Difference between PAL and SECAM
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eldalote_faelivrin
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harakiris -
harakiris -
Hello,
I am currently in a class on video signals and I can't understand a fundamental element: the difference between PAL and SECAM.
I know that:
PAL: phase alternation line, we inject the Dr into every other line while keeping the amplitude
SECAM: the transmission consists of sending the color signals Db & Dr on every other line.
I can't find the difference even with books (that I borrowed specifically from the library) and with research... Can you explain it to me in simple words, perhaps with examples? =S
Thank you in advance
Configuration: Windows 7 / Firefox 3.6.15
I am currently in a class on video signals and I can't understand a fundamental element: the difference between PAL and SECAM.
I know that:
PAL: phase alternation line, we inject the Dr into every other line while keeping the amplitude
SECAM: the transmission consists of sending the color signals Db & Dr on every other line.
I can't find the difference even with books (that I borrowed specifically from the library) and with research... Can you explain it to me in simple words, perhaps with examples? =S
Thank you in advance
Configuration: Windows 7 / Firefox 3.6.15
7 réponses
Hello (it brings back memories) well, it's good to study history "because all of this is now in the past. Take a look at the WIKIPEDIA site, it's explained quite well. I won't give you the whole lesson, mine are in the cellar, and I'm retired. Just a bit of history then (that I lived): the American pioneers of your color TV used NTSC. This is a system based on the transmission of information separate from the signal where the VIDEO or LUMINANCE content (the black and white image = gray scale) and the CHROMA (color information encoded) overlapped in the television to reproduce a colored image. The three information channels GREEN, BLUE, and RED added together at tiny points on the cathode-ray image (luminophore delta) in a triangle smaller than a millimeter gave the eye a reproduced colored image. This NTSC encoding system had a major flaw related to the instability of the phase shift of the transmitted signal. A manual adjustment of the television called HUE control allowed for correcting errors. The need to use and broadcast color TV in Europe created a more elaborate and especially more stable color system called PAL. The color phase was transmitted alternately by pairs of lines, the phase shift limited to 90° and stabilized by a quartz oscillator. The choice of this process initiated by the Germans prevailed almost everywhere as a successful evolution. The whole of Europe (except France and its "overseas departments," Africa, and options in the USSR) chose PAL. In France, engineer Henri de France invented SECAM (Sequential with Memory), a color encoding where the RED and BLUE signals were transmitted one after the other, sequentially guided (switching) to a direct line or a delay line (64 µS = the duration of a scanning line) to arrive further along at the same time, taking the time to reconstruct the GREEN by differentiation (matrixing) and finally all this color information overlaps with the VIDEO or LUMINANCE to feed the cathode tube generating the colored image. Today we fill history books and forget all these incompatible systems, which thus create a sort of market protection (manufacturers). Nowadays, due to globalization, the digital DVB-(T or S or C depending on the transmission mode) process is universal, you can "travel" with your "throwaway" TV built mostly by the Chinese and Koreans. Our European factories are struggling to survive and are shutting down one after another. Even the maintenance profession is threatened.
Good luck
Good luck
harakiris
Thank you for all the time devoted to others.
Don't go too fast or I misspoke:
signal encoding for transmission
-NTSC (old and unstable USA Japan)
-PAL (Europe then the rest of the world except France and colonies and USSR
alternative encoding of RED and BLUE one line out of two by stabilized phase
Alternative Phase Line)
-SECAM (sequential with memory = France, colonies Africa USSR) the RED and BLUE color signals are coded and sent one after the other. To reassemble them at the same time, one line out of two goes through a 64µS delay line, this is called sequential with memory. (in a row..)
Whether in PAL or SECAM, at the output of the DECODING we obtain two lines, one Red and one Blue synchronized. A circuit called MATRIXING produces the GREEN information from the red and blue
Finally, we have decoded three pieces of information BLUE, GREEN, and RED which we map and then apply respectively on the "Grilles G1" (X3) of the cathode ray tube with three delta guns in the first versions and PIL Phase in line (in line) on the more recent tubes (more stable in "convergences than the delta)
The VIDEO or common luminance information is amplified and then transmitted to the cathodes of the cathode ray tube (mandatory reference to the courses on the cathode ray tube) which "matrixes" (mixes, produces) the color image
Phew, this comes from far away, hello! (it was in October 1967 for me)
PS it is necessary to distinguish between the "encoding" of PAL or SECAM signals found in VIDEO (band recordings or other media) and the reproduction of an image on a color television which of course includes the PAL or SECAM DECODER or both.
signal encoding for transmission
-NTSC (old and unstable USA Japan)
-PAL (Europe then the rest of the world except France and colonies and USSR
alternative encoding of RED and BLUE one line out of two by stabilized phase
Alternative Phase Line)
-SECAM (sequential with memory = France, colonies Africa USSR) the RED and BLUE color signals are coded and sent one after the other. To reassemble them at the same time, one line out of two goes through a 64µS delay line, this is called sequential with memory. (in a row..)
Whether in PAL or SECAM, at the output of the DECODING we obtain two lines, one Red and one Blue synchronized. A circuit called MATRIXING produces the GREEN information from the red and blue
Finally, we have decoded three pieces of information BLUE, GREEN, and RED which we map and then apply respectively on the "Grilles G1" (X3) of the cathode ray tube with three delta guns in the first versions and PIL Phase in line (in line) on the more recent tubes (more stable in "convergences than the delta)
The VIDEO or common luminance information is amplified and then transmitted to the cathodes of the cathode ray tube (mandatory reference to the courses on the cathode ray tube) which "matrixes" (mixes, produces) the color image
Phew, this comes from far away, hello! (it was in October 1967 for me)
PS it is necessary to distinguish between the "encoding" of PAL or SECAM signals found in VIDEO (band recordings or other media) and the reproduction of an image on a color television which of course includes the PAL or SECAM DECODER or both.
In fact, I don’t have a lesson on the cathode ray tube or anything else. I actually have a lesson on “video signal” and I have component/composite video, YDbDr, YCbCr... and then I have:
2.5: PAL and SECAM coding standards:
PAL: Phase Alternating Line
SECAM: Sequential Color with Memory.
And nothing else... This is not due to negligence on my part; it was actually written this way on the professor's slide... so I am searching in vain, I went to borrow some books but I find the terms too scientific, hence my coming to the forum.
Basically, PAL would be a principle by which a red line, a blue line, a red line... is sent and since there is a phase shift, there is a delay, so in the end the image is still composed? And for SECAM, we have for one line, the luminance and red, for the line below the luminance and blue...
Once again, I come back to the same reasoning as for PAL =S
Thank you for your patience ^^
2.5: PAL and SECAM coding standards:
PAL: Phase Alternating Line
SECAM: Sequential Color with Memory.
And nothing else... This is not due to negligence on my part; it was actually written this way on the professor's slide... so I am searching in vain, I went to borrow some books but I find the terms too scientific, hence my coming to the forum.
Basically, PAL would be a principle by which a red line, a blue line, a red line... is sent and since there is a phase shift, there is a delay, so in the end the image is still composed? And for SECAM, we have for one line, the luminance and red, for the line below the luminance and blue...
Once again, I come back to the same reasoning as for PAL =S
Thank you for your patience ^^
Hello
I believe that you are not following a training course for consumer electronics maintenance technician and that I may have gone a bit too far into a complicated explanation mixing DECODING and the viewing of a color TV image on a TV screen. The cathodic system being familiar to me (I started in 1965 and finished my TV maintenance career in 1981). What is important for you to know, and I have already insisted on this, is that all of this is already in the past. We still encounter analog equipment that uses either PAL (European) or SECAM on products limited to France. It has been a long time since all color decoders use integrated circuits for PAL/SECAM and, for economic reasons, PAL has dominated, with some decoders easily transforming SECAM into PAL. In video (Sony's Betacam used by video reporters used PAL before definitively switching to digital), you will find traces of analog technology that are quickly replaced because they are not very efficient. The main thing is to know that this once existed (we open a history book or technology moves too fast)
bye
I believe that you are not following a training course for consumer electronics maintenance technician and that I may have gone a bit too far into a complicated explanation mixing DECODING and the viewing of a color TV image on a TV screen. The cathodic system being familiar to me (I started in 1965 and finished my TV maintenance career in 1981). What is important for you to know, and I have already insisted on this, is that all of this is already in the past. We still encounter analog equipment that uses either PAL (European) or SECAM on products limited to France. It has been a long time since all color decoders use integrated circuits for PAL/SECAM and, for economic reasons, PAL has dominated, with some decoders easily transforming SECAM into PAL. In video (Sony's Betacam used by video reporters used PAL before definitively switching to digital), you will find traces of analog technology that are quickly replaced because they are not very efficient. The main thing is to know that this once existed (we open a history book or technology moves too fast)
bye
The PAL sends the two chroma components to each line using quadrature amplitude modulation of the subcarrier (analog QAM). Additionally, one of the components is inverted every other line. The SECAM only sends one of the two components to each line, using frequency modulation of the subcarrier. In both cases, it is necessary to combine two successive lines, with the previous one being stored in a delay line, to decode the color. In SECAM, because it is necessary to gather the two chroma components, and in PAL because it is necessary to average the normal and inverted components to cancel the phase shift due to transmission.
Historically, in terms of patents, SECAM arrived long before PAL, which paid royalties for many years because it had to adopt Henri de France's idea of distributing color transmission over two lines using a delay line.
Historically, in terms of patents, SECAM arrived long before PAL, which paid royalties for many years because it had to adopt Henri de France's idea of distributing color transmission over two lines using a delay line.
Thank you for this very comprehensive response. I had already consulted Wikipedia, but I found the words too technical and it was still too vague for me.
With this answer, I have already clarified quite a few points.
From what I understand:
PAL: evolution of NTSC, the electron guns scan every other line, while the luminance is transmitted over all the pixels.
SECAM: the red and blue signals are consecutive, allowing the green to be reconstructed when necessary. The scanning is more or less rapid depending on the composition of the image.
I accept being reprimanded if this is wrong ^^ I'm not good at this kind of subject which is a mandatory part of my training...
Thank you again.
With this answer, I have already clarified quite a few points.
From what I understand:
PAL: evolution of NTSC, the electron guns scan every other line, while the luminance is transmitted over all the pixels.
SECAM: the red and blue signals are consecutive, allowing the green to be reconstructed when necessary. The scanning is more or less rapid depending on the composition of the image.
I accept being reprimanded if this is wrong ^^ I'm not good at this kind of subject which is a mandatory part of my training...
Thank you again.
I may have used some technical terms to be brief. The chroma information is the "blue" and the "red." All systems also send a black and white signal obtained by combining the three colors, where green dominates largely. However, green can be precisely extracted by recombining the black and white with the decoded blue and red components. The color information is placed in the high frequencies of black and white (corresponding to the fine details of the image, hence less intrusive) by modulating a carrier around 4.5 MHz (called subcarrier). PAL and NTSC transmit red and blue simultaneously. NTSC decodes it as is and, due to the phase shifts introduced by components and transmission, makes errors in hue. PAL transmits the same information twice over two lines with an inversion, which allows recovering and canceling the phase shift, at the cost of a residual error in saturation. SECAM transmits a single component per line and has none of the phase shift issues; it is the only standard that correctly restores hue and saturation in the presence of disturbances. The principle of SECAM (alternating transmission of red and blue) was later adopted as is in MAC systems (including HD-MAC), which was anticipated as the European standard for analog transmission but mainly deployed in Nordic countries.