USB2 vs. Firewire vs. HDMI

[Donnie Wagner]

On the new generation of HDV and DVCPRO HD pro-sumer camcorders, most of them have firewire, USB, and HDMI output. As far as I know, the HDMI port is constantly outputting 1080X1920 4:2:2 NTSC.

I just read that the USB port is for photos only (yes, no?)

Is the firewire port outputting video while the camera is on? What format is it in?

We of course use the firewire port for capturing video from DVtape (or P2) to the computer, but I wondered if they are outputting a video signal while the camera is running. And if so, what is the nature of that signal (what format)

Donnie

[David Beisner]

Well, it would depend on the specific camera you're talking about... you mentioned both tape and P2 and the only camera that does that is the HVX200 which doesn't even have an HDMI port. But, it does have both USB and Firewire. Specific to the HVX200, the USB is for transferring footage from the P2 or pictures or doing firmware updates. The Firewire outputs signal while you're recording and that signal is 4:2:2 and whatever format the camera is set on (1080p/720p/480i). HDV cameras' firewire outputs will output the signal while the camera is on at 4:2:0 and usually at whatever format the camera is on, though I'm not certain on that--it would might differ with the camera.

[Harm Millaard]

Originally Posted by Donnie Wagner

As far as I know, the HDMI port is constantly outputting 1080X1920 4:2:2 NTSC.

Donnie

This is a misconception. HDMI is a video transfer, not a data transfer like USB and firewire.

HDMI puts out a VIDEO signal that it gets fed from the camera. If the source is live recording, it is a poor man's HD-SDI connection at best with 4:2:2 signal, but on most consumer cameras only 4:2:0 signal due to the location of the DSP in relation to the HDMI chip. If the source is tape or card it is 4:2:0 all the time, possibly repackaged in a 4:2:2 signal but without the color information, that was thrown out in the compression to tape or card.

Apart from the flimsy connectors and the short cable length, there are a lot of disadvantages to using HDMI. You lose all timecode information, all meta data like time and date stamp, exposure data, scene detection capabilities, etc. There are no benefits in using HDMI.

HDMI was designed for playback connection (video transfer), not for editing. For editing use firewire or USB (data transfer) that keeps your timecodes, metadata and all the rest intact.