D* compression

[ljp416jmp]

Folks,

First off, this forum is the best. Better by far than the others out there, with the most knowledgeable people.

Now, I for one am getting quite upset about the declining quality of D* "HD" broadcasts....I didn't spend $5K on an HDTV to have them squeeze out additional bogus channels like the "worm farm" channel. In fact, the HD "pkg" stinks....most of the relevant content is on the networks (Superbowl, Masters, etc.) which is independent of the HD pkg (I'm in the New York DMA).

Now, I know they're adding significant bandwidth shortly. So, here's the question for everyone: When the new birds are up and running, will the MPEG4 compression look BETTER than the overcompressed crap they're running through us now?

Appreciate any input.

 

[hancox]

Honestly, anyone claiming to "know the answer" to this question is speculating.

I can only say through a series of educated guesses that there will be *some* improvement, mostly due to the combination of:

1) Channels moving from 101/110/119 to the Spaceways, freeing space (specifically NFLST)
2) Infinite space (comparitively) on the Spaceways, considering markets will take ages to roll onto them
3) MPEG4 taking up less space for a comparable picture

Again, D* could decide to not up the PQ when they roll over, but I would bet they will at least a little, mostly because I have a feeling the "freebie HD package" stuff is more a CYA for them.

 

[ScottChez]

This week I will have the HD Tivo and Dish HD 942 on the same TV


Whats the best way to do a Pic quality comparision.

 

[hancox]

do a same input/output look at, say, ESPN-HD and HDNet (takes the 720p/1080i thing out of play too)

 

[dragon002]

Honestly, anyone claiming to "know the answer" to this question is speculating.

I can only say through a series of educated guesses that there will be *some* improvement, mostly due to the combination of:

1) Channels moving from 101/110/119 to the Spaceways, freeing space (specifically NFLST)
2) Infinite space (comparitively) on the Spaceways, considering markets will take ages to roll onto them
3) MPEG4 taking up less space for a comparable picture

Again, D* could decide to not up the PQ when they roll over, but I would bet they will at least a little, mostly because I have a feeling the "freebie HD package" stuff is more a CYA for them.

hancox,

congratulations, that was the BEST answer to that question that ive seen posted ANYWHERE.

dragon

 

[vurbano]

So, here's the question for everyone: When the new birds are up and running, will the MPEG4 compression look BETTER than the overcompressed crap they're running through us now?

I think thats a great question. I was excited when Voom started talking about mpeg4. BUT, mpeg4 is supposed to double the capacity of everyones current bandwidth. I.E., if your running 19 mbps under mpeg2 you can run 9 mbps under mpeg4 and the picture is equivalent "they" say. But as a consumer you have to ask yourself a question. Mpeg4 must compress 2x as much as mpeg2. Correct? It fits in half the space. I sure hope the experts are right, but Im skeptical about doubling the compression on a video signal and coming up with a better looking product. This will be interesting to see. If anyone has some screen shots of the same material in Mpeg2 at 19 mbps vs mpeg4 at say 9 mbps it would be a great post!

 

[Dino]

MPEG4 really does offer the same quality at half the size (or less!). I don't have any quick links for comparisons, but I do occasionally watch large video files from the internet, and here's an example:

A typical 45 minute video file in NTSC format (standard definition) encoded in SVCD (MPEG2): ~850 megs.

A typical 45 minute video file of something originally in high definition, still widescreen, encoded in XVID (an MPEG4 variant): ~350 megs.

NOTE: NEITHER of these is broadcast quality of either standard or high definition quality, BUT this is a good example of relative compression capabilities. The XVID files typically look really good; I pipe them from my computer through my HD television and the 'unitiated' still think it's real HD, while the SVCD just looks like a real good VHS recording.

Trust me, they really can simultaneously double bandwidth and slightly improve image by going from MPEG2 to MPEG4.

--Dino

 

[colofan]

So the question is on live programs how much predictive buffer to they need in time to do a "good" job of compression.

With films and other pre-recorded material I can see the compression being done well but I have issues even now with the mpeg-2 stuff with live broadcast. Of course I consider temporal data as important as resolution.

 

[Dino]

That's an excellent point, colofan-- MPEG4 is has much higher processing demand than MPEG2, both for encoding and decoding, which is one of the reasons it has been adopted somewhat slowly. I would think the chances of artifacting in live, high-motion video would be increased with MPEG4.

Another question that I have wondered for a time-- since MPEG2 and MPEG4 do not have a 'standard' cross-compression algorithm (that is, there is no straightforward formula for MPEG2 to MPEG4, it's more like decompress from MPEG2 then recompress into MPEG4), will we see an increased loss of picture quality when native MPEG2 (like from the broadcast networks) gets recompressed to MPEG4, because the original MPEG2 compression is lossy and the MPEG4 recompression is lossy on top of that?

Unlike my last post, I am not as sure about all the claims I made in this one. Maybe a compression expert can weigh in on this for us. I am especially worried that recompression will mean that LIL HD channels will never look as good as OTA.

--Dino

 

[vurbano]

Good points Dino. Id just like to see it on HD and on at least a 50 inch 1080i monitor. Ive heard about it for over a year, but never seen a real HDTV bigscreen comparison of the images.

 

[hancox]

That's an excellent point, colofan-- MPEG4 is has much higher processing demand than MPEG2, both for encoding and decoding, which is one of the reasons it has been adopted somewhat slowly. I would think the chances of artifacting in live, high-motion video would be increased with MPEG4.

Another question that I have wondered for a time-- since MPEG2 and MPEG4 do not have a 'standard' cross-compression algorithm (that is, there is no straightforward formula for MPEG2 to MPEG4, it's more like decompress from MPEG2 then recompress into MPEG4), will we see an increased loss of picture quality when native MPEG2 (like from the broadcast networks) gets recompressed to MPEG4, because the original MPEG2 compression is lossy and the MPEG4 recompression is lossy on top of that?

Unlike my last post, I am not as sure about all the claims I made in this one. Maybe a compression expert can weigh in on this for us. I am especially worried that recompression will mean that LIL HD channels will never look as good as OTA.

--Dino

I wouldn't worry too much. ALL DBS content is already going through something similar now, as content doesn't come to the DBS companies in the same format it gets beamed down to the sats.

Yeah, I don't expect the mother feed from the broadcasters to be *perfect* - but I expect it to be sig. better then the DBS feeds we're all getting now. The hope is that MPEG4 will allow the DBS companies to have a feed closer to the source quality, while allowing enough bandwidth to have current/better selection

 

[Dino]

This is what I suspected and wanted to hear-- that the original source is higher quality than anything we see, then converted to MPEG2 at whatever squeezed rate the accountants tell the providers will make for the most subscribers. If this is the case, then it is perfectly possible for the MPEG4 compression to give us better or at least equal video quality at half the bandwidth.

Thanks, hancox.

There is still the question of how well the conversion will go on-the-fly with MPEG4 compared to MPEG2, especially since this information from hancox seems to indicate that ALL signals are compressed on-the-fly from the original content.

--Dino

 

[colofan]

Well if D* can get the video feed lets say via dedicated line and OTA then I would agree with the MPEG4 could look better. The conversions that are lossy though between MPEG2 and MPEG4 could cause new problems.

 

[ljp416jmp]

Thanks a lot for the replies folks...i guess we'll have to wait and see...my guess it'll look better initially, since they'll have plenty o' bandwidth, then crank up the compression as they add more HD locals. Nothing beats OTA though for PQ.

 

[jgold50]

I dont think 4 is better than two but that it takes up less bandwidth so from the providers point of view it increases capacity. What I have seen of cable digital channels makes me sick and I dont think the HD at 720p will be any different at mpeg4 vs 2
Now direct is supposed to have the new birds up by july and that it will be a costly service. You will have to own your own reciever which will be time relevant to be replaced when newer technologies are available. That is the upside of cable vs satellite HD.


Jgold

 

[jgold50]

I dont think 4 is better than two but that it takes up less bandwidth so from the providers point of view it increases capacity. What I have seen of cable digital channels makes me sick and I dont think the HD at 720p will be any different at mpeg4 vs 2
Now direct is supposed to have the new birds up by july and that it will be a costly service. You will have to own your own reciever which will be time relevant to be replaced when newer technologies are available. That is the upside of cable vs satellite HD.


Jgold

 

[charper1]

You will have to own your own reciever which will be time relevant to be replaced when newer technologies are available. That is the upside of cable vs satellite HD. Jgold

It has been shown numerous times that the rate at which new devices are required generally lends to owning being the cheaper method (even if you didn't obtain it for free in the first place). With cable you constantly pay a per month fee for your device and over the life span of that device you end up paying more; This also assumes that D* continues the free trade up subsidy policy. The ONLY thing cable has ever had over satellite is that you at least think you have a local person to talk too, although that rarely means they know any more or less so it is merely cosmetic.