My cable HD looks like crap - bitrate?

Discussion in 'TiVo Series3 HDTV DVRs' started by MickeS, Sep 6, 2007.

  1. Sep 6, 2007 #1 of 43
    MickeS

    MickeS Active Member

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    I just watched the NFL pre-game show on NBC. I have used OTA before to get HD, and today is the first time I'm using cable. I'm using a Series 3 with SA CableCARDs.

    The show looked AWFUL. Seriously, it seemed like it was some sort of higher-res version of a youtube video. EVERY transition, smoke, flashing light etc during the show was pixelated. Just simple panning over the cheerleaders made the glitter on them pixelated. It looked horrible.

    It could just be that this was very motion intense, which it was... but still, I have a hard time believing I would have not seen something like this before on OTA.

    So I looked at the file size. It's 2.82GB, for 30 minutes of video. What bitrate does that equal? It seems REALLY small to get 1920*1080 (since it's NBC) at 5.64GB/hour. The only conclusion I can draw is that TWC is compressing the signal so much that it comes out like crap. Or is there another reason?

    This was so freaking awful I am inclined to drop HD altogether. I prefer the unpixelated less detailed analog images!

    This is the first thing I've watched in HD so far after getting the CCs... maybe I should hold my horses, I guess it could have been a fluke. I'll see if the game itself, or other shows look better...
     
  2. Sep 6, 2007 #2 of 43
    moyekj

    moyekj Well-Known Member

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    Mission...
    2.82GB * 1024MB/GB * 8 bits/B / (30*60 secs) = 12.8Mbps

    As was mentioned in another thread if you have both the OTA feed and cable feed available to your S3/THD you can record from both at same time and compare file sizes to see how much (if any) bitrate shaping your cable company is doing to the HD locals.

    NOTE: NBC historically has had awful HD broadcasts - the last 2 Olympics come to mind...
     
  3. Sep 6, 2007 #3 of 43
    MickeS

    MickeS Active Member

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    I have no OTA available anymore unfortunately.

    12.8 seems like it falls way short of the theoretical capacity? Isn't it 19.x something MBps?

    I haven't watched any live sports on NBC except golf before, which is way less motion intensive... that looked fine OTA, as did Heroes, The Office and My Name Is Earl. I guess I'll have to record those and see how they look on cable next week or whenever they start.

    "Grey's Anatomy" on ABC looks good right now on cable. Maybe it is just the NBC broadcast...
     
  4. Sep 6, 2007 #4 of 43
    mike_camden

    mike_camden New Member

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    I would bet that it's NBC and not necessarily your cable. NBC's HD presentation of Sunday Night Football was pretty poor last year with softness, loss of camera focus everytime it's zoomed, and just a poor, washed out look. I noticed this on the cable feed for our local NBC channel during most games as well as when I was at a friend's house watching the HD feed via OTA.

    Tonight, I think the pregame show looked very poor (via Comcast) and the game itself has shown a lot of issues with PQ. NBC has a lot of catching up to do with CBS and ABC/ESPN for live games in HD.
     
  5. Sep 6, 2007 #5 of 43
    MickeS

    MickeS Active Member

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    The game itself looks like poor too, IMO. Faces during motion-intensive closeup have lots of pixelation, as does the field and the mesh-parts of the shirts.

    If this was my first exposure to HD, I'd be one of those who just didn't see the big deal.
     
  6. Sep 6, 2007 #6 of 43
    MickeS

    MickeS Active Member

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    I just looked at the Grey's Anatomy recording, it is 2.34GB over 26 minutes. So that would be about the same bitrate, but resolution on that one is 1280*720. Maybe that explains why it looks better?
     
  7. Sep 6, 2007 #7 of 43
    joneSi

    joneSi New Member

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    Watching the Thursday game right now, Colts vs Saints, and it isn't anything to write home about. I'm on Mediacom in Davenport, IA (yes, D-port it is as great as it sounds) and FOX and CBS games do look better. Is it NBC?

    joneSi
     
  8. Sep 7, 2007 #8 of 43
    bkdtv

    bkdtv New Member

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    NBC distributes their feeds at over 20Mbps, so the network itself is not the problem (most of the time). Every broadcaster has 19.4Mbps to work with, but many affiliates divide that bandwidth between the HD feed and another SD feed for weather or traffic.

    About 16Mbps (and 17+Mbps is preferable) is required to produce a MPEG-2 picture with consistent quality on live video broadcasts like sports. If your broadcaster or cable company is supplying significantly less than 16Mbps, then quality will suffer on football. You -- and your broadcaster or cable company -- may not have noticed the problem before because film-sourced material like movies and series programming requires less bandwidth.

    Some cable providers re-compress the local network feed while others do not. If your local NBC affiliate is taking that >20Mbps NBC feed and compressing it down to 12Mbps -- which is completely inadequate for sports -- then they are to blame for the poor quality. On the other hand, if your local NBC affiliate is sending that feed at 16Mbps or 17Mbps, and your cable provider is re-compressing that down to 12-13Mbps, then they (the cable provider) is to blame.

    How do you find out who is responsible for the poor quality so you know where to direct your complaint? Simple, you record the same program from cable and off-air (antenna) and compare the file sizes by hitting Info. Higher quality recordings consume more space.

    By comparing the file sizes of the same program recorded from cable and off-air (antenna), you can determine who is to blame for the poor quality.

    If the recording sizes are the same, then the local NBC affiliate is to blame, and you should call and complain to their engineering department (usually linked on their web site) -- tell them their feed looks ok for series, but is unwatchable with pixelization and macroblocking during sports. If their engineering department does nothing, then you send the same complaint to the station manager. If the station manager does nothing, you send the message to their boss -- the parent company who owns the station, usually listed at the bottom of their web page.

    If the recording from the cable company is smaller in size, then that means they are degrading the quality of the feed. They may not be entirely responsible for the poor quality (depending on the off-air bitrate), but they are contributing to it.
     
  9. Sep 7, 2007 #9 of 43
    MickeS

    MickeS Active Member

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    bkdtv, thanks for your input.

    I just checked 4 OTA recordings of "The Tonight Show" from the NBC affiliate in Tucson, AZ. They range in size from 7.90 to 7.94 GB. That would give a bitrate of roughly 17.44 Mbps (they are 62 minutes long).

    I will record "The Tonight Show" tonight off of TWC here in San Antonio. Even though they are from different broadcast markets, I assume that the OTA/cable comparison should still be valid?
     
  10. bkdtv

    bkdtv New Member

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    NFL football on NBC should do pretty well in 17.4Mbps ABR.

    The bitrate varies on Jay Leno from one night to the next, depending on the content complexity of each show. However, in my experience, the spread from one night to the next is pretty small -- typically less than 0.3 Mbps ABR.

    Many 750MHz Time Warner systems use statistical multiplexing to squeeze three HD channels in every 38.8Mbps QAM slot. Bandwidth is allocated as it is required; if only one channel requires 17+Mbps, and the other two need just 10Mbps to produce a quality picture, then PQ remains good. However, if all three channels require 16+Mbps at the same time, then each is bit-starved with less than 13Mbps and a softer picture with macroblocking is the result.

    For that reason, recording Jay Leno -- a late night program -- from TWC may not be the best way to show you what is happening during primetime hours, because if that is the only channel on that QAM slot running high-def video, it will have more bits available. A better test would compare recordings made during primetime, when more high-definition programming is shown across different channels.

    There was a TWC system in NY that stuck one of the HD RSNs on the same QAM slot with two local networks. The PQ on the local networks would look fine most of the time, but it would degrade badly -- especially on live video broadcasts like sports -- whenever there was an actual high-definition game shown on the RSN.
     
  11. MickeS

    MickeS Active Member

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    bkdtv, thanks again for your information.

    I recorded The Tonight Show off of TWC cable in San Antonio, and the size was 5.89GB. So the bitrate on cable here is 12.97 Mbps, compared to the 17.44 Mbps I had OTA in Tucson.

    I checked one scene in the opening credits, where the camera quickly pans across a TV. It is a noticeable difference between the OTA recording and the cable recording there - the OTA recording displays no artifacts, but the cable recording does.

    I think it's pretty safe to say that my cable company is compressing the signal too much and that it is what is causing this lousy PQ (probably in combination with other factors when it came to the NFL game). I can't imagine that 12.97 Mbps will be enough to even show artifact-free regular programming in 1920*1080?

    Does anyone think that it's worth trying to talk to anyone at TWC regarding this? I mean, obviously they know what they are doing, I guess they just figure most people don't have less compressed OTA to compare to, and will accept this crap.
     
  12. bkdtv

    bkdtv New Member

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    It's unfortunate the TWC in your area degrades their picture to such a large degree. Although cable typically offers a better HD picture than DirecTV, I think in your case, your picture would likely be better with DirecTV.

    I don't suppose Verizon FiOS is available in your area? They don't touch the OTA signal (i.e. identical to off-air bitrate).

    That ~13 Mbps can be sufficient to produce a good picture on episodic series and movies, but it is completely inadequate for live high-definition 1080i video.

    I would complain. That bitrate is just not acceptable for a 1080i channel.

    If you are able to receive channels OTA, I would set your season passes to use those channels instead.
     
  13. MickeS

    MickeS Active Member

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    Nope, no FiOS - only TWC.

    I am watching golf right now on NBC. It looks as awful as the football did, and it never looked this bad OTA in Tucson. Steve Stricker's red shirt is all pixelated when he's walking down the course. This is bad.

    I think I'm just going to buy a DB4 antenna and mount on the wall behind the TV and hope that'll do it (can't receive OTA with my old antenna here, that's why I decided to try cable). Will save me a few bucks per month too. I'm going to write an email to TWC now too.

    I understand people who just don't see the big deal about HDTV, if this is what they're used to. :) I didn't understand it until I had OTA at my house - up until then I had only seen poorly calibrated TV displays in the stores.
     
  14. MickeS

    MickeS Active Member

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    I keep bringing this up... :)

    I recorded 1 NFL game on Fox today, 1 on NBC, and the PGA tournament on NBC.

    Bitrate at NBC was just under 13 Mbps for both broadcasts, and on Fox it was just over 13 Mbps.

    The NBC broadcasts both looked pretty crappy. LOTS of artifacts again, and generally unpleasant to look at as soon as there was motion.

    The NFL game on Fox looked very good - few if any motion artifacts of the kind I saw on NBCs broadcasts. They broadcast in720p. Does the fact that they broadcast in 720p vs 1080i on NBC create less artifacts at around the same bitrate? I'm starting to doubt that the lower bitrate is the only thing that's wrong with the NBC broadcasts...
     
  15. Al-Mann

    Al-Mann New Member

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    Having worked for TWC in San Antonio... I know it's TWC (At least in San Antonio. I can't speak for other cities.) compressing the video too much. It's noticeable on MORE than JUST sporting events.

    BTW... Also having worked for a cable company I shake my head in disgust when people call it "pixelating". The term is actually "tiling" when you see blocks of color...
     
  16. gschoen

    gschoen Member

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    If you are comparing the bitrates between Tucson and San Antonio, it wouldn't tell you who is compressing the signal. Tucson may be broadcasting OTA at 17.44Mbps but that doesn't mean San Antoinio is doing the same. If your bitrate in San Antonio is low, it could be either the affiliate or TWC. You'd have to check their OTA bitrate.
     
  17. moyekj

    moyekj Well-Known Member

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    It's just NBC - after all these years they still haven't figured out how to record/broadcast in HD. They are by FAR the worse HD broadcaster of all the big networks. 720p is in general better for sporting events (60 frames per second for fast action is better than 30 frames per second you get with 1080i which is one reason ESPN* went with 720p). That said CBS does a pretty good job with their broadcasts and they are also 1080i. I wouldn't lay blame on your cable company for this - I record NBC via OTA and there still is a lot of artifacting especially for close up shots on moving bodies. As I mentioned before their Olympic HD broadcasts are atrocious and generated much outrage by AVS Forum folks who bought HDTVs a few years ago for the Olympics only to find it looked like crap most of the time...
     
  18. bkdtv

    bkdtv New Member

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    Any 1080i feed broadcast at less than 16Mbps isn't going to produce a consistently good picture on high-definition video with motion, like football. Hopefully, TWC is the problem in your area so you can eliminate it with that antenna.

    NBC distributes a 20+ Mbps feed and the affiliates compress it as they see fit. Some affiliates deliver that feed at 19.4Mbps, but 16-17Mbps is probably average.

    FOX is unique in how it distributes its HDTV feed. That network distributes their feed at 14.6 Mbps peak, with an average bitrate 10-14Mbps depending on the content. However, unlike ABC, CBS, and NBC, the affiliates do not re-compress these feeds. FOX supplied affiliates with the equipment to pass this signal through without any extra processing or compression. As a result, the quality on FOX's high-definition programming tends to look just as good on every affiliate.
     
  19. jtown

    jtown New Member

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    Just to throw in my two cents, I watched four games yesterday. Two on FOX, one on CBS, one on NBC. NBC's looked like crap. No question. Fox had the best image quality (tho only 720, of course). CBS looked good in 1080 but was noticeably washed out. NBC just looked like crap. Lots of compression artifacts.

    BTW, a high bitrate is not an absolute indication of high quality. It just means the potential is there. Crap in = crap out.
     
  20. nathanziarek

    nathanziarek New Member

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    Anyone able to test this in Milwaukee? I live by the airport and get ultra-lousy OTA reception, so I can't. The game last night was awful...so bad I switched to SD. At least I was getting a known quantity. If it turns out it is the NBC affiliate compressing, I think you have a much stronger case for getting it fixed. They've got a lot of shows they want me to watch and I simply won't at that quality.
     

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