Ive been using my converter box on all of my "everyday" tv sets thoughout the house. I figured Id just start using them and get used to it, which has been pretty consistent for about 2 months now. Ive noticed a particular annoying flaw. It has to do with pixilation, not due to reception though. Whenever I watch a program and the screen fades into a black screen, or vice versa, you notice a very bad pixilated image on the screen during the transition period. I also notice that fast moving objects on the screen are more likely to look distorted with a pixilated image. Its like a step backwards, also when you factor in the numerous intermittent drop outs of audio, it just adds to the frustration.
With my antenna in the attic, TV reception is perfect on analog, yet digital is nothing but a nuisance.
I can't wait to see what happens come 2-17.......

The annoyance with fast moving objects being distorted is the only reason I have not a purchased a "new" television.

I have browsed new technology tv's (LCD's/PLASMA/DLP) for at least the last 3 years and they all suffer from a slow response. No brand is better or worse. No technology is better or worse. No price is better or worse. From the 400$ wallyworld sets to the gargantuan multi -thousand dollar sets.

That being said, even a $397 wallyworld set produces a great picture when given a good signal, and one is not watching a fast moving object.

I haven't yet gone to a set top box for digital. I do use the General Instruments cable box from mediacom cable on an old Curtis Mathes daily watcher console. The rest of the tv's are fed direct from cable. Within the last month I have noticed the very problems you describe coming direct from the cable. It is really annoying. I expect it not to get any better, whenever the plug is pulled on all the analog xmitters.

Pixelation during a low-light scene or fast-moving scene can be very annoying. It happens on digital cable channels as well. I could be wrong, but always considered it to be caused by lack of bandwith and/or over use of compression.

While it may seem like a step backwards, we may as well embrace digital since it ain't going away. :scratch2: At least there's no snow or herringbone interference.

Doug -

Which channels are you seeing this on? I've been noticing it on 26 mostly. I too have heard that it's most likely a compression issue. There's plenty of signal according to the signal meter.

If you happen to have a digital tuner card (or USB TV stick) available, you can use a program called TSReader Lite to examine the streams and see how much bandwidth is assigned to each subchannel. Each digital channel has 19 megabits/second available for distribution among its subchannels.

A good source for further information is the Chicago OTA thread over on avsforum. There are quite a few knowledgeable folks there, including an engineer from WCIU.

-Jim

The pixelation during fast motion is one nusience that gets to me. I don't know how sports fans can live with it.

The converter boxes do not offer the faster refresh rates that the upper tier LCD sets have now. For good rendition of fast motion (i.e. sports), the typical digital artifacts that appear at the 60hz refresh rate mostly disappear at 120hz. Since DTV STB's convert everything to an equivalent of 480i, the picture is literally crushed to death (high compression ratio).

After watching OTA DTV on my 32" LCD set for the last few years, I've [sadly] grown used to it. The STB's on the other hand, offer a much lesser quality picture. I hooked one up to my LCD to gauge the difference between the TV tuner and the STB and was shocked to see how much - even on 480i source material - is lost thru the RF modulator. The line outputs offer a little better picture, but still really shabby compared to what the Tv's built-in tuner can render. That said, you really can't expect much from 480i. It's actually less sharp than a good NTSC signal. We have RTN on one of our DTV subchannels here, and seeing those old programs on DTV is horrid, as the broadcast format is very unforgiving to poor quality video sources. (RTN doesn't exactly have the greatest copies of their programs on hand, either) In contrast, my old DVD player has a DTV tuner built in, and when hooked up via the composites to a compatible CRT set, it looks pretty decent. Not sure why the older unit outperforms the newer STB's.
720 & 1080 on the other hand outperforms NTSC by a mile, assuming that you can overcome reception issues. If the weather is calm, I get great reception from 30 miles out. If the wind is blowing, then my UHF's are all futzed up (too many trees/forest around here). In contrast, my brother has DTV via cable, and the compression the cable company adds to save bandwidth is very noticeable, esp. on 1080i programming. Maybe if they ditched 20 or 30 channels that nobody ever watches they could offer up the local HD shows at the quality they're broadcast at.

I like the fact that analog broadcasting was still usable even in weak signal instances (and more easily DX'ed - another hobby going bye-bye for me), but I don't think I'd give up my widescreen HDTV to go back to NTSC on a daily basis, especially for movies, sports in HD and anything graphics heavy like the local HD newscasts.

I think one of the things we have to admit here is that unlike NTSC, we're seeing a broadcast format that has the capability of exceeding the source material's quality. In other words, with NTSC the video at the station was always better than what went out thru the transmitter, and the comparatively low resolution of CRT sets hid most of that quality loss. With OTA digital, what is seen at the station's master control is exactly what is seen on the LCD/Plasma screen at the other end.

AndyMack has confused two different effects (or maybe 3). All the observations of picture quality are valid, but there are independent cauises for some of the effects.

Fist thing mentioned in above posts was the quality during fade to black. This is an artifact of low bit rate (high compression) and occurs because MPEG2 does not have a tool to determine when this is occurring and signal it with a few bits. (MPEG4 does.) Unfortunatley, when MPEG2 was standardized, with the bit rates the encoders needed, all pictures including fades needed lots of bits compared to today's encoders, so it wasn't apparent that fades would become a special case. The problem is that the encoder sees a difference from frame to frame that is large everywhere in the picture, and can't transmit enough bits to create those completely new frames, which is what it has to do (since it has no way to simply signal "the next frame is the same as the last one, but attenuated"). So now, when encoders can successfully encode most images in fewer bits, and therefore multi-programs are broadcast, the cases with reduced quality stand out. If it's any consolation, the encoder designers have been steadily improving things, although broadcasters tend to push to the limit how many programs they multiplex. An exception has been CBS (at least on CBS -owned stations), who have refused to do multi-cast.

A related encoding degradation can occur during fast motion. Usually this is not so severe, since bits are not needed to update the whole picture. However, the visibility will depend strongly on how close you are sitting to the TV.

A completely independent degradation that was mentioned above is motion smear in LCD TVs. 120Hz LCDs reduce or eliminate this, at the risk of introducing some strobing instead. Some 240 Hz LCDs will be introduced this year, but it's not clear if this is a large improvement compared to 120 Hz for live material. It should improve movies, since it is a multiple fo the 24 Hz movie frame rate.

The third thing mentioned, down conversion to 480i in the converter boxes, has nothing at all to do with data compression. The major variable in the conversion quality is the filtering used to do the line-number and horizontal resolution conversion. Too much filtering, and the picture looks soft; too little, and all the old analog defects like interlace twitter, vertical aliasing, and chroma dot crawl are exaggerated. Down converted DTV brtoadcasts viewed on an analog set may show some improvement in color detail, the same as for DVD playback.

I was going to comment on the compression being the cause of the "fade to black" pixellation. This happens on some DVDs, too - especially those where the data is overcompressed or the picture is just dark. Lots of annoying pixellation in the Star Trek: Deep Space Nine DVDs - both from overcompression on Paramount's part and due to the fact that the series has a very "dark" look, with lots of shadows.

Another time you can see weird pixellation is during some sporting events - I've noticed that FOX has very little motion blur during football games on my 47" Philips LCD, but that CBS tends to have quite a bit more.

One other cause of pixellation on digital OTA broadcasts - weak signal due to being too far from the transmitter, something interfering with the transmission or a badly aimed antenna.

Another misconception is that TX DX is going "bye bye". One just turns to DXing digital TV instead. It is more challenging than analog TV DXing, but far from impossible. DXers have seen DTV at over 1000 miles by both tropospheric effects and sporadic-E skip, and some have seen more than 300 digital stations from one receiver point.

That's pixelation caused by the networks being greedy bastards and over-compressing their broadcasts. The official term for it is macroblocking.

This is why I detest satellite TV. I can't fucking stand the over-compression, and I have no clue how it is that most people don't notice. I really wish they didn't use the antiquated MPEG format. I download a lot of DivX videos and they look great on my computer, I've never noticed ANY macroblocking on any DivX video I've ever dowloaded.

It's not the TV's though, it's what you're feeding them. On the plasma downstairs (Panasonic 42PX80U on OTA), macroblocking is VERY noticeable whenever The CW is pumping out HD. I don't notice it much when they're playing SD stuff. I don't see it much on Fox, and NBC is so-so but it seems to be almost non-existant during Saturday Night Live. And of course when you feed it Blu-Ray, you don't see any at all.