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What Are The Differences In Lines Of Resolution Between Broadcasted And Recorded Video Sources?
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64026402
Senior Member
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4. September 2004 @ 17:41 |
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I have more fun watching the sparks between the Mac and PC camp then actually participating.
I just need my computer fix reguardless of were it comes from.
Donald
This message has been edited since posting. Last time this message was edited on 4. September 2004 @ 17:44
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4. September 2004 @ 17:46 |
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In an odd sort of way we're on point since we're discussing grapics. Yes I agree in fact IBM clones are faster in all respects.
" Please Read!!! Post your questions only in This Thread or they will go unanswered:
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64026402
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4. September 2004 @ 17:50 |
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It looks like Francis is stalling on the coast. Hows the wind.
Donald
This message has been edited since posting. Last time this message was edited on 4. September 2004 @ 21:04
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4. September 2004 @ 17:52 |
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The wind is gusting and we're getting patches of rain but nothing unpleasant yet.
" Please Read!!! Post your questions only in This Thread or they will go unanswered:
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64026402
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4. September 2004 @ 19:45 |
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Still there Sophocles?
Lights on anyone home?
Donald
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4. September 2004 @ 21:02 |
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Since I haven't had a chance to respond to the original topic I'll start there ;) First off, let me start with a disclaimer. Despite what my guides and some of my posts may suggest, I haven't been working with video for very long. In fact besides being able to follow some simple instructions, I didn't know much of anything until about a year and a half ago when my computer died from a lightning strike and I got a replacement from the insurance company that had a capture card. I've learned a lot about digital video since then, mostly because I had to figure out CCE SP, and you can't really make good use of it without understanding quite a bit. I've never read any books or taken any classes on it, and my only sources of information have been from the internet and my own personal experiences with it. That may surprise some of you, but trust me, I learn more from others here (and other places) than anybody learns from me. I just happen to pick it up quickly and make a lot of good deductions.
Analog video, on the other hand, is more like PFM to me. Since my capture card uses a hardware encoder, and there is almost no software besides what came with it that can control it at all, I've learned a lot less about the subject. I understand the basics, mostly from reading and re-reading (and re-reading and re-reading) the articles, guides, posts both on and linked to from Doom9. I won't pretend to know as much about the resolution of different analog video sources as others here, but I will share what I've personally observed and the conclusions I've drawn from it. I wouldn't be surprised to find that I've come to some incorrect conclusions, so please correct away.
You should be happy with that Sophocles - already a long post and I haven't said anything yet ;-)
Let me start by restating and expanding on the point I was trying (ineffectively) to make in the other thread. I believe it's inaccurate to say that all analog (SDTV) captures are no better than VHS quality. That's not to say that they're DVD quality, because I have yet to see one I wouldn't be able to distinguish from a correctly transferred and encoded DVD of the same material. When I say analog captures, I'm not talking exclusively about video that's been purely analog from beginning to end. I also include digital cable and satellite signals that have been decoded for display on a TV. Since neither receiver I used to use for digital cable and the ones I currently use for satellite reception have any digital outputs, I've done a lot of experimenting with both formats, and have been able to make visual comparisons of both to analog cable and VHS.
Let's start with the VHS since (IMO) it's clearly the lowest quality of the lot. Many people think exclusively about the amount of information that can be stored on a video tape, which is clearly not anywhere near the equivalent of D1 resolution, but this is really not the only problem with capturing from that medium. The worst flaws from VHS (once again IMO) are from the physical characteristics of the tapes and the playback mechanisms. The susceptibility of tapes to wear and tear, and the differences between one VCR and another (at least those anywhere near my budget) lead to picture distortion that I find very annoying, and as a result those things catch my eye immediately. For more informative discussion of capturing VHS than I could ever hope to provide I recommend reading this thread: http://forum.doom9.org/showthread.php?s=&threadid=34122 I don't pretend to understand where a lot of the calculations come from, but for anyone interested in testing things for themselves (or getting information from knowlegdable people who have) it's a good place to start.
Then there's analog cable. Since there's not consumer level video tape playback involved (hopefully), some of the playback flaws are all but eliminated. I know next to nothing about the actual amount of information stored in these signals, but I will say that I find them to be higher quality than what I got from most channels I had on digital cable, but that's due to the bandwidth limitations intentionally imposed by the cable company in order to provide internet service. Cable signals have their own physical problems from being transmitted long distances. Obviously, the signal can never be better than what the poorest section of transmission media allows, and of course most people have substandard media in their homes anyway. Additionally, since this is a purely analog transmission, some of the signal will be replaced by noise, and if it needs to be amplified, the noise will be amplified along with the signal.
Digital cable is, in theory, a better approach. Being a digital signal that's just transmitted in analog, it can be periodically repeatered to avoid signal loss. Unfortunately, digital cable normally means cable internet as well, so the bitrate of the signal is compromised in order to save bandwidth for internet service. As a matter of fact, I found that on the local system here, premium channels had enough flaws that they were often unwatchable. I've never looked into what the resolution of a digital cable signal is, but I do know it's often higher than it should be for the bitrate used for transmission. Whether that's because it's encoded with that bitrate in mind and that causes the picture quality to suffer or it's encoded at a reasonable bitrate for the resolution and information is lost due to a lack of transmission bandwidth I don't know. To be honest, I didn't understand digital video nearly as well when I had cable, so I just didn't think too much about it at the time. Like analog cable, the signal can also suffer due to poor transmission media at any point from the origin to your receiver.
Satellite television (standard definition) has higher quality than any comparable cable signal (and certainly any VHS signal) I've ever watched. It's sharper, and barring interference from atmospheric conditions (or solar flares) it has a lower occurence of artifacts that can be clearly traced either to lack of bits for encoding or loss of bits to be decoded. The exact resolution for the 2 major satellite services in the US (DirecTV and Dish Network) seem to be closely guarded secrets, but from the research I've done it seems that either 480x480 or 540x480 is used for nearly everything, although it's possible that pay per view programs may use higher resolutions than that, and from the few I've seen myself, they certainly have higher bitrates than regular programming or premium channels. Likewise, the bitrate seems to vary among the regular subscription channels. My biggest dissapointment with Dish Network has been their paranoia about computer based receivers, which is the only reason I can't get a capture card that would allow me to save the data stream directly to my PC.
As I mentioned, my captures were done with a Sony hardware MPEG encoder. The encoder chip used is one that's also used in standalone PVRs available in Japan, but not the US. It captures at 352x480 or 720x480, and can capture at a bitrate that far exceeds what either digital cable or satellite signals are encoded at. For most of my captures I connected the S-Video and RCA audio outputs from the back of the receiver directly to my PC. For analog cable I connected the cable directly to a VCR and used that for a tuner (to avoid interference from the PCI bus which causes problems for the internal tuner), connecting the RCA video and audio outputs to the PC.
The biggest flaw it has is an intra DC precision of 8, which is DVD compliant, but not as high as the maximum compliant value of 10. There's very little information available anywhere about this card, and pretty much all of it is in Japanese. Initially I was only able to find a page that referenced the MPEG encoder chip (by searching for the part number) being used in the Sony standalone PVR. Eventually I ran across it referenced with the name YUZU, and was able to find a little more information, but not much of any real use.
My initial captures were done from cable. The channel I was capturing from looked pretty good when using the digital cable signal, but overall the quality was much better from the analog version. Mostly it was just a question of consistency. The best parts looked better from digital, but the analog quality rarely fluctuated. Neither was particularly sharp.
When I replaced my cable with satellite service I kept capturing from the same channel, but the signal was much sharper, and had a lot more detail. There were still times when it didn't look good, but I could always trace those to reception issues. Aside from occasionally not having any signal, the video is always better than my cable ever was. When I was doing a lot of experimenting, I even captured a pay per view movie, and the results were amazing. I'd compare it to laser disc quality. Obviously that's not representative of the quality of most programming, but it's definitely possible.
Before I wind up this already long winded post, it's worth mentioning that when I discovered that my card only encoded with an intra DC precision of 8 I figured there wasn't any point in re-encoding with an intra DC precision of 10 because that would be trying to get more detail than the source. I did a lot of testing trying verify that, and I was surprised to find that in every case, setting it to 10 in CCE resulted in a higher quality encode. To me that's significant because it means that a good encoder can do a better job of filling in the "missing" details than my TV. This may not apply to better TVs, but it seems to apply to mine.
And with that I'll wrap up my dissertation ;-)
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64026402
Senior Member
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4. September 2004 @ 21:23 |
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Now that was the post we were all waiting for.
And it was well worth the wait.
Since it was my comment about the TV capture not being better than a VHS I'd comment first.
I was WRONG.
I was over generalizing the poor old NTSC standard and didn't take into account he might be using satellite. VHS is a poor recording medium.
I was also hasty about not using CCE. It could be very usefull with adjustments to clean up or maintain the quality of a compressed show.
I personally have a Directv DVR and love it.
Donald
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Staff Member
2 product reviews
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4. September 2004 @ 21:30 |
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Quote:
Now that was the post we were all waiting for.
Or dreading ;-) Maybe I should have divided it into chapters.
Oh, and thanks to everyone for cleaning up the other thread. I realize it's far from the only one that's gotten way off topic, but I'd hate to see all the effort we already went to in keeping it clean go to waste.
This message has been edited since posting. Last time this message was edited on 4. September 2004 @ 21:33
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64026402
Senior Member
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4. September 2004 @ 21:35 |
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Your posts are alway well written, interesting and informative. No wonder you write good guides.
Most super long posts are annoying but I look foward to yours.
Donald
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4. September 2004 @ 21:59 |
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Damn Vurbal got here before the Hurricane did and he's hit twice as hard.
" Please Read!!! Post your questions only in This Thread or they will go unanswered:
Help with development of BD RB: Donations at: http://www.jdobbs.com/. This message has been edited since posting. Last time this message was edited on 5. September 2004 @ 08:20
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4. September 2004 @ 22:11 |
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So do you have any corrections? Or have you not been able to read it all without getting a headache?
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5. September 2004 @ 09:55 |
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Vurbal
I haven't got time for corrections just now, Frances is knocking on my front door. So far it's taken the roof off of my tool shed and there are sparks flying from the electrical wires over my neighbors yard. Across the street a power line is down. I expect to be without power anytime now. Its still a hurricane and I'm dead center in the path of its eye but I have to say it's an awesome sight, expecially to see a 200 year old oak bend in the wind like a weed. I'm reporting this because Donald asked, if I don't report back then it's because I'm unable to.
" Please Read!!! Post your questions only in This Thread or they will go unanswered:
Help with development of BD RB: Donations at: http://www.jdobbs.com/. This message has been edited since posting. Last time this message was edited on 5. September 2004 @ 09:56
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64026402
Senior Member
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5. September 2004 @ 10:12 |
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Wow,
Tales from the front line.
I have been watching the hurricane on satelite. Its right there on you.
Hold on tight Sophocles.
Donald
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5. September 2004 @ 11:05 |
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The power here is off and on and my computers has been shut down by power failurs so many times that it was difficult just to get it to boot. I can't believe I'm still able to ge online. Nature holds no punches. am I glad this thing slowed down to a category 1.
" Please Read!!! Post your questions only in This Thread or they will go unanswered:
Help with development of BD RB: Donations at: http://www.jdobbs.com/. |
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64026402
Senior Member
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5. September 2004 @ 11:28 |
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Are you on the laptop now.
I hope your not powerless for long. If the storm would just leave. It seems to be just hanging around.
Oh yeah, VCR, blah blah, broadcast tv, blah blah.
Donald
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5. September 2004 @ 11:39 |
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Power is down all around me but mine is still up more or less. When charlie came near by my powerline went down so I think when they repaired it they strengthened it. The storms is just hanging to the east and I'm waiting for it to hit and I'm hoping it will get down graded. I'm not checking spelling don't have time. Be back later.
" Please Read!!! Post your questions only in This Thread or they will go unanswered:
Help with development of BD RB: Donations at: http://www.jdobbs.com/. |
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5. September 2004 @ 11:41 |
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Hope you make it through alright. We'll be waiting for news.
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5. September 2004 @ 23:27 |
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A bit rushed but considering how many times my power has been out today, I'm lucky to have finished anything.
First let me start by conceding that non HD Digital TV is capable of 480i by 480p lines of resolution which is the limit of standard TV, and provided these capabilities are in use, it?s as good as one can expect outside of HDTV.
To access DTV?s resolution the TV/PC tuner, must be connected through a high quality connector such as component connectors for optimum quality or S-Video connectors which are still almost as good but limited to 400 lines of resolution. Super VHS is also capable of 400 lines, so if we?re comparing DTV cable against VHS quality, then SVHS can?t be excluded and Donald?s original allegation still stands.
Like Vurbal, I was unable to discover the actual picture quality produced by DTV (and it does seem to be a well guarded secret) and so I?m still conceding to its maximum potential. Because it is an on air captured signal it is as are all such signals, subject to the defects that standard radio is such as bad weather and atmospheric conditions. It?s reasonable to assume that the ultimate quality of such a transmission will therefore vary in quality (I verified this while surfing for info) based on location and other environmental conditions.
This however was not the substance of Donald?s statement regarding picture quality which was in regards to a recording made on an ATI all in wonder tuner. Even if this tuner or any other equivalent capture device was connected to a DTV signal it would still be limited by its design and have to be connected by either an S-Video or component input to realize anything better than an antenna pickup, a composite patch, or a standard RF cable connection.
Although PC tuners have the software capability to reproduce 720 by 480 lines, unless it has HD capabilities it?s only capable of receiving 330 lines by antenna with an optimal transmission and reception. But rarely are antennas optimal and at their very best they produce about a 24% line increase over VHS quality (yes I did the math).
Quote:
Let me start by restating and expanding on the point I was trying (ineffectively) to make in the other thread. I believe it's inaccurate to say that all analog (SDTV) captures are no better than VHS quality.
I don?t recall anyone stating that all SDTV captures were no better, only that they are in general no better than VHS and in all my statements I gave them a slightly better to marginal superiority over VHS. I only included S-VHS because Vurbal included DTV. I think that I?ve proved that it depends on which VHS format and cable format we?re referring too. If we can leap from standard cable to DTV while still maintaining that cable is cable then it?s only fair that we do the same and make a leap to S-VHS and maintain that VHS is still just VHS.
All this and still shorter than Vurbal.
" Please Read!!! Post your questions only in This Thread or they will go unanswered:
Help with development of BD RB: Donations at: http://www.jdobbs.com/. This message has been edited since posting. Last time this message was edited on 6. September 2004 @ 06:25
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64026402
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6. September 2004 @ 06:19 |
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He's alive!
Good morning Sophocles. Are things slowing down at all.
It still looks like your covered by the storm.
Your post would indicate that you believe that in general a TV signal capture would yield little improvement over a VCR tape.
I would agree.
Donald
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6. September 2004 @ 06:27 |
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I'm fine but the winds still blowing and it's causing the branches of a tree to blow against the power line in my neighbors yard. It sonds like a fireworks display and sparks are flying everywhere. I called the power company but they're too busy with more important issues.
" Please Read!!! Post your questions only in This Thread or they will go unanswered:
Help with development of BD RB: Donations at: http://www.jdobbs.com/. |
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64026402
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6. September 2004 @ 08:05 |
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Don't try to fix the tree yourself.
Not that you would but some people around here have done so with dire consequences. Just keep an eye out for fires.
I don't want you to loose your house.
Donald
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6. September 2004 @ 08:07 |
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@Sophocles
I'm glad to hear things aren't as bad as they could have been.
I don't know if you've ever done any video capturing, but I can say from personal experience that my captures from VHS are much lower quality than my analog cable, digital cable, or Dish Network captures. I attribute this largely to the physical characteristics of both the tape itself and the VCR, but since most people don't have significantly better equipment than I was using, I have to respectfully disagree with your conclusion.
There's also another factor that I didn't understand when I did my initial research, but have at least a basic understanding of now, which makes a difference in determining the resolution you should capture and encode at. That factor is the chroma compression. MPEG compression uses the YV12 colorspace, which essentially means that for each 4x4 block of pixels (every other pixel on every other line), there's only a single pixel that contains the chroma information. As a result, the chroma carrying lines (sounds like a disease) of a 720 pixel wide frame can only have 360 distinct chroma samples.
This message has been edited since posting. Last time this message was edited on 6. September 2004 @ 08:09
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6. September 2004 @ 08:31 |
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@Vurbal
Things are fine but I'll be glad when it's over.
I only included S-VHS in my response because you included DTV but neither were really a part of the original debate.
I?ve done lots of captures of home movies (about 30 or so) and numerous recordings of Star Trek and other TV shows. I have a Hauppauge Win PVR 350 which has a hardware encoder and a WinFast pro XP 2000.
S-Video input allows for a separation of the Chrominance and Luminance and thus results in a better picture quality, a component connection is very close to that of an RGB connection in that two of the lines carry the chrominance and 1 the luminance (providing I remember correctly}. If you are taking a signal from a DTV receiver, in order to get the quality the signal has to be fed by either S-Video or component to benefit from it. A composite or and RF connection fully optimized, will only be slightly better than a standard VHS HQ signal. In other words, you can't make a racing horse out of a jackass. The same principle with ripping a CD to MP3 128K, you can encode it to 196K or even to wav 1410 but it can?t put back what was taken out.
" Please Read!!! Post your questions only in This Thread or they will go unanswered:
Help with development of BD RB: Donations at: http://www.jdobbs.com/. This message has been edited since posting. Last time this message was edited on 6. September 2004 @ 08:48
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64026402
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6. September 2004 @ 08:32 |
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Vurbal,
I have no doubt that your experiences yeilded the poorer results from VHS but you are taking the worst of the video tape world and comparing to the best available tv signal.
If you had the best source on the best video tape against CBS over rabbit ears then you can get different results.
My only contention was that the average tv signal over the air I don't believe is any better than VCR quality, extreme cases not withstanding.
I'm not saying VHS is better than TV. Just tv is not that great overall.
Donald
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6. September 2004 @ 08:47 |
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My reason for including DTV is that the original discussion wasn't actually clear on what the original source was (or I simply didn't notice it) so I assume that it could be the highest possible quality. I'm not questioning your conclusions regarding the transmission of the signal. What I'm saying is that when capturing you have to consider the lowest resolution (luma or chroma) the encoded video will use. Obviously the actual chroma information will be interpolated down to the actual resolution available for any given output, but in order to capture accurate information, you need to make sure the number of pixels with chroma is sufficient to represent each piece of chroma information in the original signal.
I have more to add to this, but I have to go fix a computer so I'll have to get back to it later. In the mean time, my question to you, for purposes of clarification, is how many distinct pieces of chroma information (I don't want to use the word pixel and confuse people) are contained in a single line, as transmitted via an S-Video connection?
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