Capturing Uncompressed 24p from the HD-100
 

Hi all,

I'm trying to better understand uncompressed the 720p60 out from the JVC HD-100. Specifically, I want a 720p24 project, and need to know if this is even possible with the HD-100.

I understand that the sensor has a constant rate of 59.94hz, which, I assume, translates into 60 full progressive frames of 720x1280 each. (In other words, if I were shooting a film, I'd be shooting 60fps.)

So how does it deliver 24p when going to HDV? More specifically, how does it get the motion blur that's characteristic of film? If if simply drops enough some frames while repeating others so that 24 distinct frames are delivered, won't the motion take on an awful jerky, almost undercranked quality? And if the motion blur IS there, how does the camera combine frames from the sensor scanning at 60hz so that the 24 frames that are actually recorded have the requisite softness?

More importantly, how do I recreate this processing when tapping the uncompressed output? Or, if I want to use the Uncompressed out, am I forced to accecpt video with the super high dynamic resolution common to video games, and abandon any hope of getting 24p material from this camera in anything but HDV?

I'm not sure you can.

To the best of my knowledge 60p is all you get out of the component connections.

You're right, but that shouldn't be a problem. After all, the camera itself manages to take that same 720p60 stream coming off the sensor and turn it into a 24p MPEG file that it records to tape.

So if I'm simply bypassing the MPEG encoder by taking the uncompressed out, shouldn't I be able to conduct some operation on this signal that the camera uses when deriving 24p material, but without putting my signal through the brutality that is MPEG-2 compression?

What is this operation? And is it something my capture card could handle (say, Black Magic) or do I need to get another box that would go between the camera and the capture card (assuming I'm recording direct to disk in this scenario.)

A

I believe I read that the best possible quality the JVC 100 can produce is when you digitize directly out as you're shooting via the three component outputs (NOT the firewire).

I believe this gives 4:2:2 color space as oppossed to 4:2:0. This is, as you say, because you are bypssing the encoder. So this method would be the best route for doing greenscreen work....

But someone please correct me if this is wrong.

john
evilgeniusentertainment.com

that is correct. now all you need to do is a 2-3 pulldown if you want 24p cadence.

^^ by that logic one should be able to capture 60P from component live (8 or 10-bit uncompressed)

then just add the pulldown with cinematools?

has anyone done this successfully?

somehow I don't think its that simple, but I could be wrong.

I understand that component out will give you 4:2:2, but may I ask why not fully uncompressed. If it's bypassing the encoder, what else is reducing the footage?

The component out IS fully uncompressed, 4:2:2

Regards,

strike me if I'm wrong but isn't 4:4:4 full uncompressed?

It depends on what camera head your getting the uncompressed off of. In the case of JVC HD-100 (ProHD et al) 422 is the sensor A/D converter and it's the uncompressed analog signal's format. It comes directly off the camera head and does not get compressed. The signal is a whopping 869Mb/s.

I've provided you with an uncompress clip off of the HD-100 below.

Click Here for Clip (580MB)

This clip will only be up for a short while to give you an idea of what kind of bandwidth it takes to work in uncompressed. The clip is only 5 seconds long and weighs in at a whopping 580MB. Needless to say you need an ultra fast SATA or SCSI array (Raid 0) to handle it. Now imagine the uncompressed 1080p requirement!

Anyway you can try your 24p pulldown technique on the file.

Regards,

Stephen

Thanks Stephen

Unfortunately, I don't have the capture path I'm after set up yet, but where I'm going is this:

SDI out from the JVC, into a BlackMagic card (with a Miranda box for an A/D conversion, if necessary) with the card applying the 3:2 pulldown to extract 24p from the 720p60 signal coming out of the camera, compressed at 2:1 (lossless) before going to disk. Capture is managed via FCP.

Has anyone else tried this out?

A

sorry, but its no where near 869mbytes/sec, not even 1920 is that high

10bit 1920X1080 @ 59.94 = 331Mb/sec
10 bit 1280X720 @ 59.94 = 149mb/sec
8bit 1280X720 @59.94 = 110mb/sec
8 bit 1280X720 @29.97 = 55mb/sec
8bit 1280X720 @23.976 = 44mb/sec


next there seems to be some mass confusion about the basics of this camera.

the CCD can be clocked out at 60,30,25,24 and actually slower with the shutter adjustment, but this is basic defaults. what the CCD gets clocked out at has nothing to do with whats going to tape or out the video outs because its all being buffered in the camera into a suitable output format.

what the camera seems to be doing in 30(29.97) mode is simply putting out 2 frames @ 59.94. visually its 30P, but techincally its 60 with frame doubling. this makes for a "legal" video signal. with some ram for buffering the image in the camera, its not a big deal to do this. likewise you can clock the CCD@24/23.976 and output 59.94 by basically treating each frame more like a field in 29.97 - that is you add 3:2 pulldown into the signal using full frames so that 23.976->3:2->59.94 and you can record that to tape, or send it out as a standard 720 video signal and all is well.

I wish that JVC would publish a white paper on this and really specify what the camera is doing, rather than leaving it up to educated guessing and math on the end user's part. for example, while the camera does 30P, you can't capture it @ 29.97 in FCP.... yet. you have to capture it at 59.97 which doubles the disc space for no good reason. its up to your NLE to detect this through various means - either bits in the FW stream indicating duplicate frames, or in the vertical interval data in analog/SDI in the case of DVCpro. I don't know if HDV supports VI metadata, but certainly in the basic FW data stream.

I've tried to capture from the camera with a kona LH to DVCpro100 just as a test, and found that the audio went wildly out of sync in FCP. I'd like to do a few things in uncompressed, but this test was not helpful. I think that there are still some FCP and Kona driver problems to be fixed before this will work, at least in FCP 5.0.4

Steve Oakley

That's Mb (small b). My system reports 869Mb/s as the datarate for uncompressed 1280x720 for the clips I capture. Do you think the system is misreporting them???

Mb not MB. you multiple the MB by 8 to get the mb. For example 25 mb DV uses 3.125 MB. There are 8 bits in one byte. 869 mb/s = 108.625 MB/s. or pretty close to the 110 MB/s rate of 59.94 720p.

This is 869 mb compared to 19.7 used for 720p HDV for a 44 to 1 compression ratio.

1280X720 8bits @ 59.94 = 110.48Mbytes/sec X 8 = 883Mbits/sec

thats not including any audio...

Steve Oakley

Through component there is no way to capture just 24p or 30p. It all has to come out as 60p. There is just no way around it with an analog connection. The Varicam actually builds flags into the SDI stream that tell the capture device which frames to scrap. This is why odd framerates such as 23p and 33p work with the Varicam. Sadly any sub market HD camera is going to have this issue with uncompressed/low compressed output. The Canon series will send out 60i from the component/SDI ports with 3:2 pulldown and the JVC will send it as 60p with 3:2 pulldown. Even the HVX200 would have the same issue if you wanted to capture live uncompressed from the component output. Everything would either come out as 60p or 60i depending on what mode you were in. Sadly at this stage if we want uncompressed quality 24p we will have to use tools to extract the raw frames or edit as a 60i or 60p video.

It sure would have been nice if JVC could have added the Panasonic flavor of flagging the frames across SDI with the HD250.

I'm not sure about the AJA hardware but I thought the Blackmagic cards could capture as 30p since all the capture tool has to do is drop every other frame. No matter how the signal is coming in if you drop every other frame you will end up with 30p. This however does not help for 24p.

This is why in many ways I still prefer to work with 25p if possible. 25p is a lot easier to pull out of a 50p stream then 24p is. In the case of 50i you can just capture 25p material as 50i so no processing needs to be done at all except for the 4% audio shift and frame shift in the end.

Might sound stupid, but....

People find ways to Hack and XBox to rip DVD's and Play ripped games, or a PS3, or hack a cell phone to shoot a laser.

Point is, is this a hardware limitation, or a software limitation. If it is software limitation, how about writing new software for the camera? Software gets created to produce an uncompressed HD stream.

Me, I love my camera. If I want true 24P, I will rent a film camera. I am very happy with what I have now.

FCP can remove pulldown after capture Tools->remove advanced pulldown, so can cinema tools, but you'll still have to capture 59.94, which eats a huge amount of drive space considering that to start, its 50% or higher duplicate data. very much a stupid and time consuming workaround. its not practical for long form projects at all. I think Kona can strip out 3:2 PD... I'll have to try it.

yes they could of even of put the data in analog, as part of VITC, which I think the panasonic gear also does.


Steve Oakley

HD100 Camera Head Operates At 48p in 24p mode
 

Sorry for butting in, however I am 99.99% sure that the JVC HD100 camera head outputs a 48p component stream in 24p mode and a 60p component stream in 30p mode. This has been mentioned in many threads over the months. For example:

http://www.dvinfo.net/conf/showthread.php?t=65949

"The HD100 and HD101 are both capable of capturing, encoding and recording 24P, 25P, & 30P as 720P HDV to tape. The camera is also capable of capturing and outputting 48P, 50P and 60P live as 720P to the analog component outs."

So while 24p is recorded to tape in a 60p stream with repeat flags, the head should be outputting 48p out of the components.

I'm not sure if any capture cards support the 48p however. I think the cards are mostly limited to 60p with 50p just starting to be used. I'll have to look into that.

Could someone tell me what it outputs in 25p mode?

50p. This is much easier to deal with then uncompressed 24p since all you have to do is drop every other frame. It does still however take up twice as much space. Maybe there is a way with Blackmagic cards to only capture every other frame.

I'm pretty sure VITC is only on SDI. According to the Blackmagic website only SDI on the cards will read VITC. Based on that only the HD250 could be made to even use VITC. Most people that use a Varicam would only use SDI and never even think of using component so why even think of putting VITC in component?

It's been reported however it's false (at least on my system).

I'm capturing 24p uncompressed from the components and it still is a 59.94 stream coming out of the component's when the camera is in 24p mode.

Alex,

You can do this with the Blackmagic by using the 24P Varicam settings in FCP with SDI & Blackmagic, as uncompressed... with the following catch.

As Thomas mentioned, you are now talking about using the HD250 since it has SDI, the HD100 & HD200 do not. If you are serious about the uncompressed route and want the quality, then stay clear of the component from the JVC at any cost, the image is simply too soft IMO even compared to the HDV/tape. All you gain is 4:2:2 from the process, and it's just not worth the loss in detail.

Beg, barrow, rent or steal the HD250 with it's SDI, or simply stick with the HDV. Otherwise you may learn the hard way that doing a conversion from component (if I'm reading this right) to SDI is going to disappoint and be an even bigger waste of money.

With the Blackmagic and HD250 at a true 24P stream you no longer need a $$ fast drive array, or nearly as much storage due to a lower data rate, so that's another plus that offsets the cost (some).

We have some true 24P test clips somewhere from the HD250 that was on loan from JVC that we ran through our Decklink Multibridge. Nothing with much real movement though, so I doubt it's of much interest if looking at motion blur.

Good luck regardless!! Peace!

VITC came from the analog world. it got really popular from the BVW series VTR's that could record it without needing any external boxes to insert it into the signal. I've got some 1" with VITC too :)

anyways, did some research and indeed I was right. 720 always runs at 59.94 and lower frame rates are simply putting duplicate frames into the stream.

so maybe tomorrow I'll look at analog capture again with my kona LH if I can get the time.


Steve Oakley

Test Results
 

Using a BlackMagic Decklink HD Extreme, I'm able to capture the uncompressed output from my HD-110 direct to disk.

The issue I've run into is that I'm stuck with 60/24 capture.

The camera allows the user to set the clock-speed of the CCD to 60 or 50 Hz. FCP simply won't see the devise if it's outputting at 50Hz. When set to 60 Hz, the data captures, but it's in a 24 fps Quicktime. I've not found any way to control this. And of course, it's all 60 frames, so playback is all slo-mo. Very nice slo-mo, but still slo-mo.

Speeding it up by 250% brings it back to realtime, but this isn't a very elegant way to capture data. And you still don't have sync sound.

Wondering if the 'Varicam flag' featured in the HD-250 is part of the solution. Or are people making this work with the HD-110?

Cinema Tools?
 

Have you tried Apple's Cinema Tools to convert the 60P footage back to its original 24P? I think I heard someone say this was the intended work-around, but I've never tried it. Please post any results you find, as I have a 110 and will soon be getting a Decklink card for uncompressed capture myself. Thanks

I would highly suggest starting with the proper preset for 720P capture. if you need to change the codec, you can. I'd also suggest trashing FCP prefs too, and finally reinstall the BM drivers of the most recent vintage and FCP updates, ect.

finally, if you are shooting 24p with a 110 north american (60hz) native model, you should then be able to capture using the 720P 59.94 uncompressed preset. 24(23.976) will come in at 59.94. there are no metadata bits in the analog to flag frames like the varicam does.

it should just work