5
57
Guest
Here's a post from the Shaw thread discussing bitrate:
http://www.digitalhome.ca/forum/showpost.php?p=395866&postcount=23
http://www.digitalhome.ca/forum/showpost.php?p=395866&postcount=23
D
diogen
Guest
Never heard about 8PSK as a compression method, only as a modulation scheme.
I don't know the details how this is done by the broadcasting companies, but I don't think those are two different processes.
If the broadcasters do the compression/bitrate reduction part, they just use a hardware real-time MPEG encoder and define the bitrate of the output. Any special measures/pre-filtering (e.g. grain removal: allows for more efficient compression) are defined in the same encoder (if it is capable of doing it).
In other words, compression reduces bit rate and is used (overused?) to fit the program into the alotted "pipe".
Diogen.
I don't know the details how this is done by the broadcasting companies, but I don't think those are two different processes.
If the broadcasters do the compression/bitrate reduction part, they just use a hardware real-time MPEG encoder and define the bitrate of the output. Any special measures/pre-filtering (e.g. grain removal: allows for more efficient compression) are defined in the same encoder (if it is capable of doing it).
In other words, compression reduces bit rate and is used (overused?) to fit the program into the alotted "pipe".
Diogen.
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57
Guest
I believe only the SA STBs allow for a passthrough mode. (SA8300HD, SA3250HD and some of the Pace models)
To be honest, I've done a lot of setups in different homes and the subject of how to set up the box comes up in each instance. We do a test of 720P, 1080i, passthrough, etc and it's rare that a client has a distinct preference.
Often, for SA STBs, we even set up the STB to "upconvert" or eliminate 720P (or 1080i), so that the switching between HD channels of different formats is faster, without the "mad scramble" that appears on screen when switching formats.
There were even a couple of TVs recently that failed the bobbing test, where we tried 720P and 1080i - 720P should possibly have been superior and the client (and I) saw little/no difference - even with the HDNet test pattern in place to test... I think you need really good testing, with various sources, various STBs, etc to be able to get a definitive answer to this question.
I CAN tell you that when you have a good channel, like HDNet, or some of the Discovery programmes, the quality comes through, no matter what the setting, provided it's HD, on a properly set up HDTV.
To be honest, I've done a lot of setups in different homes and the subject of how to set up the box comes up in each instance. We do a test of 720P, 1080i, passthrough, etc and it's rare that a client has a distinct preference.
Often, for SA STBs, we even set up the STB to "upconvert" or eliminate 720P (or 1080i), so that the switching between HD channels of different formats is faster, without the "mad scramble" that appears on screen when switching formats.
There were even a couple of TVs recently that failed the bobbing test, where we tried 720P and 1080i - 720P should possibly have been superior and the client (and I) saw little/no difference - even with the HDNet test pattern in place to test... I think you need really good testing, with various sources, various STBs, etc to be able to get a definitive answer to this question.
I CAN tell you that when you have a good channel, like HDNet, or some of the Discovery programmes, the quality comes through, no matter what the setting, provided it's HD, on a properly set up HDTV.
For a final time, I work with the most senior technical engineers and managment at BGM, its first hand info from them.
You can't tell me CRS's are the most relaible source.
Take form my comments what you'd like. I've made the info very clear in this forum. It is 100% accurate. But fell free to continue arguing the issue back and forth.
You can't tell me CRS's are the most relaible source.
Take form my comments what you'd like. I've made the info very clear in this forum. It is 100% accurate. But fell free to continue arguing the issue back and forth.
For all those who think otherwise. BEV does NOT broadcast 1080i at this time on its HD network. They do recieve 1080i from many of their providers including CTV and CBS and NBC but they do not have the technical capacity to direct that signal out in its native format.
I have spoken directly with a number of senior members of the engineering team at BEV and BGM. They have confirmed this. There are no immediate plans to broadcast in 1080i for 2 reasons. 1...1080i takes up a greater amount of bandwith and BEV would have to stop sending out a certain amount of HD channels as they would not have enough room to air them all and 2...switching to 1080i is more than just an encoding issue it requires an entire technical makeover at BEV.
Hopefully this puts the debate to rest.
I have spoken directly with a number of senior members of the engineering team at BEV and BGM. They have confirmed this. There are no immediate plans to broadcast in 1080i for 2 reasons. 1...1080i takes up a greater amount of bandwith and BEV would have to stop sending out a certain amount of HD channels as they would not have enough room to air them all and 2...switching to 1080i is more than just an encoding issue it requires an entire technical makeover at BEV.
Hopefully this puts the debate to rest.
D
diogen
Guest
A nice summary of the state of the codec prrformance and acceptance by the broadcasting world (haven't seen this posted)
http://www.newvideobusiness.com/content/view/74/26/
6Mbps for hard to encode sporting events!
If they are off by 50% it's still very good.
Diogen.
http://www.newvideobusiness.com/content/view/74/26/
6Mbps for hard to encode sporting events!
If they are off by 50% it's still very good.
Diogen.
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57
Guest
That may be true, but the max bitrate cannot exceed that of the transponder, even if only one channel were on it (which it's not), so the average bitrate would be around 15 (two channels), which can only be calculated by looking at the filesize and dividing by the time.
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I_Want_My_HDTV
Guest
You are right about 8PSK being a modulation scheme. It can result in higher bandwidth with EV/Dish equipment when combined with MPEG2.
I do not know the exact details of how bit rates are reduced. You may be right that is is part of the compression process. i.e. more lossy compression vs standard compression. A lot of digital channels now reduce bandwidth for OTA HDTV so that several channels can be broadcast simultaneously. This can result in bandwidths of about 13 Mbps for the HD channel. If a BDU relays these channels it results in channels that fits into a smaller space. However, BDUs are not allowed to do this themselves. Canadian channels appear to be reducing the bandwidth of their signals for delivery to EV. This is an interesting loophole that needs to be challenged.
I do not know the exact details of how bit rates are reduced. You may be right that is is part of the compression process. i.e. more lossy compression vs standard compression. A lot of digital channels now reduce bandwidth for OTA HDTV so that several channels can be broadcast simultaneously. This can result in bandwidths of about 13 Mbps for the HD channel. If a BDU relays these channels it results in channels that fits into a smaller space. However, BDUs are not allowed to do this themselves. Canadian channels appear to be reducing the bandwidth of their signals for delivery to EV. This is an interesting loophole that needs to be challenged.
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DominicSimard
Guest
In my case, my display is 720p native (Samsung Joe Kane front projector SP-H710AE) but it could handle properly a 1080i resolution (1080i to 1080p to 720p)
This is why I would like to have the native resolution of the channel.
This is why I would like to have the native resolution of the channel.
J
johnny_marin
Guest
Well editor,
I am in discussion right now with the head of platform performance from BEV regarding this issue (along with another issue I am having with my HD receiver) and he emphatically stated that the signals being distributed to the satellite is in NATIVE format, either 1080i or 720P depending on what signal the channel broadcaster is providing to BEV. That presentation link above is incomplete in what is being shown. And my credibility is that I work for Bell.
John
I am in discussion right now with the head of platform performance from BEV regarding this issue (along with another issue I am having with my HD receiver) and he emphatically stated that the signals being distributed to the satellite is in NATIVE format, either 1080i or 720P depending on what signal the channel broadcaster is providing to BEV. That presentation link above is incomplete in what is being shown. And my credibility is that I work for Bell.
John
Thanks John.
My experience is that people spew a lot of crap. Rather than saying they don't know, they simply spout off answers because they want to appear knowledgeable and they figure they'll never be called to account for it.
This is a situation where I believe John / editor / Falcon myself and others have all spoken to "senior" or "technical" people at Bell who all "believe" they know the answer but obviously some of them don't.
Rather than going back and forth ad nauseum, if anyone actually gets an "official" answer from a senior ExpressVu official in writing then please let me know and I will post it in a separate thread.
Closing until we get some "official" clarification or definitive proof one way or another!
Until then!
My experience is that people spew a lot of crap. Rather than saying they don't know, they simply spout off answers because they want to appear knowledgeable and they figure they'll never be called to account for it.
This is a situation where I believe John / editor / Falcon myself and others have all spoken to "senior" or "technical" people at Bell who all "believe" they know the answer but obviously some of them don't.
Rather than going back and forth ad nauseum, if anyone actually gets an "official" answer from a senior ExpressVu official in writing then please let me know and I will post it in a separate thread.
Closing until we get some "official" clarification or definitive proof one way or another!
Until then!
P
Pinza
Guest
Cosmic, I think you just won the award for resurrecting the oldest Thread..... 34 Months.....
Well Done......lol.
Ironically, when this thread was new Bell did broadcast some Channels in 1080i, they do not do that now.
Well Done......lol.
Ironically, when this thread was new Bell did broadcast some Channels in 1080i, they do not do that now.
W
Wanderlustus
Guest
And as I read this thread I find there is still no definitive answer to this question?
I'm in one of these outposts, as it were, that has no alternative, other than analogue cable or Starchoice (or whatever the hades they are now). So yeah, one might like to know.
Honestly, trying to get straight answers from Bell is like getting Stephen Harper to answer a question with transparency.
Is it or ain't it? Sheesh.
I'm in one of these outposts, as it were, that has no alternative, other than analogue cable or Starchoice (or whatever the hades they are now). So yeah, one might like to know.
Honestly, trying to get straight answers from Bell is like getting Stephen Harper to answer a question with transparency.
Is it or ain't it? Sheesh.
D
diogen
Guest
Every program broadcast by BEV is given a constant bandwidth (bitrate). This is true for any broadcast system - DVB-T, -S, -C , QAM, etc.
If the original program is VBR (as claimed in BEV case, i.e. BEV doesn't do the encoding/compression), the "leftover" bandwidth is stuffed with null-packets.
All movie channels on BEV are ABR 11.7Mbps MPEG-2 program stream.
Diogen.
If the original program is VBR (as claimed in BEV case, i.e. BEV doesn't do the encoding/compression), the "leftover" bandwidth is stuffed with null-packets.
All movie channels on BEV are ABR 11.7Mbps MPEG-2 program stream.
Diogen.
J
johnny_marin
Guest
Well, that explains why the HD picture is full of artifacts. Still pictures without alot of movement are fine at these bit rates but once there is alot of action on the screen then the picture problems start to appear. Compare this MPEG2 bit ratre to the VC-1 bit rate on HD-DVD. The average VC-1 bit rate is around 12 Mbps and the picture looks outstanding. So reducing the ABR from around 19 Mbps to 12 Mbps on MPEG2 is reducing picture quality substantially. This is comparable to what SONY has provided on MPEG2 with Bluray and we all know how that picture compares to HD-DVD with VC-1.
John
John