Realtime downconversion clarification

[Luke Maslen]

Hi Ric,

Here are the answers to your questions but I also have a question for you at the end 🙂

The DeckLink HD Extreme provides both 1080i and 720p down conversion. In HD720, Final Cut Pro does not include native 720p50 support so we simply support 720p59.94 to NTSC down conversion. In HD1080, we support down conversion of both 1080i59.94 to NTSC as well as 1080i50 to PAL down conversion. All SDI and analog outputs of DeckLink HD Extreme output SD when down conversion is switched on so we simply use software down conversion for that. Multibridge Extreme and DeckLink HD Pro 4:4:4 PCI-X have two SDI outputs so we have the additional feature of split HD1080 down conversion with those products so they can simultaneously output both SD and HD1080 video. Alternatively they can use software down conversion to output SD on all outputs from HD1080 or HD720 video. The software down conversion is useful for monitoring if you don’t have an HD monitor and its a feature we’ve added to the drivers at no extra cost. If you are using a HD deck, then you might well have the optional hardware downconvertor board in the deck and these will often cost around US$15000 but will provide a sharper picture than software down conversion.

Now here is my question for you. Have you considered monitoring in HD? In the past HD monitoring was expensive but the price has dropped thanks to pioneering products such as HDLink, Multibridge Pro and Multibridge Extreme. These products enable you to use a 23″ display (such as an Apple Cinema HD 23″ monitor) or a large screen HDMI TV for your HD monitoring. The advantage of using an LCD computer display is that you can have pixel for pixel display of your HD material. A 23″ or 24″ screen with a resolution of 1920 x 1200 pixels is perfect for display of HD1080 material. If you are doing most of your work in 720p59.94, then you might even want to consider the Multibridge Extreme which supports the Apple 30″ display as well as the smaller displays. The resolution of the Apple Cinema HD 30″ display is high enough to display HD720p at x2. This is great for pixel for pixel monitoring of HD720p material on a big display. If you just need a big display but pixel for pixel mapping is not so important, then you might consider using a Multibridge Pro instead of a DeckLink HD Extreme. The functionality of the Multibridge Pro is essentially the same as the DeckLink HD Extreme except the Multibridge also includes HDMI monitoring which is perfect for use with a large plasma or LCD TV.

Presumably you want to keep monitoring costs down if you are considering using an SD monitor for your HD video and HDLink parterned with a 23″ LCD computer display, or Multibridge Pro partnered with a HDMI TV provide inexpensive ways to monitor your video in high definition. I hope this helps!

Regards,

Luke Maslen
Blackmagic Design

[Ric Shellhammer]

Thanks Luke for the quick reply. So, the Decklink HD Extreme does software only downconversions and Multibridge Extreme and DeckLink HD Pro 4:4:4 PCI-X have the capability for hardware downcoversions. Right?

Not sure what you meant by “If you are using a HD deck, then you might well have the optional hardware downconvertor board in the deck and these will often cost around US$15000 but will provide a sharper picture than software down conversion.” Please explain.

Finally, yes, I’m aware of the option to monitor HD with LCD computer display and I’ll probably end up doing that. The issue is most of our work is still SD. It just seems silly to me to view HD on one monitor, SD on another. If the downconversion is at least as good as a LCD for color correction, I’d like to do that for now. At least until other options become available.

Ric

[Luke Maslen]

Hi Ric,

[rshellhammer] “So, the Decklink HD Extreme does software only downconversions and Multibridge Extreme and DeckLink HD Pro 4:4:4 PCI-X have the capability for hardware downcoversions. Right?”

That is correct.

[rshellhammer] “Not sure what you meant by “If you are using a HD deck, then you might well have the optional hardware downconvertor board in the deck and these will often cost around US$15000 but will provide a sharper picture than software down conversion.” Please explain.”

HD decks often have optional internal cards you can add to them such as a down conversion card so you can output SD from your HD tapes. There is no little this would provide a sharper SD image but there is a price to pay for the card and for a deck I use it was about $15000.

[rshellhammer] “The issue is most of our work is still SD.”

If that is the case, then stick with your SD CRT monitor as it is probably better ro SD work than a LCD or Plasma display.

[rshellhammer] “It just seems silly to me to view HD on one monitor, SD on another.”

While it initially would seem strange to do that, CRT monitors are great for showing SD interlaced material whereas LCD displays are progressive displays and are better for HD. So a lot of people would use an LCD display for HD and an old CRT monitor for SD. So don’t throw away your old CRT 🙂

Regards,

Luke Maslen
Blackmagic Design

[Paul Provost]

Hi Luke
Is the hardware downconversion of the multibridge extreme as good as the $15,000 option on a HD deck?
Also can you get better results in a downconvert in final cut putting an HD clip in a BMD 10 bit SD sequence (easy setup) and rendering out instead of using a decklink extreme for realtime downconvert?
thanks

[Zak Mussig]

Luke,
I have what I think is a similar question about DeckLink down-conversion. I just got and installed a DeckLink HD Extreme and a few minutes ago was the first chance I’ve had to hook it up. I’m working with HDV, and my plan was to monitor down-converted HDV on my NTSC monitor. It looks awful and I can’t get anything to playback in real-time. In looking at the Blackmagic website I didn’t realize that the down-conversion takes place in software. I only noticed that when I opened up the system preferences to turn it on. I can only assume I missed something on the site.
I guess with all of that said my question is how do I get the best possible performance out of my setup? What are the best output settings for my system?
Quad 3GHz Mac Pro
5GB RAM
Decklink HD Extreme
NTSC monitor (using component in)
FCP 5.1.2

Thanks for any advice,
Zak

[Mactrix]

High quality realtime down-conversions require a lot of processing power,
something you currently can’t put on a small video I/O board like with BMD
or AJA cards. You need more space for image processing units. To reach
the same quality you can do it by software like with After Effects, Shake or
others but this won’t work in realtime. Also FCP offers a good software
down-conversion but currently there is a small bug if you down-convert
from 1080i to SD interlaced. You have to render the down-conversion as
the antialiasing won’t take effect in realtime. By the way antialiasing is more
like a blur effect when scaling the image down to preserve a smooth image
quality. If you won’t do that the image is too crisp, too sharp and you would
lose image details. So concerning to sharpness … well you blur the image
but you do it preserve more details … the real question is how good is this
antialiasing algorithm and normally that’s what makes the difference of
price. BMD and AJA down-scaling is more like a preview mode – not a
mastering function!

[Paul Provost]

so whats the workflow in fcp downconvert.
do you just drop the HD clip into a SD 10 bit timeline and render it out?

[Mactrix]

HD interlaced to SD progressive = Yes
HD progressive to SD progressive = Yes
HD interlaced to SD interlaced = No
HD progressive to SD interlaced = No

[John Ladle]

” BMD and AJA down-scaling is more like a preview mode – not a mastering function! ”

that information is not correct. Please do not obfuscate the issue and make a completely false statement about another manufacter in the process of doing so. One of the main purposes of AJA’s Kona LH, LHE, 2 or 3 is their hardware downconvert (and cross convert and upconvert), it is a true professional downconvert for broadcast.

If you need convincing, line up whatever card you think has a decent downconvert, a real expensive HDCAM or D5 deck and AJA. Then compare their downconverts on a hardware scope you have laying around your facility. I have done this before and you can do this same experiment and draw your own conclusions.

i am not over here trolling, it should be for BMD support and sales, but when obviously wrong information like that is put out there, i would like to make sure the facts are there. OK, on with solving this guy’s issue!

cheers!

uncompressed

[Luke Maslen]

Hi Zak,

Are you downconverting from HDV 720p59.94 or HDV 1080i59.94? Once I know the format you are working with, I can test it here and get back to you as it should look fine.

Regards,

Luke Maslen
Blackmagic Design