Last night I was messing around figuring out the datarates of some of the HD channels off C-Band from 58W to 137W. I was finding quite a variance between some of them, and some of this explained the difference in apparent PQ that can be seen with the naked eye. What started me on this was seeing in close succession the PQ on PBS HD01 from 125W ku and then PBS HD from C-band. I thought the ku feed looked not as good, so i compared some recordings and began making new ones. For example, last night off PBS feeds, the C-Band was somewhere around 14 Mbps and the ku feed was down around 7 Mbps (numbers from my memory). I was going to compile a list for comparison and would jack up the priority if there was interest, or forget it if it's already been done (if so give me a pointer
). A few sports feeds were up there at ~30 Mbps, expaining why ther usually look so damn good!
Has anyone compiled a spreadsheet with data rates observed for the various channels "up there"?
The picture quality is the reason I participate in this hobby.
Three things matter when it comes to picture quality: resolution, codec, bitrate.
It doesn't matter how high the bitrate is if the resolution is only 720p. It takes some serious bitrate starvation to make 1080i look worse than even a high bitrate 720p feed. This is why News Corporation/Disney owned networks look so awful. ESPN backhauls are easily the worst I have ever seen and they often have a bitrate exceeding 40 Mbps! 40 Mbps is the highest possible bitrate allowed within the specifications for
Blu-ray. If you've ever watched a CBS backhaul, you know they tend to be the same bitrate as ESPN - 35+ Mbps, MPEG-2. The key difference? They are 1080i. That is why CBS utterly
destroys ESPN and Fox backhauls. Most 18 Mbps 1080i MPEG-2 backhauls I have seen are also significantly better than ESPN's 40+ Mbps backhauls in the picture quality department. All that extra bitrate is wasted when the resolution is only 720p. I've watched 1080i NBC and CBS affiliates over the air and they look better than any ESPN, Fox, or ABC backhaul I have ever seen.
We are also aware of how pathetic quality ABC's fronthaul feeds are, even though they are encoded
identical to NBC's fronthaul! ABC is L4.1 H.264 video @ 24 Mbps. NBC is L4.1 H.264 video @ 24 Mbps. They even seem to be using the same Tandberg encoder with the phase-aligned MP2 audio pairs. So why does ABC look so much shittier than NBC? Because NBC is twice the resolution.
The second thing we know is that the codec is also important. H.264 is twice as efficient as MPEG-2 and it's been designed to prevent macroblocking, the worst enemy of the MPEG-2 codec. A H.264 feed can be bitrate starved and still look pretty damn good. It's really only when a H.264 feed is assigned a bitrate lower than 10 Mbps that it starts to look sh!tty.
NBC's backhauls blow most others out of the water. The reason? They tend to be 25-35 Mbps 1080i H.264. You can have a 40+ Mbps 1080i MPEG-2 backhaul and and a 25 Mbps 1080i H.264 NBC backhaul will easily kick its ass.
The last thing is the bitrate. We all know this hobby takes a dump all over the plebs watching over the air, cable, or pizza satellite. OTA and cable both exclusively use MPEG-2 at horrendous bitrates. The bitrate of an over-the-air affiliate can be no higher than 18 Mbps per the ATSC specification; but with the recent subchannel craze OTA affiliates typically vary from 8-14 Mbps. There are not many 18 Mbps affiliates left. Cable is similarly terrible, with most companies now packing 3 to 4 HD channels to a QAM frequency. A QAM256 frequency has the same amount of bandwidth as your typical DVB-S transponder at a high SR and FEC of 3/4 - 38.8 Mbps. If cable companies only put
one HD channel on an entire QAM frequency then they could deliver the same quality as the 30+ Mbps backhauls we are used to; instead, they re-encode everything to 9-12 Mbps MPEG-2 to fit four channels to the frequency.
DirecTV and Dish Network are both terrible as they suffer from the same problem as the cable guys. DTV/DN subs don't have motors so the hundreds of channels these companies carry can't be spaced out; they are limited to a couple of satellites only and there simply isn't enough transponder capacity to deliver proper bitrates for HD on pizza. The only redeeming factor of DirecTV and Dish Network is that their equipment does not consist of decade-old hardware so they use H.264. They ruin this advantage however by bitrate starving the H.264 so severely down to ~6 Mbps - half of what the cable companies give MPEG-2 - so Dish/DirecTV don't end up looking any better than the cable companies.
So with that in mind here's some of the bitrates we know of from channels in the clear, ranked in terms of highest quality:
NBC - 1080i; H.264; up to 25 Mbps
CBS - 1080i; MPEG-2 (4:2:2); 36 Mbps
CW - 1080i; MPEG-2; 40 Mbps
PBS - 1080i; H.264; 12 Mbps
NHK World - 1080i; H.264; 12 Mbps
ABC - 720p; H.264; up to 24 Mbps
HispanTV - 1080i; H.264; 9 Mbps
RT America - 1080i; H.264; 9 Mbps
Pentagon Channel - 1080i; H.264; 9 Mbps
NASA - 720p; MPEG-2; 15 Mbps
PlumTV - 1080i; H.264; 6 Mbps
Reelz - 720; H.264; 6 Mbps
Last night I was messing around figuring out the datarates of some of the HD channels off C-Band from 58W to 137W. I was finding quite a variance between some of them, and some of this explained the difference in apparent PQ that can be seen with the naked eye. What started me on this was seeing in close succession the PQ on PBS HD01 from 125W ku and then PBS HD from C-band. I thought the ku feed looked not as good, so i compared some recordings and began making new ones. For example, last night off PBS feeds, the C-Band was somewhere around 14 Mbps and the ku feed was down around 7 Mbps (numbers from my memory).
This is incorrect. The feeds on AMC 21 are always 12 Mbps 1080i H.264. They look better than the C band feed.
