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Posted Oct 10, 2010
6:22:47 AM
PQ on U-verse -- 720p vs 1080i

I recall reading a post somewhere that someone mentioned the 720p sourced broadcasts look better than the 1080i sourced broadcasts on U-verse.  I think the theory was the extra overhead of the 1080i resolution and that progressive sources compress better.  I was wonderig if this was perhaps true?  

 

I've made the observation that HLN HD has issues the pixelation with sudden graphic and camera fade in/outs.  In watching similar things happen on ESPN I did not see  the pixelation bursts that were happening on HLN.  

 

A little wiki research shows that HLN is 1080i and ESPN is 720P. 

I recall reading a post somewhere that someone mentioned the 720p sourced broadcasts look better than the 1080i sourced broadcasts on U-verse.  I think the theory was the extra overhead of the 1080i resolution and that progressive sources compress better.  I was wonderig if this was perhaps true?  

 

I've made the observation that HLN HD has issues the pixelation with sudden graphic and camera fade in/outs.  In watching similar things happen on ESPN I did not see  the pixelation bursts that were happening on HLN.  

 

A little wiki research shows that HLN is 1080i and ESPN is 720P. 

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PQ on U-verse -- 720p vs 1080i

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Oct 10, 2010 8:02:56 AM
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Well, not too many opinions yet but I found this article.

 

http://www.bluesky-web.com/numbers-mean-little.htm

 

The basic premise is that compressing 1080i results in more artifacts compared to 720p.  Unfortunately, most HD networks are 1080i and the U-verse compression is rather aggressive.  

Well, not too many opinions yet but I found this article.

 

http://www.bluesky-web.com/numbers-mean-little.htm

 

The basic premise is that compressing 1080i results in more artifacts compared to 720p.  Unfortunately, most HD networks are 1080i and the U-verse compression is rather aggressive.  

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Oct 10, 2010 9:06:02 AM
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Edited by michail77 on Oct 10, 2010 at 9:33:18 AM

So far I've watched a few of the 720p networks and I really think this is the case. They do seem to have better picture quality on U-verse compared to the 1080i source.

 

So if 720p is a much better format for delivery of compressed sources why are so many networks delivered over compressed providers 1080i?

So far I've watched a few of the 720p networks and I really think this is the case. They do seem to have better picture quality on U-verse compared to the 1080i source.

 

So if 720p is a much better format for delivery of compressed sources why are so many networks delivered over compressed providers 1080i?

Re: PQ on U-verse -- 720p vs 1080i

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Oct 10, 2010 9:44:34 AM
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ACE - Expert

That was me that mentioned it here in regard to football, have to say the Michigan/Michigan State game onABC HD (720p) looked absolutely great yesterday, even hardly any weird grass look (compressionartifact). 


Now I won't totally agree w/regular programming on that, the 2 best looking HD programs I watch IMHO are The Mentalist and Criminal Minds, on CBS (1080i).  In many other cases 1080i channels have good HD and is really dependent on the quality of the source material.  I've seen some real stinker quality HD on ESPN/ABCs (720p) in addition to real good HD.


Actually everything is shot in 1080p, then downconverted to 1080i or 720p.  At this point they are pretty comparable.  It's when ATT puts the H.264 algorhythm on the stream and 1080i needs about 20% more bandwidth for the extra info in the signal.Smiley Wink


Chris

 


Please NO SD stretch-o-vision or 480 SD HD Channels
1-866-465-1496 for direct TS to avoid Mr. Voice recognition
Your Results May Vary, In My Humble Opinion
I Call It Like I See It, Simply a U-verse user, nothing more

 

That was me that mentioned it here in regard to football, have to say the Michigan/Michigan State game onABC HD (720p) looked absolutely great yesterday, even hardly any weird grass look (compressionartifact). 


Now I won't totally agree w/regular programming on that, the 2 best looking HD programs I watch IMHO are The Mentalist and Criminal Minds, on CBS (1080i).  In many other cases 1080i channels have good HD and is really dependent on the quality of the source material.  I've seen some real stinker quality HD on ESPN/ABCs (720p) in addition to real good HD.


Actually everything is shot in 1080p, then downconverted to 1080i or 720p.  At this point they are pretty comparable.  It's when ATT puts the H.264 algorhythm on the stream and 1080i needs about 20% more bandwidth for the extra info in the signal.Smiley Wink


Chris

 


Please NO SD stretch-o-vision or 480 SD HD Channels
1-866-465-1496 for direct TS to avoid Mr. Voice recognition
Your Results May Vary, In My Humble Opinion
I Call It Like I See It, Simply a U-verse user, nothing more

 

*The views and opinions expressed on this forum are purely my own. Any product claim, statistic, quote, or other representation about a product or service should be verified with the manufacturer, provider, or party.

Re: PQ on U-verse -- 720p vs 1080i

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Oct 10, 2010 10:08:52 AM
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I guess I'm nit picking on pixelation but on DirecTV I see less (not none) artifacts on 1080i sources compared to U-verse.  The experimental watching I've done seems to indicate 720p sources don't seem to suffer as much if at all.

 

With HLN HD (1080i) the graphics and fast source cuts are driving me crazy.  The compression just can't handle it.  It might be HLN but I think it's the compression not being able to deal with the quick changes. DTV doesn't have HLN in HD so I can't make that comparison.  ESPN does similar graphics and camera cuts and I haven't seen that make pixel fireworks.

 

Most of these non-OTA channels are delivered over networks with a bit of compression, unless I've heard your on Verizon's fios.  So if 720P is better at being compressed it seems logical they'd be in that format.

 

I guess I'm nit picking on pixelation but on DirecTV I see less (not none) artifacts on 1080i sources compared to U-verse.  The experimental watching I've done seems to indicate 720p sources don't seem to suffer as much if at all.

 

With HLN HD (1080i) the graphics and fast source cuts are driving me crazy.  The compression just can't handle it.  It might be HLN but I think it's the compression not being able to deal with the quick changes. DTV doesn't have HLN in HD so I can't make that comparison.  ESPN does similar graphics and camera cuts and I haven't seen that make pixel fireworks.

 

Most of these non-OTA channels are delivered over networks with a bit of compression, unless I've heard your on Verizon's fios.  So if 720P is better at being compressed it seems logical they'd be in that format.

 

Re: PQ on U-verse -- 720p vs 1080i

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Oct 10, 2010 10:38:16 AM
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ACE - Expert

As to HLN, 1203, I don't see anything going on like you are reporting, everything looks just fine on my 42" Panasonic plasma. Smiley Wink


Chris

 


Please NO SD stretch-o-vision or 480 SD HD Channels
1-866-465-1496 for direct TS to avoid Mr. Voice recognition
Your Results May Vary, In My Humble Opinion
I Call It Like I See It, Simply a U-verse user, nothing more

 

As to HLN, 1203, I don't see anything going on like you are reporting, everything looks just fine on my 42" Panasonic plasma. Smiley Wink


Chris

 


Please NO SD stretch-o-vision or 480 SD HD Channels
1-866-465-1496 for direct TS to avoid Mr. Voice recognition
Your Results May Vary, In My Humble Opinion
I Call It Like I See It, Simply a U-verse user, nothing more

 

*The views and opinions expressed on this forum are purely my own. Any product claim, statistic, quote, or other representation about a product or service should be verified with the manufacturer, provider, or party.

Re: PQ on U-verse -- 720p vs 1080i

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Oct 10, 2010 10:54:56 AM
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I suppose I should stop looking for artifacts.  I see them on DirecTV now as well where I didn't notice them before.

I suppose I should stop looking for artifacts.  I see them on DirecTV now as well where I didn't notice them before.

Re: PQ on U-verse -- 720p vs 1080i

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Oct 10, 2010 11:18:01 AM
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ACE - Expert

Well, you were comparing the two services, it's inevitable that you are seeing these things. Smiley Very Happy


Chris


Please NO SD stretch-o-vision or 480 SD HD Channels
1-866-465-1496 for direct TS to avoid Mr. Voice recognition
Your Results May Vary, In My Humble Opinion
I Call It Like I See It, Simply a U-verse user, nothing more

 

Well, you were comparing the two services, it's inevitable that you are seeing these things. Smiley Very Happy


Chris


Please NO SD stretch-o-vision or 480 SD HD Channels
1-866-465-1496 for direct TS to avoid Mr. Voice recognition
Your Results May Vary, In My Humble Opinion
I Call It Like I See It, Simply a U-verse user, nothing more

 

*The views and opinions expressed on this forum are purely my own. Any product claim, statistic, quote, or other representation about a product or service should be verified with the manufacturer, provider, or party.

Re: PQ on U-verse -- 720p vs 1080i

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Oct 11, 2010 10:59:22 AM
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That's been my observation based on nothing but the eyeball test. 720p content looks pretty good and high motion scenes remain mostly sharp. 1080i looks mostly the same except when theirs a lot of motion. At that point it becomes a pixelated mess. 

 

I'm on a 65" 1080p Mitsu set, new to Uverse coming from DirecTV.  Uverse picture quality definitely suffers comparatively from high compression. 

That's been my observation based on nothing but the eyeball test. 720p content looks pretty good and high motion scenes remain mostly sharp. 1080i looks mostly the same except when theirs a lot of motion. At that point it becomes a pixelated mess. 

 

I'm on a 65" 1080p Mitsu set, new to Uverse coming from DirecTV.  Uverse picture quality definitely suffers comparatively from high compression. 

Re: PQ on U-verse -- 720p vs 1080i

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Oct 11, 2010 12:13:52 PM
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I think the differences between 720p and 1080i are why we see so many conflicting reports on the PQ.  

 

I'm also careful to note that the source into AT&T's encoders could be bad to begin with.  However, I'm thinking the 1080i sources don't make it out of the encoder without suffering some. Which, unfortunately, is the bulk of what the broadcasters are using.  

 

Notice cut scenes and fast motion on ESPN and the History channels (720p).  Then do the same with the 1080i stations, such as the various Discovery channels.

 

It seems it's common practice for cable and satellite operators to re-encode 1920x1080i to 1440x1080i in order to reduce artifacts.  I'm not sure if U-verse does this or if even they should. However, the more I read up on it the more it sounds like broadcasters should stick to 720p.  

 

Perhaps one of the engineers will chime in Smiley Happy.

I think the differences between 720p and 1080i are why we see so many conflicting reports on the PQ.  

 

I'm also careful to note that the source into AT&T's encoders could be bad to begin with.  However, I'm thinking the 1080i sources don't make it out of the encoder without suffering some. Which, unfortunately, is the bulk of what the broadcasters are using.  

 

Notice cut scenes and fast motion on ESPN and the History channels (720p).  Then do the same with the 1080i stations, such as the various Discovery channels.

 

It seems it's common practice for cable and satellite operators to re-encode 1920x1080i to 1440x1080i in order to reduce artifacts.  I'm not sure if U-verse does this or if even they should. However, the more I read up on it the more it sounds like broadcasters should stick to 720p.  

 

Perhaps one of the engineers will chime in Smiley Happy.

Re: PQ on U-verse -- 720p vs 1080i

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Oct 11, 2010 12:40:37 PM
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Here're some SomeJoe (he authors and edits HD material) posts on the subject:


http://forums.att.com/t5/TV-Programming/World-Cup-HD-picture-quality-just-as-poor-as-superbowl-and-o...


http://forums.att.com/t5/Equipment/720-or-1080-Installer-told-me-that-720-is-more-reliable/m-p/22037... Smiley Wink


Chris

 


Please NO SD stretch-o-vision or 480 SD HD Channels
1-866-465-1496 for direct TS to avoid Mr. Voice recognition
Your Results May Vary, In My Humble Opinion
I Call It Like I See It, Simply a U-verse user, nothing more

 

Here're some SomeJoe (he authors and edits HD material) posts on the subject:


http://forums.att.com/t5/TV-Programming/World-Cup-HD-picture-quality-just-as-poor-as-superbowl-and-other/m-p/2047827#M8110


http://forums.att.com/t5/Equipment/720-or-1080-Installer-told-me-that-720-is-more-reliable/m-p/2203785#M28730 Smiley Wink


Chris

 


Please NO SD stretch-o-vision or 480 SD HD Channels
1-866-465-1496 for direct TS to avoid Mr. Voice recognition
Your Results May Vary, In My Humble Opinion
I Call It Like I See It, Simply a U-verse user, nothing more

 

*The views and opinions expressed on this forum are purely my own. Any product claim, statistic, quote, or other representation about a product or service should be verified with the manufacturer, provider, or party.

Re: PQ on U-verse -- 720p vs 1080i

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Oct 11, 2010 1:01:18 PM
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I gave those a read over but I don't think that addresses what's going on at encoding time.  

 

I see numerous comments about Dish's PQ being so much better than U-verse.  The interesting thing is Dish supposedly down converts 1080i to avoid compression issues within the allocated bandwidth.  The theory being reduced compression issues are better than a messy higher resolution picture.

I gave those a read over but I don't think that addresses what's going on at encoding time.  

 

I see numerous comments about Dish's PQ being so much better than U-verse.  The interesting thing is Dish supposedly down converts 1080i to avoid compression issues within the allocated bandwidth.  The theory being reduced compression issues are better than a messy higher resolution picture.

Re: PQ on U-verse -- 720p vs 1080i

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Oct 11, 2010 4:12:52 PM
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Maybe he'll pop in here later to give you his detailed take on the subject. Smiley Wink


michail77 wrote:

I gave those a read over but I don't think that addresses what's going on at encoding time.  

 

I see numerous comments about Dish's PQ being so much better than U-verse.  The interesting thing is Dish supposedly down converts 1080i to avoid compression issues within the allocated bandwidth.  The theory being reduced compression issues are better than a messy higher resolution picture.


 

Maybe he'll pop in here later to give you his detailed take on the subject. Smiley Wink


michail77 wrote:

I gave those a read over but I don't think that addresses what's going on at encoding time.  

 

I see numerous comments about Dish's PQ being so much better than U-verse.  The interesting thing is Dish supposedly down converts 1080i to avoid compression issues within the allocated bandwidth.  The theory being reduced compression issues are better than a messy higher resolution picture.


 

Re: PQ on U-verse -- 720p vs 1080i

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Oct 11, 2010 6:32:41 PM
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The picture quality (i.e. artifact level) is dependent on the bitrate and the complexity of the source material.

 

A 1080i source is more complex than a 720p source, both because there are more pixels to encode (62.2 Mpixels/sec for 1080i vs. 55.3 Mpixels/sec for 720p), and because interlaced video is inherently more difficult to encode than progressive material (there are less opportunities to use accurate motion prediction).  To get the same artifact level (picture quality) for 1080i, you need about 20% more bitrate (about 10% for the additional pixels and another 10% to make up for the difficulty of interlaced video).

 

But, most providers, U-Verse included, do not make special consideration for 1080i material.  On U-Verse, both 720p and 1080i material are encoded and transmitted at 5.7 Mbps.  This is why the 1080i material doesn't look as good as it could.

 

If the bitrate for 1080i were upped to 6.8 Mbps, it would look (artifact-wise) as good as the 720p material.

 

The encoders that AT&T are using for U-Verse are the Motorola SE-5100 units, and they're using the constrained fidelity (capped VBR) mode.  The H.264 output from these units isn't the best MPEG-4 you can get, because these encoders don't implement all features of the codec, but they perform quite well anyway.

 

The picture quality (i.e. artifact level) is dependent on the bitrate and the complexity of the source material.

 

A 1080i source is more complex than a 720p source, both because there are more pixels to encode (62.2 Mpixels/sec for 1080i vs. 55.3 Mpixels/sec for 720p), and because interlaced video is inherently more difficult to encode than progressive material (there are less opportunities to use accurate motion prediction).  To get the same artifact level (picture quality) for 1080i, you need about 20% more bitrate (about 10% for the additional pixels and another 10% to make up for the difficulty of interlaced video).

 

But, most providers, U-Verse included, do not make special consideration for 1080i material.  On U-Verse, both 720p and 1080i material are encoded and transmitted at 5.7 Mbps.  This is why the 1080i material doesn't look as good as it could.

 

If the bitrate for 1080i were upped to 6.8 Mbps, it would look (artifact-wise) as good as the 720p material.

 

The encoders that AT&T are using for U-Verse are the Motorola SE-5100 units, and they're using the constrained fidelity (capped VBR) mode.  The H.264 output from these units isn't the best MPEG-4 you can get, because these encoders don't implement all features of the codec, but they perform quite well anyway.

 

Re: PQ on U-verse -- 720p vs 1080i

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Oct 11, 2010 7:56:50 PM
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Thanks, SJ, for popping in with your wisdom. Smiley Happy

Thanks, SJ, for popping in with your wisdom. Smiley Happy

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SomeJoe7777 wrote:

The picture quality (i.e. artifact level) is dependent on the bitrate and the complexity of the source material.

 

A 1080i source is more complex than a 720p source, both because there are more pixels to encode (62.2 Mpixels/sec for 1080i vs. 55.3 Mpixels/sec for 720p), and because interlaced video is inherently more difficult to encode than progressive material (there are less opportunities to use accurate motion prediction).  To get the same artifact level (picture quality) for 1080i, you need about 20% more bitrate (about 10% for the additional pixels and another 10% to make up for the difficulty of interlaced video).

 

But, most providers, U-Verse included, do not make special consideration for 1080i material.  On U-Verse, both 720p and 1080i material are encoded and transmitted at 5.7 Mbps.  This is why the 1080i material doesn't look as good as it could.

 

If the bitrate for 1080i were upped to 6.8 Mbps, it would look (artifact-wise) as good as the 720p material.

 


 

This is the most coherent answer to the PQ questions I've seen on these boards.  Somehow, resolution became everyone's standard for quality.  It simply isn't the whole story.  I really wish manufacturers and service providers would quit confusing people by marketing purely based on resolution.  High bitrate is the reason Blu-ray looks better on a 1080i set than a 1080i signal from U-Verse. 

 

I want to puke every time the subject of 1080p comes up around here.  Subscribers think that the reason their HD isn't as good as it should be is because it's not 1080p.  HD is such a cool technology.  Too bad bandwidth limitations leave it somewhat neutered.

 


SomeJoe7777 wrote:

The picture quality (i.e. artifact level) is dependent on the bitrate and the complexity of the source material.

 

A 1080i source is more complex than a 720p source, both because there are more pixels to encode (62.2 Mpixels/sec for 1080i vs. 55.3 Mpixels/sec for 720p), and because interlaced video is inherently more difficult to encode than progressive material (there are less opportunities to use accurate motion prediction).  To get the same artifact level (picture quality) for 1080i, you need about 20% more bitrate (about 10% for the additional pixels and another 10% to make up for the difficulty of interlaced video).

 

But, most providers, U-Verse included, do not make special consideration for 1080i material.  On U-Verse, both 720p and 1080i material are encoded and transmitted at 5.7 Mbps.  This is why the 1080i material doesn't look as good as it could.

 

If the bitrate for 1080i were upped to 6.8 Mbps, it would look (artifact-wise) as good as the 720p material.

 


 

This is the most coherent answer to the PQ questions I've seen on these boards.  Somehow, resolution became everyone's standard for quality.  It simply isn't the whole story.  I really wish manufacturers and service providers would quit confusing people by marketing purely based on resolution.  High bitrate is the reason Blu-ray looks better on a 1080i set than a 1080i signal from U-Verse. 

 

I want to puke every time the subject of 1080p comes up around here.  Subscribers think that the reason their HD isn't as good as it should be is because it's not 1080p.  HD is such a cool technology.  Too bad bandwidth limitations leave it somewhat neutered.

Re: PQ on U-verse -- 720p vs 1080i

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SomeJoe7777 wrote:

The encoders that AT&T are using for U-Verse are the Motorola SE-5100 units, and they're using the constrained fidelity (capped VBR) mode.  The H.264 output from these units isn't the best MPEG-4 you can get, because these encoders don't implement all features of the codec, but they perform quite well anyway.


I looked at the Motorola SE-5100 specs. It mentions "Main Profile Encoding" for HD services, but I didn't see "High Profile Encoding" anywhere on this model. I don't see why a provider would need to skimp on that. Do you think we would see a noticeable improvement they switched to High Profile? As far as I've known, Main Profile is generally not supposed to be used for HD content. I mean even a quick read on Wikipedia for H.264's Main Profile states "It is not, however, used for high-definition television broadcasts, as the importance of this profile faded when the High Profile was developed in 2004 for that application."

 

 


SomeJoe7777 wrote:

The encoders that AT&T are using for U-Verse are the Motorola SE-5100 units, and they're using the constrained fidelity (capped VBR) mode.  The H.264 output from these units isn't the best MPEG-4 you can get, because these encoders don't implement all features of the codec, but they perform quite well anyway.


I looked at the Motorola SE-5100 specs. It mentions "Main Profile Encoding" for HD services, but I didn't see "High Profile Encoding" anywhere on this model. I don't see why a provider would need to skimp on that. Do you think we would see a noticeable improvement they switched to High Profile? As far as I've known, Main Profile is generally not supposed to be used for HD content. I mean even a quick read on Wikipedia for H.264's Main Profile states "It is not, however, used for high-definition television broadcasts, as the importance of this profile faded when the High Profile was developed in 2004 for that application."

 

Re: PQ on U-verse -- 720p vs 1080i

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Oct 12, 2010 5:28:54 AM
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Thanks, that confirms what I was noticing with my eyes.  

 

The irony is most satellite providers down convert the 1080i signals to lower interlaced resolutions.  So it seems odd to me that most non OTA broadcast channels choose to go 1080i.  The slight advantage 1080i has in resolution is getting killed by compression.

Thanks, that confirms what I was noticing with my eyes.  

 

The irony is most satellite providers down convert the 1080i signals to lower interlaced resolutions.  So it seems odd to me that most non OTA broadcast channels choose to go 1080i.  The slight advantage 1080i has in resolution is getting killed by compression.

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chrisw wrote:

 

I looked at the Motorola SE-5100 specs. It mentions "Main Profile Encoding" for HD services, but I didn't see "High Profile Encoding" anywhere on this model. I don't see why a provider would need to skimp on that. Do you think we would see a noticeable improvement they switched to High Profile? As far as I've known, Main Profile is generally not supposed to be used for HD content. I mean even a quick read on Wikipedia for H.264's Main Profile states "It is not, however, used for high-definition television broadcasts, as the importance of this profile faded when the High Profile was developed in 2004 for that application."


 

The main profile is used vice high profile to reduce decoder complexity.  This enables a lower cost and lower complexity decoder chip to be used in the DVR/STB units.

 

However, truth be told, the decoder used in the U-Verse STBs (the Sigma Designs 8634) is quite capable of decoding high profile without any issues, so I don't see a reason that they couldn't use encoders that do high profile at a later date.

 

 


chrisw wrote:

 

I looked at the Motorola SE-5100 specs. It mentions "Main Profile Encoding" for HD services, but I didn't see "High Profile Encoding" anywhere on this model. I don't see why a provider would need to skimp on that. Do you think we would see a noticeable improvement they switched to High Profile? As far as I've known, Main Profile is generally not supposed to be used for HD content. I mean even a quick read on Wikipedia for H.264's Main Profile states "It is not, however, used for high-definition television broadcasts, as the importance of this profile faded when the High Profile was developed in 2004 for that application."


 

The main profile is used vice high profile to reduce decoder complexity.  This enables a lower cost and lower complexity decoder chip to be used in the DVR/STB units.

 

However, truth be told, the decoder used in the U-Verse STBs (the Sigma Designs 8634) is quite capable of decoding high profile without any issues, so I don't see a reason that they couldn't use encoders that do high profile at a later date.

 

 

Re: PQ on U-verse -- 720p vs 1080i

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Oct 12, 2010 1:37:46 PM
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SomeJoe7777 wrote:

...

 

If the bitrate for 1080i were upped to 6.8 Mbps, it would look (artifact-wise) as good as the 720p material.

 ...

 


This probably isn't the best comparison as I'm sure there are some differences between real-time encoding and VOD.  However, the premium  HD VOD seems to run somewhere around 6-7 Mbps (through the RealTime app) and comparatively looks great.   Any idea what the VOD specs are?

 

 


SomeJoe7777 wrote:

...

 

If the bitrate for 1080i were upped to 6.8 Mbps, it would look (artifact-wise) as good as the 720p material.

 ...

 


This probably isn't the best comparison as I'm sure there are some differences between real-time encoding and VOD.  However, the premium  HD VOD seems to run somewhere around 6-7 Mbps (through the RealTime app) and comparatively looks great.   Any idea what the VOD specs are?

 

Re: PQ on U-verse -- 720p vs 1080i

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Oct 12, 2010 1:47:37 PM
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UVRT is reasonably accurate at bitrate measurements, but not as accurate as other methods.

 

I have a more accurate bitrate measurment mechanism with MRTG.  One night I will have to put on a VOD movie and get a long-term average bitrate.

 

UVRT is reasonably accurate at bitrate measurements, but not as accurate as other methods.

 

I have a more accurate bitrate measurment mechanism with MRTG.  One night I will have to put on a VOD movie and get a long-term average bitrate.

 

Re: PQ on U-verse -- 720p vs 1080i

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Oct 13, 2010 10:13:49 AM
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I did a VOD HD bitrate measurement today with a Cinemax HD On Demand movie.

 

The MRTG-measured long-term average bitrate for HD VOD comes in at 7.4 Mbps.  This is over 30% more bitrate than the standard live feeds.

 

If you want higher quality HD, I would definitely recommend watching a movie on VOD if available.

 

Note that this is a single test with a single movie, and that other movies or shows, including those from a different network other than Cinemax, may be different.

 

I did a VOD HD bitrate measurement today with a Cinemax HD On Demand movie.

 

The MRTG-measured long-term average bitrate for HD VOD comes in at 7.4 Mbps.  This is over 30% more bitrate than the standard live feeds.

 

If you want higher quality HD, I would definitely recommend watching a movie on VOD if available.

 

Note that this is a single test with a single movie, and that other movies or shows, including those from a different network other than Cinemax, may be different.

 

Re: PQ on U-verse -- 720p vs 1080i

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Oct 13, 2010 10:31:01 AM
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Thanks, that additional bitrate sure does make a major difference in PQ.  

 

Unfortunately, I'm sure it would be difficult to get the live streams up that high, they'd cause issues on marginal lines and stream counts.  AT&T would need more bandwidth on the back end.  Also, total DVR record time would be impacted.   However, I'd be happy to give up DVR space for some quality.

Thanks, that additional bitrate sure does make a major difference in PQ.  

 

Unfortunately, I'm sure it would be difficult to get the live streams up that high, they'd cause issues on marginal lines and stream counts.  AT&T would need more bandwidth on the back end.  Also, total DVR record time would be impacted.   However, I'd be happy to give up DVR space for some quality.

Re: PQ on U-verse -- 720p vs 1080i

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Oct 13, 2010 12:41:40 PM
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Purely speculation here...but could the higher bitrate on the VOD stuff be due to "pre-encoding" -- in other words, could the VOD stuff be encoded and stored on VOD servers, so that the encoding doesn't happen real time?

 

Nah, the more I think about it the less sense that makes.

 

Hmm.

Purely speculation here...but could the higher bitrate on the VOD stuff be due to "pre-encoding" -- in other words, could the VOD stuff be encoded and stored on VOD servers, so that the encoding doesn't happen real time?

 

Nah, the more I think about it the less sense that makes.

 

Hmm.

Re: PQ on U-verse -- 720p vs 1080i

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Oct 13, 2010 12:48:12 PM
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Actually, I believe that is correct.  The VOD content is probably pre-encoded and stored on a hard drive array.  VOD is also sent to the STB via unicast IP, using HTTP protocol as opposed to the live TV, which is multicast IP, using RTP/UDP.

 

Actually, I believe that is correct.  The VOD content is probably pre-encoded and stored on a hard drive array.  VOD is also sent to the STB via unicast IP, using HTTP protocol as opposed to the live TV, which is multicast IP, using RTP/UDP.

 

Re: PQ on U-verse -- 720p vs 1080i

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Oct 13, 2010 12:59:35 PM
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Edited by JefferMC on Oct 13, 2010 at 1:00:17 PM

SomeJoe7777 wrote:

Actually, I believe that is correct.  The VOD content is probably pre-encoded and stored on a hard drive array.  VOD is also sent to the STB via unicast IP, using HTTP protocol as opposed to the live TV, which is multicast IP, using RTP/UDP.

 


Hm... that would imply fewer artifacts due to lost packets due to the built-in retry mechanisms in TCP/IP.

 

It would also imply that some of that increased bandwidth is TCP/IP protocol overhead vs. the usually slimmer UDP.

 

 


SomeJoe7777 wrote:

Actually, I believe that is correct.  The VOD content is probably pre-encoded and stored on a hard drive array.  VOD is also sent to the STB via unicast IP, using HTTP protocol as opposed to the live TV, which is multicast IP, using RTP/UDP.

 


Hm... that would imply fewer artifacts due to lost packets due to the built-in retry mechanisms in TCP/IP.

 

It would also imply that some of that increased bandwidth is TCP/IP protocol overhead vs. the usually slimmer UDP.

 

 

*The views and opinions expressed on this forum are purely my own. Any product claim, statistic, quote, or other representation about a product or service should be verified with the manufacturer, provider, or party.

Re: PQ on U-verse -- 720p vs 1080i

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Oct 13, 2010 1:16:28 PM
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JefferMC wrote:

 

Hm... that would imply fewer artifacts due to lost packets due to the built-in retry mechanisms in TCP/IP.

 

It would also imply that some of that increased bandwidth is TCP/IP protocol overhead vs. the usually slimmer UDP.


 

TCP header size is 20 bytes vs. UDP header size of 8 bytes, so there's only an additional 12 bytes using TCP.  That's < 1% for 1500-byte packets.

 

Though TCP does provide for error correction, if the retransmission is too late, then the STB will have no choice but to drop the packet because that portion of the video stream will have already been processed.  I suspect the STB has a large buffer for VOD to make up for this, probably on the order of  5 seconds or more as opposed to 1-2 seconds for live TV.

 


JefferMC wrote:

 

Hm... that would imply fewer artifacts due to lost packets due to the built-in retry mechanisms in TCP/IP.

 

It would also imply that some of that increased bandwidth is TCP/IP protocol overhead vs. the usually slimmer UDP.


 

TCP header size is 20 bytes vs. UDP header size of 8 bytes, so there's only an additional 12 bytes using TCP.  That's < 1% for 1500-byte packets.

 

Though TCP does provide for error correction, if the retransmission is too late, then the STB will have no choice but to drop the packet because that portion of the video stream will have already been processed.  I suspect the STB has a large buffer for VOD to make up for this, probably on the order of  5 seconds or more as opposed to 1-2 seconds for live TV.

 

Re: PQ on U-verse -- 720p vs 1080i

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Oct 14, 2010 4:23:44 PM
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Until I read this post I never checked what my system aspect ratio was on, and I'm very happy now. I have 3 plasma's all of them are 720p and I switched the aspect ratio to that yesterday. WOW, picture looks amazing now.

 

thanks

Until I read this post I never checked what my system aspect ratio was on, and I'm very happy now. I have 3 plasma's all of them are 720p and I switched the aspect ratio to that yesterday. WOW, picture looks amazing now.

 

thanks

Re: PQ on U-verse -- 720p vs 1080i

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