DirecTV increases compression on HDTV!

[Ken_F]

This week, DirecTV increased the compression on Hdnet by more than 20%. In the past few days, they've dropped the video data rate from 16.8Mbps to about 13.6Mbps, as reported by the 169time recording product, and observed by comparing the file sizes of recordings from this week to those of past weeks. This week, people on the DBSDish and AVSForum are reporting softer sports broadcasts on Hdnet (specifically, less detail on MLS games and hockey), and significantly more pixelization during motion, something that was uncharacteristic of most Hdnet broadcasts before.

It looks like DirecTV may be putting the squeeze on Hdnet, evidently to make room for more HDTV channels, or more locals.

[Scott Greczkowski]

Who would want a Hi Def Channel if it is compressed and no longer in Hi Def?

Smarten up DirecTV

[sampatterson]

I hate the idea that they will compress HD (which is already compressed using MPEG2 to 19.x mb). This is as bad as Faux only doing 480p instead of 720p or 1080i.

Hopefully Dish will not do this. It would be a big differentiator for them. They could advertise "real HDTV" instead of over-compressed HD.

[Curtis0620]

And how does DISH plan on getting 3 HDTV channels on one transponder?

[Mark Lamutt]

8PSK allows 3 HD channels per transponder.

[Curtis0620]

But isn't that compressing the signal?

[Mark Lamutt]

Yes, but it provides much better results than the normal compression scheme used on the non-8PSK channels. Occasionally I'll see a little compression artifacting on D-HD, but pretty rarely. Most of the time, it looks almost identical to the 19.2 Mbps datarate I get with my PBS-HD channel over the air.

[Ken_F]

Curtis,

No, 8PSK modulation does not have anything to do with compression! It's a newer, more efficient means of sending the signal from satellite to your dish. Receivers must support 8PSK modulation before a satellite provider you can use it.

On a 27Mhz transponder, QPSK with 5/6 FEC nets ~30.7Mbps for video, while you get over 46Mbps for video with 8PSK at the same FEC level (which does require higher gain). When a 1080i HDTV movie channel requires 14.2Mbps (HBO HD), that means you can fit at least three of those per transponder at exactly the same quality and compression level, instead of two. Hdnet is originally delivered at 19.3Mbps; you can't even fit two of these on a standard QPSK transponder.

Cable does the same of thing. Rather than using the 8-VSB modulation of OTA broadcasters to get 19.4Mbps per 6MHz channel, they can take advantage of the high reliability of the cable connection to get 38Mbps per 6Mhz channel by using 256QAM modulation. Cable can get 38Mbps for video in 6Mhz of spectrum, while satellite can only do about 10Mbps in the same 6Mhz, obviously because more efficient means of modulation can be used with direct cable delivery than can be used from space.

[Curtis0620]

Thanks.

[markh]

This is just my opinion based on what my brother, who is a broadcast engineer, told me. It sounds like most OTA stations will broadcast a 12-15 Mbps high def signal with another standard def or maybe 2 signals with their bandwidth. This is what they're planning currently where he works. This is subject to change, probably based on how much flak they take over this from enthusiasts of HDTV, like you guys. It will be interesting to see what reaction DirecTV gets over this.

[durl]

Now this is going to make me paranoid. I was watching HDNet one night this week and it seemed that there was some pixelation during fast camera moves. DirecTV better NOT mess with the picture.

Can anyone share the source of the report?

[Ken_F]

durl,

One of the guys at 169time brought it up here (http://www.avsforum.com/avs-vb/showthread.php?s=&threadid=256305) and others have since confirmed. The change evidently took place some time in the last week.

Recordings from Hdnet (using 169time and modified DTC100 with Firewire) are now around 6.5 gigabytes per hour, when they used to be much larger - up around 8.0 gigabytes per hour. Without any extra compression, the Hdnet feed--as delivered to cable and DirecTV--would consume approximately 8.6 Gb/hour.

The drop will probably have the greatest impact on motion and video broadcasts like sports.

[durl]

Well, that pretty much trashes the theory that DirecTV will put together an HD package and charge for it. I'm not going to pay for "enhanced definition." Guess I'll be making a phone call...

[Ken_F]

durl,

Why do you say that? DirecTV could just be testing the compression temporarily, or they could be using it to make space for more Hd channels -- maybe Hdnet Movies or ESPN-HD?

Hdnet still looks great of course, just perhaps not quite as good as it did before-- during program sequences with lots of motion, and for some sports broadcasts. It's still a helluva lot better than enhanced definition.

[durl]

Gut reaction is to be ticked, I suppose. The compression on standard broadcasts is pretty strong and my picture quality is a bit lacking. (Part of that is my fault since I have a projection TV that's a tad too large for our room and that accentuates the pixelation.) Anyway, I was hoping that HD signals wouldn't be compressed to the point where picture suffers.

I just got off the phone with DirecTV and after a couple minutes of checking, the guy said that there was no official notification of modifying the signal. He said that didn't mean that they're not doing anything to the signal but just that they hadn't received word of it. They suggested that I keep checking it and to see if the quality improves.

[raj2001]

Originally posted by sampatterson
I hate the idea that they will compress HD (which is already compressed using MPEG2 to 19.x mb). This is as bad as Faux only doing 480p instead of 720p or 1080i.

Hopefully Dish will not do this. It would be a big differentiator for them. They could advertise "real HDTV" instead of over-compressed HD.

Based on DISH's record with SDTV, I think that DISH will do this and eventually get alot worse.

[sampatterson]

I would not want to pay $10 for an HDTV package if they were not going to be passing the full 1080i(or 720p) stream from the broadcaster. I don't mind them using different modulation schemes (8psk, et al) as that does not effect the actual data (unless of course it introduces errors).

[Compression Sucks]

Originally posted by markh
This is just my opinion based on what my brother, who is a broadcast engineer, told me. It sounds like most OTA stations will broadcast a 12-15 Mbps high def signal with another standard def or maybe 2 signals with their bandwidth. This is what they're planning currently where he works. This is subject to change, probably based on how much flak they take over this from enthusiasts of HDTV, like you guys.

As one who has seen different rates OTA; I can tell it makes a difference.

I get WKYC-DT NBC Cleveland OTA and WDIV-DT Detroit NBC via Star Choice

There is a large difference in detail between the 12 Mbs WKYC HD picture and the 16 Mbs WDIV HD signal.

WKYC sends out HD + 2 SD signal whereas WDIV is HD + 1 SD signal

[Jacob S]

This is why Dish went to the 8PSK standard, so they would not have to compress so much and lose the true HDTV picture. DirecTv must be getting ready to add more HDTV channels or needs more space for locals.

Dish could compress theirs as well and get 4 instead of 3 on a transponder but I wonder how much that would affect their picture quality. If they would do this then it would be worse to do it later than sooner when more people have the special receivers, dishes and tv's to pick them up with.

[DarrellP]

13.6 Mbps, Holy Cow! I wish I had that much for my local CBS. They cram it down into a 12 Mbps signal and claim that is "good enough". BS! CSI looks like crap at that bitrate. They also run a standard def and a weather channel, destroying our HD picture.

[Ken_F]

Darrell,

The ~13.6Mbps data is for the video portion only; the total MPEG-2 bit rate is a bit higher. DirecTV probably also has better HD encoders than most network affiliates.

It's been reported over on AVS that Hdnet is originally distributed as a 19.3Mbps feed to cable and satellite providers, which can then do with it as they please.

[waydwolf]

    Hmmm... From what I'm seeing in the cable industry magazines and speaking with engineers, there is plenty of bandwidth for HD without overcompression on cable, and they have no plans to follow the lead of Dish and DirecTV in this area.

:grin:

    I can hardly wait till Cox rolls HD in CT.

 

[Ken_F]

According to the AVS Forum, DirecTV went back to it's original, higher bit rate last night (i.e. no more extra 20% compression).

[Scott Greczkowski]

Good to see them fix the problem. Let's hope that teaches them a lesson. :D

[sampatterson]

Good. As I posted on AVS forum, there could be a good conspiracy theory here... Mudoch of Fox buys directv, directv HD starts to compress HD to make it like Faux Widescreen...

[RWebb71980]

Does anybody know what the bitrate of the standard 480i channels is on E* and D*?

If HD is 15-20 Mb/s then the standard def. must be around 5 Mb/s.

Just wondering,
Rob

[Ken_F]

RWebb,

It varies by SD program. Sports channels require more bandwidth; premium channels are given somewhat more bandwidth. For Twilight Zone on SciFi recorded on January 23:

peak bitrate 6.670 Mbps
avg bitrate 2.106 Mbps
peak Q level 17.45
avg Q level 9.91

Most SD programs apparently average about 3Mbps (well above that on sports channels); they can go higher than that on intense scenes, and well below that on scenes with no motion or action.

[Mike123abc]

Actually Dish can get even more bandwith through their 8PSK than mentioned above. Dish runs 20million symbols on QPSK, but on the 8PSK transponder they are doing 21.5 million symbols. So, 21.5 x 3 x 5 / 6 x 188 / 204 = 49.5 mbit/sec. So, if they want 3 channels it is about 16.5 mbit/sec each.

On standard def using QPSK Dish is running 5/6 FEC or about 30.7 mbit/sec and Direct is running 7/8 FEC or about 32.25 mbit/sec.