Strange 628 * 582 resolution

Dear Steve,

"If the camera supports both then there must be either a switch or some software configurability."

This is what I initially thought that it would be. Thanks very much for confirmation.

"What these numbers often mean is that a standard CVBS video signal is generated, but the image is scaled, windowed and/or clipped to fit in a standard video window (720x480 for NTSC 720x525 for PAL)."

So you mean that although these numbers (628 x 582 PAL, 510 x 492 NTSC) differs from standard BT.601/656 sampling for PAL/NTSC, the output is after all converted to the standard analog PAL/NTSC CVBS signal (in terms of

1. field/frame rate
2. active lines within a field
3. active video portion within a line
4. line retracing and field retracing time
5. HSYNC and VSYNC

), so in this way it is therefore safe to sample the analog CVBS signal just as sampling a standard PAL/NTSC TV signal, by devices such as TI 5150?

"They are most likely analog cameras, outputting CVBS video. "

But the size of one (I bought) is extremely small, with its size in all dimensions small than two inches. I don't know analog camera, but I would imagine if the sensor is not CCD or CMOS based, then there need to be an electronic gun scanning the image focused on the screen behind the lens, in an interlaced manner if it is to output conventional (PAL, NTSC) signal.

But within such a miniature size component, how can there be the structure as complex as a electronic gun? Actually, this camera cost me only ten bucks from a Chinese vendor.

Still another question to bother you on TVP5150 sampling:

According to the manual SLES043A, TVP5150 has 9 bit A-to-D converter.

But

1. According to BT.656 there either 8 or 10 bit representation, so there are 2^8=256 or 2^10=1024 levels of quantitization. But here TVP5150 gives 2^9=512 levels. How should the compatibility be dealt with here? Should I

1) If I intend to output 8-bit data, then divide the 9-bit representation by 2 (right shift one position)

2) if to output 10 bit data, multiple by 2 (right shift one position)

Sincerely, 

Jim

Jim,

When I say "analog camera" I mean that the output is analog, not the scanning technology. If there is only a single output wire, then the camera is analog output. The sensor technology itself is probably where the numbers for the image size come from and sill most likely be CMOS or CCD (probably CMOS at that price).

Regarding the TVP5150, the analog front end uses a 10 bit ADC to digitize the waveform. There is a significant amount of signal processing being done by the TVP5150, including gain, offset, color separation, color demodulation, data formatting etc... The result of all this processing is a digital output stream which conforms to the BT656 standard.

The analog front end resolution has nothing to do with BT656 and is more relevant to the quality of the signal processing. The video decoder is not simply an  ADC.

In theory you should be able to feed this camera's CVBS signal into a TVP5150 to retrieve the image. Having said this we have seen many, many cameras from China which do not really generate a truly compliant CVBS signal. The TVP5150 decoder is excellent at dealing with many non-standard signals but until you actually try this camer is is difficult to say 100% for sure. Depending on how the camera generates its CVBS signal you may find the image is scaled, cropped etc... As I mentioned previously, this is very much camera dependent.

BR,

Steve

Dear Steve,

Many thanks for your answer. I will study more into this.

Jim

Jim, You are more than welcome.

Please don't hesitate to ask more questions when you have them :)

BR,

Steve