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Guest Message by DevFuse

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Any news on 4K?


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47 replies to this topic

#21 OFFLINE   SledgeHammer

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Posted 09 October 2013 - 11:02 AM

How does that work? I thought bitrate and bandwidth were inextricably tied together. 

 

PQ / Bitrate of the uncompressed signal. HEVC/H.265 is a much more effecient compression algorithm. See here:

 

http://en.wikipedia....ding_efficiency



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#22 OFFLINE   Laxguy

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Posted 09 October 2013 - 12:08 PM

I get that it's a superior compression scheme, but if the bitrate is decreased so is bandwidth, no? You can have higher PQ with the same bitrate/bandwidth, or the same PQ with lower bitrate/bandwidth.


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#23 OFFLINE   Jason Whiddon

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Posted 09 October 2013 - 12:15 PM

 

You can have higher PQ with the same bitrate/bandwidth, or the same PQ with lower bitrate/bandwidth.

That is the way I usually explain it.


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#24 OFFLINE   SledgeHammer

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Posted 09 October 2013 - 01:31 PM

Bandwidth is how much data you *CAN* transfer in a time interval (per second in this example).

 

Bitrate is how much data you *ARE* transfering in a time interval. This is more related to the frames per second and the quality of the video.

 

They have nothing to do with each other as it relates to the H.265 discussion.

 

All it's saying is that a video takes X MB/s using MPEG4 and X/2 MB/s using H.265 given the same bitrate.

 

Bandwidth stays the same

Bitrate of the video stays the same

Size of the compressed video is 50% smaller


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#25 OFFLINE   slice1900

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Posted 09 October 2013 - 02:26 PM

It looks like you think bit rate doesn't mean the same thing as "Mb/s for the video". It does. The abbreviation "Mb" stands for megabits, after all, and the "/s" is a rate of the number of such bits per second :)

 

If you have a video and compress it with MPEG4/h.264 and HEVC/h.265 the file size for the latter will be about half as much. That means the bit rate is about half as much to stream it.


Edited by slice1900, 09 October 2013 - 02:27 PM.

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#26 OFFLINE   SledgeHammer

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Posted 09 October 2013 - 02:38 PM

It looks like you think bit rate doesn't mean the same thing as "Mb/s for the video". It does. The abbreviation "Mb" stands for megabits, after all, and the "/s" is a rate of the number of such bits per second :)

 

If you have a video and compress it with MPEG4/h.264 and HEVC/h.265 the file size for the latter will be about half as much. That means the bit rate is about half as much to stream it.

 

It looks like you misread my post. I said:

 

"All it's saying is that a video takes X MB/s using MPEG4 and X/2 MB/s using H.265 given the same bitrate."

 

bitrate of the UNCOMPRESSED video. You understand there are TWO DIFFERENT bitrates we are talking about, right? Compressed and Uncompressed. Uncompressed bitrate does not change, but it COULD...

 

Why do you think YouTube videos look like garbage? Cuz the uploader reduced the UNCOMPRESSED bitrate to reduce the file size.

 

H.265 reduces the file size while NOT reducing the bitrate of the original uncompressed video.

 

If you want to be pedantic (even though I clearly stated this in my response), yeah, the "bitrate" of the compressed video gets cut in half.

 

Personally, I don't care about compressed bitrate, that's DirecTVs problem :).


Edited by SledgeHammer, 09 October 2013 - 02:41 PM.


#27 OFFLINE   JosephB

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Posted 09 October 2013 - 02:43 PM

It looks like you misread my post. I said:

 

"All it's saying is that a video takes X MB/s using MPEG4 and X/2 MB/s using H.265 given the same bitrate."

 

bitrate of the UNCOMPRESSED video. You understand there are TWO DIFFERENT bitrates we are talking about, right? Compressed and Uncompressed. Uncompressed bitrate does not change, but it COULD...

 

Why do you think YouTube videos look like garbage? Cuz the uploader reduced the UNCOMPRESSED bitrate to reduce the file size.

 

H.265 reduces the file size while NOT reducing the bitrate of the original uncompressed video.

 

If you want to be pedantic (even though I clearly stated this in my response), yeah, the "bitrate" of the compressed video gets cut in half.

 

There is no such thing as "uncompressed bitrate". The video comes in as raw images. Yes, I know that the signal is compressed by the content provider when it's transmitted to DirecTV or your cable company, but when it hits DirecTV's encoder, is is completely decompressed. We're talking about image quality from the point it hits the encoder at DirecTV to the point it hits your TV screen, and for that discussion "bitrate" and "bandwidth consumed" are exactly the same thing.



#28 OFFLINE   SledgeHammer

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Posted 09 October 2013 - 03:10 PM

There is no such thing as "uncompressed bitrate". The video comes in as raw images. Yes, I know that the signal is compressed by the content provider when it's transmitted to DirecTV or your cable company, but when it hits DirecTV's encoder, is is completely decompressed. We're talking about image quality from the point it hits the encoder at DirecTV to the point it hits your TV screen, and for that discussion "bitrate" and "bandwidth consumed" are exactly the same thing.

 

Are we even having the same conversation? I've been saying the "filesize" when using H.265 is 50% smaller then H.264 since day 1 of this thread.

 

Doesn't change the fact that the original video was recorded at 3840 × 2160 / 60fps or whatever. That is a bitrate too, you know.  And that bitrate has nothing to do with the encoding scheme used to transmit it. If I wanted to upload to Youtube or whatever and I wanted crappier video quality, I could reduce that bitrate / down res to say 30fps or reduce resolution or do BOTH before compression even comes into play.

 

So for clarification AGAIN... and what I have been saying for two pages is that:

 

3840 × 2160 / 60fps when encoded using H.265 is 50% smaller then when encoded using H.264. The original

3840 × 2160 / 60fps remains 3840 × 2160 / 60fps in both cases.

 

Thus the original uncompressed bitrate of the video is unaffected. Only the compressed bitrate is affected.


Edited by SledgeHammer, 09 October 2013 - 03:18 PM.


#29 OFFLINE   Diana C

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Posted 09 October 2013 - 03:11 PM

There is no such thing as "uncompressed bitrate"...

 

Of course there is. For 1080p video the bit rate, prior to any compression, is 1080(pixel height) x 1920(pixel width) x 32 (the number of bits per pixel) x 30 (the number of such fields of video transmitted each second) or 1,990,656,000 bits per second, or roughly 2Gbits per second (this is just one of the various 1080p formats).  This is compressed (via MPEG2 usually) within the camera to 18Mbps, or about 1% of the "uncompressed" bitrate.  DirecTV will further process this using MPEG4 to get down to around 10Mbps or less.

 

Multiply these numbers by about 3.75 for 4K. 


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#30 OFFLINE   JosephB

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Posted 09 October 2013 - 03:20 PM

Are we even having the same conversation? I've been saying the "filesize" when using H.265 is 50% smaller then H.264 since day 1 of this thread.

 

Doesn't change the fact that the original video was recorded at 3840 × 2160 / 60fps or whatever. That is a bitrate too, you know.  And that bitrate has nothing to do with the encoding scheme used to transmit it. If I wanted to upload to Youtube or whatever and I wanted crappier video quality, I could reduce that bitrate / down res to say 30fps or reduce resolution.

 

So for clarification AGAIN... and what I have been saying for two pages is that:

 

3840 × 2160 / 60fps when encoded using H.265 is 50% smaller then when encoded using H.264. The original

3840 × 2160 / 60fps remains 3840 × 2160 / 60fps.

 

You're not having the same conversation as anyone here.

 

When it comes to the image quality and the amount of bandwidth the transmission takes up on the satellite, that is the bitrate. The bitrate of the incoming video is irrelevant once it crosses DirecTV's encoders, especially since it is not something that can be adjusted by DirecTV.

 

The relevant comparison is between the bitrate AND compression ratio/algorithm of two codecs when presented with the exact same source material. You're mixing up two or three different things and you're just not right. Two videos at the same size and framerate compressed with two different codecs at the same "image quality" (which is subjective) will not have the same bitrate. You keep talking about file size but that has nothing to do with a stream. The number of bits transmitted in a specified period of time is the bit rate. It also happens to correspond exactly to the amount of bandwidth required to transmit it. Bitrate and bandwidth are the same exact thing.



#31 OFFLINE   JosephB

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Posted 09 October 2013 - 03:23 PM

Of course there is. For 1080p video the bit rate, prior to any compression, is 1080(pixel height) x 1920(pixel width) x 32 (the number of bits per pixel) x 30 (the number of such fields of video transmitted each second) or 1,990,656,000 bits per second, or roughly 2Gbits per second (this is just one of the various 1080p formats).  This is compressed (via MPEG2 usually) within the camera to 18Mbps, or about 1% of the "uncompressed" bitrate.  DirecTV will further process this using MPEG4 to get down to around 10Mbps or less.

 

Multiply these numbers by about 3.75 for 4K. 

 

But that is irrelevant because it is a fixed bitrate that will never change. The raw 1080p signal, whether you're talking about the 2Gbps digital signal or an analog signal over component is the same regardless of what it's ultimately compressed into and transmitted as over DirecTV's satellite.



#32 OFFLINE   SledgeHammer

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Posted 09 October 2013 - 03:39 PM

You're not having the same conversation as anyone here.

 

When it comes to the image quality and the amount of bandwidth the transmission takes up on the satellite, that is the bitrate. The bitrate of the incoming video is irrelevant once it crosses DirecTV's encoders, especially since it is not something that can be adjusted by DirecTV.

 

The relevant comparison is between the bitrate AND compression ratio/algorithm of two codecs when presented with the exact same source material. You're mixing up two or three different things and you're just not right. Two videos at the same size and framerate compressed with two different codecs at the same "image quality" (which is subjective) will not have the same bitrate. You keep talking about file size but that has nothing to do with a stream. The number of bits transmitted in a specified period of time is the bit rate. It also happens to correspond exactly to the amount of bandwidth required to transmit it. Bitrate and bandwidth are the same exact thing.

 

Hmm... weird... I thought that's what I said lol...

 

* Two videos (same video) starting out at the same resolution and frame rate... check... yeah, I said that...

* Compressed with two different codecs... check.. yeah, I said that too...

* AFTER COMPRESSION, you end up with two different "file sizes" / bitrates / bandwidth consumed / etc... check... damn...3 for 3 so far...

* original PQ is unaffected... yup... check again...

 

I'm not quite sure what you are arguing about, other then just arguing for the sake of arguing.

 

Are you mad because I said the original bitrate (PQ) is not reduced / altered by the compression scheme selected? That my friend is true. Sorry, that is the whole point of H.265. To reduce the "file size" / bitrate / bandwidth consumed by 50% WITHOUT affecting PQ.

 

Bitrate and Bandwidth are most definitely NOT the same thing. Bitrate and Bandwidth CONSUMED are though... I have cable internet in my house. The BANDWIDTH for coax is certainly more then the 25Mbps/sec BITRATE I get.

 

Bitrate can not exceed bandwidth, but bitrate can certainly be much less then bandwidth.


Edited by SledgeHammer, 09 October 2013 - 03:52 PM.


#33 OFFLINE   Diana C

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Posted 10 October 2013 - 09:32 AM

Bit rate <> PQ, simply because all the compression algorithms in use today and in the future are lossy - the "restored" video stream displayed on our TVs does not contain all the data the original video stream contained.  So, although the bit stream that flows over the HDMI cable to the TV is at the same bitrate that enters the compression process, the PQ is NOT the same.  If it were, there would be no visible macro-blocking in the video.

 

MPEG4 produces an acceptable quality digital video stream that is 50% to 60% the size of the same content using MPEG2, but the PQ is not exactly the same.  MPEG4 discards more information than does MPEG2.  MPEG4 is just smarter about what it discards, discarding first the information that the human eye generally does not perceive well, whereas MPEG2 discards data on a purely statistical basis.  As a result, MPEG4 can produce a smaller acceptable quality output than MPEG2.

 

The same is true of H.265 - it produces a smaller output than H.264 while keeping the apparent quality constant.  But it remains to be seen if H.265 can have significant impact on transmission rates when used in a realtime environment.  The 50% reduction claims I have seen so far were all from multipass processing - something you can't do in a linear broadcast environment.


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#34 OFFLINE   harsh

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Posted 10 October 2013 - 10:46 AM

And don't forget 110!!!!! ;)

DIRECTV surely has.

I'm not convinced that the bandwidth partitioning of a Ku satellite will meet the needs of 4K. If they get only one channel per one transponder that's not a very good yield. Having cut a good chunk of the subscribers out of access to 110W and 119W will haunt them if they do choose to return there.

3D pretty convincingly disproved the Field of Dreams theory as applied to television and 3D is arguably a much bigger deal than incrementally better PQ.

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#35 OFFLINE   harsh

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Posted 10 October 2013 - 10:49 AM

Bit rate <> PQ, simply because all the compression algorithms in use today and in the future are lossy - the "restored" video stream displayed on our TVs does not contain all the data the original video stream contained.  So, although the bit stream that flows over the HDMI cable to the TV is at the same bitrate that enters the compression process, the PQ is NOT the same.  If it were, there would be no visible macro-blocking in the video.

This is the high-bitrate BUD SD .vs. low-bitrate DBS HD argument. If they must jettison the additional detail to make 4K work, they would be better served by taking the HD detail to the max so that many more would be able to take advantage of it.

Edited by harsh, 10 October 2013 - 10:51 AM.

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#36 OFFLINE   JosephB

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Posted 10 October 2013 - 11:04 AM

DIRECTV surely has.

I'm not convinced that the bandwidth partitioning of a Ku satellite will meet the needs of 4K. If they get only one channel per one transponder that's not a very good yield. Having cut a good chunk of the subscribers out of access to 110W and 119W will haunt them if they do choose to return there.

3D pretty convincingly disproved the Field of Dreams theory as applied to television and 3D is arguably a much bigger deal than incrementally better PQ.

 

4K would require new receivers, so adding a new LNB wouldn't be a huge deal for a new 4K service, so if they put it on 110/119 I don't see that being an issue. Though, the bandwidth per transponder is something to consider. I would think by the time they lit up any 4K at all, they'd be on something better than MPEG-4 anyway.

 

This is the high-bitrate BUD SD .vs. low-bitrate DBS HD argument. If they must jettison the additional detail to make 4K work, they would be better served by taking the HD detail to the max so that many more would be able to take advantage of it.

 

This is a valid point, if they have bandwidth to spare they'd probably get better overall results out of bumping up the PQ of all the channels. That's harder to market, though, than "Hey look, we've got 4K movie channels!". 



#37 OFFLINE   fleckrj

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Posted 10 October 2013 - 01:20 PM

4K would require new receivers, so adding a new LNB wouldn't be a huge deal for a new 4K service, so if they put it on 110/119 I don't see that being an issue. Though, the bandwidth per transponder is something to consider. I would think by the time they lit up any 4K at all, they'd be on something better than MPEG-4 anyway.

 

The bigger issue than the LNB is that far too many of us on the east coast do not have LOS to 119.



#38 OFFLINE   JosephB

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Posted 10 October 2013 - 04:12 PM

The bigger issue than the LNB is that far too many of us on the east coast do not have LOS to 119.

 

If that's where they have space, that's where they have space. It's a CONUS slot, so, I doubt that will be a major limiting factor. It may be why they don't have national channels there but for example Dish Network has/had core channels there so it's not an insurmountable issue.



#39 OFFLINE   peds48

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Posted 10 October 2013 - 06:44 PM

If that's where they have space, that's where they have space. It's a CONUS slot, so, I doubt that will be a major limiting factor. It may be why they don't have national channels there but for example Dish Network has/had core channels there so it's not an insurmountable issue.

DirecTV will surely have less customers if the use the 119 for "main" channels 


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#40 OFFLINE   KyL416

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Posted 10 October 2013 - 06:46 PM

If that's where they have space, that's where they have space. It's a CONUS slot, so, I doubt that will be a major limiting factor. It may be why they don't have national channels there but for example Dish Network has/had core channels there so it's not an insurmountable issue.

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