DTV HD compression rate?

[Broe67]

Really ?

It starts on a Thursday ?
I thought the opening ceremony was always on a Friday ...

Sochi is 10 hours ahead of Illinois with Daylight Savings Time. As of 4:17am on 11/22/13, they are 77 days, 5 hours, 56 min's, 15 sec's away. The official opening day is Feb. 7th, runs until the 23rd. The Winter Para-Olympics are March 7th through the 16th of 2014. https://www.sochi2014.com/en/

[h=2]Broadcasting rights[edit][/h]Main article: List of 2014 Winter Olympics broadcasters
In most regions, broadcast rights to the 2014 Winter Olympics were packaged together with broadcast rights for the 2016 Summer Olympics, but some broadcasters obtained rights to further games as well. Domestic broadcast rights were sold by Sportfive to a consortium of three Russian broadcasters; Channel One, VGTRK, and NTV Plus.[SUP][71][/SUP] In the United States, the 2014 Winter Olympics will be the first in a US$4.38 billion contract with NBC, extending its broadcast rights to the Olympic Games through 2020.[SUP][72][/SUP] In Canada, after losing the 2010 and 2012 Games toCTV, the 2014 Winter Olympics will mark the return of the Olympics to CBC Television and French sister network Ici Radio-Canada Télé for the first time since 2008.[SUP][73][/SUP] In Australia, after all three major commercial networks pulled out of bidding on rights to both the 2014 and 2016 Games due to cost concerns, the IOC awarded broadcast rights to just the 2014 Winter Olympics toNetwork Ten for AUD$20 million.[SUP][74][/SUP][SUP][75][/SUP][SUP][76]
http://en.wikipedia.org/wiki/Sochi_2014#Broadcasting_rights[/SUP]

 

[goaliebob99]

Let's ask an engineer why dont we!

As broe67 says, there is no specific number anyway. Channels are allocated bandwidth using adaptive statistical multiplexing, based on the channels requirments - fast action sports gets more bandwidth. At one time there was a group monitoring bandwidth but I haven't seen any posts on this for a long time.
Here's some data though, which I think is still valid. An HD transponder has about 32 Mbps capacity (after you remove guard bands and such). DirecTv puts 5 HD channels per transponder, although this might be increasing with better encoding. I seem to remember at one time the DirecTV contract with HBO required DirecTv to give HBO's main channel 8Mbps although this was some time ago.

But my question is - why are you asking? You can't really compare bitrates between providers because they all use different encoders and some are more effective than others. (This is apart from the MPEG-2 vs MPEG-4 differences, MPEG-4 is much more efficient than MPEG-2 in delivering the same PQ)

In DirecTV's system all channels have equal merit per-say. No one channel gets better quality over the other, but instead it is based upon content as said above. I have seen channels as low as 4 megs, and as high as 14. DirecTV uses minimally 6 per transponder, and I have seen 7, but the way the transponder is packed, its with lower end content that doesn't take up as much bandwidth packed in with some medium to higher end content that needs more bandwidth. Compression has come a long way and continues to do so. The way that encoders encode on the fly in one example it takes four different encodes at once and then selects the best one is amazing. Especally when you get into the science behind it with the DCT math involved in making a micro block. (yes micro block) The math is enough to make your mind go poof!

On some, yes.

More than you think. And the future looks awesome when directv rolls out 4k and how they get those channels on air. It's a very cool process is all I can say.

I would imagine that D* does put 6 channels on some transponers, more than likely they can do that alot with a group of channels that are mainly stationary, such as talking head shows, that type of thing.

Yes this is the idea. DirecTV has become very good at how they pack their channels. Alot of times a good mpeg4 signal on DirecTV looks like its a small step below the master, and often is on par with the OTA signal given to Directv. IT's almost a 1:1 exchange given that some local tv signals are giving providers a 7 meg HD signal in MPEG2 and we often step it up to 4-10 megs in MPEG4.

I'm trying to get my stuff set up so I can capture in HD from my DirecTV DVR to the computer. I just figured if the bitrate was always below 10 there wouldn't be much sense in setting the capture bitrate at 20....I understand the variablity of it all, I just hadn't read much on the bitrates that they use...
As for DTV/Digital TV/DirecTV/D* - sorry, I didn't even think of DTV being misread as Digital TV.

I would set it for around 12. Most programming is going to be between 4 and 10 megs, with NFL games peaking upto 14.

 

[raoul5788]

Let's ask an engineer why dont we!



In DirecTV's system all channels have equal merit per-say. No one channel gets better quality over the other, but instead it is based upon content as said above. I have seen channels as low as 4 megs, and as high as 14. DirecTV uses minimally 6 per transponder, and I have seen 7, but the way the transponder is packed, its with lower end content that doesn't take up as much bandwidth packed in with some medium to higher end content that needs more bandwidth. Compression has come a long way and continues to do so. The way that encoders encode on the fly in one example it takes four different encodes at once and then selects the best one is amazing. Especally when you get into the science behind it with the DCT math involved in making a micro block. (yes micro block) The math is enough to make your mind go poof!



More than you think. And the future looks awesome when directv rolls out 4k and how they get those channels on air. It's a very cool process is all I can say.



Yes this is the idea. DirecTV has become very good at how they pack their channels. Alot of times a good mpeg4 signal on DirecTV looks like its a small step below the master, and often is on par with the OTA signal given to Directv. IT's almost a 1:1 exchange given that some local tv signals are giving providers a 7 meg HD signal in MPEG2 and we often step it up to 4-10 megs in MPEG4.



I would set it for around 12. Most programming is going to be between 4 and 10 megs, with NFL games peaking upto 14.

Where have you seen more than six on a transponder? The last I heard they moved many from five to six, but not all.

 

[texasbrit]

Where have you seen more than six on a transponder? The last I heard they moved many from five to six, but not all.

I think I might have seen transponders with as many as eight channels, where some of them are fairly static like QVC; my HD locals are still five.

And 7 megs for an OTA HD channel in MPEG2 is very low, and certainly compromises signal quality. Each OTA channel gets 19 megabits/second under the ATSC spec. If your local station just has one HD channel, that channel gets all the bandwidth OTA. If the station has say one HD channel and two SD channels, the HD channel typically gets around 11 meg and then the two SD channels around 3.8 each. To get only 7 meg OTA on an HD channel, the station has to be delivering two HD signals (at only 720p each) and an SD signal. There are a handful that do that, where the company has the affiliates for two national networks broadcast as subchannels, but I would hate to have to see the picture quality! And if the MPEG-2 signal is only 7 meg, there's not much point in delivering an MPEG-4 signal with a bandwidth higher than that.

Because the conversion from MPEG-2 to MPEG-4 is "lossy", the DirecTV local picture quality can "never" be better than the OTA signal. There's one major exception; that's where the station has subchannels but delivers the signals directly to DirecTV using fiber. there it's possible for the OTA signal for the HD channel to use say 11 meg but the signal going to DirecTv to use 19 meg. But in many cases the DirecTV HD local PQ is pretty well the same as OTA, assuming the encoders are set up correctly. Encoder setup has an effect on picture quality which has nothing to do with bandwidth as such. For example, we had a situation here in DFW recently where the DirecTV HD locals started to suffer from very high levels of "chroma noise", that's the noise you see when the picture has large areas of solid dark color (black, dark red mainly). My first thought was that DirecTV had thrown a couple more channels onto a transponder, but no, there were still five. Apparently it was just poor setup because after complaints the PQ improved dramatically.


And all of this discussion is really not relevant to the OP's original post, because it turned out he was trying to capture the HDMI or component output from the DirecTV receiver, which has nothing to do with the bandwidth of the original signals!!

 

[CK SatGuy]

Sochi is 10 hours ahead of Illinois with Daylight Savings Time. As of 4:17am on 11/22/13, they are 77 days, 5 hours, 56 min's, 15 sec's away. The official opening day is Feb. 7th, runs until the 23rd. The Winter Para-Olympics are March 7th through the 16th of 2014. https://www.sochi2014.com/en/

Really ?

It starts on a Thursday ?
I thought the opening ceremony was always on a Friday ...

Honestly I didn't even think about the time difference, I was just going by CBC's commercials that seem to keep showing up in every commercial break (unlike NBC which I've yet to see a single commercial for the olympics so far.) You figure if the opening ceremony is 8pm Sochi Time, the eastern time zone is 9 hours back so it would be 11 AM ET on the 7th. However, there are some figure skating, freestyle skiing, and snowboarding events happening on the 6th before the opening ceremony happens. Full schedule here: http://sochi2014.blob.core.windows.net/storage/games/schedule_sochi_en.pdf

 

[Broe67]

They always have a few events that happen before opening day. Especially those that end sooner, or those participating in them, have another event that they are also attempting to get a medal in. Even on Closing day, they still have events going on up to the next day if they run into weather issues, such as what happened in Vancouver.

 

[goaliebob99]

I think I might have seen transponders with as many as eight channels, where some of them are fairly static like QVC; my HD locals are still five.

And 7 megs for an OTA HD channel in MPEG2 is very low, and certainly compromises signal quality. Each OTA channel gets 19 megabits/second under the ATSC spec. If your local station just has one HD channel, that channel gets all the bandwidth OTA. If the station has say one HD channel and two SD channels, the HD channel typically gets around 11 meg and then the two SD channels around 3.8 each. To get only 7 meg OTA on an HD channel, the station has to be delivering two HD signals (at only 720p each) and an SD signal. There are a handful that do that, where the company has the affiliates for two national networks broadcast as subchannels, but I would hate to have to see the picture quality! And if the MPEG-2 signal is only 7 meg, there's not much point in delivering an MPEG-4 signal with a bandwidth higher than that.

Because the conversion from MPEG-2 to MPEG-4 is "lossy", the DirecTV local picture quality can "never" be better than the OTA signal. There's one major exception; that's where the station has subchannels but delivers the signals directly to DirecTV using fiber. there it's possible for the OTA signal for the HD channel to use say 11 meg but the signal going to DirecTv to use 19 meg. But in many cases the DirecTV HD local PQ is pretty well the same as OTA, assuming the encoders are set up correctly. Encoder setup has an effect on picture quality which has nothing to do with bandwidth as such. For example, we had a situation here in DFW recently where the DirecTV HD locals started to suffer from very high levels of "chroma noise", that's the noise you see when the picture has large areas of solid dark color (black, dark red mainly). My first thought was that DirecTV had thrown a couple more channels onto a transponder, but no, there were still five. Apparently it was just poor setup because after complaints the PQ improved dramatically.


And all of this discussion is really not relevant to the OP's original post, because it turned out he was trying to capture the HDMI or component output from the DirecTV receiver, which has nothing to do with the bandwidth of the original signals!!

It's actually not via fiber. Most of the time its via ASI signals delivered to the local collection facility. The ASI signal usually is 19 megs or around there, off of the top of my head. From there it is encoded depending upon content and statistical multiplexing needs.

 

[texasbrit]

It's actually not via fiber. Most of the time its via ASI signals delivered to the local collection facility. The ASI signal usually is 19 megs or around there, off of the top of my head. From there it is encoded depending upon content and statistical multiplexing needs.

ASI is 19.2 megs, corresponds to the bandwidth of one ATSC channel. But ASI only defines the protocol, not the delivery medium. ASI can be over copper or SM fiber, whatever is available. I believe both are in use for delivery to the Local Receive Facility, although receiving the OTA signal off-air is more common.

 

[cypherstream]

Wow great discussion!

Our local ABC affiliate packs Live Well HD alongside it's ABC HD feed. And I guess there's an ABC SD and LiveWell SD feed to. ABC looks washed out compared to other networks.

DirecTV doesn't carry LiveWell in SD or HD, but were not missing much. I can get it in ClearQAM from the cable feed and theres nothing to write home about. The one thing is that the 10:1 MPEG2 SD channels on the cable feed blow the SD channels on DirecTv out of the water. DirecTV's SD is very overcompressed. Some of the Cable's QAM SD looks so good that from a distance its hard to tell its not SD.

 

[texasbrit]

Wow great discussion!

Our local ABC affiliate packs Live Well HD alongside it's ABC HD feed. And I guess there's an ABC SD and LiveWell SD feed to. ABC looks washed out compared to other networks.

DirecTV doesn't carry LiveWell in SD or HD, but were not missing much. I can get it in ClearQAM from the cable feed and theres nothing to write home about. The one thing is that the 10:1 MPEG2 SD channels on the cable feed blow the SD channels on DirecTv out of the water. DirecTV's SD is very overcompressed. Some of the Cable's QAM SD looks so good that from a distance its hard to tell its not SD.

With all those subchannels, no wonder ABC PQ is poor.

DireCTv's SD channels, particularly the locals, are very poor. DirecTv reduces the resolution of the SD channels to get more into the available bandwidth.
Some cable systems are almost as bad, probably the best SD quality comes from FIOS.

 

[cypherstream]

Well my local cable system's SD looks fantastic. Some QAM's only have 7 or 8 SD channels on them, and some only have 10. They are all 256QAM too which is 38.8mbps. I know a few miles away Comcast has more like 12 to 14 SD channels in a QAM so it all varies by provider.

Here is the ClearQAM chart published from my provider:
http://www.secv.com/cdocs/qam_birds.pdf

I switch to the ClearQAM input if there is bad rain fade or DirecTV HR24 is recording two shows and I want to watch a third that happens to be accessible in ClearQAM.


It's increadable how different an SD channel looks on DirecTV. Now HD channels look amazing on DirecTV, but unfortunately not every channel that provides an HD feed is available in HD on DirecTV. They really should fix that at DirecTV. If they can't do the HD then at least invest in better encoders so they can continue to overcompress and squeeze more SD than they should be per transponder.

They did a good job with the new Ericsson encoders on a few HD transponders because when they moved from squeezing 5 HD's to 6 HD's, there was no visible deficit on picture quality. Maybe they should invest in some of those encoders for SD too.

 

[tigerfan33]

My local ABC hd looks very soft and washed out too compared to my other local hd channels. No telling how many sub channels they are carrying. I've emailed and called the engineer but to no surprise have heard nothing back.

 

[raoul5788]

My local ABC hd looks very soft and washed out too compared to my other local hd channels. No telling how many sub channels they are carrying. I've emailed and called the engineer but to no surprise have heard nothing back.

It may not be because of how many subchannels the station is carrying. If the feed to Directv is fiber, it most likely is a full bandwidth signal. If it's ota, then probably not.

 

[Broe67]

With all those subchannels, no wonder ABC PQ is poor.

DireCTv's SD channels, particularly the locals, are very poor. DirecTv reduces the resolution of the SD channels to get more into the available bandwidth.
Some cable systems are almost as bad, probably the best SD quality comes from FIOS.

They send what they get. If the feed to them is crap, it is going to be crap when the customer watches.

I have heard that FiOS is pretty bad about screwing with PQ, by cramming the QAM's to max, then what Direct does. Now for granted that there are a couple of channels that are downscaled, but nothing like Verizon or Dish does.

 

[goaliebob99]

ASI is 19.2 megs, corresponds to the bandwidth of one ATSC channel. But ASI only defines the protocol, not the delivery medium. ASI can be over copper or SM fiber, whatever is available. I believe both are in use for delivery to the Local Receive Facility, although receiving the OTA signal off-air is more common.

ASI is not 19.2 its actually 270 megs with the SDI clock standard. What happens is the station packages the ASI signal the way they want it to be presented to the viewer, usually its a mirror directly out of the stations encoder or multiplexer (if more than one sub exists) at the rate that the encoder / multiplexer is set to. That is usually 19.2 or what ever they are giving their OTA signal. You can technically package multiple HD channels in an ASI signal as long as it doesn't exceed 270 megs, but most stations package it like their OTA signal because it's what the end user gets and it's easier to handle when everything is the same. You also forget overhead is in that in that ASI signal and then the ASI signal is usally piggy backed onto an ATM network, or IP network. IP more common in long haul applications. Yes, off air is more common at the Local Collection Facility (LCF). Your belief is wrong. Fiber is only used in the back-haul from the LCF to the uplink as that is a long haul application. ASI signals from the station to the LCF are copper, not fiber when there is an ASI signal is present. Usually ran over ATM networks. It is very rare for an ASI fiber feed to come in as usually the LCF is located within the TV station itself or in an area that is relatively close to the stations that makes running a copper loop feasible. Copper is less expensive than fiber. That is the key!

 

[goaliebob99]

With all those subchannels, no wonder ABC PQ is poor.

DireCTv's SD channels, particularly the locals, are very poor. DirecTv reduces the resolution of the SD channels to get more into the available bandwidth.
Some cable systems are almost as bad, probably the best SD quality comes from FIOS.

SD channels are going away soon. Expect them to be gone in a few years, as HD is the new standard.

It may not be because of how many subchannels the station is carrying. If the feed to Directv is fiber, it most likely is a full bandwidth signal. If it's ota, then probably not.

Most likely via OTA. Could be ASI depending on the market and station, even then some stations package their OTA feed on their ASI signal. So the benefit of full bandwidth may not be there. It all depends on how they have their ASI signal packaged, how many streams are on it. The real benefit of having an ASI signal is that if the station goes down for transmitter maintenance there is no downtime and there are also no weather conditions that could effect an asi signal. Fiber is only used in back haul cases from the LCF to the uplink and that is due to cost. It makes no sense to run an expensive fiber when the station can run a copper line locally. Yes while there are cases where fiber is ran, but that is very slim. Hawaii and Alaska are one of these rare cases due to the distance.

They send what they get. If the feed to them is crap, it is going to be crap when the customer watches.

I have heard that FiOS is pretty bad about screwing with PQ, by cramming the QAM's to max, then what Direct does. Now for granted that there are a couple of channels that are downscaled, but nothing like Verizon or Dish does.

Most of the time its the HD feed downresed and center cut. Especially for the local channels as there is no separate SD feed from an atsc signal unless the station provides it. The only time that I have seen an SD feed would be something on a subchannel and usually is completely different from their main content channel, so DirecTV takes the main HD and downgrades it to an SD feed.

 

[texasbrit]

K9sat - I don't think we are really disagreeing. The three main delivery mechanisms for the off-air stations are OTA (as we both agree, the most common), copper and fiber. You posted that fiber was not used but then you reversed that by saying fiber was RARELY used, used only where distance made it cost-effective and I am sure that's the case.
It's good to see a posting from someone who actually understands how all this works.

broe67 - other than being center-cut from the HD channel (which has its own issues) the "SD signal" could be pretty good quality, but DirecTV actually deliberately reduces the resolution so as to get more SD channels on each transponder.
I think your comments on FIOS are incorrect though. FIOS is the only provider that delivers HD locals in their full OTA resolution (in MPEG2) and you can't do better than that.

 

[raoul5788]

SD channels are going away soon. Expect them to be gone in a few years, as HD is the new standard.

Won't this require every sd sub to have their equipment switched out to hd (mpeg4)? If so, why hasn't Directv be doing this for years?

 

[Hutch1814]

Won't this require every sd sub to have their equipment switched out to hd (mpeg4)? If so, why hasn't Directv be doing this for years?

Directv has started rippling out mpeg4 markets. It's a huge under taking to say the least. Lots of man power and resources are used. I don't see directv going away from SD in the next several years though. Takes too much money, and too many man hours to switch a market over once their is 18X20's and round 18's up everywhere

 

[raoul5788]

That's to my point of why have they been installing sd only setups all these years if the plan is to drop sd carriage at some point.