BNC or Firewire

[bouncybabybucket]

Hmmmmm.....

The TV station I work for captures everything from BNC output off DVCAM.

I was under the impression that Firewire was best, because it was digital to digital. Although, taking compression into consideration, which will give the best resolution??

[Phil Rhodes]

Hi,

 

The digital will always look better off DVCAM. Capturing analogue video from a DVCAM deck implies that it's being compressed, decompressed, converted to analogue, converted back to digital, and then recompressed. This is a Very Bad Idea.

 

However, you'd be surprised how many outfits do this sort of thing because firewire is somehow "amateur".

 

Phil

[Patrick Neary]

If it's just the composite BNC out, then that seems kind of like listening to a CD through a fast-food drive-through speaker...

[Olivier Egli]

hold on, what BNC connection is it? SDI uses BNC cables as well but it is truly digital in high bandwidth. I know that DVCam is a 4:1:1 (NTSC) or 4:2:0 (PAL) component signal and not a truly 4:2:2 component signal as Digibeta but there might still be decks that output luma and the two substractive color channels in digital form over SDI as discreet channel information... so if your company does just that and uses RS422 as deck controller the BNC way is much much better than the firewire.

Firewire is amateurish because the deck control information are known to be about 6 frames offset which can be a pain especially for tight insert edits. also the troughput of firewire is not nearly as good and reliable as the one BNC has to offer. IMO there are cards that supersample the 4:1:1 video signal to less compressed 4:2:2 D1 or maybe even truly uncompressed (?).

In the case of DVCam you are fine because it does not take more data throughput than normal DV which is, to my opinion, about 3.6 megs/ second.

check if they are working with SDi and seperate serial controllers.

[mohab]

Isent it true that the firewire signal never hold the same rich color information as

a even composit signal ?

3.6 mbit are not much for a video signal but iam not a dvcam spezialist.

Greatings from vienna

 

 

mohab

[Phil Rhodes]

Hi,

 

Theoretically, the composite and Y/C outputs of even an amateur level video deck have better colour information than the compressed digital output. However, in practice the electronics on those outputs are often so basic that the pictures are pretty smeary and nasty anyway - I'd go for the digital every time, unless you've got a very good and test-proven reason to do otherwise.

 

NB it's around 25mbit/seconds; the data stream to a hard drive is about 3.6Mbyte/sec.

 

Phil

[Alvin Pingol]

Theoretically, the composite and Y/C outputs of even an amateur level video deck have better colour information than the compressed digital output.

Hmm... I always thought it worked like this:

 

                        composite or Y/C out
                      /
analogue ----> digital        
                      \
                       digital (1394) out

 

i.e., the composite or Y/C outputs are converted from the already digitized/compressed signal? Or is this compressor placed further down the processing chain (past the analogue outs), like so:

 

       composite or Y/C out
     /
analogue ----> digital        
                      \
                       digital (1394) out

 

?

[Phil Rhodes]

Hi,

 

I always understood situation 2 to be usual, but I could be wrong. I'll check the workshop manual for my camera.

 

Phil