issues). But if others in your area haven't had similar problems, I may be off the mark here.
LameLefty
12-07-06, 09:15 PM
Tonight we watched CSI: and ER and the contrast between the two was interesting. CSI: on CBS has a much sharper picture but is much more subject to macroblocking and occasional horizontal glitches - lines running halfway to two-thirds of the way across the screen during fast, bright transitions. By contrast, ER on NBC was noticeably less sharp (though still miles better than SD) but displayed no macroblocking and no visible picture glitches.
Tonight we watched CSI: and ER and the contrast between the two was interesting. CSI: on CBS has a much sharper picture but is much more subject to macroblocking and occasional horizontal glitches - lines running halfway to two-thirds of the way across the screen during fast, bright transitions. By contrast, ER on NBC was noticeably less sharp (though still miles better than SD) but displayed no macroblocking and no visible picture glitches.
So I can cancel my simultaneous appointments with my eye doctor and psychiatrist? :grin:
sigma1914
12-08-06, 06:09 AM
Meklos & Lefty...
I notice Lefty has a DLP set, and I think this may be a small reason why they see less problems. We have 2 HDTVs and 2 HR20s in my home. The DLP 46" Sammy in the den has much less noticeable blocking, if any, then my 32" LCD Sammy on the same Mpeg-4s.
Just food for thought.
Blitz68
12-08-06, 06:21 AM
Meklos & Lefty...
I notice Lefty has a DLP set, and I think this may be a small reason why they see less problems. We have 2 HDTVs and 2 HR20s in my home. The DLP 46" Sammy in the den has much less noticeable blocking, if any, then my 32" LCD Sammy on the same Mpeg-4s.
Just food for thought.
Well I have a 62" Mits HD DLP and an HR20 with MPEG4 Locals and it is always perfect. I do get the ocassional DD dropouts tho.
And yet to some of us, OTA is worthless. The Erie, PA market has HORRIBLE OTA with NO high-def programming. Heck, they've resisted even going DIGITAL!
I have a large bar-like powered Terk antenna that I bought a year and a half ago for indoor or outdoor mounting. I'm within five miles of just about every station here. Signal reception is poor and snowy.
OTA - big whoopty doo for people in Erie, PA.
Is it any wonder I "moved" to Pittsburgh a few years ago? :-P
That is a very poor antenna. If you are within 5 miles of your stations OTA, you could find many antennas that would give you very good signals, unless you are in the bottom of a mountain valley. If you have anything even remotely resembling line of site to the tower sites 5 miles away, you should be able to get a decent signal with a decent antenna.
If I were in a valley, but that close to the transmitting antennas, I would get a Radio Shack U-75 and point it at the top of the "mountain ridge" in the direction of the transmitters. The transmit signal is "knife edge diffracting" off that ridge and at that range, you should get it with the antenna mentioned. (You have to tilt the antenna UPwards ..not at the horizon...stand behind it and aim it at the top of the ridge. The antenna I suggested costs all of 25 bucks...much cheaper than your non-peforming Terk.
Meklos & Lefty...
I notice Lefty has a DLP set, and I think this may be a small reason why they see less problems. We have 2 HDTVs and 2 HR20s in my home. The DLP 46" Sammy in the den has much less noticeable blocking, if any, then my 32" LCD Sammy on the same Mpeg-4s.
Just food for thought.
If they were moving images I would agree. These are static screen pauses, however. This is going near the spot I see while viewing it live, pausing slightly before, then pressing the FF button to go frame by frame.
It's in the recording itself.
Spoke to an engineer at the station where these images are originating. He was very nice on the phone, willing to listen to my information and observations. He confirmed that D* is taking the output of their MPEG2 OTA encoder and feeding that to D*s encoder farm. The SD signal, however... it is being grabbed in raw digital format (the best quality available) via SDI270 (a 270Mbit/sec data feed consisting of R/G/B at 90Mbits/sec each).
He basically said that his interest had been piqued, and that they did have a D* receiver and would try to see what I am seeing (receiver isn't working right now, he said). He also said that it would be difficult for him to point the finger at D*, but I told him that it was my intention to record the OTA and MPEG4 versions of a program I know will show the problem.
Also gave him information on this forum and this thread. He may be lurking here soon. Would be really nice to have someone who is on the broadcast side of this problem who is able to help rule out the local station as the cause of the isssues. He said that at most, they would just be able to complain - but I have hope that they would listen to the signal source more than they would generic complaint calls coming in to their CSRs.
I'll try to post more captures over the upcoming days, and also to start recording the OTA versions as soon as my HR20 gets the new code.
LameLefty
12-08-06, 12:14 PM
Meklos - I'm glad you called the guy at WTVF. As I said last night, CBS is MUCH worse for these glitches (though mine aren't as bad as yours apparently) than the other networks. Some people in other cities have speculated that D*'s MPEG4 issues are worse with 1080i broadcasts from NBC and CBS than with the 720p stuff from ABC and Fox, and I might tend to agree - not really sure yet. NBC was glitch-free and macroblocking-free but noticeably less detailed, as if NBC is somehow dialing-down the sharpness of their source material.
Anyway, please keep up with your posts and what you determine.
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