HD PQ Question

[buckchow]

Looking at a Dish "HD" mux right now, I see:
- Mux bitrate = 41.2Mbps
- 7 HD channels, which are only using about 76.4% of the capacity (31.5Mbps) for video and 6.7% (2.76Mbps) for audio, so 83.1% (34.2Mbps) total
- 3 SD channels using up 10.78% of the capacity (4.44Mbps) for audio and video
- Null data (unused bandwidth) = 1.91% (0.79Mbps)
- Subscription/entitlement data = 1.79% (0.74Mbps)
- Other = 2.4% (0.99Mbps)

The average bitrates for the video on each of the seven HD channels after 15 minutes vary greatly, from 2.90Mbps up to 6.25Mbps.

From highest bitrate to lowest:
CBS C - College Lacrosse - 1920x1080i - 6.25Mbps - Upscaled SD
GREEN - Emeril Green - 1440x1080i - 5.96Mbps - Real HD
WGN - Alf - 1440x1080i - 4.54Mbps - Upscaled, Pillarboxed (4:3) SD
ENCOR - Back to the Future - 1440x1080i - 4.29Mbps - Real HD
STRZW - Nutty Professor II - 1440x1080i - 4.19Mbps - Upscaled Widescreen (16:9) SD
CI - Crime 360 - 1280x720p - 3.44Mbps - Real HD
SEDGE - Find Me Guity - 1440x1080i - 2.90Mbps - Real HD

Anything look wrong with these figures? The channel with the lowest bitrate is airing a 1080i-lite premium channel that is airing real HD content, and the channel with the highest bitrate is full-res 1080i but is airing a horribly ugly SD upscale (jagged edges on every bit of the field, players, etc).

Also, what are those SD channels doing stealing away bandwidth on an 8PSK transponder?

Note that if you add up the percentages from the channel-by-channel breakdown and it doesn't match the totals given above them, it's because they were sampled at different times.

 

[buckchow]

Has anyone ever actually measured the bitrate of DirecTV's HD? I haven't read of any actual measurements... just lots of guessing.

I have some bitrates for DIRECTV's MPEG-4 HD, although it's not entirely current.

Transponder 3 on 99W - March 2008:
- 4 HD channels (all H.264) in a 38.7Mbps mux
- Minimum bitrate: 7.52Mbps
- Maximum bitrate: 10.76Mbps
- 90.9% of the capacity used for HD video (35.2Mbps)
- 4.3% of the capacity used for AC-3 audio (1.66Mbps)
- 4.54% of the capacity not used / null data (1.76Mbps)
- 0.0025% used for other data

So, DIRECTV's lowest bitrate exceeds Dish's highest.

Also, DIRECTV is making more efficient use of the total capacity of their transponders. DIRECTV seems to take full advantage of the fact that their MPEG-4 receivers tune Ka-band and Ku-band separately. This allows them to have stuff like EPG data, subscriber entitlement data, etc. coming in from a Ku-band transponder, and use the Ka-band transponders exclusively for audio and video data. This cuts down on redundancy of system data and increases available bandwidth where it is needed most. On both 99W and 103W, there is nothing but audio, video, null data (which varies with the bandwidth requirements of the channels present), extremely minimal data to meet the 13818-1 transport stream format requirements, a very low bitrate data stream for transponder identification (10.06kbps), and one stream for each channels conditional access data at about 1.5kbps per channel.

Everything is encrypted that I've seen on 103W and 99W, so I can't see what the video resolution is. D'oh!

 

[buckchow]

For DIRECTV's transponder 11 on 103W back in October of 2007, I see 5 HD channels in the mux with bitrates of 4.26Mbps, 6.76Mbps, 7.81Mbps, 7.93Mbps, and 8.54Mbps.

I'd be willing to bet the one at 4.26Mbps is so much lower because it's pillarboxed 4:3, but I can't see what it is so I can't say for sure.

 

[codee]

That's too bad, hopefully people will start to realize that more HD isn't necessarily better. PQ was one of the main reasons I switched to Dish from Uverse and will probably look to another provider if Dish doesn't correct the problem. Thing is, my only other option is Comcast and aside from them being an evil company, they compress their HD just as much.

Before I get too far, I want to say out of "disclosure" that I'm a field services Lead Tech for Comcast Inhouse.

That being said, I moved recently and at my previous house I had Dish, along with Comcast. I get Comcast for free, just have to pay for anything above 2 boxes. When I moved in, I didn't get Dish again for the 1st few months - and I had it installed the 1st of the year, and between the time I had it installed and the time I moved something has changed drastically. The entire reason I had dish to begin with considering I get every channel aside from PPV for free, was that Dish had better picture quality, period. Better SD, better HD, better no matter what was on no question about it. Now, things are much different. SD, along with HD on Comcast looks better then Dish I'd say about 95% of the time.

Even the previously worst channels on Comcast in my area (MTVHits, and Noggin/The-N) look much better. Previously the static logos on SD stations had jagged edges, but not anymore. I'm not sure if Dish got worse in this same time, if Comcast just improved that much, or a combination of both (my guess) but I almost don't find it worth the $98 a month I am paying for Dish (2-722s, 250+platinum HD) but I really really like the Dish DVRs and interfaces plus the 3-4 channels the 722k records at once is a HUGE plus. Comcast is still putting 3 channels into each QAM as far as I know, but the compression algorithms have been tweaked and the picture quality IS better now, which makes me debate cancelling Dish almost every day...

*on a side note, reading a lot of threads and opinions lately, Direct seems to be hailed as the king of HD picture quality, I'd like to experience a side by side comparison out of curiosity - I haven't had direct since USSB was a side service with them but I'd be willing to give them a shot again too.

 

[gadgtfreek]

I think Cable has come a long way, but they need to do something about their DVR's. Cox here isnt bad, but they only have a DVR that will record 20 hours of HD with no ext HDD support.

 

[Hemi 6.1]

I think Cable has come a long way, but they need to do something about their DVR's. Cox here isnt bad, but they only have a DVR that will record 20 hours of HD with no ext HDD support.

Same with my cable company, Though not quite as good as D* and E* as far as HD PQ But they make up for that with Tons of Programming they carry over Both Satellite services, In my area anyway.
But those Motorola Boxes are not the same as Fios uses, Fios has a good Box Just short on Hard drive space. My Cable company DVR is Like what the Directv HR-20 was the first day it came out, except half the HD Hard Drive space.

 

[buckchow]

Looking at another "HD" mux on Dish today in a bit less detail:
- 8 HD channels ranging from 3.16Mbps to 5.40Mbps
- A total of 35.2Mbps (85.3%) of the 41.2Mbps in the mux is used for HD video and AC-3 audio
- No SD channels
- 2.72Mbps unused (null data)
- 1.65Mbps used by the MTDTA channel's data stream (whatever that is)

Channel breakdown:
5.34Mbps - Upscaled SD
5.17Mbps - Possibly HD, Possibly upscaled SD
4.03Mbps - Upscaled SD
4.03Mbps - Upscaled SD
3.61Mbps - Unknown, TMP channel without EPG entry
3.36Mbps - Real HD
3.34Mbps - Real HD
3.18Mbps - Upscaled SD


Once again, upscaled SD generally gets more bits than channels carrying real HD programming. Completely backwards, a bit like the net subscriber additions in recent quarters.

 

[JEFFinINDY]

Looking at another "HD" mux on Dish today in a bit less detail:
- 8 HD channels ranging from 3.16Mbps to 5.40Mbps
- A total of 35.2Mbps (85.3%) of the 41.2Mbps in the mux is used for HD video and AC-3 audio
- No SD channels
- 2.72Mbps unused (null data)
- 1.65Mbps used by the MTDTA channel's data stream (whatever that is)

Channel breakdown:
5.34Mbps - Upscaled SD
5.17Mbps - Possibly HD, Possibly upscaled SD
4.03Mbps - Upscaled SD
4.03Mbps - Upscaled SD
3.61Mbps - Unknown, TMP channel without EPG entry
3.36Mbps - Real HD
3.34Mbps - Real HD
3.18Mbps - Upscaled SD


Once again, upscaled SD generally gets more bits than channels carrying real HD programming. Completely backwards, a bit like the net subscriber additions in recent quarters.

Wow, we're getting down into UVerse territory here. Dish's encoders must be much better than what AT&T has. If those are averages over 15 minutes, it would be interesting to know the min and max over the interval on each channel as well, since it's a variable bit rate system. It's possible we could have a lot of talking heads (little motion) in this sample.

 

[buckchow]

Wow, we're getting down into UVerse territory here. Dish's encoders must be much better than what AT&T has. If those are averages over 15 minutes, it would be interesting to know the min and max over the interval on each channel as well, since it's a variable bit rate system. It's possible we could have a lot of talking heads (little motion) in this sample.

The averages for this one were over about 60 minutes.

I've been planning to generate graphs of SD bitrates over time to see whether or not channels with high-activity or lots of close-up detail are really allocated bits when they should be, and how much damage is caused by bitrate reductions in one channel triggered by increases in other channels. I suppose I could do something similar for the HD channels if I manage to ever get around to it. I have a sneaking suspicion that the backward nature of their operations extends to the VBR/load-balancing system, but it would be interesting to know for sure.

 

[gadgtfreek]

3.36mbps for "real hd" is a bit of a concern for me. How low can we go?

I have a feeling we'll be back into HD lite at full throttle within a year or two

 

[buckchow]

3.36mbps for "real hd" is a bit of a concern for me. How low can we go?

I have a feeling we'll be back into HD lite at full throttle within a year or two

It has been HD-lite regardless of bitrate and the other factors contributing to picture quality since the resolution is 1440x1080i instead of 1920x1080i. But I know what you mean, it's heading back to how it was in the worst MPEG-2 HD days.

 

[gadgtfreek]

I know Mpeg4 is more efficient, but after seeing the D* average and then the Dish numbers, I dont guess why D* looks better to me.

 

[JEFFinINDY]

I know Mpeg4 is more efficient, but after seeing the D* average and then the Dish numbers, I dont guess why D* looks better to me.

Maybe I've been watching Dish HD for too long to be objective anymore. Nearly all the Dish HD I watch looks good to me. When I visit friends with DirecTV, their HD doesn't look much different than mine.

 

[gadgtfreek]

It looks good, but on the same tv it just appears softer to me.

Dont get me wrong, not the end of the world, I just wish quality was more important than quantity.

 

[BuddyBoy]

3.34Mbps is significantly lower than any HD I have recorded off Dish with my R5000. I think the smallest file I've ever seen from a 1 hour show was 2.2GB, which ends up being about 1.5x 3.34Mbps (around 5Mbps). This was for Stargate Atlantis on Sci Fi HD. I was quite surprised how decent the quality was at that bitrate, but I'm sure I'd be a lot less impressed with 3.34Mbps.

 

[buckchow]

3.34Mbps is significantly lower than any HD I have recorded off Dish with my R5000. I think the smallest file I've ever seen from a 1 hour show was 2.2GB, which ends up being about 1.5x 3.34Mbps (around 5Mbps). This was for Stargate Atlantis on Sci Fi HD. I was quite surprised how decent the quality was at that bitrate, but I'm sure I'd be a lot less impressed with 3.34Mbps.

The 3.34Mbps was one of the Cinemax channels. You'll have to pay a bunch more than for Sci-Fi for the privilege of being "a lot less impressed."