Downconverting Delay *(Miranda DVC- 800)

26th March 2004

Florian Rettich originally posted :

> Does anyone know the exact delay of a Miranda 800 Downconverter?

We own two of the Miranda DVC-800 HD-SDI adapter / downconverters and with the latest software revisions they are working very nicely.

Gilbert Besnard is the product manager for the DVC-800, and I will forward this to him to make sure all is correct.

There is no delay that you worry about if you stay digital. The HD-SDI output uses the same 50 pin connector that the Sony factory HD-SDI adapter uses, and at the standard def SDI and Firewire outputs (which have 3:2 added and the time code is properly converted) the video with embedded digital audio and time code are all in perfect sync.

So where there are delays the Miranda gets everything together by the time you need it if you stay digital. Just like the Sony F500 vir you MUST just use a single BNC cable to run to the SDI input or your Digibeta or DVCAM vtr to get proper downconverts.

An exception is that older Sony DSR-40 60 and 80 DVCAM's have a delay issue on their SDI inputs, and I cannot speak about Panasonic DVCPro, but I have been told the JVC D-9 is okay.

Where everyone gets in trouble is if they try to use the ANALOG signals, or convert the digital to analog externally, then there are delays.

Also, there could be delay issues if you are jam syncing multiple cameras with external LTC time code, I will hope that Gilbert can clarify that situation.

Again, functionally all these delays do not matter if you are making downconverts out to the camera because the Miranda compensates and gets everything in proper sync. We would never have bought these units if we had to do our own compensation externally.

For anybody using ANALOG outputs here are the specs in the manual:

Video Processing delay :

HD input to HD SDI output: < 2uS
HD input to SD SDI and COMPOSITE outputs:
Frame rate 59.94 Hz = 34ms
Frame rate 59.94 Hz = 41ms
Frame rate 59.94 Hz = 83ms
HD input to DV output: same as for composite + 1.5 SD Frame
DV input to SD SDI and COMPOSITE output: 1.5 SD Frame

Audio processing delay :

AES to analog out
Frame rate 59.94 Hz = 34ms
Frame rate 59.94 Hz = 41ms
Frame rate 59.94 Hz = 83ms

If you monitor analog audio out of the Sony F500 HDCAM vtr it is out of sync
with the picture so don't freak if you are listening on headsets.

-- Jeff Blauvelt
HD Cinema
NY/NE (Westport, CT)
LA/West (Pacific Palisades, CA)

>Should a DP be asking what an f/stop is and whether there are any ?

If Video equipment manufacturers succeed in replacing them with percentages, I could see this as a possible CML question in 2008.

Really, the difference is an f/stop is an f/stop for now, but onboard downconverters are a moving target.... no ?

I mean, a DIT who doesn't have Jeff Cree's # is at a disadvantage to one who does, am I wrong ?

Sam Wells

Sam Wells wrote :

>I mean, a DIT who doesn't have Jeff Cree's # is at a disadvantage to one >who does, am I wrong?

Could be, but Jeff's not the only one who holds the holy grail to this information, and I wasn't sure if the question was in reference to Sony or Miranda or Evertz... ? I assumed he meant D to A conversion since that's where the delay issues come to play. Ask any Steadicam Operator that works with a Miranda 5 frame delay.

By itself the original question was not specific or just really basic (have a look at it again if you want). That's all. I simply said that I'd hope a DIT could tell me more (even tell us more in posing the original question !). Not a bad hope to have.

In the meantime Jeff Blauvelt gave a very detailed post so that should pretty much cover the issue.

Mark Doering-Powell

>Rather than a DIT be discouraged, I encourage them to either ask more >specific questions or know their jobs a little more thoroughly before they >take on the title. Should a DP be asking what an f/stop is and whether >there are any ?

In all the HD shoots I've done in this area, with Jay as my DIT on all but one, we have never had to deal with downconverts during production. Perhaps allowances should be made for different markets.

When we spoke about this the other day during a shoot I was impressed that he even knew the problem existed. I certainly had no idea.

And then, needing more light for an appropriate exposure, I asked him to get me a bag of f/stops from the truck...

Art Adams, DP
Mountain View, California - "Silicon Valley"
http://www.artadams.net/

> By itself the original question was not specific or just really basic (have >a look at it again if you want). That's all. I simply said that I'd hope a DIT >could tell me more (even tell us more in posing the original question !).

I'm not a DIT, but I can give you the parameters we are using with Evertz 9155 Afterburners. We empirically found the delay to be 6, 23.976 frames. We use a total delay of 250.24 mSec (6 * 41.708) for our on-set downconvert. We are downconverting the SDI picture and T/C from Panavision 900's and inserting the audio directly from the board through the delays. In our setup, the downconverted SDI is feeding the SDI inputs of Panasonic DVCPRO 50 decks and the audio is going in analog. It's certainly possible that there are additional time differentials in the decks themselves, but the resultant tapes are in sync with these numbers. I don't know what the numbers would be if we were feeding the video to the analog inputs instead of SDI. I would expect it to be different.

John Gilman - Zoundz Audio

5 frames. Can I get a confirmation? -Jay Farrington

My apologies for the brevity of my answer. To proliferate :

I don't personally own a Miranda DVC-800 unit. I've read that the downconversion delay of a Miranda DVC-800 is a 5 frame delay. Due to my age, I tend to trust very little that I read, so I prefer to hear confirming information from more than one source. Always. As no one had responded yet to Florian's post, I thought I'd get the ball rolling with at least the limited knowledge that I had to offer, awaiting confirmation or a welcome correction.

Since we still have yet to actually see the answer here, including my response, I'll repost Florian's question to get things back on track :

Does anyone know the EXACT delay of a Miranda 800 Downconverter (HD to SD)?

Jay Farrington HD DIT

Hey guys! I was cutting and pasting and neglected to change the frame rate info so this clarifies the delays for 50 Hz and 23.98 Hz.

Again Digital is all in sync but here is the analog info.

For anybody using ANALOG outputs here are the specs in the manual:
Video Processing delay :

HD input to HD SDI output : < 2uS

HD input to SD SDI and COMPOSITE outputs :

Frame rate 59.94 Hz = 34ms
Frame rate 50 Hz = 41ms
Frame rate 23.98 Hz = 83ms

HD input to DV output: same as for composite + 1.5 SD Frame
DV input to SD SDI and COMPOSITE output: 1.5 SD Frame

Audio processing delay :

AES to analog out
Frame rate 59.94 Hz = 34ms
Frame rate 50 Hz = 41ms
Frame rate 23.98 Hz = 83ms

Jeff Blauvelt
HD Cinema

Jay Farrington wrote :

>Does anyone know the EXACT delay of a Miranda 800 Downconverter

Here you go a Steadicam operator that has to deal with the issues of frame delay.

Miranda 5 Frames, it sucks.

Eric Fletcher SOC
Steadicam/"A" Camera Operator
Los Angeles, CA USA

>Miranda 5 Frames, it sucks. -Eric Fletcher SOC

That's what I had read. Thanks for the info Eric.

Florian, I hope this helps answer your question? If you're worried about audio sync, just keep in mind that if you input sound to the DVC-800, the DV/IEEE-1394 connector outputs a DV signal that includes embedded audio, time code, etc - so you're already in sync as it records to the DV deck (or laptop).

Jay Farrington fellow HD DIT

After working with the Miranda DVC 800 DV IEEE signal into a Power Book laptop and a DVCAM deck, I found it a great tool for "on the day" rough daily footage for directors and editors to use as a vector. However I couldn't sign off on that being the final downconvert product. And I don't believe Miranda has marketed this product this way. I agree Steadicam warriors have a rough time with frame delays - I have as well with some helicopter shoots trying to save money(nightmare)with standard def monitors in the bird.

I would recommend a live downconvert for broadcast go HD-SDI out of the F900 into a chain consisting of an Evertz HD9155Q-AUD afterburner downconverter then onto preferably a Digi-beta deck. If I'm asked to present live downconverts on the series I'm about to start this will be my path.

My two cents (here we go!) about the discussion on what a DP should know on an HD project using a DIT....Everybody should know as much as they can....and why not? The engineering of HD pictures and production workflow really isn't that hard when you connect the dots. You may have to spend time, test, ask questions and even drag yourself to some of those dreaded workshops....But didn't we do that when new film stocks and cool cameras came out?. Maybe that was just me? But I will agree that a "truly" competent DIT is worth their weight to keep the flow of one's and zero's during the heat of the battle.

Mike Spodnik SOC
DP HD-Film
Ashland, OR

Mark Doering-Powell wrote :

>Rather than a DIT be discouraged, I encourage them to either ask more >specific questions or know their jobs a little more thoroughly before they >take on the title. <snip>

Jay should not be discouraged from posing questions merely due to my
fleeting comments which should be of little consequence <snip>

>Rather I encourage him to seek answers to basic questions directly >from the rental houses and vendors of the equipment he uses, or the >DP's and mentors in his circle. <snip>

Failing all that, I encourage bringing a little more to the table and pose a more specific question on the matter.

Jay may not be the only person discouraged by "fleeting comments."

I have been listening in on a number of discussion lists within the CML and am not sure if it is my imagination or not... are these lists solely for the use of people who know MOST of the answers already? Should I skip posting to the cml-lighting list for fear that, after thirteen years as a gaffer, I might have a dumb question about exposure or not be sure if I'm "bringing a little more to the table?"

Also, technically, how do I know when I get to call myself a gaffer?

Piotr Jagninski
Gaffer / NYC

Piotr Jagninski writes :

>are these lists solely for the use of people who know MOST of the >answers already?

This is where I really need audio.

Noooooooo but, (that's a very long drawn out no and an abrupt but!)

Well some of the lists are actually, particularly Pro, but also HD to an extent and certainly 2K 4:4:4.

I think the problem arises because these lists were originally set up and aimed at working professionals only, they have widened since but some of the lists really are just for those people, and yes I do make this clear to people joining they just ignore it.

So, as the lists were set up for Pro's the concerns of Pro's come through, one of those concerns is the number of people out there assuming a title/role with inadequate knowledge.

Now I don't think any of us have any problem with anyone asking questions in general, after all that's what CML is for, however, it's a bit of a red rag to a bull when we get questions from people signing as DP/Cinematographer/gaffer who have only been in the business a few minutes.

Now that does not apply to the specific DIT message that you are commenting on but I can see how someone reading it could react by saying shouldn't you know that before you sell yourself as an expert.

Cheers

Geoff Boyle FBKS
Director of Photography
EU Based
www.cinematography.net

CML Listmum wrote :

>Now I don't think any of us have any problem with anyone asking >questions in general, after all that's what CML is for, however, it's a bit of >a red rag to a bull when we get questions from people signing as DP/ >Cinematographer/ gaffer who have only been in the business a few >minutes.

Mr. Boyle,

Thank you for your reply. I'll take your encouragement to heart and-- with your permission-- maintain my subscription to cml-lighting…

I couldn't agree more that people who sell themselves something they are not are... possibly inviting trouble. That said, your conditions of membership state "Members will also fully identify themselves in all messages posted, we don't ask a lot, name, job and location is fine."

Now I don't know what a DIT is and I would be curious to know, but I'm assuming one is not born one. If that's the case, how would a budding DIT know to sign his message? Should he call himself a "Budding DIT?"

Respectfully,

Piotr Jagninski
Gaffer / NYC

Piotr Jagninsky wrote :

> Jay may not be the only person discouraged by "fleeting comments."

Jay was discouraged by my opinion? His posts didn't seem to indicate that (unless I missed something). On the other hand he explained the brevity of his original question on downconversions as a follow up to a previous, unanswered thread.

Right ?

> Should I skip posting... for fear that, after thirteen years as a gaffer, I >might have a dumb question about exposure or not be sure if I'm >"bringing a little more to the table?"

In my opinion one should "bring to the table" a clear and specific question. I wouldn't want you to post simply: "should I use an incident meter or spot meter ?" and that's it.

But even if you did it wouldn't necessarily mean you were no longer a Gaffer since that's how you make a living, right ?

Should we be afraid to post professional opinions because somebody might be offended or it awakens some insecurity ? I wasn't suggesting to squash free speech, but asking for "more speech", a more specific question when its within one's field of expertise.

Mark Doering-Powell
LA based DP

CML Listmum wrote :

>Now that does not apply to the specific DIT message...but I can see how >someone reading it could react by saying shouldn't you know that >before you sell yourself as an expert.

I've been meaning to put more effort into resolving the concerns I seem to have created with the recent "downconversion" subject - but work's prevented me from keeping up.

I was misled by the vagueness of the original question Jay posted - I think I've made that clear along with my opinion of what DIT's should know. However, at the time I did not realize Jay's query was a follow-up to a previous thread that had apparently been left unanswered.

Its apparent that Jay is not new to his line of work (as Art Adams and Jay's subsequent posts indicate), and I'll bet he's currently one of the most well-versed DIT's on downconversion issues.

Apparently some people may have been "intimidated" by these events, and therefore I sincerely apologize for discouraging anyone from posting on this list - such an environment would not fit within the spirit of CML as I've seen it grow through the years.

I hope this may clear the air and lets things move on.

Mark Doering-Powell
LA based DP

Mark Dowering-Powell writes :

>Apparently some people may have been "intimidated" by these events, >and therefore I sincerely apologize for discouraging anyone from >posting on this list - such an environment would not fit within the spirit of >CML as I've seen it grow through the years.

I'd just like to say that Mark is one of the people who have helped CML to grow, his willingness to help and share information is what CML is supposed to be about.

Cheers

Geoff Boyle FBKS
Director of Photography
EU Based
www.cinematography.net

I've been following this thread with great interest. Many clients request the option of having capability to do an on-location clone in Digibeta (or other) format for immediate load to their non-linear post system so they can begin to edit the next morning. The most precise and successful way we've seen is using an SDI signal to an Evertz 9155 AUD afterburner. Not a highly "portable" process for steadicam work with the HDW-F900 but fine for budgeted film-style productions selecting HD24p for its immediacy.

All told it seems this thread -- on-location real time HD24p downconversion options with their plus / minus virtues -- seems like a real good opportunity for all the DIT's (Digital Imaging Technicians) and Video Controllers on the list to give their professional feedback.

Bob Zahn
BVR, New York
www.bvr.com

>The most precise and successful way we've seen is using an SDI signal >to an Evertz 9155 AUD afterburner.

>seems like a real good opportunity for all the DIT's (Digital Imaging >Technicians) and Video Controllers on the list to give their professional >feedback.

I've used the Evertz 9155QAD afterburner on set a couple of times, and used its SDI output in those instances to pull live mattes, and found the quality to be completely acceptable for that purpose. It was also a bonus to have the embedded audio and code be in time when it dribbled out of the box.

It's not a Terranex quality-wise, but doesn't cost like one either, and has very few user adjustments available (I generally consider that to be a Good Thing(tm)).

Bob Kertesz
BlueScreen LLC

>seems like a real good opportunity for all the DIT's (Digital Imaging >Technicians) and Video Controllers on the list to give their professional >feedback.

The professional feedback would be :

Stop mobbing the cameraman with accessories disturbing his work. Rent a cheap HD playback deck on the set deck and downconvert the whole tape once it is finished.

Matthias Buercher

>Does anyone know the exact delay of a Miranda 800 Downconverter?

To make a long story short, there is 1 frame delay for the down-conversion and another 1 frame delay for the 3:2 pulldown process (when you shoot at 23.98fps). In other word the maximum delay is only 2 frames.

As for the video out quality, it's a high quality 10-bit down-converter, not just for monitoring...

Thanks,

Gilbert Besnard
Director, Product Development
Miranda Technologies Inc.
www.miranda.com

Hello everyone,

Thanks to all the responses, especially the off list replies.

So - yes, my result is (in 25p/50i world) ONE frame and we are happy with the quality for offline use.

+++ Florian Rettich +++
+++ Europe based DIT / vision control +++