DV Codec? What gives!?!?!?

[drdobs]

Okay, I'm going to ask what may appear to be a very dumb question to the majority of members around here but I can't seem to find the answer to this at anywhere.

This is in regards to the various DV Codec's that are out there. Canopus is well known for producing a solid hardware DV Codec as well as Apple's DV Codec, AVID, etc.

My question is, why in the world would this be necessary for capturing video via Firewire from my DV camera? I was 99.9% sure that the WHOLE point of DV was that when you shot with DV, the compression (thus CODEC) was *IN* the camera and all the camera did was simply write a digital file to the tape.

Assuming this is the case, why would I want to recompress the data capturing it into the computer? Ideally, the camera should be hooked up to the computer, recognized as a drive letter by the computer and I could simply just copy the file over to my computer.

I'm also not sure how this would apply to various formats such as 24p, 30p, & 60i. When recording with a DVX100b camera in 30p format, are we still using the DV codec inside the camera to encode the video into the DV file? In other words, are we still applying a 5-1 compression ratio and a fixed datarate of 3.5Mb/sec? Is the resolution still recording at native DV resolution of 720 X 480 ?

Okay, last one while I'm on my gripe here (because this is a little frustrating for me).... If I'm capturing at 24p or 30p @ 720X480 lines of resolution, is that not a high def resolution? Isn't 720p HD?

Thanks for anybody who can provide some help on these matters!

Jon

 

[Barry_Green]

My question is, why in the world would this be necessary for capturing video via Firewire from my DV camera?

It's not. You could capture DV data to a computer that doesn't even have a DV codec installed.

But a codec is necessary if you want to view those files, or edit them, etc.

I was 99.9% sure that the WHOLE point of DV was that when you shot with DV, the compression (thus CODEC) was *IN* the camera and all the camera did was simply write a digital file to the tape.

This is correct.

why would I want to recompress the data capturing it into the computer?

You wouldn't.

Ideally, the camera should be hooked up to the computer, recognized as a drive letter by the computer and I could simply just copy the file over to my computer.

Well, if you shot to a nonlinear acquisition media like a P2 card or a FireStore, that's exactly how it works. Tape is a linear acquisition device, so you have to import the file linearly to get it off the tape.

When recording with a DVX100b camera in 30p format, are we still using the DV codec inside the camera to encode the video into the DV file?

Yep.

In other words, are we still applying a 5-1 compression ratio and a fixed datarate of 3.5Mb/sec?

Yep.

Is the resolution still recording at native DV resolution of 720 X 480 ?

Yep.

If I'm capturing at 24p or 30p @ 720X480 lines of resolution, is that not a high def resolution? Isn't 720p HD?

You're referring to the wrong 720 (don't you just love confusing standards?) The number that references a resolution is the vertical resolution, so 720x480 is named after the 480, and would be called 480i (for interlaced) or 480p (for progressive). In 720p, the spatial grid is 1280x720 (around three times as many pixels as standard-def 480). So each one has a 720 (hence the confusion) but the one that counts is the vertical resolution, hence the 720 in DV doesn't factor into the discussion. It's 480p/i or 720p that we look at.

 

[drdobs]

THANK YOU BARRY!

I really appreciate you taking the time to respond. Helps me out a lot and I will definately be picking up your DVX book when my camera arrives!

Thanks again!

 

[ryan brown]

Wow, Barry. Excellent (and very thorough I might add) answers.