Understanding 24p

Sean Michael

Sean Michael

Well-known member
Is the 24p of the DVX purely a result of software programming, or is there a hardware component also?

If 24 frames-per-second video is a software achievement, when will Panasonic (and other manufacturers) port it into their consumer cams?
 
It isn't really software nor hardware exclusively, its really firmware and hardware. Here is how it is accomplished (extremely simplified):

1) CCDs output are quantized at 23.976 samples per second by the A>D converters.
2) CCDs row enable is driven active to match the "shutter speed" being used by the camera
3) Output of the quantizers is processed by a dedicated processor (DSP) to "fit' the signal onto a 25 Mb/s miniDV tape mechanism as well as the 1394 interface.

Since the signal path must also include the necessary hardware (and processing power) it isn't exclusively a "no cost" software solution. I wouldn't expect to see 24p support on general consumer goods at any time in the near future.
 
khmuse said:
Since the signal path must also include the necessary hardware (and processing power) it isn't exclusively a "no cost" software solution. I wouldn't expect to see 24p support on general consumer goods at any time in the near future.
Click to expand...

Unless they do a 24P-only camera. It's the multiple rates that drive the cost up, most likely.
 
Actually, the multiple rates are not a real cost at all. The ability to support different modes is actually much closer to a software issue as it is the most complex path that must be supported by the hardware. For lesser taxing configurations, sections of programable hardware (either ASICs or PLDs) and software (DSP or general purpose) can simply bypass the extra processing sub sections. Things like rates are controlled by the master clock's (27 MHz) divider to obtain the different pixel and sample clocks, this is easily accomplished (again without any real impact on the BOM - Bill Of Materials) by programable logic and software.

The line between hardware and software was long ago blurred by the use of PLDs and DSPs. There are literally SOC (System On a Chip) solutions that are used nowadays, the product (hardware) looks identical (and is infact identical) only its firmware (boot code) changes based upon the mission that the system is expected to perform.
 
Sean Michael said:
Is the 24p of the DVX purely a result of software programming, or is there a hardware component also?

If 24 frames-per-second video is a software achievement, when will Panasonic (and other manufacturers) port it into their consumer cams?
Click to expand...

It's not a result of purely software; it's definitely hardware. The CCD in most consumer cameras has been designed to scan and produce interlaced pictures; the CCD in the DVX is actually a multi-scan-rate progressive-scan chip. It scans at 24Hz, 30hz, or 60hz depending on the mode the camera's set in.

So no, it's not just software. And it'd be implemented in consumer cameras if consumer cameras were interested in it, or if the manufacturer thought there was a market for it, and that the market would pay enough to cover the cost of making the chips. Right now consumer cameras seem focused on 1/4" (or even 1/6") CCDs, and there are no progressive-scan 1/4" or 1/6" CCDs out there, AFAIK, not to mention multiple-scan-rate progressive-scan CCDs in that size. There'd have to be substantial market demand for the manufacturers to justify the r&d costs to create the new hardware.
 
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