Capture NTSC tape on a PAL camcorder ?

[matzed]

Hi,

I have a PAL Digital8 Cam (TRV 330 from Sony) and a friend of mine cam e from the USA with a NTSC tape recorded on a similar camcorder (Digital8).

My camcorder can read the tape on TV or on LCD, but when i want to capture with Premiere (or any software indeed), i have an horrible AVI, with big blocks, where nothing can be recognized except very big coloured blocks... Beside, the avi frame size is 720 x 576 @ 25 fps, which is PAL settings...

I have this using Premiere (with a NTSC settings), Scenalyzer, DVIO, and Vegas, specifying NTSC where ever it's possible on each software.

I think the codec is trying to capture using PAL system...

Any ideas ?

[matzed]

A guy from another forum gave me the solution : i must launch the camcorder on "play" position BEFORE launching any capture utility. And that's working...

The firewire interface is certainly "by default" on PAL on my french system, and it can't switch to NTSC if i play NTSC tape after it has been intialized.

When i play the NTSC tape before launching the software, the interface intializes itself to NTSC because it is receiving a NTSC signal...

Hope it'll help someone...

Matz

[FredThompson]

Yup, you've basically got a streaming tape drive hooked to an optics unit. I've pulled an NTSC recording out as PAL during a thunderstorm. The trick is, I can't figure out how to over-ride the default stream type. FWIW, my camcorder is a Canon. Don't know if it will play PAL, doubt it. I did send a tape to the author of WinDV for testing this concept. No progress yet. There are Linux programs which will let you read/write either format to a DV camcorder. If you know a way to do it in Windows, please let me know.

[SeeMoreDigital]

Yes,

This whole issue of NTSC/PAL camcorders makes me think that some models may infact be the same inside. Which I suppose would make sense from a manufacturing stand point.

I really wonder if this is the case!

[FredThompson]

If you do the math you'll see both formats have almost identical data size requirements. I cannot imagine any good reason for different tape mechanisms. CCDs might be done a little differently (NTSC is frequently described as 500 lines) and, obviously, the format-specific encoding. My ZR65MC takes 1024x768 stills so maybe the CCD is the same in either unit, it's just scaled differently.

[SeeMoreDigital]

It is indeed a mystery.

Shame we don't have any members working at one of the manufacturing bases!

Having combined PAL/NTSC camcorders would really make things interesting!

[FredThompson]

There are some pro DV cmcorders that will work with both formats. However, I wasn't talking about shooting video, just reading and writing. Your file would have to be the proper format. Seems pretty interesting that the Sony mentioned will playback either format. Maybe their design was cheaper to make that way. It would sure make sense to me if the only difference was a little switch on a circuit board inside. Imagine the cost savings in manufacture.

[SeeMoreDigital]

There's got to be a way of finding out about this!

I wonder if there are any circuit diagrams / engineers repair manuals we could get hold of? The Sony range of camcorders would seem to be starting point. What model would you suggest?

[FredThompson]

That's not important. When a camcorder is connected via firewire it's really just a streaming tape drive. The goal is to override the ID which states NTSC/PAL. There are some links on the page I keep on Donald Graft's site that have Linux source code. Thing is, the info we need is inside of the core DV support for Windows and I'm not an MSDN developer. There are documents on the M$ site which talk about using AVI as a container for DV. That might be a place to start but with the developer access to technical specs...

To me, it's pretty important. I'd far prefer to send DV tapes across the ocean than have to buy PAL camcorders as well.

Remember, this is just to read and write the files. It doesn't mean anything about standard conversions.

[matzed]

Hi,

I'm currently working on a utilitity that will be able to change the recording date / time (i will publish it here soon ofr course). Doing that, i had to read some info about DV format. I could get the SMPTE 314M (i think it's the ref) that describe the encoding. It seems that the differences between NTSC and PAL are only an encoding thing, that is, onlt software differences, not hardware.

The info on M$ site are really basic. You won't get enough info there.

You can have a look to :
http://www.adamwilt.com/DV-tech.html
and to :
http://seaspray.trinity-bris.ac.uk/~altwfaq/graphics/video/1394/1394formats.html (a lot of technical info about mechanics)

In the second link, they say :

To maintain maximum commonality between 525/60 (NTSC) and European 625/50 video formats, the DV format changes the number of tracks per frame. NTSC uses 10 tracks per frame (at 29.97 fps +/- 1 percent) and PAL requires 12 tracks per frame (at 25 fps).

This is also well and detaily explained in the SMPTE 314M document : this confirm that the difference between NTSC and PAL is encoding related, not mechanical related. That's also why some camcorders can read NTSC though they are natively recording PAL.

I think that any PAL camcorder will be able to READ NTSC. But i think that the contrary is not true. It's like home video recorder (VHS) : in Europe, they are PAL and most of them can read NTSC. But NTSC recorder generally can't read PAL...

Maybe European people want to be able to read american tapes, but americans don't want to read european tapes.

Concerning recording, it's normal that camcorders sold in countries where PAL is the reference format record in PAL, and camcorders sold in countries where NTSC is the reference record in NTSC (it's more simple for dubbing on a VCR or on a TV etc...).

Matz

[SeeMoreDigital]

Now that is interesting. It's about time us PAL equipment owners had one over you NTSC guys!

This whole topic certainly warrants more investigation!

Cheers for that!

[matzed]

SeeMoreDigital,

I think i edited my post after tour reading and reply, sorry about that.

Don't say it, but NTSC is lower in quality thant PAL... :p

[FredThompson]

No.

European PAL VCRs "play" NTSC because they have added circuitry to throw away frames. There's nothing inherently special about PAL equipment. If Hollywood was located in Belgium, it would be the other way around.

Again, at the firewire level, DV (and Digital8) camcorders are streaming tape drives. Most of the time they are accessed is through the OS interface which includes the format-specific ID stuff. This is where most people get confused. They see how the OS enforces the ID from handshaking with the tape drive and falsely assume it means that is the only option. You have to go deeper than that for low-level I/O or come up with a way to override the default format as determined by the handshaking. THAT'S what I'm talking about as the simple, elegant way to make it work.

wrt quality, it depends on how you measure it. Again, the bandwidth is the same, it's just used differently. PAL is generally considered to have more fidelity for the chroma BUT with fewer frames. In that regard, PAL is inferior for recording motion. PAL DV is 4:2:0 so there can be an assumption that it is better if you want to go to MPEG2 (also 4:2:0). However, not necessarily. The best option is to get to 4:2:2 (or 4:4:4), do whatever editing and filtering you need, then let your MPEG2 encoder take things to 4:2:0. PAL DV has "better" horizontal use of color, NTSC DV has better vertical use of color. Both are lossy.

Having said that, it looks like it won't be long until we have the ability to shrink then enlarge chroma with edge detection to get a really nice result in 4:2:2. If you poke around you'll see some discussion about the NTSC 4:1:1 problem and 2 solutions from trbarry and Xesdeeni.

[matzed]

FredThompson

Concering quality, i wad just joking : i think this is a never ending discussion to know if NTSC is better than PAL. As you mention it, it depends what you are focusing on.

Concerning PAL that read NTSC, i agree with you : it's only a marketing choice. Besides, Hollywood, in its massive marketing power aspect (not sure this is really good english, but i hope you understand what i mean), is on NTSC side. As a result, European VCR can read NTSC.

But why is it the same for DV camcorder ? I will never have to read an Hollywood movie on my DV Camcorder !!! But it could be useful for anyone if his camorder can READ any tape format (NTSC or PAL).

Concerning firewire level, yes, i'd like to know where we can find the way to change the default format. It's strange to see that if i'm playing the tape BEFORE launching the capture software, it can read NTSC. If not, it assumes it to be PAL and of course can't do anything.

Matz

[FredThompson]

I understand and wasn't bent out of shape about it. I've realized lately that too often we discuss how to work with captures but don't say if the format is PAL or NTSC. Same with "better", it all depends.

All PAL DV camcorders can read NTSC? Well, they cost about $150 USD more than NTSC and frequently have the full firewire disabled.

If you want, I can make available a PAL extraction I did on my NTSC DV camcorder. The cover is off that computer and lightning hit something close to my house just as the extraction was starting. The result was PAL DV. It's almost impossible to duplicate that method, however.

[FredThompson]

Damnit, it happened again.

I pulled video from my camcorder and it's PAL. I've already recorded over the recording.

There is no way this was due to a stray spark of some sort. It was home movie source.

I'd used Video Vegas to pull the footage. I HAVE noticed Vegas isn't recognizing the camcorder when I start it up.

AFAIC, this proves the idea of using the device as a streaming recorder. What I don't know is what kind of low-level support Vegas does or if it pulls everything through the Windows interface. If I was Sonic Foundry, I'd use my own code rather than rely on Microsoft.

There's another possibility also. What if the file was really pulled as NTSC but the ID is screwed up and claims the retrieved data is PAL?

I sure wish I knew what bytes to edit to change the header of the stored file. Anyone know this?

[matzed]

That's strange... Did you launch the tape on PLAY position BEFORE launching Vegas ? That's what i've done, and it works for any capture software. When Vegas is launched, you can stop and rewind as desired without any problem : it will still stay on NTSC.

You can't just change a flag on a header of a DV file to change his type, for several reasons :

- any info in DV format are not stored on the header of the file, it's stored on the header of each frame...
- NTSC and PAL AVI files has different structures. In each frame, on a NTSC file, you have 10 blocks of info, and on PAL you have 12. Inside eah blocks, infos are stored differently too...

So changing a flag won't change the format of the file.

I think that when the "DV interface" is in PAL position, it will transform any bit of what it is receiving in PAL file format. After that, it seems it can't switch to another format on the same "capture session". That's why, i think, you have to push on PLAY on the camcorder before launhing the capture software that will activate the "DV interface" : it helps it to be on the right format.

Besides, i think no one want to rewrite the code that capture the DV. It's part of DirectX package, and its advantage is that it gives the programmer a layer which hides the specific of each firewire adapter, letting him to focus on the application rather that on hardware.

Matz

[FredThompson]

No, the camcorder PLAYing was initiated by Vegas. I did notice earlier today the analog capture framerate setting was on 25 fps PAL. Also, on starting Vegas, even though the camera was attached, the capture routine was showing the jumpiness for an analog capture with no source (All-in-Wonder card in that computer...) Maybe that's what caused it.

In any event, it's still odd because PAL DV is 4:2:0. Givent eh transfer is a data stream, wouldn't NTSC's 4:1:1 yield a really screwed up PAL? Maybe what I have is sort of a hybrid file. Maybe the frame structure is PAL but the contents are NTSC.

In any event, it's all weird. Would be nice to know how to force the format so either could be pulled from a camcorder. Not so nice that it screwed up something for which I no longer have source.

[matzed]

Originally posted by FredThompson
Not so nice that it screwed up something for which I no longer have source.

I'm afraid you have lost the movie...

The only way i found to "force" my system to capture correctly NTSC sources is to have the cam playing before launching any capture software. If not, it wants to capture PAL by default.

This behavior of "default" captured format is certainly a flag in Windows, because in the US, it's certainly the contrary for the majority (NTSC is default).

If i found anything concerning that on my work on DV format, i'll post soemthing here.

Matz