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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#41
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NTSC versus PAL
"isw" wrote: What the heck has the transmitter got to do with it? Anything that is right or wrong with an NTSC signal is equally right or wrong BEFORE the transmitter. The transmitter is just a way to get the signal to lots of folks at once. Or does that confuse YOU? You are evidently not aware that a poorly designed or operated transmitter can introduce all sorts of distortions to the signal. Talk to the engineers who designed or operated them sometime. ** Maybe you can tell this utter imbecile what the phrase " broadcast signal " refers to ?? ...... Phil |
#42
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NTSC versus PAL
I understand that prior to the expiry of the Telefunken PAL patent,
Sony Trinitron sets for the PAL market actually threw away the chrominance signal on alternate scan lines, thus landing themselves back in NTSC territory. Those sets had a tint control, and I know from personal experience that they produced a perfectly satisfactory result (I only learnt the other day why they had a tint control). Depends on what you mean by "satisfactory". Passable, maybe. When you discuss something at length, you become aware of those things you thought you understood, but didn't. (Well, I do, anyway.) I'd always read that one could construct a PAL receiver in such a way that eliminated the need for a manual hue control. I never questioned this, but now it makes little sense. There are two reasons for having a manual hue control: The user can adjust the color rendition to their personal (and usually incorrect) taste. * The user can correct for incorrect burst phase. That seems to be "it". As we've seen, these errors can be corrected by adjusting the hue control, whereas the other error -- differential phase shift -- cannot be so-corrected, because the timing errors are not linear. Here's where I get confused. The line-to-line polarity reversal ** causes the differential phase errors to be equal and opposite, and thus cancel out when added (at the cost of desaturation -- but that's another issue). However... If the burst phase is wrong, then there is no cancellation of errors, because there are no "errors" /in the signal itself/. (Right? (???)) Therefore, I don't see how line averaging can be used to eliminate the need for a manual hue control. If anyone knows of a reference with a non-tautological explanation, I'd appreciate a pointer to it. Thanks. * Left to their own devices, the average user generally sets the color for greenish skin tones. I wonder if Vulcan viewers tended towards a pinkish error. ** It's actually line-to-line+2, because the image is interlaced. |
#43
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NTSC versus PAL
In article ,
William Sommerwerck wrote: I understand that prior to the expiry of the Telefunken PAL patent, Sony Trinitron sets for the PAL market actually threw away the chrominance signal on alternate scan lines, thus landing themselves back in NTSC territory. Those sets had a tint control, and I know from personal experience that they produced a perfectly satisfactory result (I only learnt the other day why they had a tint control). Depends on what you mean by "satisfactory". Passable, maybe. When you discuss something at length, you become aware of those things you thought you understood, but didn't. (Well, I do, anyway.) I'd always read that one could construct a PAL receiver in such a way that eliminated the need for a manual hue control. I never questioned this, but now it makes little sense. I've never seen a set designed for the PAL market with a hue control. Only ones modified from a basically NTSC design. There are two reasons for having a manual hue control: The user can adjust the color rendition to their personal (and usually incorrect) taste. * The user can correct for incorrect burst phase. That seems to be "it". As we've seen, these errors can be corrected by adjusting the hue control, whereas the other error -- differential phase shift -- cannot be so-corrected, because the timing errors are not linear. You simply don't get hue errors on PAL sets - unless the grey scale is set incorrectly. Of course some sets also used the incorrect phosphors to provide a brighter picture - but a hue control couldn't compensate for that. -- *I'm already visualizing the duct tape over your mouth Dave Plowman London SW To e-mail, change noise into sound. |
#44
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NTSC versus PAL
On 5/04/2010 10:56 PM, William Sommerwerck wrote:
I understand that prior to the expiry of the Telefunken PAL patent, Sony Trinitron sets for the PAL market actually threw away the chrominance signal on alternate scan lines, thus landing themselves back in NTSC territory. Those sets had a tint control, and I know from personal experience that they produced a perfectly satisfactory result (I only learnt the other day why they had a tint control). Depends on what you mean by "satisfactory". Passable, maybe. When you discuss something at length, you become aware of those things you thought you understood, but didn't. (Well, I do, anyway.) I'd always read that one could construct a PAL receiver in such a way that eliminated the need for a manual hue control. I never questioned this, but now it makes little sense. There are two reasons for having a manual hue control: The user can adjust the color rendition to their personal (and usually incorrect) taste. * The user can correct for incorrect burst phase. That seems to be "it". As we've seen, these errors can be corrected by adjusting the hue control, whereas the other error -- differential phase shift -- cannot be so-corrected, because the timing errors are not linear. Here's where I get confused. The line-to-line polarity reversal ** causes the differential phase errors to be equal and opposite, and thus cancel out when added (at the cost of desaturation -- but that's another issue). However... If the burst phase is wrong, then there is no cancellation of errors, because there are no "errors" /in the signal itself/. (Right? (???)) Therefore, I don't see how line averaging can be used to eliminate the need for a manual hue control. Think of the chroma signal as a vector with its y coordinate equal the red difference component, and the x coordinate equal to the blue difference component. A phase error rotates that vector about the z axis. Effectively, the blue difference component receives a bit of the red difference component, and vice versa. On alternate lines the phase of the red difference component *only* is inverted. In our view, this has the effect of reflecting the vector in the x axis - what was a positive y value becomes negative. The same phase error causes this vector to rotate in the same direction about the z axis, but because of the reflection, the mixing of the components has the opposite sign. If you then negate the resulting red difference component of the second line, and average with the red difference component of the first line, the parts received from the blue difference component cancel out, leaving a red different component that equals the original, multiplied by the cosine of the phase error. The same applies to the blue component. The result is that the hues are correct, but not as saturated as they shoud have been. Sylvia. |
#45
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NTSC versus PAL
However... If the burst phase is wrong, then there is no cancellation of
errors, because there are no "errors" /in the signal itself/. (Right? (???)) Therefore, I don't see how line averaging can be used to eliminate the need for a manual hue control. Think of the chroma signal as a vector with its y coordinate equal the red difference component, and the x coordinate equal to the blue difference component. A phase error rotates that vector about the z axis. Effectively, the blue difference component receives a bit of the red difference component, and vice versa. On alternate lines the phase of the red difference component *only* is inverted. In our view, this has the effect of reflecting the vector in the x axis - what was a positive y value becomes negative. The same phase error causes this vector to rotate in the same direction about the z axis, but because of the reflection, the mixing of the components has the opposite sign. If you then negate the resulting red difference component of the second line, and average with the red difference component of the first line, the parts received from the blue difference component cancel out, leaving a red different component that equals the original, multiplied by the cosine of the phase error. The same applies to the blue component. The result is that the hues are correct, but not as saturated as they shoud have been. No argument. That's always been my understanding. But... If the burst phase gets screwed up somewhere along the line, no amount of line averaging will fix the problem, because there's nothing "wrong" with the subcarrier to fix. Granted, this problem hardly ever happens. But the argument that a fully implemented PAL set is inherently immune to color errors is hard for me to swallow. |
#46
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NTSC versus PAL
Sylvia Else wrote:
If you then negate the resulting red difference component of the second line, and average with the red difference component of the first line, the parts received from the blue difference component cancel out, leaving a red different component that equals the original, multiplied by the cosine of the phase error. The same applies to the blue component. The result is that the hues are correct, but not as saturated as they shoud have been. Since PAL TV sets have a saturation (color level) control, isn't that a "non-problem". If it matters, you just adjust it to compensate. My experience is that people set the color saturation too high, if I hold my hand up to the screen my skin looks pale in comparison to everyone on it. Geoff. -- Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM New word I coined 12/13/09, "Sub-Wikipedia" adj, describing knowledge or understanding, as in he has a sub-wikipedia understanding of the situation. i.e possessing less facts or information than can be found in the Wikipedia. |
#47
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NTSC versus PAL
In article ,
Geoffrey S. Mendelson wrote: My experience is that people set the color saturation too high, if I hold my hand up to the screen my skin looks pale in comparison to everyone on it. Especially CSI. ;-) -- *If I throw a stick, will you leave? Dave Plowman London SW To e-mail, change noise into sound. |
#48
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NTSC versus PAL
Dave Plowman (News) wrote:
In article , Geoffrey S. Mendelson wrote: My experience is that people set the color saturation too high, if I hold my hand up to the screen my skin looks pale in comparison to everyone on it. Especially CSI. ;-) That's funny, I was thinking of last Thursday night's episode of CSI when I wrote that. Geoff. -- Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM New word I coined 12/13/09, "Sub-Wikipedia" adj, describing knowledge or understanding, as in he has a sub-wikipedia understanding of the situation. i.e possessing less facts or information than can be found in the Wikipedia. |
#49
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NTSC versus PAL
On 6/04/2010 12:53 AM, William Sommerwerck wrote:
However... If the burst phase is wrong, then there is no cancellation of errors, because there are no "errors" /in the signal itself/. (Right? (???)) Therefore, I don't see how line averaging can be used to eliminate the need for a manual hue control. Think of the chroma signal as a vector with its y coordinate equal the red difference component, and the x coordinate equal to the blue difference component. A phase error rotates that vector about the z axis. Effectively, the blue difference component receives a bit of the red difference component, and vice versa. On alternate lines the phase of the red difference component *only* is inverted. In our view, this has the effect of reflecting the vector in the x axis - what was a positive y value becomes negative. The same phase error causes this vector to rotate in the same direction about the z axis, but because of the reflection, the mixing of the components has the opposite sign. If you then negate the resulting red difference component of the second line, and average with the red difference component of the first line, the parts received from the blue difference component cancel out, leaving a red different component that equals the original, multiplied by the cosine of the phase error. The same applies to the blue component. The result is that the hues are correct, but not as saturated as they shoud have been. No argument. That's always been my understanding. But... If the burst phase gets screwed up somewhere along the line, no amount of line averaging will fix the problem, because there's nothing "wrong" with the subcarrier to fix. If the burst has a random phase relationship to the colour subcarrier on each line, then my analysis falls apart because the vectors would have random orientations. In such a situation a PAL receiver would do no better than NTSC, and they'd both perform awfully. If the burst just has a fixed phase offset from the true colour subcarrier, then the averaging will work. Indeed it will work if the colour subcarrier drifts in a consistent way relative to the burst - or if the receiver's oscillator similarly drifts. The effect of such a drift on an NSTC picture would be a variation of tint from left to right. However, a tint control wouldn't be able to address that problem - it would simply move the horizontal position on the screen where the colours are accurate - suggesting that it doesn't occur in practice except in equipment that is recognisably broken. Granted, this problem hardly ever happens. But the argument that a fully implemented PAL set is inherently immune to color errors is hard for me to swallow. I don't think there's a claim that it is inherently immune to all colour errors, only those caused by consistent differences between the phase of the subcarrier and the burst. Sylvia. |
#50
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NTSC versus PAL
On 6/04/2010 1:09 AM, Geoffrey S. Mendelson wrote:
Sylvia Else wrote: If you then negate the resulting red difference component of the second line, and average with the red difference component of the first line, the parts received from the blue difference component cancel out, leaving a red different component that equals the original, multiplied by the cosine of the phase error. The same applies to the blue component. The result is that the hues are correct, but not as saturated as they shoud have been. Since PAL TV sets have a saturation (color level) control, isn't that a "non-problem". If it matters, you just adjust it to compensate. If it's a fixed phase error, yes. If the phase error is changing slowly over time the the picture will have a saturation that varies over time which would be annoying if the effect were high enough. However, I've never noticed such an effect. Sylvia. |
#51
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NTSC versus PAL
If the burst just has a fixed phase offset from the true colour
subcarrier, then the averaging will work. Right. I missed that. I don't think there's a claim that [PAL] is inherently immune to all colour errors, only those caused by consistent differences between the phase of the subcarrier and the burst. |
#52
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NTSC versus PAL
"Sylvia Else" wrote in message ... On 6/04/2010 12:53 AM, William Sommerwerck wrote: However... If the burst phase is wrong, then there is no cancellation of errors, because there are no "errors" /in the signal itself/. (Right? (???)) Therefore, I don't see how line averaging can be used to eliminate the need for a manual hue control. Think of the chroma signal as a vector with its y coordinate equal the red difference component, and the x coordinate equal to the blue difference component. A phase error rotates that vector about the z axis. Effectively, the blue difference component receives a bit of the red difference component, and vice versa. On alternate lines the phase of the red difference component *only* is inverted. In our view, this has the effect of reflecting the vector in the x axis - what was a positive y value becomes negative. The same phase error causes this vector to rotate in the same direction about the z axis, but because of the reflection, the mixing of the components has the opposite sign. If you then negate the resulting red difference component of the second line, and average with the red difference component of the first line, the parts received from the blue difference component cancel out, leaving a red different component that equals the original, multiplied by the cosine of the phase error. The same applies to the blue component. The result is that the hues are correct, but not as saturated as they shoud have been. No argument. That's always been my understanding. But... If the burst phase gets screwed up somewhere along the line, no amount of line averaging will fix the problem, because there's nothing "wrong" with the subcarrier to fix. If the burst has a random phase relationship to the colour subcarrier on each line, then my analysis falls apart because the vectors would have random orientations. In such a situation a PAL receiver would do no better than NTSC, and they'd both perform awfully. If the burst just has a fixed phase offset from the true colour subcarrier, then the averaging will work. Indeed it will work if the colour subcarrier drifts in a consistent way relative to the burst - or if the receiver's oscillator similarly drifts. The effect of such a drift on an NSTC picture would be a variation of tint from left to right. However, a tint control wouldn't be able to address that problem - it would simply move the horizontal position on the screen where the colours are accurate - suggesting that it doesn't occur in practice except in equipment that is recognisably broken. Many years back, Bush in the UK produced a colour decoder which was 'revolutionary' compared to other manufacturers' efforts, in that the subcarrier was regenerated in the decoder directly from the burst, rather than being a free-running oscillator just locked to the burst with a PLL. They did this by deriving a phase-adjustable pulse from the H-flyback, and using this to 'notch out' the burst from the back porch period. The 10 cycles of burst thus recovered, were then applied directly to the 4.43MHz crystal, which caused it to ring at exactly the same frequency and in exactly the same phase as the original subcarrier. Always seemed to work pretty well, and they continued to use this system over a period of probably 10 years or more, covering three chassis designs / revisions. Arfa Granted, this problem hardly ever happens. But the argument that a fully implemented PAL set is inherently immune to color errors is hard for me to swallow. I don't think there's a claim that it is inherently immune to all colour errors, only those caused by consistent differences between the phase of the subcarrier and the burst. Sylvia. |
#53
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NTSC versus PAL
"Sylvia Else" wrote in message ... On 6/04/2010 1:09 AM, Geoffrey S. Mendelson wrote: Sylvia Else wrote: If you then negate the resulting red difference component of the second line, and average with the red difference component of the first line, the parts received from the blue difference component cancel out, leaving a red different component that equals the original, multiplied by the cosine of the phase error. The same applies to the blue component. The result is that the hues are correct, but not as saturated as they shoud have been. Since PAL TV sets have a saturation (color level) control, isn't that a "non-problem". If it matters, you just adjust it to compensate. If it's a fixed phase error, yes. If the phase error is changing slowly over time the the picture will have a saturation that varies over time which would be annoying if the effect were high enough. However, I've never noticed such an effect. Sylvia. I would guess that you never would see such an effect, as all of the decoders that I can remember working on, had ACC circuits which worked very well ... Arfa |
#54
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NTSC versus PAL
Many years back, Bush in the UK produced a colour decoder which was
'revolutionary' compared to other manufacturers' efforts, in that the subcarrier was regenerated in the decoder directly from the burst, rather than being a free-running oscillator just locked to the burst with a PLL. They did this by deriving a phase-adjustable pulse from the H-flyback, and using this to 'notch out' the burst from the back porch period. The 10 cycles of burst thus recovered, were then applied directly to the 4.43MHz crystal, which caused it to ring at exactly the same frequency and in exactly the same phase as the original subcarrier. Always seemed to work pretty well, and they continued to use this system over a period of probably 10 years or more, covering three chassis designs / revisions. This was first done by GE, circa 1966, in the Portacolor set, mostly because it was cheaper. Another way of looking at this system is that the crystal was an extremely narrow-band filter that removed the "Fourier sidebands" around the subcarrier frequency created by transmitting the 10-cycle burst only once on each scanning line. |
#55
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NTSC versus PAL
Sylvia Else wrote:
On 3/04/2010 10:04 PM, Michael A. Terrell wrote: isw wrote: Sylvia Else wrote: If we were building an analogue colour TV transmission infrastructure now, then maybe we'd go the NTSC route, since it eliminates the delay line. NTSC? No delay line? Moron. The luminance data had to be delayed to allow time to process the Chroma data. An open delay line in a NTSC video display caused a very dark image with moving blotches of color. I found and replaced several, in NTSC TVs and Video Monitors. In which case you'd know that a PAL TV contains two delay lines. One provides a short delay and addresses the difference in delay between the chroma path and the luminance path. The other provides a full scan line delay to allow averaging of the chrominance signal. It should be obvious from context that "the" delay line that I was referring to was the latter. But I suppose calling people morons is easier than doing your own thinking. It is, for people who consider one as zero. -- Service to my country? Been there, Done that, and I've got my DD214 to prove it. Member of DAV #85. Michael A. Terrell Central Florida http://www.flickr.com/photos/materrell/ |
#56
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NTSC versus PAL
On 7/04/2010 10:08 AM, Arfa Daily wrote:
"Sylvia wrote in message ... On 6/04/2010 12:53 AM, William Sommerwerck wrote: However... If the burst phase is wrong, then there is no cancellation of errors, because there are no "errors" /in the signal itself/. (Right? (???)) Therefore, I don't see how line averaging can be used to eliminate the need for a manual hue control. Think of the chroma signal as a vector with its y coordinate equal the red difference component, and the x coordinate equal to the blue difference component. A phase error rotates that vector about the z axis. Effectively, the blue difference component receives a bit of the red difference component, and vice versa. On alternate lines the phase of the red difference component *only* is inverted. In our view, this has the effect of reflecting the vector in the x axis - what was a positive y value becomes negative. The same phase error causes this vector to rotate in the same direction about the z axis, but because of the reflection, the mixing of the components has the opposite sign. If you then negate the resulting red difference component of the second line, and average with the red difference component of the first line, the parts received from the blue difference component cancel out, leaving a red different component that equals the original, multiplied by the cosine of the phase error. The same applies to the blue component. The result is that the hues are correct, but not as saturated as they shoud have been. No argument. That's always been my understanding. But... If the burst phase gets screwed up somewhere along the line, no amount of line averaging will fix the problem, because there's nothing "wrong" with the subcarrier to fix. If the burst has a random phase relationship to the colour subcarrier on each line, then my analysis falls apart because the vectors would have random orientations. In such a situation a PAL receiver would do no better than NTSC, and they'd both perform awfully. If the burst just has a fixed phase offset from the true colour subcarrier, then the averaging will work. Indeed it will work if the colour subcarrier drifts in a consistent way relative to the burst - or if the receiver's oscillator similarly drifts. The effect of such a drift on an NSTC picture would be a variation of tint from left to right. However, a tint control wouldn't be able to address that problem - it would simply move the horizontal position on the screen where the colours are accurate - suggesting that it doesn't occur in practice except in equipment that is recognisably broken. Many years back, Bush in the UK produced a colour decoder which was 'revolutionary' compared to other manufacturers' efforts, in that the subcarrier was regenerated in the decoder directly from the burst, rather than being a free-running oscillator just locked to the burst with a PLL. They did this by deriving a phase-adjustable pulse from the H-flyback, and using this to 'notch out' the burst from the back porch period. The 10 cycles of burst thus recovered, were then applied directly to the 4.43MHz crystal, which caused it to ring at exactly the same frequency and in exactly the same phase as the original subcarrier. Always seemed to work pretty well, and they continued to use this system over a period of probably 10 years or more, covering three chassis designs / revisions. Arfa I'm left wondering what exactly was the *real* problem that PAL was intended to fix. It appears that the NTSC tint control could only address a fixed phase offset between the colour burst and the subcarrier, with both transmitters and TV sets able to maintain that offset sufficiently closely that the hue wouldn't vary from left to right of the picture. Other issues, such as non-linear phase shift would have been a problem for NTSC viewers, regardless of the tint control. So were NTSC viewers tolerating colour pictures that couldn't be set right even with the tint control? Or is there something else that I've missed? Sylvia. |
#57
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NTSC versus PAL
In article ,
Sylvia Else wrote: --snippety-snip-- I'm left wondering what exactly was the *real* problem that PAL was intended to fix. Political. The Europeans didn't want US companies selling sets there. Isaac |
#58
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NTSC versus PAL
In article ],
isw wrote: In article , Sylvia Else wrote: --snippety-snip-- I'm left wondering what exactly was the *real* problem that PAL was intended to fix. Political. The Europeans didn't want US companies selling sets there. Didn't stop the Japanese, etc. But US companies would have to do other mods to their products for European sales anyway. Like mains voltage and frequency. Most couldn't be bothered - even when that's all which had to be changed. -- *Letting a cat out of the bag is easier than putting it back in * Dave Plowman London SW To e-mail, change noise into sound. |
#59
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NTSC versus PAL
I'm left wondering what exactly was the *real* problem that PAL
was intended to fix. It appears that the NTSC tint control could only address a fixed phase offset between the colour burst and the subcarrier, with both transmitters and TV sets able to maintain that offset sufficiently closely that the hue wouldn't vary from left to right of the picture. Correct. Other issues, such as non-linear phase shift would have been a problem for NTSC viewers, regardless of the tint control. Also correct. So were NTSC viewers tolerating colour pictures that couldn't be set right even with the tint control? Or is there something else that I've missed? You /have/ missed something, which I explained "long ago and far away". grin The US TV-distribution system DID NOT generally suffer from non-linear group-delay problems, whereas the European system DID. That's it. Even without the extra delay line, there is some degree of visual color averaging, which tends to mitigate the phase error. |
#60
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NTSC versus PAL
Political. The Europeans didn't want US companies selling
sets there. Didn't stop the Japanese, etc. But US companies would have to do other mods to their products for European sales anyway. Like mains voltage and frequency. Most couldn't be bothered -- even when that's all which had to be changed. I don't buy that. US sets would have been fairly expensive in Europe, even in the mid-60s. Not to mention the strong competition from Thomson, Philips, etc. |
#61
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NTSC versus PAL
On Wed, 07 Apr 2010 12:29:40 +1000, Sylvia Else
wrote: On 7/04/2010 10:08 AM, Arfa Daily wrote: "Sylvia wrote in message ... On 6/04/2010 12:53 AM, William Sommerwerck wrote: However... If the burst phase is wrong, then there is no cancellation of errors, because there are no "errors" /in the signal itself/. (Right? (???)) Therefore, I don't see how line averaging can be used to eliminate the need for a manual hue control. Think of the chroma signal as a vector with its y coordinate equal the red difference component, and the x coordinate equal to the blue difference component. A phase error rotates that vector about the z axis. Effectively, the blue difference component receives a bit of the red difference component, and vice versa. On alternate lines the phase of the red difference component *only* is inverted. In our view, this has the effect of reflecting the vector in the x axis - what was a positive y value becomes negative. The same phase error causes this vector to rotate in the same direction about the z axis, but because of the reflection, the mixing of the components has the opposite sign. If you then negate the resulting red difference component of the second line, and average with the red difference component of the first line, the parts received from the blue difference component cancel out, leaving a red different component that equals the original, multiplied by the cosine of the phase error. The same applies to the blue component. The result is that the hues are correct, but not as saturated as they shoud have been. No argument. That's always been my understanding. But... If the burst phase gets screwed up somewhere along the line, no amount of line averaging will fix the problem, because there's nothing "wrong" with the subcarrier to fix. If the burst has a random phase relationship to the colour subcarrier on each line, then my analysis falls apart because the vectors would have random orientations. In such a situation a PAL receiver would do no better than NTSC, and they'd both perform awfully. If the burst just has a fixed phase offset from the true colour subcarrier, then the averaging will work. Indeed it will work if the colour subcarrier drifts in a consistent way relative to the burst - or if the receiver's oscillator similarly drifts. The effect of such a drift on an NSTC picture would be a variation of tint from left to right. However, a tint control wouldn't be able to address that problem - it would simply move the horizontal position on the screen where the colours are accurate - suggesting that it doesn't occur in practice except in equipment that is recognisably broken. Many years back, Bush in the UK produced a colour decoder which was 'revolutionary' compared to other manufacturers' efforts, in that the subcarrier was regenerated in the decoder directly from the burst, rather than being a free-running oscillator just locked to the burst with a PLL. They did this by deriving a phase-adjustable pulse from the H-flyback, and using this to 'notch out' the burst from the back porch period. The 10 cycles of burst thus recovered, were then applied directly to the 4.43MHz crystal, which caused it to ring at exactly the same frequency and in exactly the same phase as the original subcarrier. Always seemed to work pretty well, and they continued to use this system over a period of probably 10 years or more, covering three chassis designs / revisions. Arfa I'm left wondering what exactly was the *real* problem that PAL was intended to fix. It appears that the NTSC tint control could only address a fixed phase offset between the colour burst and the subcarrier, with both transmitters and TV sets able to maintain that offset sufficiently closely that the hue wouldn't vary from left to right of the picture. Other issues, such as non-linear phase shift would have been a problem for NTSC viewers, regardless of the tint control. So were NTSC viewers tolerating colour pictures that couldn't be set right even with the tint control? Or is there something else that I've missed? Sylvia. Part of the difficulity in understanding is that perhaps you don't have experience with early American color televisions... I certainly remember how in the 60s we had to adjust the tint control on a regular (show by show) basis, because of lack of consistancy. Today, with predominatly digital systems, it has been so long since I've touched a tint control, that I wonder if they still exist! Anyone who had one of those old, tube (valve) color sets, with the 21" round color CRT, will remember seeing green skies, and blue grass while having skin colors set to the proper shade. Get the sky blue, and the skin turned red, or blue, or green! |
#62
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NTSC versus PAL
Part of the difficulity in understanding is that perhaps you
don't have experience with early American color televisions... I certainly remember how in the 60s we had to adjust the tint control on a regular (show by show) basis, because of lack of consistancy. Yes -- a lack of consistency. That was not the fault of NTSC, but of the broadcasters. Anyone who had one of those old, tube (valve) color sets, with the 21" round color CRT, will remember seeing green skies, and blue grass while having skin colors set to the proper shade. Get the sky blue, and the skin turned red, or blue, or green! I don't think that's correct. The cameras (and/or encoders) would have had to have been very badly set up for that to happen. On a related subject... I remember reading long, long ago that the first RCA color TV had /four/ controls for adjusting the color, which the author described as a "combination lock"! Anyone know anything about this? |
#63
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NTSC versus PAL
On 7/04/2010 10:12 PM, William Sommerwerck wrote:
I'm left wondering what exactly was the *real* problem that PAL was intended to fix. It appears that the NTSC tint control could only address a fixed phase offset between the colour burst and the subcarrier, with both transmitters and TV sets able to maintain that offset sufficiently closely that the hue wouldn't vary from left to right of the picture. Correct. Other issues, such as non-linear phase shift would have been a problem for NTSC viewers, regardless of the tint control. Also correct. So were NTSC viewers tolerating colour pictures that couldn't be set right even with the tint control? Or is there something else that I've missed? You /have/ missed something, which I explained "long ago and far away". grin OK, I vaguely remember your saying that now. In the UK, colour was only transmitted on a new 625 line service (newish, in the case of BBC2), in parallel for a long time with a monochrome 405 line service (except BBC2), and I'd have thought the new transmission infrastructure could have been built to obviate the non-linear group-delay, given that it existed in the USA. And, as I commented before, the Sony Trinitron sets, which didn't implement PAL, performed acceptably according to my memory. Sylvia. |
#64
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NTSC versus PAL
On 7/04/2010 11:23 PM, William Sommerwerck wrote:
Part of the difficulity in understanding is that perhaps you don't have experience with early American color televisions... I certainly remember how in the 60s we had to adjust the tint control on a regular (show by show) basis, because of lack of consistancy. Yes -- a lack of consistency. That was not the fault of NTSC, but of the broadcasters. I have to wonder what the broadcasters were doing to achieve that. Contriving to get the colour burst phase consistent amongst cameras in a studio (so that the tint stayed the same for a show), but inconsistent with the actual colour subcarrier, would take some doing. Sylvia. |
#65
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NTSC versus PAL
In the UK, colour was only transmitted on a new 625-line
service (newish, in the case of BBC2), in parallel for a long time with a monochrome 405 line service (except BBC2), and I'd have thought the new transmission infrastructure could have been built to obviate the non-linear group-delay, given that it existed in the USA. You're probably correct. |
#66
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NTSC versus PAL
Yes -- a lack of consistency. That was not the fault
of NTSC, but of the broadcasters. I have to wonder what the broadcasters were doing to achieve that. Contriving to get the colour burst phase consistent amongst cameras in a studio (so that the tint stayed the same for a show), but inconsistent with the actual colour subcarrier, would take some doing. There is no subcarrier or burst signal in the cameras. They aren't needed at that point, and are added during the encoding process. Setting them up is another matter. The early episodes of "Barney Miller" provide a good example of poor setup, with inconsistent color, and poor convergence. |
#67
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NTSC versus PAL
On 8/04/2010 12:21 AM, William Sommerwerck wrote:
Yes -- a lack of consistency. That was not the fault of NTSC, but of the broadcasters. I have to wonder what the broadcasters were doing to achieve that. Contriving to get the colour burst phase consistent amongst cameras in a studio (so that the tint stayed the same for a show), but inconsistent with the actual colour subcarrier, would take some doing. There is no subcarrier or burst signal in the cameras. They aren't needed at that point, and are added during the encoding process. Ok, so the separate colour signals (and luminance?) are sent from the cameras. Still, at some point the colour signals have to be encoded using the colour subcarrier, and a bit of the latter has to be included as the burst. Failing to keep them in phase would require a considerable amount of indifference. Which I think you've also said Setting them up is another matter. The early episodes of "Barney Miller" provide a good example of poor setup, with inconsistent color, and poor convergence. Poor convergence? The mind boggles. Sylvia. |
#68
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NTSC versus PAL
William Sommerwerck wrote: Part of the difficulity in understanding is that perhaps you don't have experience with early American color televisions... I certainly remember how in the 60s we had to adjust the tint control on a regular (show by show) basis, because of lack of consistancy. Yes -- a lack of consistency. That was not the fault of NTSC, but of the broadcasters. And AT&T who provided the coaxial cables that fed the video to all the stations on a network. The tint and chroma level could be adjusted at every facility in the system. I knew someone who worked for AT&T at the time, and he told me what a pain it was to compensate for the cable. When the network switched to a different studio or city for a show, it threw everything out of calibration. Anyone who had one of those old, tube (valve) color sets, with the 21" round color CRT, will remember seeing green skies, and blue grass while having skin colors set to the proper shade. Get the sky blue, and the skin turned red, or blue, or green! I don't think that's correct. The cameras (and/or encoders) would have had to have been very badly set up for that to happen. On a related subject... I remember reading long, long ago that the first RCA color TV had /four/ controls for adjusting the color, which the author described as a "combination lock"! Anyone know anything about this? He may be talking about the three 'drive' controls that set the gain for each channel. These are set up to provide equal gain to get a white line during setup. They are service adjustments on TVs, but on an early design they may have been easier to get to. Some TVs still had hollow plastic shaft extenders that passed through the rear of floor model cabinets to adjust these and other pots. The fourth would be the actual dolor intensity control. -- Lead free solder is Belgium's version of 'Hold my beer and watch this!' |
#69
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NTSC versus PAL
Setting them up is another matter. The early episodes of
"Barney Miller" provide a good example of poor setup, with inconsistent color, and poor convergence. Poor convergence? The mind boggles. Oh, yes. The pickups had to be aligned. The "modern" system, in which solid-state sensors are attached to a prism/beamsplitter was not practical with vidicons and Plumbicons. |
#70
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NTSC versus PAL
On a related subject... I remember reading long, long ago
that the first RCA color TV had /four/ controls for adjusting the color, which the author described as a "combination lock"! Anyone know anything about this? He may be talking about the three 'drive' controls that set the gain for each channel. These are set up to provide equal gain to get a white line during setup. They are service adjustments on TVs, but on an early design they may have been easier to get to. No, these were supposedly user controls. Anybody got a photo of the user controls for a CT-100? |
#71
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NTSC versus PAL
In article ,
William Sommerwerck wrote: There is no subcarrier or burst signal in the cameras. They aren't needed at that point, and are added during the encoding process. Setting them up is another matter. The early episodes of "Barney Miller" provide a good example of poor setup, with inconsistent color, and poor convergence. So camera setup was poor - as was the later stages of transmission? This certainly wasn't the case in the UK - despite the transmitters being fed with land lines. -- *Where do forest rangers go to "get away from it all?" Dave Plowman London SW To e-mail, change noise into sound. |
#72
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NTSC versus PAL
In article ,
William Sommerwerck wrote: Setting them up is another matter. The early episodes of "Barney Miller" provide a good example of poor setup, with inconsistent color, and poor convergence. Poor convergence? The mind boggles. Oh, yes. The pickups had to be aligned. The "modern" system, in which solid-state sensors are attached to a prism/beamsplitter was not practical with vidicons and Plumbicons. Registration on cameras. Convergence on monitors? Did you have videcon colour cameras? First UK ones were plumbicon. Apart from the ancient IO RCA ones used for tests. -- *24 hours in a day ... 24 beers in a case ... coincidence? * Dave Plowman London SW To e-mail, change noise into sound. |
#73
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NTSC versus PAL
Registration on cameras. Convergence on monitors?
Yes. Thanks for the correction. Did you have videcon colour cameras? First UK ones were Plumbicon. Yes, because you started so late. The first RCA cameras used vidicons (I think) -- though they might have used image orhticons. They later had a four-pickup camera that used an image orthicon to generate a perfectly registered (by definition) luminance signal, plus three vidicons. |
#74
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NTSC versus PAL
William Sommerwerck wrote: Setting them up is another matter. The early episodes of "Barney Miller" provide a good example of poor setup, with inconsistent color, and poor convergence. Poor convergence? The mind boggles. Oh, yes. The pickups had to be aligned. The "modern" system, in which solid-state sensors are attached to a prism/beamsplitter was not practical with vidicons and Plumbicons. Local stations weren't immune, either. Some locally produced shows in Dayton, ohio aired from poorly converged cameras in the '70s & '80s -- Lead free solder is Belgium's version of 'Hold my beer and watch this!' |
#75
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NTSC versus PAL
In article ,
William Sommerwerck wrote: Registration on cameras. Convergence on monitors? Yes. Thanks for the correction. Did you have videcon colour cameras? First UK ones were Plumbicon. Yes, because you started so late. The first RCA cameras used vidicons (I think) -- though they might have used image orhticons. Three 3 inch IO were the ones I remember. Being used for tests long before colour broadcasting started in the UK. They later had a four-pickup camera that used an image orthicon to generate a perfectly registered (by definition) luminance signal, plus three vidicons. That's a configuration I never saw. The first colour cameras here were all four tube plumblicons. I was taught the colour response of a videcon wasn't suitable. BTW I'm not surprised your setup engineers had problems - with a mixture of IO and videcon. ;-) -- *Santa's helpers are subordinate clauses* Dave Plowman London SW To e-mail, change noise into sound. |
#76
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NTSC versus PAL
"Dave Plowman (News)" wrote: In article , William Sommerwerck wrote: Registration on cameras. Convergence on monitors? Yes. Thanks for the correction. Did you have videcon colour cameras? First UK ones were Plumbicon. Yes, because you started so late. The first RCA cameras used vidicons (I think) -- though they might have used image orhticons. Three 3 inch IO were the ones I remember. Being used for tests long before colour broadcasting started in the UK. They later had a four-pickup camera that used an image orthicon to generate a perfectly registered (by definition) luminance signal, plus three vidicons. That's a configuration I never saw. The first colour cameras here were all four tube plumblicons. I was taught the colour response of a videcon wasn't suitable. RCA built their TK44 color studio cameras with Vidicons. They changed the model number to TK46 when they switched to Plumicons. Most of the parts were interchangeable, so I used a pair of TK44 cameras for spare modules & as a test jig to keep three TK46 cameras working the way we wanted. The TK44s were used by TV stations for years, but needed brighter studio lighting. -- Lead free solder is Belgium's version of 'Hold my beer and watch this!' |
#77
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NTSC versus PAL
In article ,
"Dave Plowman (News)" wrote: In article ], isw wrote: In article , Sylvia Else wrote: --snippety-snip-- I'm left wondering what exactly was the *real* problem that PAL was intended to fix. Political. The Europeans didn't want US companies selling sets there. Didn't stop the Japanese, etc. But *they* wanted to sell sets *here*. Isaac |
#78
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NTSC versus PAL
In article ,
"William Sommerwerck" wrote: Registration on cameras. Convergence on monitors? Yes. Thanks for the correction. Did you have videcon colour cameras? First UK ones were Plumbicon. Yes, because you started so late. The first RCA cameras used vidicons (I think) -- though they might have used image orhticons. Iconoscope first, then orthicon, then image orthicon. Vidicons were first used for film chains, and later as the color (as opposed to luminance) pickups in *some* cameras. Isaac |
#79
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NTSC versus PAL
On Apr 7, 5:26*pm, "Michael A. Terrell"
wrote: "Dave Plowman (News)" wrote: In article , * *William Sommerwerck wrote: Registration on cameras. Convergence on monitors? Yes. Thanks for the correction. Did you have videcon colour cameras? First UK ones were Plumbicon. Yes, because you started so late. The first RCA cameras used vidicons (I think) -- though they might have used image orhticons. Three 3 inch IO were the ones I remember. Being used for tests long before colour broadcasting started in the UK. They later had a four-pickup camera that used an image orthicon to generate a perfectly registered (by definition) luminance signal, plus three vidicons. That's a configuration I never saw. The first colour cameras here were all four tube plumblicons. I was taught the colour response of a videcon wasn't suitable. * *RCA built their TK44 color studio cameras with Vidicons. *They changed the model number to TK46 when they switched to Plumicons. *Most of the parts were interchangeable, so I used a pair of TK44 cameras for spare modules & as a test jig to keep three TK46 cameras working the way we wanted. *The TK44s were used by TV stations for years, but needed brighter studio lighting. -- Lead free solder is Belgium's version of 'Hold my beer and watch this!' I thought TK-44s had plumbs. I _know_ that TK-45s had plumbs as I have a used one from a TK-45. The TK-28 film camera had vidicons but AIUI, the vidicon had its own level non-linearity that was not present in plumbicons (Leddicons for you EEV fans) or Saticons. Vidicons required different electronic gamma to achieve an overall gamma of 2 to 2.2. For a film camera the vidicon issue wasn't as bad as the light levels were much more predicable. You can look at some of the dinosaurs here. http://www.oldradio.com/archives/hardware/TV/RCA-TV.htm G² |
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