PDW700 and XDR/Nanoflash

[James Venturi]

Has anyone tried the PDW700 with the Convergent Design's XDR product?

It is my understanding that they will be adding the capability of removing the pull-down in January.

Plus ofcourse their quality is 100 instead of 50.

[Alister Chapman]

Not sure there will be a great deal to be gained, the 50Mb is pretty good. I've been doing a lot of tests comparing various XDCAM bit rates against ProRes and uncompressed and to be honest the only one that really looked any different to the original XDCAM material was the uncompressed. My tests involved going down 4 generations and the difference between 50Mb and 100Mb was extremely difficult to see even on the 4th pass.

[John Richard]

Alister:

Thank you for your very valued observations. Would appreciate your description of the subject(s) being shot and compared.

What I am finding so far is that for most shots the 50mbps is great ... but when we go to a shot containing a lot of fine detail AND motion or panning the step up to 100mbps is valuable in a reduction in mosquito and aliasing.

Example would be a panning wide shot of a forest at a small aperture with everything in focus... lots of fine details - that the extra available 100mbps data rate handles the shot more asthetically - using a Blackmagic card to throw up onto a 67" DLP monitor via HDMI - the differences are very apparent.

Conversely, if you take a CU of a subject filling the screen at a large aperture with the background thrown out of focus/soft, the 50mbps is just beautiful.

[Alister Chapman]

Most of my sample clips have been fairly static and I can see where something like a pan across a forest would show a larger difference.

My full test rsults will be published in due course. Some other interesting things did come out of the tests. FCP/Declink realtime conversion of XDCAM Mpeg to HDMI/SDi is not clean with a lot of mosquito noise that is not apparent if you take the Mpeg 2 material and render it to uncompressed before playing back. This should not be the case and indicates poor realtime decoding of the Mpeg2. The biggest difference between the uncompressed and the 50 and 100 Mbps Mpeg2 was mosquito noise. Certainly there is less noise on the 100Mb material but the difference between uncompressed and the 100Mb material is much bigger than the difference between the 50 and 100Mb material.

Now it could be that the software Mpeg encoder I was using is not as good as the hardware encoder that Convergent are using. But I still believe that the difference between 50Mb and 100Mb Mpeg is not that great.

[James Venturi]

I have a similar experience with the EX1. The tight shots with a shallow depth of field look great, the wide, not so much. I was unsure if this was caused by the size of the chip or the limitations of the 35Mb codec and therefore the nanoflash could be of help in this case. Any thoughts?

thanks,

Jim

[Paul Cronin]

John and Alister,

I am not using the 700 but the EX1 and Flash XDR for the last two weeks. From my test John is right to use 100Mbp/s on any pans with detail or fast moving. I see a huge difference at full size QuickTime since that is the only way I can view 100 vs. 50 at this time. It is close to the difference I see with 35Mbp/s and 50Mbp/s. Hoping that Final Cut adds HDCam 100Mbp/s 422 soon.

I look forward to your results Alister and I would post links to mine if I could find the bandwidth that will do it justice.

[James Venturi]

Originally Posted by Paul Cronin

John and Alister,

I am not using the 700 but the EX1 and Flash XDR for the last two weeks. From my test John is right to use 100Mbp/s on any pans with detail or fast moving. I see a huge difference at full size QuickTime since that is the only way I can view 100 vs. 50 at this time. It is close to the difference I see with 35Mbp/s and 50Mbp/s. Hoping that Final Cut adds HDCam 100Mbp/s 422 soon.

I look forward to your results Alister and I would post links to mine if I could find the bandwidth that will do it justice.

Paul,

Do you notice a difference between wide and tight with the XDR on the EX1 (vs. without it)? What about 50/100 differences?

It was my understanding that FCP supports 100Mb 422 input, just not new content, so it can be therefore transcoded to ProRes. No?

thx,

Jim

[Simon Wyndham]

I have a similar experience with the EX1. The tight shots with a shallow depth of field look great, the wide, not so much. I was unsure if this was caused by the size of the chip or the limitations of the 35Mb codec and therefore the nanoflash could be of help in this case. Any thoughts?

Well, there's also the lens.

When the EX1 is running at full datarate the compression ratio is the same as the 700. Its just that the 700 has 4:2:2 colour. So could that be accounting for the extra detail with the XDR?

During movement things could possibly be different if the EX codec doesn't catch up with what is happening because the 700's codec is CBR not VBR.

So I think the optics are playing a big part in this. I was told by some Sony guys once that once you go above a certain datarate with MPEG2 you aren't helping matters at all. Dunno how accurate that statement was.

[Paul Cronin]

James I have not done enough tests between wide and tight with the XDR to make a judgment. Once I have two edit jobs done I will have full time with the XDR for two weeks over the holidays to really dig in.

FC supports 100Mbp/s 422? Are you talking under the uncompressed setting? I am trying to stay away from Prores and in the native codec for a few reasons.

Simon you hit the nail on the head with that statement. "Well, there's also the lens."
That has pushed me to start my upgrade hunt. Do I go EX3 with better glass or do I have to go 2/3" to have the optics keep up with the 100Mbp/s 422 or when 160Mbp/s I frame comes out.

I would love to do a detailed test with Flash XDR comparing at 50 and 100Mbp/s the following: EX1, EX3 (nice 1/2 glass), PDW 700, Panasonic 2700, and see the difference. I wonder if the guys at AbelCineTech would be interested? I had a great visit there last week and they are set up for this.

I think the Sony guys have a point but what bit rate will that happen 50, 100, 160? I am sure they are fighting for the PDW700 at 50 which is a excellent camera and on my list to check out.

[Paul Cronin]

James you are correct an I was wrong Final Cut does support Log GOP 100Mbp/s 422.
http://www.dvinfo.net/conf/convergen...00mb-50mb.html

[Alister Chapman]

While there is no magic number at which increasing the bit rate suddenly results in no improvement I think Sony chose 50Mb for 4:2:2 and 35Mb for 4:2:0 because above these bit rates the improvements are harder and harder to get. Above 100Mbps I don't believe you can see any real difference.

[Jack Zhang]

What about chroma keying and ring artifacts? How about that plus high motion? Which would fare better in a limited compressed format only workflow?

[James Venturi]

There might be an issue with bitrate for the bluray disc to capture at 100mb and 50mb is reliable. Perhaps this is the reason they are adding SxS support to the 700.

[Andy Shipsides]

I have compared Flash XDR at 100Mb to original XDCAM 50Mb. The difference wasn't huge but there was something there. When we enhanced the difference between the two the improvement was pretty obvious. I-frames where very similar but the XDR did better in fine details. On motion the XDR had less artifacts and still more info in the fine details.

James, I know you got your 700 at our competitor in town but you can come check it out sometime.

[Paul Cronin]

Andy and James I would be interested to see some clips or stills from fast action footage. I am renting the PDW-700 with XDR to test and the more I know ahead of time the better.