Red/Pink line ?

[Dan Keaton]

Dear Lance,

Here is a chart that we created from our tests of the nanoFlash using the Video Clarity system.

Note: A lower number equals a better image based on Video Clarity's modeling of human perception of image quality.

Lower numbers plot higher on the chart, thus as the line gets closer to the top of the chart, the footage is higher in quality according to Video Clarity.

Our tests were performed using a high quality test file of a football game and this is not representative of all types of footage.

Just click on the chart to enlarge it, otherwise it i not large enough to actually read.

[Mark Job]

Originally Posted by Dan Keaton

Dear Mark,

Sorry, but I do not understand your comments.

The Flash XDR and nanoFlash always records full raster.

Full Raster for 720p = 1280 x 720 (1280 horizontal pixels, 720 vertical pixels).

Full Raster for 1080 = 1920 x 1080

The DVCPro HD is the codec that throws away resolution, then encodes the video stream.

The nanoFlash does not throw away any resolution.

Hi Dan: Wasn't I clear enough ? I was commenting on how surprised I was to learn that DVCPRO 100 throws away resolution. I was asking if what you wrote about the Nano always giving the Full Raster Maximum Resolution also was the case for the XDR ? Sorry you misunderstood my post. :-(

[Dan Keaton]

Dear Mark,

Yes, I completely misunderstood your post.

You wrote "I assume this is also an accurate statement covering the Flash XDR?"

So I thought the following statement applied to the Flash XDR. But now I know that it didn't.

Yes, both the Flash XDR and nanoFlash record full raster and apply the full bit-rate (per frame) to each frame recorded.

For example, if one shoots 100 Mbps and 1080i50.94 which is actually 29.97 frames per second, then the bit-rate per frame is 100 Mbps / 29.97.

If one shoots 100 Mbps and 1080p23.976, then the bit-rate per frame is 100 Mbps / 23.976, a slightly higher bit-rate per frame.

On the other hand, DVCPro HD, dramatically reduces the bit-rate, down to 40 Mbps (according to Wikipedia), when shooting at 24p.

[Mark Job]

Hi Dan:
Specifically, I knew about XDR & Nano giving full raster, but what surprised me was the DVCPRO 100 spec was throwing away resolution to make 1080i 59.94 ! Panasonic outta know better than that !

[Dave Sperling]

Mark, as I understand it, this all goes back to the Varicam tape cameras, which ALWAYS recorded 60 frames per second. If you were using a Varicam for 24P, it would still record all 60, but only use 24 of the frames. If you have the overall recording being at 100 Mbps, then at 24 you are actually using (24/60)*100Mbps = 40Mbps.
Therefore when you record on a P2 card at 24PN, you are also only recording at 40Mbps, and thereby extending your record time significantly, while keeping the same compression ratio. (And when you record at 24P using the full 100Mbps, 60% of your data is going into unused frames.
It's actually amazing that at the time the Varicam seemed to look so good; but as time has marched forward the Long-GOP compression system has proved far more efficient than the old DVCproHD, and of course DVCproHD in my opinion has really never been up to the task of recording full raster 1920x1080.

[Mark Job]

Hi Dave:
The thing which caught my attention for a big wow- was how Dan was pointing out how the DVCPro 100 format actually threw away temporal resolution to accomplish 1080 59.94 i. It seems like an unreasonable compromise to drop from full raster HD to 960 x 1080 Ugghhhhhh ! Yuk ! Who cares about compression rate at this point, when you throw away pixels out of the raster.

[Mark Job]

Originally Posted by Dan Keaton

Dear Lance,

Here is a chart that we created from our tests of the nanoFlash using the Video Clarity system.

Note: A lower number equals a better image based on Video Clarity's modeling of human perception of image quality.

Lower numbers plot higher on the chart, thus as the line gets closer to the top of the chart, the footage is higher in quality according to Video Clarity.

Our tests were performed using a high quality test file of a football game and this is not representative of all types of footage.

Just click on the chart to enlarge it, otherwise it i not large enough to actually read.

Hey Dan: I was checking out the chart you posted, and I couldn't help but notice a significant gain in quality between 100 Mbps and 280 Mbps in both the Chrominance and Luminance signals.