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#21
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If I were running a cable company..
I would un-encrypt QAM for the extended basic tier of channels and let users pull them in with service like they do today by hooking up to the QAM tuner in their spiffy digital TVs. B |
#22
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Cable vs OTA
It's important to keep in mind that the digital files received OTA are not the same as those received by cable or satellite. A friend of mine was surprised when he saw the quality of my OTA HD programs. He recently upgraded to HD on his satellite subscription, thinking he would be getting the best quality HD picture available.
For those people with high quality 50+" HD sets, the difference is quite noticeable. Unfortunately, the file size of OTA programming is also larger than satellite or cable. But that's the price one pays for quality. |
#23
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That's true, but there is a significantly limited content available OTA. In addition, satellite digital is not necessarily HD and would be better to compare to SD in most cases. The HD on satellite is nowhere near the quality of HD OTA, but nobody is forcing you to change to HD, only digital.
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#24
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I agree that when using satellite or cable, the difference in file size between SD and DTV won’t vary much, if at all. However, OTA isn’t the same. SD and HD files are about the same size OTA—big! So if a person is using an antenna, s/he will notice a significant difference when changing from analog to digital tuners. And as I understand it, that’s the subject of this thread. I myself enjoy the much higher quality of OTA broadcasts, especially with giant screen HD. Furthermore, when we switched from DirecTV to an antenna, I thought everyone would miss the selection available on satellite. Surprisingly that was not how it turned out. Without satellite, the family has more TV recorded than they have time to watch. And of course it’s a whole lot cheaper. (free, that is!) And for those of you who would miss reruns and movies, there’s always a $20 subscription to Blockbuster or Netflix. That about covers it for most everyone except maybe the sports and news junkies. And for those wondering why I ditched satellite TiVo and DirecTV for an antenna, the answer is simple. So I could afford a new giant screen HDTV. The high quality recordings were just a nice bonus. Last edited by wtsitmn; 07-13-2007 at 11:04 AM. |
#25
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This brings up another issue I've been wondering about. Since all OTA HD broadcasts are 16x9, will owners of older 4x3 sets get black bars on the top and bottom of their screens? Last edited by wtsitmn; 07-13-2007 at 11:15 AM. |
#26
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It's true that a lot of OTA primetime programming is HD, so those recordings will be bigger than analog users are accustomed to, by about the factor of three I cited earlier, i.e. 6-8 GB/hr.
However it's also true, at least in my area, that some digital OTA stations broadcast some of their programming in SD, and these recordings are comparable in size to what I used to record with my analog tuners, i.e. about 2-3 GB/hr. I give the actual numbers, now and in my previous post, in the spirit of being helpful rather than pissy. I also think it helps, when someone says "your existing system can't handle HD", to post counterexamples of systems that can and do handle it with fairly run-of-the-mill components. And again, I gave the numbers to back that up. Sorry if that came off as "mine's bigger" to you; that wasn't the intention. If you want specific advice on how to troubleshoot your system, the first step (as I tried to imply earlier, apparently not very successfully) is to figure out where the bottleneck actually is. Windows 2000 and XP include performance monitoring tools that should help you narrow it down to disk, network, CPU, or what have you. My guess, based on the numbers and on my own experience, is that it's not your disk.
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-- Greg |
#27
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2x2x2=8
Isn't that odd. When I recorded programs using my old analog tuner, they took just under 2GB/hr with a Sage setting of "Great". With a digital tuner, the very same programs used just under 4GB/hr. I know this because I used to record many episodes of Cheers and noticed the files were really hogging the disk space when recorded with my new digital tuner. Then I switched back to using the analog tuner to record those programs, and the size of the files was cut in half.
The other point I was making was that someone who is accustomed to recording a program which is broadcast in HD will find the size of the recording to be at least 4 times larger when they stop using an analog tuner because they will be forced into recording the HD version, which runs about 8GB/hr. So when I first said DTV files were humungous, that's what I was talking about. Yes, HD is twice the size of SD, but SD is at least twice the size of analog. So with many new programs now being broadcast in HD, there is much to consider when converting from analog to digital tuners. At least when using an antenna. BTW Greg, would you care to include your computer specs in your profile? Then I and others would have a basis for comparison. Thanks for your help. Last edited by wtsitmn; 07-13-2007 at 01:35 PM. |
#28
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So we've determined that DTV file sizes vary depending on the program and the broadcaster, which isn't too surprising. A factor of two either way isn't a big deal for me, since I generally delete recordings after watching them. For archival purposes, Sage V6 has built-in conversions that let you compress things down to smaller files sizes if you like.
Here's another current thread specifically about HD system specs (including mine): http://forums.sagetv.com/forums/showthread.php?t=26297 There are also a number of current threads about HD troubleshooting.
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-- Greg |
#29
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Thanks
Thanks Greg.
I see you have a rather robust system, to say the least. Clearly superior to what I'm using now. No wonder you're not experiencing performance issues. The 1000MHz FSB alone should help your throughput considerably. That added to your dual core 64 bit processor would significantly outperform older machines. BTW, in all this discussion perhaps I didn't make clear that when my system has problems is when it's simultanously recording three HD programs and playing another HD program. Have you ever tried doing this particular combination? It would be much more stressful on a system than recording SD 4GB/hr programming. But with your particular configuration you may have no trouble. |
#30
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Whoah there, back up a bit, you're mixing terminology there and that can lead to confusion. There are basically two "format" categories, SD (480i/525i) and HD (720p+). In the strictest technical sense, these are independent of the transmission scheme. Ie they can be analog or digital (I believe Japan had analog "HiVision" for a while). Separately, there are two categories of transmission scheme, Analog (NTSC/PAL) or Digital (ATSC, Digital Cable, Digital Satellite). But the video format is independent of transmission scheme. Now in practice, if we're talking analog here, we mean SD because nobody broadcasts analog HD and there are no tuners available. When we're talking digital, we have to be careful because it can be either. Now regarding file sizes for "digital" Cable/Sat, that's not a simple answer as you make out. For digital SD, file sizes will generally be quite small, usually on the order of 1GB/hr, maybe 1.5GB/hr. For Digital HD from Cable/Sat it will be significantly larger, but probably only on the order of 5-6GB/hr*. What you should note is that you can't use size to directly compare quality between our analog recorders and the cable/sat digital feeds. Why? Because the cable/sat companies have multi-thousand-dollar realtime encoders that are far more efficient than even the best hardware PC encoders. You'll find that the cable/sat companies can get roughly the same quality at probably 1/2-1/3 the size our encoders can. *With the move to MPEG-4 HD, HD from Satellite will proably be on the order of 2-3GB/hr due the significantly higher encoding efficiency of the codec+encoder. Quote:
Again, note that size depends on format (HD or SD). Now, the complication with "HD" broadcasts. Most OTA channels broadcast their HD sub as HD all the time, regardless of whether the source content is HD or not. They will upconvert the majority of their non-primetime programming. To summarize, size is tied mostly to broadcast format (HD or SD), that will determine the general magnitude of the size, though there is a general tendency for OTA to be slightly larger than Cable/Sat due to the later's bandwidth restrictions. But you just can't say OTA is bigger than Digital Cable/Sat. Quote:
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Realize that most content is still not HD, and that satellite, while digital (and generally better than NTSC), is not usually HD, so of course OTA HD will be better. Quote:
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Cable companies are also moving to "Switched Digital" to free up more bandwidth as well. As analog "dies". I think the cable companies are going to be bolder and bolder WRT forcing STBs on people. Of course as they do it, they'll risk losing a significant number to satellite as I think many shy away from Sat due to the STB requirement. As for sat users, well, nothing will change as Sat is already all digital and everybody already needs boxes. Quote:
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As you noted in the previous paragraph, the difference is closer to 2x ratio. And that depends on what analog quality setting you were using. Many record at closer to 3GB/hr. Quote:
No, actually digital SD, if actually broadcast in SD, is on the order of 1/2 to 1/3 the size of analog SD. When I've recorded SD off digital cable or Dish, they end up right about 1GB/hr, sometimes a bit less, sometimes a bit more. They're actually so small, that for some of the ones I've pondered archiving, I'm having a tough time justifying the effort to compress them as they'd only be 30% smaller. The Cheers example you use above is almost certainly of upconverted SD. So what you're recording is actually an HD broadcast, HD file, but the content is SD sourced. |
#31
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Stanger89 - Thanks for the explanation, that answered a lot of my questions.
I always wondered why some HD channels looked so bad, now I know it's because they are upconverted & not true HD. You're also right on that the cable company's equipment is far superior to anything we can get. I rented a DVR from the cable company about 2 years ago & I couldn't believe not only how much better the pq was of the analog channels, but that the recordings were only 1GB/hr. I really don't like paying a cable tax (renting a stb), but the quality is so much better I'm tempted to give in. BTW, do you own an '89 Stang? |
#32
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#33
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..snip
Well not quite. Sats going through a big change as well. To also increase bandwidth (more HD channels) they are switching over from MPEG2 to MPEG4. It means subscribers will have get new dishes and new equipment to receive these newly offered HD channels. TIM |
#34
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For me it's going to change the way I get the cabletv now by the end of the year that project will be finish. All digital no more analog... Does SAGETV 5.9x support HVR1600 if I would need to buy one since 4x analog PVR150s won't work and I need to get my media on 5x MediaMVP.
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#35
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The biggest thing to remember is that the digital change over date only applies to over the air broadcasts. Cable does not have to change a thing and in most cases wont. When more HD channels come on line I expect them to require cable boxes since it won't be feasible to do it all over analog but hopefully by then solutions similar to HD homeruns only internal will be available.
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#36
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__________________
- Jack __________________________________________ Server: AMD Phenom 9750, 2GB RAM, 2 Hauppauge PVR500, 1 Firewired DCT6200, 1 HDHomerun tuning 2 QAM channels, Vizio 37" HDTV LCD, 1 USB-UIRT Clients: 1 MediaMVP, 1 Placeshifter Client, & 1 SageTV Client. |
#37
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Remember, the bandwidth required by one SD analog channel can carry at least 2 digital HD channels, or upwards of 16 digital SD channels. Oh, and as for analog HD, well, that would take probably 6 analog channels worth of bandwidth, and there's no standard for analog HD broadcast. |
#38
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Remember, you will still be able to use an analog tuner from a cable box (via S-video). The digital switch over applies from the cable co to your house.
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#39
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There is perhaps, a bit of hope though, that the current "clear" analog channels with transition to "clear" digital channels, maintaining the current status quo of not needing to rent anything to receive the "basic" or "expanded basic" tier. Slim hope of that though. |
#40
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Stanger, I was just trying to make the point that no one should be panicking that their analog tuners will suddenly become useless.
With h.264 encoding a cable co can cram about 3 times as many digital HD channels as analog SD. So there's the motivation right there. If cable doesnt move to all digital there's no way theyd be able to offer nearly as many HD chans as satellite. |
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