DV footage: SDI in/digibeta out vs FW in/dvcam out

B

Bill_Hooper

Active member
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Okay technophiles. Anybody have any experience with this? We shot a short film on mini DV with the Xl1 (PAL) with the mini35 adapter. I'm trying to decide if I want to capture the footage using SDI in on an uncompressed FCP system, then output the 10bit sequence to digibeta. Obviously this is not cheap. We're talking about $1000 to rent the decks and system.

How much better video quality would there be doing it this way uncompressed than doing it with FW in, regular compressed DV footage, then export via firewire onto DVCam for my master? Maybe you could guestimate a percentage how much cleaner the image is?

Please chime in if you have any practical experience with anything like this, please speak up. But if you don't, please take a back seat. I want to keep this discussion practical, away from speculation.

Thanks very much
Bill
 
Dear Bill,

You may want to get up to speed with Graeme Nattress' recent article on this exact topic. It is very helpful and Graeme is a very cool fellow.

Chroma Sampling: An Investigation
Graeme Nattress said:
In this article I hope to be able to show if there are any picture quality benefits to bringing in DV (I'll refer to miniDV, DVCAM and DVCPro as DV as they all share the same codec) to Apple's Final Cut Pro over uncompressed SDI compared to the "normal" route of transfer over Firewire and using the Apple DV codec. . .
Click to expand...
http://www.nattress.com/Chroma_Investigation/chromasampling.htm
 
Brian - Nice find. Tough technical read though.
So it appears the SDI will look a bit better if you did the type of Y,Cb,Cr comparison that Graeme did but I doubt anyone looking at straight footage could tell the difference. (Let me correct that - Any Joe Blow looking at it........someone that really knows what to look for like Graeme or maybe yourself might see the difference.)
 
Personally I would go with Firewire. Technically you footage will retain more quality this way, as there is no generational loss until it is undigitised for viewing, but that is all but impossible to avoid.

Using SDI and uncompressed capture does NOT improve the quality of the footage technically. However it has certain effects which MAY make the footage look nicer to the human eye, such as smoothing the chroma from DV's 4:1:1 (or 4:2:0 PAL).

Like Sirius said, this difference will be very slight and may even look worse. The chroma can be smoothed by the (far cheaper) use of one of Graeme's filters for a very similar efffect.

If money is tight, definately save it for elsewhere on the production. However, if you need to perform a lot of effects and colour correction on the footage, especially multiple generation effects, uncompressed capture will begin to show its strengths.

DV won't stand up to multiple recompression like 10 bit uncompressed, and will look very nasty, very quickly. However, if you are careful, you can normally get by with a single recompression of the original footage or none at all if you don't colour correct.

As for a percentage of how much "cleaner" an SDI route is to a firewire, simple, it isn't! Firewire CAN (but not always) provide a lossless edit, SDI can't. Therefore about -1% is my guess!
 
Great responses, guys. Thanks. I read Graeme's article. Very deep.

Importing through SDI doesn't sound like it's worth the money. So I'll stick with what I got and work with it. I will have some color correcting to do. With color correcting, does it make any sense to 'bump up' in final cut pro all the footage to uncompressed 10 bit, color correct, then bump down and output to DVCam? I assume I would need to bump down in order to output via firewire.

Also, in Graeme's article, he talks of using final cut's 4:1:1 smoothing filter. Would I be using that before or after I "bump up" to 10 bit uncompressed within Final Cut?

Thanks
Bill
 
I would just stick with the DV codec and only recompress once after the CC. If going to DVD, you can compress straight to MPEG2 from original DV footage in FCP and Compressor, which is great.

If you go to 10bit for CC, you are just wasting time, because you will only have to recompress back to DV anyway, so it will be worse that way.

I don't know much about 4:1:1 I'm afraid, so I won't comment - I'm a PAL land man.
 
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