Editing in DVCPRO HD?

[Bryan McCullough]

I've got an FX1 that I've been capturing MT2 files and then converting to DVCPRO HD for editing in FCP.

I've read a few places that says this isn't a good idea because of artifacts that can pop up after a few genreations.

Now, I've not done any real editing at this point, only converting to DVCPRO HD to see it in FCP and cut some stuff for fun. So I've not seen what can happen once you start putting effects and stuff on the footage.

Ok, all that to ask: What's wrong with editing in DVCPRO HD?

If people are saying not to do it for FX1 footage, how can it be ok for Panasonic material?

My hope is that because it works for Panasonic that there's really no reason why I can't just convert my stuff to DVCPRO HD and edit in that.

I guess I'm just trying to understand the format.

Thanks!

[Jan Crittenden Livingston]

Originally posted by Bryan McCullough :

<< I've read a few places that says this isn't a good idea because of artifacts that can pop up after a few generations. >>

What happens is that you end up hain a concatenation of compression algorithms and they can look pretty nasty. If there were some of those motion artifacts in the HDV footage, and as that tranfers, it grows to be uglier, and then ... well lets just say it doesn't get any better, only worse.

<< Now, I've not done any real editing at this point, only converting to DVCPRO HD to see it in FCP and cut some stuff for fun. So I've not seen what can happen once you start putting effects and stuff on the footage. >>

You need to understand that the conversion is turning the 4:2:0 color space in HDV into 4:2:2, that alone could cause some disfunction in the picture.

<< Ok, all that to ask: What's wrong with editing in DVCPRO HD? >>

There is absolutely nothing wrong with editing in DVCPROHD. Works great for DVCPROHD origination. But in taking the HDV, which is heavily compressed to 25Mbs, with a long string of frames, 15 frame GOP, there could be concatenation issues. You need a good HD monitor to see them. To pretend that they are not there because you cannot see them, is not the best idea.

<< If people are saying not to do it for FX1 footage, how can it be ok for Panasonic material? >>

The FX1/Z1 material is a 15 frame GOP with color at 4:2:0, and only 25Mbs of data. The DVCPROHD is 100MBs, I frame only, that is each frame stands on its own, and is 4:2:2. Big difference.

<< My hope is that because it works for Panasonic that there's really no reason why I can't just convert my stuff to DVCPRO HD and edit in that. >>

You can, but I think you would be better served to move your footage to an uncompressed HD format instead. That way you don't have one compression engine colliding with another.

I hope this helps,

Jan

[Barry Green]

To add:

DVCPRO-HD uses a different pixel frame size than HDV. HDV from the FX1/Z1 uses a pixel grid of 1440x1080, with 4:2:0 color sampling. DVCPRO-HD uses a pixel grid of 1280x1080, with 4:2:2 color sampling.

So i fyou edit HDV footage in DVCPRO-HD mode, you'll be uncompressing the HDV frame, resizing it and generating new color sampling data, and then transcoding it to DVCPRO-HD compression. Then when making a final HDV master version, you'll be uncompressing the DVCPRO-HD file, up-sampling the pixel resolution from 1280x1080 to 1440x1080, then decimating the color from 4:2:2 down to 4:2:0. Then re-compressing in MPEG-2, adding compression artifacts on top of compression artifacts on top of compression artifacts.

It is not a lossless process.

Some editors (like Vegas) can read the HDV file natively, uncompress it directly, and don't need to do any transcoding. I think that's a theoretically better way to go (provided the editor/computer can handle the data at full speed).

For DVCPRO-HD, it works just like DV does... you can transfer the data directly to the computer, edit it natively at full resolution (no transcoding), keep the color space the same, and render back into the same codec, which should be relatively clean.

Native editing beats transcoding, whenever you can do it.

Lots of HDV solutions seem to be based around transcoding to an intermediary codec, because the HDV codec is *extremely* processor intensive to edit. However, those intermediary codecs appear to be specifically designed to work with HDV data, so there shouldn't be much loss when using them. At the bare minimum, they won't require a pixel resizing step, such as you'd have to do if editing HDV on a DVCPRO-HD editor.

[Jan Crittenden Livingston]

Hey Barry,

You are good. And folks that is why the concatenation happens, they are not the same and thus the resampling causes errors.

Thanks Barry,

Jan

[Ignacio Rodriguez]

> HDV from the FX1/Z1 uses a pixel grid of 1440x1080,
> with 4:2:0 color sampling. DVCPRO-HD uses a pixel grid
> of 1280x1080, with 4:2:2 color sampling.

So it is not only a problem of resampling the color, you are also resampling and thus losing horizontal spatial resolution.

[Bryan McCullough]

Well thanks for throwing me deeper into HDV depression. :D

[Ignacio Rodriguez]

Oh I think if Panasonic plays the cards right even Sony will go into HDV depression.