SDHC vs CF vs P2 vs SXS

[gint12b]

Alright, please help my math out here but I'm just throwing this out there...

Shouldn't you be able to record P2 HVX200 footage (100Mbps) onto an SDHC card which can transfer at speeds up to (240Mbps)...

Now I know P2 has an advantage with a RAID built in and I'm sure it has other features but for the price difference. I hope we are given the choice in the future to get higher bitrates on SDHC. I think this is only the beginning and the less proprietary the format (P2 and SXS) the better.

Why is AVCHD limited to only 24Mbps? It seems like we could use some more data (especially in the 1080 mode) and receive 4:2:2. I guess this is what AVCIntra solves but why not offer it on SDHC cards instead of P2 cards and stick it in prosumer cameras?

Lastly what are some advantages of SDHC to CF? It seems like still cameras switch from CF in pro (D3) to SDHC in prosumer (D90).

I know I've asked a lot of questions in this thread but overall, what are your predictions for the future of tapeless media?

[gint12b]

Just to quickly compare the 4:

SxS = 800Mbps (100MBs)

P2 = 640Mbps (80MBs)

CF = 368Mbps (46MBs)

SDHC = 240Mbps (30MBs)

[BobDiaz]

Just to go through the math on the cards...

SDHC Class 4 = 4 M Bytes/second x 8 bits to the byte = 32 M bits per second.

Notice that upper case "B" = Bytes and lower case "b" is bits. There are 8 bits to a Byte.

SDHC Class 6 = 6 MB/second x 8 = 48 Mb/second

CF 20 MB/second x 8 = 160 Mb/second


Keep in mind that I'm giving common speeds, there are faster chips that higher rates, but these are typical rates.


Bob Diaz

[mcsmooth]

Now I know P2 has an advantage with a RAID built in and I'm sure it has other features but for the price difference. I hope we are given the choice in the future to get higher bitrates on SDHC. I think this is only the beginning and the less proprietary the format (P2 and SXS) the better.

Speeds will only increase, so time will tell. There is going to be some time before common consumer cards can reliably do 100Mbps. For now, the capacities are increasing much faster than the speeds.

Why is AVCHD limited to only 24Mbps? It seems like we could use some more data (especially in the 1080 mode) and receive 4:2:2. I guess this is what AVCIntra solves but why not offer it on SDHC cards instead of P2 cards and stick it in prosumer cameras?

It's a consumer codec that is already pretty difficult to process at 24Mbps. It is a pretty damn impressive consumer format, but you can get more from pro codecs. As mentioned above, AVCIntra would not work with current SD speeds... but you also need to spend a lot of money to get a camera that can encode it.

Lastly what are some advantages of SDHC to CF? It seems like still cameras switch from CF in pro (D3) to SDHC in prosumer (D90).

Mainly size, and it is becoming the standard that won with consumers (like blu-ray over hd-dvd). I've read that CF is good with burst speeds whereas SD is better at sustained speeds (needed for video).

I can't predict any major tapeless media changes in the near future other than sizes doubling (and doubling again) and speeds climbing. Solid state cards and drives are finally reaching capacities that can replace the need for tapes and (non-massive) hard drives, so I would expect to see this takeover continue its path.

[gint12b]

Hmmm, are you guys sure? Check out this link...

It has a minimum of 30MB/second sequential write and read speed.
http://www.bhphotovideo.com/c/produc....html#features

SanDisk today set a new speed record of 30 megabytes per second for SD flash memory...
http://technorati.com/posts/USuqJQwQ...IaNr9TvbQD8%3D

I'm pretty sure my math was accurate! Am I missing something here? Otherwise this is some serious false advertising...

[mcsmooth]

I must have glanced at your numbers too quickly (I saw 100MBps thinking you were referring to P2 writing 100Mbps with current codecs, and the SDHC rate didn't look familiar, etc). So your math IS correct, I just wasn't sure where you were getting some of those rates.

On that note though, I'm pretty sure those really high rates that are being advertised are maximum data transfer rate. Video requires a sustained minimum transfer speed, so those numbers come down quite a bit (not to mention they need to leave some headroom and use common cards). I haven't heard of cards above "class 6", but if they don't already exist, I'm sure they will soon enough. Everything will be possible in the future, but I don't see P2 leaving the pro cameras anytime soon. I've seen talk of expresscard to SDHC adapters that work for the EX-1, maybe a similar option for P2 will come about.

AVCHD is capped at 24Mbps though, so it can't go any higher. Someone could make a variant of it that allows for more down the road similar to how XDCam HD expanded on HDV. This is a prosumer camera that uses consumer media/codec just like DVX did, the massive savings outweigh the few setbacks in this class. Since these cameras don't do much above 720, I don't think it's an issue right now, but might be thirsty for some more bandwidth if/when the sensors are improved.

[gint12b]

"Video requires a sustained minimum transfer speed, so those numbers come down quite a bit"

I actually just came across this amazing article describing how Redcode RAW is transferred to CF Cards and it pretty much goes all the way up to the maximum data transfer rate of these cards without any fault:

http://provideocoalition.com/index.p...fo_on_redcode/

You can't get much more professional than RED and if they are shooting to CF cards successfully, one mode RC28 with a maximum data rate of 28MB/s (224 megabits), and one RC36 with a maximum data rate of 36 MB/s (288 megabits), I don't see the real need for all that extra bitrate that SxS and P2 offer...

I think what upsets me the most is that it seems completely possible to record P2 to CF cards or even SDHC cards at a fraction of the cost to the customers but these big camera companies won't allow it because they can make over 1000 dollars per P2 or SxS card...

Technology is rapidly changing, I just predict that P2 and SxS won't last. Just my humble opinion...

[accelv]

Sony and Panasonic gulped down a bitter pill with the onset of digital production and the loss of business from declining tape deck sales. My 2 SVHS editing decks cost close to $9,000. back in the day. So with proprietary products like SXS they can hold on to some profitability. Panasonic is not likely to offer AVCHD Intra in a prosumer product anytime soon, or until a company like RED forces their hand.

That's why I like to see products like RED come along and shake the ground under these powerful companies

[gint12b]

"That's why I like to see products like RED come along and shake the ground under these powerful companies"

Well Said!!!

[mcsmooth]

I have to say I do agree that a lot more IS possible (whether or not it is feasible). I have thought about and wished for the same features you brought up as I love hi-tech toys at a price I can actually afford. It seems that the companies have to draw the line somewhere between pro and prosumer features/price (and another line for consumer) to help make a profit. That line keeps getting narrower every year, even the consumer cams are really impressive for a lot less. If Red's Scarlet delivers as promised, it will def stir things up at this level. What we have to realize is that the 150 (like the DVX) is tailored to a slightly different market and is meant to be more consumer friendly. I do wonder if AVCIntra will ever make it down to the hpx170 or even hpx500 level pricing.

There are some threads on P2 that mention how there are a lot of people/companies bought into it that it wont be going away anytime soon at the pro level. They could offer cams with both drives to transition though, it would just be questionable if they would spend money developing this feature to lose out on earning money for the cards (like you pointed out). For "us", we would just have to hope for a new codec that can be used on our cheap cards, I just wouldn't hold my breath until things get sorted out with the current one.