[QuadList] looking for Type C to DVCam in Europe - color encoding

[C. Park Seward]

Ted,

Here is perhaps why PAL uses 4:2:0 encoding:

"In the early 1970s some Japanese set manufacturers developed decoding systems to avoid paying royalties to Telefunken. The Telefunken licence covered any decoding method that relied on the alternating subcarrier phase to reduce phase errors. This included very basic PAL decoders that relied on the human eye to average out the odd/even line phase errors. One solution was to use a 1H delay line to allow decoding of only the odd or even lines. For example the chrominance on odd lines would be switched directly through to the decoder and also be stored in the delay line. Then on even lines the stored odd line would be decoded again. This method effectively converted PAL to NTSC. Such systems suffered hue errors and other problems inherent in NTSC and required the addition of a manual hue control."

"Different variants of 4:2:0 chroma configurations are found in:
	• All versions of MPEG, including MPEG-2 implementations such as DVD (although some profiles of MPEG-4 allow higher-quality sampling schemes such as 4:4:4)
	• PAL DV and DVCAM
	• HDV
	• AVCHD and AVC-Intra 50
	• Apple Intermediate Codec
	• most common JPEG/JFIF, H.261, and MJPEG implementations
	• VC-1

The PAL and SECAM color systems are especially well-suited to this kind of data reduction. Most digital video formats corresponding to PAL use 4:2:0 chroma subsampling, with the exception of DVCPRO25, which uses 4:1:1 chroma subsampling. Both the 4:1:1 and 4:2:0 schemes halve the bandwidth compared to no chroma subsampling."

http://en.wikipedia.org/wiki/Chroma_subsampling

PAL broadcast video bandwidth is slightly greater than NTSC (4.2 vs. 5) but  think the bandwidth of Type "C" was about the same. PAL color difference signals have 1.5 MHz bandwidth.

"Most PAL receivers use a delay line which stores the received color information on each line of display; an average of the color information of the current line and that of the previous line is then used to drive the picture tube. This reduces vertical color resolution compared to the NTSC system, however since the human retina also has a color resolution that is much lower than its brightness resolution, this effect is not visible."

But NTSC could be improved. Remember YC Faroudja?

"A chroma modulation method for extending the bandwidth of baseband plural chroma components of an NTSC format quadrature modulated chroma subcarrier color television signal, such as I and Q components, with reduced susceptibility to ringing and with compatibility with existing NTSC color television receivers comprises the steps of: separating the baseband I and Q components into narrow bandwidth segments and extended bandwidth portions not including the narrow bandwidth segments; q u a d r a t u r e modulating the narrow bandwidth segments into a narrow band double sideband quadrature modulation envelope about the subcarrier frequency; alternately selecting and putting out the extended bandwidth portions of the I and Q components on a basis related to a predetermined scanning period of the television signal, such as the field period; modulating the alternately selected extended bandwidth portions at the subcarrier frequency to produce a lower single sideband; and, combining in corrected time relationship the double sideband quadrature modulation envelope and the lower single sideband of the extended bandwidth portion modulation envelope to provide chroma modulation having an extended bandwidth. A compatible demodulation method is also described."

http://www.freepatentsonline.com/5081521.html

Best,
Park

C. Park Seward
Cell: 818-535-2747
Home: 949-679-1870
2" Quad and 1" "C" transfers
Visit us: http://www.videopark.com




On Jun 16, 2010, at 3:57 PM, Ted Langdell wrote:

> Hi, Park,
> 
> On Jun 16, 2010, at 3:13 PM, C. Park Seward wrote:
> 
>> "In the NTSC system, if the luma is sampled at..."
> 
> 
> What does your resource show for the same parameters in PAL?
> 
> Ted
> 
> Ted Langdell
> Secretary
> 
> 
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