codec question

[Graeme Nattress]

All you’ve avoided is the render back to the DV codec. You’ve done two different things:

a) DV -> Firewire -> FCP (DV gets uncompressed, Effect added, DV recompressed) ! -> Firewire -> DV Tape

b) DV -> SDI (DV gets uncompressed) -> FCP (Effect added) ! -> SDI (DV gets compressed) -> DV Tape.

Exactly the same things happen, but in different orders. From what you’re describing, you’re viewing the footage from a) & b) workflows at the ! point, and hence, as you can see in a) you’ve just compressed back to DV, but in b) you’re still uncompressed, and hence it looks better. Nothing magic going on here.

Now, if in workflow b) you subsititute a Digital Betacam deck for the DV tape, you avoid the DV compression and decimation back to 8bits, and will preserve 99.9% of the uncompressed quality you see at that point. If you’re mastering back to DV tape, there is no point capturing the DV uncompressed, as things may look better at the ! but as soon as you get back to tape, you’ve completed the decompression and recompression, lost your digital generation and there’s nothing you can do to avoid that.

Also, I should point out that FCP does not do the DV codec justice onscreen in the canvas, whereas it does display the uncompressed codecs with very much higher quality, so there’s a bit of an unlevel playing field there too, for viewing at the !.

Graeme

– http://www.nattress.com – Film Effects for FCP

[Justin Heaney]

Thanks Graeme.

Both Codecs viewed on a PAL moniter.

Just to confirm. Am I correct in assuming that DV material once captured to a 10bit uncompressed sequence is basically “unzipped” to reveal its highest quality? Then zipped (or compressed) again when going to DV tape. some sort of loss reversal???????

Cheers

Justin

[Graeme Nattress]

Ziping is lossless compression, so it’s not quite an appropriate analogy. But that’s reasonably close, remembering that DV is quite lossy.

Graeme

– http://www.nattress.com – Film Effects for FCP