The Target Market For The AF-100/101

[Barry_Green]

Uncompressed but with 8bit 4:2:2 croma sub-sampling you mean. 4:4:4 does not come out of the HD-sdi.

Nor does it come out of any HD-SDI port. You have to use dual-link with two SDI cables to get 4:4:4 output. HD-SDI outputs 4:2:2. There is no way to get 4:4:4 out of an HD-SDI port on any camera anywhere. Someday in the future we'll see the new standard 3G-SDI, which will support 1080p 4:4:4, but that's a different standard. We're talking about HD-SDI.

The only compromise in the AF100's HD-SDI output is that it's 8-bit instead of 10.

On that note, I would think there will be a big demand for external recorders that cover all the frame rates, over and undercranking, intra codecs and even JPEG2000. I hope this demand will be met and there will be many to choose from.

It really doesn't even have to be that expensive. I saw this video using a laptop as a portable recorder. I wouldn't want to record video this way but if one put the parts together in a more robust dependable fashion, you could get a highly versatile and inexpensive option.

They're already popping up. The NanoFlash, Wafian, Cinedeck, and Ki Pro were first, and now we're seeing low-cost options like the Ki Pro and Ninja ($795 MSRP). And there will obviously be more.

 

[Steve Kahn]

Another way would be to record uncompressed onto the SDXC cards. I'm not sure if this is a possible firm ware hack but the SDXC spec allows for up to 2 tetrabytes per card.

Of course the write rate would have to be at least ~95MiB/second. This is extremely fast as current cards are only ~10MiB/second but still within in the foreseeable future.

So if this a possible hack it may be a great one if and when >100MiB/second write cards are on the market.

 

[Razz16mm]

SDXC or any form of SD card won't handle raw uncompressed data rates. You are talking around 75 mega BYTES per second continuous write capability to capacity without meltdown or dropping a frame, reliably and repeatedly. Not much out there short of fast SSD's that will do that yet.

 

[BobDiaz]

Uncompressed video takes a lot of memory space:

1270x720 @ 24p, 4:2:0 = about 33 MB per second, almost 2 GB per minute

1920x1080 @ 30p, 4:2:2 = about 124 MB per second, almost 7.5 GB per minute

That's "B" as in Bytes.



Bob Diaz

 

[Steve Kahn]

Video bitrate calculator

Video bitrate calculator

Video bitrate calculator

Understood.

My point is that perhaps we are moving in this direction. Even USB2 has data transfer rates greater than 100 MB/second.

So theoretically if we do HD-sdi to some sort of an array of 4 SDXC cards which at the moment can do 25MB/second we're there.

I know that pushes the envelope but my point is that we're closer. Perhaps very close to this being an option.

2TB with read/write speeds to 104MB per second. SDXC card

 

[Barry_Green]

I don't think we're anywhere near as close as we'd need to be, for a reliable solution.

USB2 doesn't transfer data at greater than 100MB/sec; on the contrary, it's just over half that. 480 megabits/sec = 60 megabytes/sec. And even then, that's a burst rate, not sustained data transfer.

As for writing it, keep in mind that SDHC cards only are rated to support Class 10. Which is 10 megabytes per second. You'd need a RAID of 13 of them to support writing 1080p uncompressed.

It'll get there over the next several years, but we're not near yet. The link to the SDXC card mentions a "maximum" speed of 104 megabytes per second. But that's a) an announcement for a specification, not for a product, and b) the "maximum" speed doesn't mean the card will do that speed; it only means that the card will not exceed that speed. What's important in evaluating cards isn't what their theoretical maximum is, it's what their guaranteed minimum is. And with SDHC cards, that guaranteed minimum doesn't go any higher than 10 megabytes per second yet. Even the new UHS-1 SDXC cards aren't listed for what their sustained minimum write speed is, so we don't know what they'll be capable of.