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AJA SDI to Firewire Box

Published : 2nd September 2003


I just saw a blurb for a SDI to Firewire converter box from AJA ( http://www.aja.com ) in "Computer Graphics World". According to the article and AJA's website it works with Mac G4s and better and has a list price of about $3000. Does anybody know of a similar device in the Windows world? Also, a while back Panasonic announced that it would include a Firewire port on upcoming HD devices. Does anybody know when they might become available?

It seems that either would make HD editing much more cost effective.

Cheers, Paul

Paul Heinrich
5770 Timberline Trails



> I just saw a blurb for a SDI to Firewire converter box from AJA

Before Geoff jumps on you - the SDI that the AJA box is dealing with is not HD.

>Also, a while back Panasonic announced that it would include a >Firewire port on upcoming HD devices.

A Firewire port, even the 800 is not fast enough to pass HD-SDI. It could pass a compressed HD signal.

Dale Launer
Writer/Filmmaker
Santa Monica



Dale Launer wrote:

> A Firewire port, even the 800 is not fast enough to pass HD-SDI.

Um, be careful with your terms here. You can (and often do) pass compressed signals over HD-SDI. For example, HDCam has a tad of compression, I hear. So does D5, so does HDCam SR, Varicam, and most other HD signals these days. So you can't differentiate HD-SDI from "compressed" as often they are one and the same.

Given that Panasonic is dealing with not only some compression, but also a much smaller 720P frame, Firewire 800 is probably fast enough for them.

Jeff "compression police" Kreines



> Does anybody know of a similar device in the Windows world?

There’s a SDI to Firewire Bridge available from Miranda, check the website...

Florian Rettich
Europe based DIT / vision control



Florian Rettich wrote:

>There’s a SDI to Firewire Bridge available from Miranda, check the >website...

ProMax makes them, and they're supposed to be better than some of the others (AJA isn't the one I'm referring to, they make good stuff too).

Jeff Kreines



>A Firewire port, even the 800 is not fast enough to pass HD-SDI.

Sorry, I mis-typed - I mean couldn't pass an HD-SDI signal.

For example, HDCam has a tad of compression, I hear.

Dale Launer
Writer/Filmmaker
Santa Monica



> For example, HDCam has a tad of compression, I hear.

Jeff, thanks for reminding me, sometimes I forget that HDCAM is a compression format. I'd swear, if you didn't remind me every coupla weeks, I might just forget.

HD-SDI passes a compressed signal? Where'd you get that?

Dale Launer
Writer/Filmmaker
Santa Monica



Dale Launer wrote :

>HD-SDI passes a compressed signal? Where'd you get that?

So can (and often does) SDI. Digibeta is compressed. DVCam is compressed. Both formats have SDI I/Os.

The signal that is passed over an HD-SDI port may or may not have been compressed, but it's not in a compressed form when passing through that port. However, one shouldn't assume a signal on an HD-SDI port hasn't been compressed, because it probably has been or is about to be!

Jeff Kreines



Jeff,

Sorry, but I've always thought that SDI is generally uncompressed. Of course, the question is where it comes in the process, but if it comes before the compression stage - straight off the camera head - then it's uncompressed. I would have thought that cameras with SDI (generally higher-end models) would have allowed the signal to be taken before compression.

Every review of transfer methods I've seen has always ranked SDI or HDSDI as the equivalent of digital component. For point of reference, the Varicam has two HDSDI ports, one is pre-compression and one is post compression. If you want to take a raw camera feed direct to disk for keying work, you use the one on the side, and if you're playing back off of tape, you use the one on the back (ok, you can use the one on the side too since on PB it sends it to both).

Take care,

Chris Cooke-Johnson
Creative Junction
Barbados



Chris Cooke-Johnson wrote:

> Sorry, but I've always thought that SDI is generally uncompressed.

SDI or HD-SDI is just a data communication pipeline. What you or the manufacturer sends down that pipeline could be anything from HD –Uncompressed to SD at 50-1. It has nothing to do with compression.

SDI has standard parameters that must be met to be labelled SDI.

One of them is the signal must meet a certain data rate which could be considered a uncompressed data rate. All the VTR’s do is upconvert from whatever format compression is being used (BetaSX, DVCPro, DVCPro50, DVCAM, Digital Betacam) to SDI then downconvert on the other side back to the recording formats compression scheme. Does this up and down convert affect the signal? You betcha! If the manufacturers do a proper job in the design of the VTR the signal for the most part is unaffected.

Remember Y,R-Y,B-Y? That was a standard analog connection set. Uncompressed or compressed signals could be sent down component lines. The component connection format could have cared less about the compression used.

All the SDI or HD-SDI label guarantees is that any spigot labelled SDI or HD-SDI will work with anything that has inputs or outputs of the same name
such as monitors, scopes, VTR’s etc.

Tom McDonnell
DP
New Orleans, La



Paul Heinrich wrote:

>According to the article and AJA's website it works with Mac G4s and >better and has a list price of about $3000.

The AJA IO retail about 2200 dollars, designed for FCP on the G4, G5. I haven't seen an equivalent for windoze. You can check out AJA's site for details, its a pretty impressive box for the $.

Mark Smith



Tom McDonnell wrote:

> Remember Y,R-Y,B-Y? That was a standard analog connection set.

I explained this poorly. Uncompressed could never be sent down component. Betacam Component eliminated the color cross talk that composite was famous for. It was and is a standard connection protocol like SDI.

Somebody save me...

Tom "I'll have Tabasco on my size 12 shoe" McDonnell
DP
New Orleans, La



Hey Paul

> Does anybody know of a similar device in the Windows world?

Have used the Miranda DvBridge - was Beta site for that, is super clean signal path, ran a series called "lonely planet" through it & all delivery's were sweet - that was then (99 or so) this is now, and it was limited to Fw400 as that was the only game in town back then.

>It seems that either would make HD editing much more cost effective.

Not really - as has been pointed out the I/O is a small part of the cost of a Hd edit system, and this (even if it could keep up with the demands of uncompressed Hd, and Fw800 clearly cannot) device would not allow output to a Hd mon, and that would preclude it's use in most applications, so you would have to get at a minimum a HD playout card from Bluefish or similar...

Dermot Shane
HD & Film Vfx guy
Vancouver, Canada & Shanghai, China



Tom,

Would you prefer pepper sauce? Plenty of that in these parts

I agree that it's just the standard for a pipe, but what I was getting at is that I would hope that camera manufactures would provide their (HD) SDI from before the compression stage.

Obviously, at tape that's being played back from an HDCAM or DVCProHD deck isn't suddenly going to "decompress" and recreate all the bits of data that were lost in the compression, but if you're playing back straight from a disk, then it should be perfect.

Jeff, remember that even though the Panasonic has a smaller frame, it's 60p,so that does a pretty good job of offsetting any reduction in data rate. From what I remember, the uncompressed HDSDI on the Varicam is about 1.1gbs - far faster than 800mbs Firewire. And remember, you'll never get 800mbs off of Firewire, that's a theoretical maximum rather than a real world transfer rate. Of course, after compression, both HDCAM and DVCProHD would happily run on 400mbs Firewire (140 and 100 mbs respectively)

We've long toyed with the idea of putting an Xserve in our mobile van and recording straight to disk from the Varicam. Maybe when the G5 Xserves come out...

On the AJA point, that little box is amazing for what it costs. Now if they'd only build something like that for HD - my issue has always been the lack of a BoB, (ok, I know the argument, but I don't want a handful of converters!) I think they might have something up their sleeve for those PC users (shudder) though, knowing those guys...

We actually had to do an HDSDI conversion to DV on the move the other day (overseas assignment, edit on the flight back). Ran through the AJA downconverter, took s-video from it and ran it though a Sony GVD -1000 deck, and straight into a powerbook. Worked perfectly)

Take care,

Chris Cooke-Johnson
Creative Junction Inc
Barbados



Chris Cooke-Johnson wrote:

>I agree that it's just the standard for a pipe, but what I was getting at is >that I would hope that camera manufactures would provide their >(HD)SDI from before the compression stage.

Ah ha! I would think HD-SDI or Dual link HD-SDI from the camera would be uncompressed. Of course I have been known to be wrong...

Tom McDonnell
DP
New Orleans, La



The 720P data rate ends up being nearly identical to the 1080/24p data rate if the published figures are correct.

Neither is likely to be available on Firewire anytime soon.

Sorry to disagree with Jeff "we love his middle names" Kreines.

Robert Goodman
author/producer/photographer
Philadelphia, PA 19146
www.stonereader.net



Robert,

> Neither is likely to be available on Firewire anytime soon.

There was an interesting comment from Panasonic somewhere along the line that basically said they were doing DVCPro50 over Firewire this year and DVCProHD over Firewire next year. They've stuck to that with the introduction of the new decks and FCP's support for it, and I suspect that it will be the hot item at NAB next year.

Given the close Apple/Panasonic relationship, I think we're much more likely to see DVCProHD over Firewire than we are to see HDCAM over Firewire in the near future.

Take care,

Chris Cooke-Johnson
Creative Junction
Barbados



Goodman wrote:

>The 720P data rate ends up being nearly identical to the 1080/24p data >rate if the published figures are correct. Neither is likely to be available >on Firewire anytime soon.

I'm guessing that this compares 720P at a speed other than 24 fps with 1080/24P -- and probably is a figure that includes the compression used in recording (more compression in HDCam than Varicam). Also don't know if these figures are comparing 10 bit with 8 bit. And remember, HDCam is recorded as 3:1:1 sampled 1440 x 1080, compressed. So many places to shade the figures!

When you're dealing with a real uncompressed system, at the same framerate, then 1920 x 1080 is going to yield 2073600 pixels (times whatever bit depth and color sampling you choose) and 720 P is going to yield 921600 pixels. So, if you are comparing true apples to apples, 720 24P is going to require a less-beefy pipeline (that sounds like a gay porn film, doesn't it?) than 1080 24P.

> Sorry to disagree with Jeff "we love his middle names" Kreines.

Not a problem...

Jeff "saw a postcard advertising Robert's film at a bookstore the other day" Kreines



Chris Cooke-Johnson wrote:

>Jeff, remember that even though the Panasonic has a smaller frame, it's >60p, so that does a pretty good job of offsetting any reduction in data >rate.

But doesn't Panasonic also make a pure 24P HD camera, that doesn't have variable speeds?

The discussion was of "720P" -- not Varicam...

Note also that other decks (D5, HDCam SR) also record 24P 720.

Jeff Kreines



Chris Cooke-Johnson wrote:

>There was an interesting comment from Panasonic somewhere along >the line that basically said they were doing DVCPro50 over Firewire this >year

If Jan Crittendon is still here, she could explain this in more detail (or perhaps a bit more accurately), but essentially DVCProHD's data rate, transferring the compressed data directly, is approximately the same as uncompressed standard def, as is Sony's HDCam compressed stream. In Sony's case, this was done with the expressed intent of being able to use standard def routers and DDR's for HD, an ability that as far as I know, only Axial (with its Showcase system) has ever really exploited. In any case, AJA and Avid have both shown that standard Firewire 400 has enough bandwidth to carry this amount of data very reliably.

Mike Most
VFX Supervisor
IATSE Local 600
Los Angeles



Jeff Kreines wrote:

>But doesn't Panasonic also make a pure 24P HD camera, that doesn't >have variable speeds?

Yes, the AK-HC931. But, like the Viper, it is a camera only and requires an outboard recorder. It seems to be intended primarily for studio use. And it does, in fact, have variable frame rates, albeit not quite like the Varicam. It allegedly will do 6, 12, 18, 24, 30, and 40 fps.

Mike Most
VFX Supervisor
IATSE Local 600
Los Angeles



Jeff,

I did the numbers quite a while ago when we were comparing our HD options.


From what I remember, Robert is right - they're pretty close.

720/24p would be lower, but there's nothing that I know of that records at that rate (unless you include Panasonic's FRC). The Varicam puts 24p to tape at 60p - the data rate is consistent regardless of the frame rate used.

At 8 bits, the raw data from HDCAM (1440x1080, accounting for 3:1:1 is 20736000 - funnily, that's the same number you quoted for just true Y HD, not including colour. I can't speak for Sony's HDSDI - if it's pre or post compression.

For the Varicam there are two numbers - one off the head and one to tape. Off the head it's 1280x720 10 bit whereas to tape its 960x720 8bit (again, if my memory is correct).

The result is:

Before Compression
(((1280x720) + (640x720) + (640x720)) * 10[bits]) * 60[frames]
1.105gbs

After Compression (6.7)
(((960x720) + (640x720) + (640x720)) * 8[bits]) * 60[frames]
100mbs

For HDCAM, I stand corrected on the numbers (does it sample at 1920 or 1440? Does it sample at 4:2:2 and downconvert to tape?):

(((1440x1080) + (480x1080) + (480x1080)) * 8[bits]) * 30 [frames]
(HDCAM does not vary the data rate for fewer frames, so 30p is used) 1.24gbs

Not sure of the compression rate for HDCAM, but to bring this down to 143mbs, you need a rate of 8.7, assuming I've got everything else right.

Take care,

Chris Cooke-Johnson
Creative Junction
Barbados



Hi John:

I'm out with Bill sisca this week. Also I am a SDX 900 owner.

Are you writing anything on this camera?

All the best
Rich Lerner


Jeff,

>But doesn't Panasonic also make a pure 24P HD camera, that doesn't >have variable speeds?

Not to my knowledge - if they do, it's not listed on their website. They do have a 1080i camera, and a 720/60p, and then the Varicam. But then, I don't work for Panasonic.

Take care,

Chris Cooke-Johnson
Creative Junction
Barbados



>Firewire 400 or 800 for DVCPro50 ? I think I asked this before, but I >want to be clear. 800 for DVCProHD ?

Sam,

Firewire 400 = 400mb/s
Firewire 800 = 800mb/s

HDCAM = 143mb/s
DVCProHD = 100mb/s
DVCPro50 = 50mb/s
DV = 25mb/s

Basically, you could run multiple streams over plain old Firewire 400.

Take care,

Chris Cooke-Johnson
Creative Junction
Barbados


>>But doesn't Panasonic also make a pure 24P HD camera, that doesn't >>have variable speeds?

> Yes, the AK-HC931.


I stand corrected. Now if only I could get the other foot out of my mouth...

Take care,

Chris Cooke-Johnson
Creative Junction
Barbados



>There was an interesting comment from Panasonic somewhere along >the line that basically said they were doing DVCPro50 over Firewire this >year

Firewire 400 or 800 for DVCPro50 ? I think I asked this before, but I want to be clear. 800 for DVCProHD ?

Sam Wells



Mike said:

>If Jan Crittendon is still here, she could explain this in more detail (or >perhaps a bit more accurately)

First, 1394 is a compressed transfer interface
SDTI is a long distance compressed transfer interface
SDI is an uncompressed transfer
HD SDI is an uncompressed HD transfer interface.

Second, Panasonic will have Firewire on the newest DVCPRO HD machine the AJ-HD1700, the architecture for it is in place, delivery on the Firewire will be sometime next year, maybe a debut at NAB, that is unknown but possible. Much like what we did with the DVCPRO50. Since the 1394 is a compressed transfer, there are a number of advantages. There is less disk space used in the transfer, the cycling of compressed to uncompressed to NLE and then back does not have to happen and on the transfer for the AJ-SDX900 24PA. The flags in the compressed stream allow for FCP4 to throw away the extra frames on the ingest, so that even more disk space is saved and time is saved because you do not have to render out the 24 frames for your edit.

Third, it can all happen over Firewire 400.

Hope that helps,

Jan Crittenden



All:

In the thread discussing 1394 for HD there was a long side conversation regarding HD-SDI and their associated data rates. It is important to remember that whenever 1394 has been used for video in the past it was used to transport the compressed video. ITU-R601 was being sent as 25Mbps, of course MPEG could also be sent. The data rate for 50Mpbs DVCPRO would be 50Mbps, for DVCPRO HD it would be 100Mbps.

David Wiswell
Panasonic



Hi Jan:

I am now an SDX 900 owner. So far have only had a little time to test but am very impressed. Looking for any set up info you might have for film looks etc. You mentioned Michael Caporale has done a lot of testing and I was wondering if he had sent you any of his set ups. also interested in any other info you might have on the camera.

all the best;

Rich Lerner
DP / film maker



Jeff Kreines wrote:

>Note also that other decks (D5, HDCam SR) also record 24P 720.

Unless I have missed a development, there is no 720P24 interface standard yet. There is an ATSC rate in the infamous Table 3 (ATSC doc A53b) for 720P24. So from a practical standpoint, there is no 720P24 HD-SDI.

This brings me to the SDI/HD-SDI discussion. It is possible to embed many types of data streams in an SDI stream and to pass them across an interface designed for that rate. It is not always safe to assume that every device which handles HD-SDI (or SDI) will properly understand the stream. For example, the original Sony HDW-500 deck does not know what a 720P SDI stream is, uncompressed or not. On the other hand, any 720P60 device properly accepts an embedded 720P24 stream because it is packaged to look like a normal 720P60 stream.

SDTI is a different beast that is packaged to look like a legal SDI stream and so passes through SDI routers and DAs or re-clocking devices but carries compressed or other types of encoded streams that are not usually recognized by devices which know about "SDI". It is possible to pass a 100Mb/s or 140Mb/s compressed HD stream or even a 25Mb/s DV stream through a 270Mb/s SDI pipe as an SDTI signal and some devices do.

So it is important to be specific about the signal that you are discussing when you talk about digital interfaces.

I assume that SDI refers to 270Mbps uncompressed 525 or 625 video (480i or 576i in the new lingo) and that SDTI means anything else - usually something compressed. Note that all SDI monitors will not handle both flavours and most recorders won't either. I don't know of any device that will display or record all flavours. Routing switchers and DA usually don't care.

I don't know of any HD-SDI-rate devices that carry other than uncompressed HD (color difference) in some format but things change rapidly. That does not mean that the signal was not compressed before it was put into the pipe, only that it was decompressed to interface as HD-SDI. As I understand it, Dual Stream HD-SDI is a variant designed to look like a standard signal on either stream so it is similar in approach to the 720P24 in 720P60 package.

Is this confusing or what? Welcome to the brave new world of multiple formats.

Charles R. Caillouet, Jr.



Charles:

Are you suggesting that the HDSDI interface was written exclusively for 1080i60 and 1080p24 formats, and that a separate HDSID interface is required for 720P60 and 24 formats; or is it Sony's position that because their recorders don't recognize the 720P streams that they (the streams) are somehow "non-standard"?.

I don't think so. As you said many types of ATSC Table 3 formats can and are commonly embedded in HDSDI streams and are routinely used for signal distribution in those systems.

GEORGE C. PALMER
HDPIX, INC.
HD and Digital Imaging Services
www.hdpix.com
www.angenieux.com



George C. Palmer wrote :

>Are you suggesting that the HDSDI interface was written exclusively for >1080i60 and 1080p24 formats

I don't think that is what I was suggesting. Let me try again.

1)Unless I am mistaken, there is no SMPTE definition of a 720P24 SDI stream. If such a signal is to passed around, it must be embedded in a 720P60 stream with pulldown.

2) All types of SDI streams are not recognized by all devices - SD or HD. I wouldn't call that non-standard if the stream meets the definition of the corresponding SMPTE standard, but it also doesn't mean that a 1080i device has to know how to handle a 1080P24 signal, which didn't exist when it was created. That's why new standards are developed. You just need to be careful when discussing "standards" not to mix up apples and oranges, or even different varieties of apples. "SDI" in itself does not necessarily define a complete standard when you get past the transport of signals.

3) I do not speak for Sony and I don't think I put any words in Sony's virtual mouth.

Charles R. Caillouet, Jr.



Panasonic has enabled DVCPro50 to be transferred via Firewire into a FCP G4 system while maintaining 4:2:2 colorspace. HD has been transfer over Firewire using only a 19 mb/s siginal. I have no idea how this is done except compression?? I know that in the Home Theatre environment many new components are including a Firewire connects for transfer of 1080i and 720p programming from OTA terrestrial receivers to D-VHS recorders. From there the signal goes out via analog component or DVI to HD projectors and plasma screens. Although I recently heard that the next generation of projectors and plasmas may/will included Firewire connections.

Illya Friedman
Senior Camera Rental Agent
Moviola
www.moviola.com



Illya,

The 19mb/s that you're referring to is standard DTV transmission in MPEG2.
The only quasi-HD camera that uses it is JVC’s consumer HD camera, although it's being made into a standard but JVC, Canon and Sony.

Take care,

Chris Cooke-Johnson
Creative Junction
Barbados



(Additional Information added to the discussion)

People were comparing the Miranda sdi-dv bridge to the AJA IO which isn't quite right. The AJA IO transfers from the SDI interface down Firewire in uncompressed 10bit 4:2:2. The Miranda DV bridge transcodes from the SDI signal INTO DV and then puts the DV down Firewire. Both have their uses (I use the Miranda to do digibeta offlines) but the Miranda DV really isn't comparable to the AJA IO. You also get quite a bit of artifacting with the Miranda because of the transcoding.

Stuart Willis

Studentish Producer/Director
Sydney