The Path to a Better Picture

As I have mentioned in a previous blog post I have on order a new type of recorder called the AJA Ki-Pro Mini®. This device attaches to any camera via either HDMI or SDI and will record at a much higher (adjustable) bit rate than the host camera can. Well, after many weeks of delays AJA finally started shipping the units about a week ago.

What does this mean for you? It means no more picture artifacts during fast action/panning/tilt shots because of too much picture compression. Codecs such as HDV, AVCHD and to a lesser extent MPEG2 are all subject to ‘breaking the codec’ because the compression can’t keep up with the action.

  • HDV’s compression rate is 15 Mbits per second
  • AVCHD’s top compression rate is 24 Mbits per second
  • MPEG2 tops out at 35 Mbits per second for XDCAM EX and some JVC cameras.

If you’re shooting for broadcast the minimum requirement is 50 Mbits per second so that leaves XDCAM HD® shoulder mount cameras which are many times the cost of the handhelds. By the way your mileage will differ depending on the network you’re trying to sell your product to.

Both AJA’s Ki Pro® and Ki Pro-Mini® are solely for the Mac crowd as they shoot directly to Apple’s Pro Res codec in 5 different compression formats, depending on how much quality is required. What’s interesting is that the proxy version of Pro Res is 45 Mbits p.s. which is 10 more than the highest quality setting in my XDCAM EX cameras.

For everyone else the recorder of choice is Convergent Design’s Nano Flash® which records to MPEG2 in many different bit rates, again depending on what sort of picture quality you require. The Nano Flash starts out at 50 Mbits p.s. and goes up to 280 Mbits p.s. ( I think). Mac editors can still use the Nano Flash but the cost for the Ki Pro-Mini is less.

Both recorders have 2 Compact Flash (CF) slots. However, when one card is full only the Nano Flash will automatically jump to the empty card without losing any video frames. The cards of both units are also hot swappable, meaning you can remove the the full CF card and replace it with an empty one while the units continue to record on the card that is not full. When the second card is full the Nano Flash will jump back to the first slot.

NOTE:

If your subject matter is talking heads, seminars etc, you won’t see much difference between your camera’s picture and the picture from the auxiliary unit because there’s not enough action to stress the codec. Keep in mind though,  that simple things such as rippling water and rustling leaves will stress the codec and the picture quality from the auxiliary unit will be obvious (depending on your camera’s standard bit rate).

Both the Ki Pro-Mini and the Nano Flash use CF cards and of course, the most expensive ones are recommended because they have to handle the high bit rates being output to the units. The secret to the success of both the Nano-Flash and the Ki Pro-Mini is that they bypass the compression stage in the camera and record the image directly from the camera head.

Here’s a price breakdown of one particular CF card manufacturer based on card capacity:

Sandisk Extreme Pro Compact Flash card®

  • 16 GB – $279.00 USD
  • 32 GB – $503.00 USD
  • 64 GB – $895.00 USD
  • 128 GB – $1499.00 USD

As you can see, the price of quality isn’t cheap. As for the price of the recording units, the Nano Flash is around $2995.00 USD and the Ki Pro-Mini is $1995.00 USD.

The card capacity that you buy would be determined by the amount of compression you’re willing to dial in. You want a bit rate that will do the job without compression artifacts but no more than that otherwise you’re wasting storage space on the CF cards. For example:

  • 35Mbits per second equals 1.4 Gbytes of storage space for every 5 minutes of video
  • Apple Pro Res 422 Proxy@45Mbits is 2.0 Gbytes of space for 5 minutes
  • Apple Pro Res 422 Light@102Mbits is 4.4 Gbytes of space for 5 min.
  • Apple Pro Res 422@147Mbits is 6.3 Gbytes of space for 5 min.
  • Apple Pro Res 422 HQ@220Mbits is 9.4 Gbytes of storage space for 5 min.

And the list goes on.

If I did the math for what I would normally shoot at which would be Apple Pro Res 422 (LT) I would fill up a 32 Gbyte CF card in 36 minutes.

It’s that old saying again: Speed costs money. How fast do you want to go? The huge advantage of the Ki Pro-Mini and the Nano Flash is that you can upgrade the picture quality of your existing hand held camera to rival shoulder mount cameras costing many times the price.

– Don


Written by:

Don Greening is the owner and both senior editor and videographer for Reeltime Videoworks. His arts background as a classical musician and composer gives him an uncompromising eye and ear for detail that is very important in video production. Don also hones his technical skills by updating them through courses at Emily Carr Institute of Art + Design.

  • Great article Don.

    I wanted to add something about CF cards. When I was researching CF cards, I found that the 133x speed on a CF card was sufficient for the h.264 codec recordings from DSLR cameras.

    For people looking at card speeds, also note that Mbit/second is different than MB/s. A Mbit (megabit) has to be divided by 8 to equal a MB (megayte). Confusing, I know. So, at a good clip of 102Mbits per second, that would be 12.75 MB per second, which is theoretically in the reach of a 133x card (which should do 20 MB/s).

    Kingston has some equations on speed over here http://www.kingston.com/flash/x/default.asp.

    Here is a chart comparing different cards http://www.robgalbraith.com/bins/camera_multi_page.asp?cid=6007-9038. I think it is mainly for photographers though.