Swapping G1 tapes on A1 Cam for HD-SDI Out

[Alexis Vazquez]

WOW I never thought I could learn so much with one single question, great!
If I'm getting this right, the recomendation is to get the signal live out of the Cam direct from HDSDI without being recorded first to MiniDV, doing it this way is like uncompressing the compressed hdv which will add artifacts, Right?

Thanks again
Alexis

so much to learn, so little time....

[Thomas Smet]

Originally Posted by Keith Wakeham

I like what you say here, a major advantage, not the only advantage.

For HDV tape playback via HD-SDI you don't get a quality advantage, but their are workflow advantages.

Like mentioned before its easier to work in a native intraframe codec like DVCPROHD rather than an intermediate codec. You can get to both with similar quality, but which is faster.

HDV or 1394 = Playback at real time over firewire + time to recompress on computer
HDV over HD-SDI = Realtime capture and encoding

HD-SDI could have just saved you hours of encoding depending on your project size.

Or a fully uncompressed workflow would also save on quality losses where more FX driven projects would see more compression artifacts. Also DVCPROHD would likely also offer a small benefit in this area because the artifacts are uniform for the whole project so it should look similar.

I think its easy to jump to conclusion about stuff in regards to quality. But Grame Nattress proved on his site that DV over SDI looks like it has better colour reproduction because its smooths the UV channels. It provided enough of an improvement that he even wrote a FCP plugin that duplicated what it did for DV footage for changing it to 4:2:2 colourspace.

These cameras aren't released and I don't know how it processes, but it has to take the 4:2:0 colourspace to 4:2:2 and it might smooth UV channels as well. Makes the footage softer but a little more natural.

This is true about the chroma sampling. While you do not gain any new chroma detail the chroma is smoothed out so it isn't as blocky. I used to do this with DV material. If I was shooting something live in front of a blue screen in my studio I would sometimes capture live to uncompressed with a YC cable. I know it wasn't as good as component and the image did suffer a little bit but it worked great. The chroma was smooth and I could pull a decent key. Since these new cameras already have SDI and component you can get very good results by capturing this way. This means you will not have to use any special filters that smooth the chroma and add to the rendering time.

Also imagine if you are working on a film where different shots get moved around to different groups or artists. Each time work is done on that segment it becomes a new video file. By the time you do editing, compositing and color grading you could be on your third or fourth generation for certain shots. With mpeg-2 your quality will suffer with this workflow. Now if we soon get a FCP, Shake, Maya and Final Touch all combined into one application then this may not be an issue but right now this is what we have to live with. By using uncompressed that fourth generation video will look just as good as the 1st generation. Not to mention all effects and animation rendering will be done a lot faster.

[Chris Hurd]

Originally Posted by Alexis Vazquez

If I'm getting this right, the recomendation is to get the signal live out of the Cam direct from HDSDI without being recorded first to MiniDV, doing it this way is like uncompressing the compressed hdv which will add artifacts, Right?

Your best route is to record directly out HD-SDI to some other external recorder on set. That can be a High Definition VTR such as an HDCAM deck, a DVCPRO HD deck, etc. Or it can be something like the Wafian box or similar recorder.

Now... about recording HDV to tape... there are folks who will insist that there's no advantage to playing that tape back out for capture into your NLE using the HD-SDI output, or by FireWire. And if you think about it, this makes sense, there should be no advantage. But... I have to admit, I have talked to some folks who insist that it *does* make a big difference, that capturing an HDV tape over SDI output makes a big difference as opposed to capturing by FireWire. It's a controversial subject and I don't think the jury has returned a verdict on that just yet.

Interesting, eh?

[Keith Wakeham]

I've seen lots of people bypass the minidv in favour of composite video into a betacam deck form an XL1 because of the increase chroma sampling. No questions HD-SDI live is way better than HDV, but what i want to know is arethe new XH with HD-SDI still 8bit or is it true 10bit.

The jury is likely out on quality and if there is any chroma smoothing but if you have an uncompressed HD edit suite, you probably don't wanna screw around with HDV if its not a bother to you and your setup for HD-SDI.

[Paul Matwiy]

Originally Posted by Thomas Smet

This is true about the chroma sampling. While you do not gain any new chroma detail the chroma is smoothed out so it isn't as blocky. I used to do this with DV material. If I was shooting something live in front of a blue screen in my studio I would sometimes capture live to uncompressed with a YC cable. I know it wasn't as good as component and the image did suffer a little bit but it worked great. The chroma was smooth and I could pull a decent key. Since these new cameras already have SDI and component you can get very good results by capturing this way. This means you will not have to use any special filters that smooth the chroma and add to the rendering time.

What you describe would be smoothing resulting from the analog anti-aliasing filters in the D/A converter. I would expect similar performance taking HDV recorded and using the analog component outputs. I would expect the HD-SDI up-sampled output to be similar to a proper transcode from MPEG-2 to a compatible 4:2:2 color sampled codec to be similar. It would be an interesting test, though.