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06/01/2003 11:51:20 PM · #26 |
Originally posted by Gordon:
On showing images, 640x480's broadcast perfectly well. I've had a couple of really small (sub 150k) image used as a backdrops on commercial TV without any real artefact problems. TV is really low resolution compared to an equivalent TV monitor and the image sizes we use here are prefectly adequate for broadcast quality, especially as a backdrop. |
thats pretty much what i thought...im pretty sure that although the vbi is 21 lines, each line arrives back at the top at two 1/60-second intervals (due to interlacing)--which adds up to 42 of the 525 scan lines allowed by ntsc. which reduces the visible lines of v. resolution to roughly 480 (483 to be exact). this leaves the screen resolution of a 4:3 ntsc screen to be about 640x480. i also agree with you in thinking that the 150k size wouldn't matter too much, since the screen resolution is fixed, the dpi resolution of an average tv is smaller than that of the web, and since the web only uses 72dpi, then i imagine a tv could get away with a lot less.
Message edited by author 2003-06-01 23:52:04. |
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06/02/2003 03:53:12 PM · #27 |
So, what ever happened with this? Was it resolved?
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06/02/2003 05:08:29 PM · #28 |
I was watching the 5 PM news cast and they didn't show it again,so I have no proof that was mine in the morning news!
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06/02/2003 05:53:16 PM · #29 |
Originally posted by Gordon:
On showing images, 640x480's broadcast perfectly well. I've had a couple of really small (sub 150k) image used as a backdrops on commercial TV without any real artefact problems. TV is really low resolution compared to an equivalent PC monitor and the image sizes we use here are prefectly adequate for broadcast quality, especially as a backdrop. |
I hate to disagree with you Gordon, as I truly do respect your technical and creative opinions.
But, it is a bit of a misconception to think of TV as low resolution when compared to a computer. I did not wish to go over the top in my initial explanation (which is my natural tendency to do anyway), but TV is not as low resolution as most folks think it is.
In fact, we have many stations, if not most stations in Canada that are already operating on the SMPTE 259M, Level C standard, which is a component digital video format. Typically, the signals are sourced from a Raid 5 computer array or a digital VTR. The signals are kept in a discrete component format so as to isolated the chrominance and the luminance information in the Y, R-Y, B-Y component matrix, which runs at a ratio of 4:2:2 times the subcarrier signal, which is 3.58 MHz.
All of this boils down to a data stream flowing at 270 Mbps. This is not low res! Yes, it is still in the old television 2:1 interlace format and yes, computers use a preferred random scan format. But, it is a serious high resolution signal just the same.
As well, we have a few early adopters broadcasting in Canada with their master control facilities in the new ATSC HDTV formats. In Canada, the 720P and the 1080i formats are accepted out of the 36 ATSC variations. One master control that I know of first hand is operating at an uncompressed 1.485 Gbps - that's Gigabits per second. All, for you TV enjoyment!
In the USA, where this photograph was shown, the stations are much farther ahead in the march towards HDTV, since it was regulated by your FCC. So, it is also very likely that the station in question is in 4:2:2 NTSC (aka SDTV) or may even be in HDTV and applying a down-res process to support the continuation of their older NTSC analog transmitter. The over-the-air NTSC signals, as well as most of the CATV signals, are still in the lower composite NTSC format for distribution. So, resolution does matter in TV since the origination facilities are typically much higher resolution than what the average viewer sees at home. I hope that this helps to clarify the issue.
Message edited by author 2003-06-02 17:56:55.
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06/02/2003 06:43:51 PM · #30 |
All I was saying was that in the two cases where I've had pictures shown on broadcast television, that 640x480, sub 150k JPEGs have been perfectly adequate. These are commonly used for broadcast purposes as still images and while the information you provided about uncompressed data rates is true, the compressed size of the input JPEG doesn't have a whole lot of relation to that.
I'm also not convinced that regional broadcast news stations are sending in HDTV formats, though I could be pleasantly surprised. Also, high bandwidth does not directly equate to requiring high resolution. (as an aside, my video card is currently driving the equivalent of about 4Gbps worth of data converted to analog, to my monitor - making it roughly 4x the performance figures you provided for TV - if I switch to 640x480 resolution, the effective data rate drops to about 1.2Gbps)
I don't know much about the details of NTSC, as most of my education in this area focused on PAL formats and HDTV hadn't been specified by the time I graduated, so YMMV, but from the evidence I've seen with the images I've had broadcast, 150kb compressed is typically plenty of resolution for display without noticeable artefacts. Also the low end of SDTV is equivalent to NTSC, and seems to be spec'ed at 640x480 at 60i or 30fps non-interlaced.
Message edited by author 2003-06-02 22:16:20. |
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06/02/2003 10:14:36 PM · #31 |
Originally posted by Gordon:
All I was saying was that in the two cases where I've had pictures shown on broadcast television, that 640x480, sub 150k JPEGs have been perfectly adequate. These are commonly used for broadcast purposes as still images and while the information you provided about uncompressed data rates is true, the compressed size of the input JPEG doesn't have a whole lot of relation to that.
I'm also not convinced that regional broadcast news stations are sending in HDTV formats, though I could be pleasantly surprised. Also, high bandwidth does not directly equate to requiring high resolution. (as an aside, my video card is currently driving the equivalent of about 4Gbps worth of data converted to analog, to my monitor - making it roughly 4x the performance figures you provided for TV - if I switch to 640x480 resolution, the effective data rate drops to about 1.2Gbps)
I don't know much about the details of NTSC, as most of my education in this area focused on PAL formats and HDTV hadn't been specified by the time I graduated, so YMMV, but from the evidence I've seen with the images I've had broadcast, 150kb compressed is typically plenty of resolution for display without noticeable artefacts. |
None of the major US networks would class Chicago as a regional station, it is a major market. The National Association of Broadcasters (NAB) updated its DTV station list last week to include 16 new stations, made up of both commercial and public broadcast facilities. This brings the NABâs current total to 901 digital stations operating in 189 U.S. markets.
Meanwhile, the FCCâs Web site lists a total of 1,081 digital stations on-the-air in the U.S. (both commercial and public stations), with 493 fully licensed and 588 operating at low-power under Special Temporary Authority (STA); as of May 21, 2003.
The FCC also reports that 1,587 stations (94 percent of the total) have been granted either construction permits or licenses necessary to build a digital facility.
Of the 843 commercial stations that sought a first-extension (six months) from the May 1, 2002 deadline to complete the construction of their DTV facilities, 772 were granted, the Commission said. 602 stations sought second-extensions and 527 were granted, 68 were dismissed, and seven are pending. Of the 84 third-extension requests, 4 were dismissed and the rest are pending.
Finally, 214 public stations asked for first-extensions. Three were dismissed, 195 were granted, and 16 are currently pending.
Of the 40 top 10 market network affiliates, that were required to begin digital broadcasts in 1999, 38 have constructed facilities and are on-the-air in digital (WNBC-DT and WABC-DT were on-the-air prior to the World Trade center collapse Sept. 11, 2001, but are now operating at low-power from the Empire State Building), according to the FCC.
In DMAs 11-30, there are 79 network affiliates that were supposed to be on-the-air by May 1, 2002. Thus far 70 have constructed their fully licensed DTV facilities and five are operating under STA.
The NAB says that 97.67 percent of U.S. TV households now have access to a digital signal delivered over the air, 78.06 percent of the more than 106 million U.S. TV households are in markets with five or more broadcasters airing DTV and 46.34 percent are in markets with eight or more broadcasters sending digital signals.
With regards to your PC's video card. It is hardly an apples to apples comparison to try to match the performance of a single PC to that of a complex broadcast facility along with an elaborate transmission grid that may encompass a million or more viewers. How many viewers will your single PC service at one time at that sustained data rate?
With regards to compressed versus uncompressed point, a still image produced by any serious digital camera may range from 3 megapixels to 14 megapixels, or beyond. If we assume a raw image of just 5 megapixels as a starting point and a compressed image of 150k, the ratio is about 33:1.
Lossless compression is generally assumed to be at a ratio of less than 8:1. So, with this level of compression there are visible artifacts and there is a significant loss to the original image.
Besides, TV has to deal with both dynamic and temporal resolution issues. Whereas, in a still image we only need to be concerned with static compression algorithms. Not really the same thing, is it?
I will not argue the point that somewhere there will be a broadcaster or cablecaster that may bring a JPEG to air. But, it is not common and in my professional experience, not very desirable. I suppose that we will not get to a common viewpoint on this subject, so I will let it ride from this point. Cheers, Michael
PS: What does YMMV mean, I am not familiar with this term?
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06/02/2003 10:20:50 PM · #32 |
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06/02/2003 10:33:49 PM · #33 |
All the technical details you provide aside, which are rather missing the point, in at least 3 cases I know of, dpc users have had images at the 150k compressed JPEG rate broadcast on TV. The data rates and resolution of broadcast quality TV are simply not that high that artefacting is really a problem to take an image of 7Mbits and display it.
You are right that my PC is not a broadcast situation. It does not have the severe bandwidth limitations placed upon it that digital or terrestrial TV has to work within. It doesn't have to deal with limited spectrum alocations or the cost of cable or the myriad of other transmission problems that exist within the commerical space. Again, that's rather the point. That's why it can move a whole lot more data at an efficient price/performance. That's why the resolution in PCs is much higher than for TV and why, in comparison, data rates for TV broadcast is low res. Now if you want to compare it to something like MPEG4 for wireless video, then yes, TV has a higher bandwidth requirement, but in the grand scheme of things the requirements aren't that high, until you start pumping multiple channels, or alternate camera angles or getting to DVD picture quality, which while the HDTV standards go there, I don't see very often coming from local cable news stations.
All the facts are very interesting, but they don't seem entirely relevant to the orginal point that is very possible to broadcast a 150k, 640x480 compressed JPEG image. I see it done every night. Paganni has had his pictures broadcast in the same way.
I realise that you work in the telecommunications industry. I'm not arguing that you know more about broadcast TV or the standards and commercial side of things either. I'm just going on the evidence of my own eyes as a photographer. While lossless compression is certainly usually maxing out at 8:1, JPEG isn't a lossless scheme. It exploits the fact that the human visual system is very forgiving. In much the same way that I can look at a 150k JPEG on a 1280x960, 21" monitor, refreshing at 100Hz and not notice the aretfacts, I can also view the same image on NTSC at 640x480 probably at around 30 frames per second and not be bothered by the quality. It would look pretty ropey if I interpolated it up to 1280x960, but we are not talking about doing that for the majority of TV sets in this country, or any other.
On the compression ratios :
a 5Mp camera typically captures a
2560x1920 (4.91 megapixels) - (cf. Nikon coolpix 5700 )
image. This would be scaled down to 640x480 pixels, which is about 7.3Mbits of information, at standard 8 bit RGB, or 921Kbytes. The compression ratio for a 150KByte JPEG of a 640x480 is only around 6:1. For a lossy scheme like JPEG encoding, 6:1 is really poor compression and really represents the very high end of quality available. Much higher compression rates can yield acceptable results (I've seen 20k and smaller JPEGs that are acceptable at that resolution, for the right image) I think some of the confusion might stem from not fully appreciating the compression schemes involved and the resolutions being considered, at least it seems that way from the above discussion.
btw - YMMV means 'your mileage may vary' which typically means take all this with a pinch of salt and not as professional advice ;)
as a further aside, after reading your data on the state of broadcast TV, the one that strikes me as often missing in this discussion and rather the chicken/egg problem for DTV, is how many viewers are actually bothering to watch those digital signals on anything other than a plain old NTSC TV ? Do you happen to have any info on consumer equipment deployed ? I see similar issues with the video systems that I design as it is often difficult to get the infrastructure in place to drive the receiver sales and vice-versa. I assume the 'great switch-off for analog' is still coming, though slower than expected.
Us telecommunication engineers sure like our TLAs and ETLAs don't we....
Message edited by author 2003-06-02 23:05:40. |
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06/02/2003 11:52:01 PM · #34 |
Hey, how did you know? I didn't tell anyone... and it was a flower photo too :) And I didn't get to see it on TV -- i got the email the next AFTER the broadcast (apparently the weather guy send it out 10 minutes before the broadcast to me, telling me it was on.... someone at work told me he saw my photo...)
Anyway, TV resolution do not exceed 640x480 right now and Gordon is right about this. The only issue we have currently is to broadcast at full rate (30 frames per second), that typically exceeds the bandwidth of many digicams out there (video cams). For a still photograph, 640x480 is enough. Sure, the larger the file, the better, but resolution wise it's plenty for TV. I think currently analog TV has scanlines of about 480 lines, and the resulting resolution is about 320 lines on the horizontal. That's 640 pixels (1 line = 2 pixels) on the horizontal, so 640x480 is really adequate.
Originally posted by Gordon:
All the facts are very interesting, but they don't seem entirely relevant to the orginal point that is very possible to broadcast a 150k, 640x480 compressed JPEG image. I see it done every night. Paganni has had his pictures broadcast in the same way.
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06/03/2003 01:02:18 AM · #35 |
Originally posted by paganini:
Hey, how did you know? I didn't tell anyone... and it was a flower photo too :) And I didn't get to see it on TV -- i got the email the next AFTER the broadcast (apparently the weather guy send it out 10 minutes before the broadcast to me, telling me it was on.... someone at work told me he saw my photo...)
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You mentioned something about it in a forum post and I guessed it was KVUE.
It's up on their website too. (Congrats btw - did you win ?) |
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06/03/2003 07:14:04 AM · #36 |
Well Gordon, I surrender.
But, an invitation is open to you to visit a broadcast facility here in Toronto the next time you get up our way. Then, you will be able to see what I am discussing first hand.
By the way, we do broadcast in a technical standard equal to DVD today. And, most distribution service providers (DTH, CATV) accept the component digital video signal via optical fibre connections and then take them directly to air in that format. They deliver these signals directly to a digital set top box, which has the ability to display the pictures in component. Many folks, including myself, do have TVs that accept this sort of signal and are able to display it in a quasi Y/C component format beautifully. This is SDTV to the home. The resolution is rather remarkable for TV.
Just for fun, let me offer another input. I have been involved in an eCinema project for the past two years. We were delighted when we viewed a quad-extrapolated image fed into two commercial-grade DLP projectors converged onto a single screen and saw an image that look rather fine. (The DLP stuff is from your old employer, right?)
Today, we are playing with 2k to 4k projected resolution and feel that we are nearly at film projection quality, perhaps beyond it. So, the world is changing and it will continue to change technically. As you pointed out, the limiting factor is still the human eye and ear, which are analog devices of sorts. Quality just needs to exceed the human being for display. I completely agree with you on this point.
It is all of the production and post-production image manipulation that takes it toll on image resolution. Some effects seen on TV today many be down 50 to 100 generations before they hit the air. So, 150 k files do not work in this environment.
I will again yield to your point that somewhere there is a station that will take a 150k JPEG live to air. In a live news environment, when the image is played out of a still store into a compressed DVC box over the anchor's shoulder as a beauty shot, it may work and be seen as suitable. But, as I said, it is not very desirable. At least in this country. I will avoid the entire PAL discussion too.
If you would still like to see the consumer HDTV TV set deployment figures for Canada and the USA, then PM me and I will send them to you directly. Or, visit the CEA web site. Cheers, Michael
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06/03/2003 09:04:57 AM · #37 |
Originally posted by Morgan:
But, an invitation is open to you to visit a broadcast facility here in Toronto the next time you get up our way. Then, you will be able to see what I am discussing first hand.
If you would still like to see the consumer HDTV TV set deployment figures for Canada and the USA, then PM me and I will send them to you directly. Or, visit the CEA web site. Cheers, Michael |
I'll take you up on that next time I get up that way. Thanks for the CEA link, plenty of useful stuff there.
and no, I never did work for TI - though I do want to find the one DLP cinema in Texas and see something at a decent resolution. I hear the only remaining problem is that it is too quiet without the click of film advancing... |
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06/03/2003 10:49:45 AM · #38 |
No, didn't win the "month" contest, just had it posted on the weather report that I didn't get to see how it looked on TV... It was the 4/3/2003 showing I think.
Originally posted by Gordon:
Originally posted by paganini:
Hey, how did you know? I didn't tell anyone... and it was a flower photo too :) And I didn't get to see it on TV -- i got the email the next AFTER the broadcast (apparently the weather guy send it out 10 minutes before the broadcast to me, telling me it was on.... someone at work told me he saw my photo...)
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You mentioned something about it in a forum post and I guessed it was KVUE.
It's up on their website too. (Congrats btw - did you win ?) |
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06/03/2003 11:51:58 AM · #39 |
Originally posted by paganini:
No, didn't win the "month" contest, just had it posted on the weather report that I didn't get to see how it looked on TV... It was the 4/3/2003 showing I think.
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Hey, you won on my birthday. I don't usually watch KVUE (or TV at all really) so didn't see it either, other than on the web site.
I won the camera last year, a 2Mp fully automatic camera - not a whole lot of use for me but made a nice christmas present |
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06/03/2003 12:03:19 PM · #40 |
Congrats on the camera :) It was my first submission... i didn't know what it was until I saw your bridge photo on KVUE last year, then early this year/march time frame I made a trip to the S.A. botanical garden, shot a bunch with the G2 and uploaded that one. Most of the time KVUE just display kids photos though, or hail (if there is a hail in the forecast, then whoever took the last hail photo gets to be displayed, i think)
Originally posted by Gordon:
Originally posted by paganini:
No, didn't win the "month" contest, just had it posted on the weather report that I didn't get to see how it looked on TV... It was the 4/3/2003 showing I think.
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Hey, you won on my birthday. I don't usually watch KVUE (or TV at all really) so didn't see it either, other than on the web site.
I won the camera last year, a 2Mp fully automatic camera - not a whole lot of use for me but made a nice christmas present |
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06/04/2003 08:44:33 AM · #41 |
Originally posted by Gordon:
Originally posted by Morgan:
But, an invitation is open to you to visit a broadcast facility here in Toronto the next time you get up our way. Then, you will be able to see what I am discussing first hand.
If you would still like to see the consumer HDTV TV set deployment figures for Canada and the USA, then PM me and I will send them to you directly. Or, visit the CEA web site. Cheers, Michael |
I'll take you up on that next time I get up that way. Thanks for the CEA link, plenty of useful stuff there.
and no, I never did work for TI - though I do want to find the one DLP cinema in Texas and see something at a decent resolution. I hear the only remaining problem is that it is too quiet without the click of film advancing... |
Clicking, what clicking? I don't hear any clicking?
Once you get older, the extremes of your auditory dynamic range fall-off significantly. So luckily, one is no longer maddened by such background sounds as the film being clawed past the pull-down gate as the huge reels turn on the film projector. This aural deterioration is further aggravated by the excessive sound pressures presented by the new THX, DTS, and other digital surround systems blasting far too many decibels at the unfortunate and unprotected eardrums of the audience.
Finally, once you get married, you develop another major condition of selective auditory discrimination. My wife complains all the time that I only hear her when I want too. So, I must have that affliction too. Needless to say, it is a suffering that is dominant in males. We can easily hear phrases such as âdinner is readyâ, âletâs have sexâ, âyou donât have to come to the in-lawâs tonightâ and yet, we are not able to hear other phrases, such as âtake out the garbageâ, âI have a headacheâ, and âput down the toilet seatâ. My wife blames George Lucas, who funded the invention of THX. In the early 80s, he pushed the R&D envelope and began this male hearing crisis. I am still not too sure if it is a good thing or a bad thing, the jury is still out.
Say, do you know who keeps ringing that dam bell?
Cheers, Michael
{Grinning all the way}
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06/04/2003 11:05:15 AM · #42 |
Originally posted by Morgan:
Once you get older, the extremes of your auditory dynamic range fall-off significantly. So luckily, one is no longer maddened by such background sounds as the film being clawed past the pull-down gate as the huge reels turn on the film projector. This aural deterioration is further aggravated by the excessive sound pressures presented by the new THX, DTS, and other digital surround systems blasting far too many decibels at the unfortunate and unprotected eardrums of the audience.
Finally, once you get married, you develop another major condition of selective auditory discrimination. |
That early high-frequency hearing loss pattern has been accelerated since the advent of amplified music. There's an organization in San Francisco dedicated to protecting the hearing of musicians and their fans.
And sorry, marriage is not the culprit ...
Caption from an old Dennis the Menace cartoon:
"Sorry mom, I didn't hear you calling the first three times."
Message edited by author 2003-06-04 11:05:48. |
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