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you have to be kidding me


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#51 OFFLINE   Meklos

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Posted 30 July 2007 - 03:18 PM

This would explain why some mpeg4 locals are better than the corresponding OTA ATSC signal.


Technically impossible.

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#52 OFFLINE   pdxBeav

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Posted 30 July 2007 - 03:40 PM

Technically impossible.



If DirecTV takes the OTA ATSC stream then I agree, but I thought there were some cases where they were getting the pre-ATSC stream. In cases where the local station reduces the HD bitrate in order to multicast then it seems possible that the mpeg4 locals *could* be better than the correspoding OTA signal because D* is starting with something better than the OTA signal.

I don't know any specific details about how D* receives the local feeds other than something I read in an interview. I think we're all saying basically the same thing that each time you compress the result gets worse and that the closer you can move to the source the better the result *can* be.

#53 OFFLINE   brianp6621

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Posted 30 July 2007 - 04:05 PM

You cannot take the output of one lossy compression scheme (MPEG-2) and feed it into another lossy compression scheme (MPEG-4) and get an output that looks any better than either the original input (probably HD-SDI) or the original compression output (MPEG-2).

It isn't possible - regardless of bitrates.

I understand that, and I NEVER said you could.

Now if you want to get more complicated and talk about how D* is doing additional MPEG-2 to MPEG-2 transcoding to get the bitrate down, that's another story. But the same thing holds true. Every artifact created by the MPEG-2 encoding process will be encoded into the MPEG-4 stream - PLUS the artifacts created by MPEG-4 itself.


Exactly. All I was saying is that if it is delivered to directv in one format and they are currently re-encoding with MPEG2 (2nd generation loss) then changing that to re-encoding with MPEG4(same 2nd generation loss) could potentially result in a BETTER image than what we have now.

No one is talking about source material because almost no-one sees it, certainly not those of use looking at DTV channels.

#54 OFFLINE   brianp6621

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Posted 30 July 2007 - 04:08 PM

Precompressed with MPEG-2. People think that somehow by getting some high-bitrate feed from the local station that they're going to be somehow getting the original data in an unmodified uncompressed format.

For network shows, the best they're going to get is the output of the MPEG-2 encoding process. The networks aren't going to drop the dime for 2 gigabits a second to each affiliate that's broadcasting, and D* can't get just 'one' feed from each network (uncompressed) to feed the pristine uncompressed show into the MPEG-4 encoders.

So until the backend architecture changes to where D* can either get an unmolested original signal via HD-SDI... or where they can get the signals to be originally compressed into MPEG-4... we're still going to be stuck with viewing the doubly-artifact-filled MPEG-4 compressed signal that was generating by transcoding an artifact-filled MPEG-2 signal.



This may be the problem with my statement. I was basing it on the fact that someone else stated that DTV was re-encoding MPEG2 material again to a lower bitrate (2nd generation loss).

Is this not the case currently or is it only the case on certain channels?

#55 OFFLINE   Stuart Sweet

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Posted 30 July 2007 - 04:22 PM

Precompressed with MPEG-2. People think that somehow by getting some high-bitrate feed from the local station that they're going to be somehow getting the original data in an unmodified uncompressed format.

For network shows, the best they're going to get is the output of the MPEG-2 encoding process. The networks aren't going to drop the dime for 2 gigabits a second to each affiliate that's broadcasting, and D* can't get just 'one' feed from each network (uncompressed) to feed the pristine uncompressed show into the MPEG-4 encoders.

So until the backend architecture changes to where D* can either get an unmolested original signal via HD-SDI... or where they can get the signals to be originally compressed into MPEG-4... we're still going to be stuck with viewing the doubly-artifact-filled MPEG-4 compressed signal that was generating by transcoding an artifact-filled MPEG-2 signal.


Completely agreed and understood. My point is more that subjective words like "better" or "worse" are not as appropriate here. We all agree that you lose integrity and detail with recompression. No argument.
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#56 OFFLINE   hasan

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Posted 30 July 2007 - 04:33 PM

I'm not arguing with hasan. I agree completely. I just want to inject that "better" and "worse" are often in the eye of the beholder. If the content provider massages the signal by adjusting brightness, contrast, black level, sharpness, noise removal, etc., the result, even when recompressed, could be viewed as "more pleasing" to the average person even if it is not as true to the original and lacks detail that the original had.

Shows are usually delivered from the networks to the local stations via satellite, precompressed and ready for broadcast. They are passed bit for bit to the transmitter without additional processing at the broadcast sites.

Most locals lack the ability to store or significantly alter HD signals. That's changing slowly.


Absolutely Lamont. There are so many variables to consider, to be sure...and subjective interpretation of picture quality is something that cannot be ignored. You still have to put your keester in front of the box and watch it!:)

I will say that my own experience pretty well lines up with the math and science of it all (on the surface). Lossy Transcoding isn't something I'm fond of. I'll get a good look at it someday....it's a race to see if I get mpeg-4's first from the new HD channels, or my local HD MPEG-4's miraculously show up some day.:rolleyes:
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#57 OFFLINE   Jeremy W

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Posted 30 July 2007 - 04:39 PM

Shows are usually delivered from the networks to the local stations via satellite, precompressed and ready for broadcast. They are passed bit for bit to the transmitter without additional processing at the broadcast sites.

Fox is the only network that works anything like you say. All of the other networks deliver HD to the affiliates at ~45mbps, and the affiliates re-encode the signal at whatever bitrate, from 19mbps down, they deem necessary.

#58 OFFLINE   sigma1914

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Posted 30 July 2007 - 05:10 PM

I don't know the specific details of how your locals are fed to DirecTV, but you're supporting my point that mpeg4 will not necessarily look like crap. There are a lot of factors that go into determining picture quality and mpeg2 vs. mpeg4 isn't the only factor.

Also, I remember reading an interview somewhere with DirecTV and the person said that some of the locals feed their pre-ATSC signal to DirecTV where it is then encoded to mpeg4. This would explain why some mpeg4 locals are better than the corresponding OTA ATSC signal.

The only point I'm trying to make is that there are many factors involved and just because DirecTV re-encodes an mpeg2 signal into mpeg4 doesn't necessarily mean it'll look like crap.


I think I misread your post the first time, I was half awake lol. :D

#59 OFFLINE   BigJ52

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Posted 30 July 2007 - 05:33 PM

I called Directv and told them about the ESPN & ESPN 2 HD issues. They acted like this was the first they heard of the problem. They said they would take this to their "Escalation" department and look into it. Now will anything get done about it I don't know...

I did tell them there were many others on the Internet who said they were having the same issues so I wasn't the only one having the problem. Probably wouldn't be a bad idea if others called regarding this same issue though.

#60 OFFLINE   Meklos

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Posted 30 July 2007 - 05:38 PM

Fox is the only network that works anything like you say. All of the other networks deliver HD to the affiliates at ~45mbps, and the affiliates re-encode the signal at whatever bitrate, from 19mbps down, they deem necessary.


45Mbits/sec, but still MPEG-2 encoded...

#61 OFFLINE   Jeremy W

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Posted 30 July 2007 - 05:41 PM

45Mbits/sec, but still MPEG-2 encoded...

Yes, but that 45Mbps signal looks way better than what they're pumping out OTA.

#62 OFFLINE   wilbur_the_goose

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Posted 30 July 2007 - 05:47 PM

I've been watching ESPN HD for about 2 hours on my HR20 - zero dropouts.

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#63 OFFLINE   Meklos

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Posted 30 July 2007 - 05:51 PM

Yes, but that 45Mbps signal looks way better than what they're pumping out OTA.


I'll have to call my local affiliate engineer and ask again, but I'm pretty sure that they feed the affiliates the max-OTA bitrate, not 45 Mbits/sec... There'd be no need to pay for the extra bandwidth. And either way, you're still going to end up with artifacts.

In any case, D* has been trying to pull the wool over people's eyes by saying that their MPEG-4-delivered locals (via sat) are going to somehow magically look better than the MPEG-2 encoded source.... and it just ain't so.

#64 OFFLINE   veryoldschool

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Posted 30 July 2007 - 06:03 PM

In any case, D* has been trying to pull the wool over people's eyes by saying that their MPEG-4-delivered locals (via sat) are going to somehow magically look better than the MPEG-2 encoded source.... and it just ain't so.

Where I am, MPEG-4 looks "almost" as good as my OTA MPEG-2, to the point that it is so close when I A/B the two, it doesn't matter [to me]. While in the same DMA, there is a users that was watching a basketball game and one of the player's dreadlocks look horrible in MPEG-4 verse OTA.
I'm sure this comes down to personal taste, but I don't care for dreadlocks much anyway.
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#65 OFFLINE   Meklos

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Posted 30 July 2007 - 06:21 PM

Where I am, MPEG-4 looks "almost" as good as my OTA MPEG-2, to the point that it is so close when I A/B the two, it doesn't matter [to me]. While in the same DMA, there is a users that was watching a basketball game and one of the player's dreadlocks look horrible in MPEG-4 verse OTA.
I'm sure this comes down to personal taste, but I don't care for dreadlocks much anyway.


Well, there are certain patterns (and sometimes even certain colors / color combinations) that end up looking horrible when put through a certain codec. They're sometimes called 'codec busters'. Each codec is different, but each has some idiosyncracy where it looks like crud. Today I saw something on one of the sports channels at lunch where one of the hosts had on a pin-striped suit. They went in for a closer shot on that guy exactly one time... and the output was so bad that they didn't do it again. Looked like it was vibrating.

And yes, it sometimes happens uncompressed, pre-codecs.

I see the breakups most often in my DMA when watching stuff that changes screen contrast very quickly. Full screen white followed by anything usually ends up in tiling and macroblocking, and even bright sections of the screen will break it up in that portion of the image.

#66 OFFLINE   veryoldschool

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Posted 30 July 2007 - 06:29 PM

Well, there are certain patterns (and sometimes even certain colors / color combinations) that end up looking horrible when put through a certain codec. They're sometimes called 'codec busters'. Each codec is different, but each has some idiosyncracy where it looks like crud. Today I saw something on one of the sports channels at lunch where one of the hosts had on a pin-striped suit. They went in for a closer shot on that guy exactly one time... and the output was so bad that they didn't do it again. Looked like it was vibrating.

And yes, it sometimes happens uncompressed, pre-codecs.

I see the breakups most often in my DMA when watching stuff that changes screen contrast very quickly. Full screen white followed by anything usually ends up in tiling and macroblocking, and even bright sections of the screen will break it up in that portion of the image.

24 on Fox last season had some fast camera pans that would drive me nuts as everything took too long to sync, but I don't know if it was my local station or not [as they are/can be crappy in their own right] .
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#67 OFFLINE   Jeremy W

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Posted 30 July 2007 - 10:43 PM

I'll have to call my local affiliate engineer and ask again, but I'm pretty sure that they feed the affiliates the max-OTA bitrate, not 45 Mbits/sec... There'd be no need to pay for the extra bandwidth.

The reason they do it is because the affiliates have to re-encode the signal to put in subchannels. It'll look a lot better if they're starting with 45mbps instead of 19mbps.

#68 OFFLINE   oenophile

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Posted 30 July 2007 - 11:55 PM

FWIW, I just watched ESPN 2's HD broadcast of the Los Angeles Galaxy soccer game (where Beckham played for the first time) and noticed the same 1 second drop outs described here. Never noticed that before. Looked to me like ESPN issue...

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#69 OFFLINE   Bathel

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Posted 30 August 2007 - 12:09 PM

I have the dropouts too, but if I 6 second skip back, the video magically is there.

Has anyone else tried to rewind and see if the video shows up the second time? This sounds more like a box issue if that's the case.

#70 OFFLINE   Jeremy W

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Posted 30 August 2007 - 04:01 PM

I have the dropouts too, but if I 6 second skip back, the video magically is there.

Has anyone else tried to rewind and see if the video shows up the second time? This sounds more like a box issue if that's the case.

What you're talking about is a box issue. It's completely separate from the ESPN HD dropouts that have been resolved.




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