Getting a handle on HD-SDI
by Trip Gould
on
Sep 30, 2008 at 5:26:14 pm
---tried posting this on the HDV Format forum, but go no responses. though I'd try here---
Hello All:
I am trying to get a handle on all of the HD-SDI output options from HDV cameras on the market. Ignoring for the moment the differences in lenses and chips (i.e. 1/3" vs. 1/2"):
1. Is there a difference between the HD-SDI output of say a Canon XL-H1 (or XH-G1) and a Sony EX-1 or a JVC HD250?
2. I've read that the Canon HD-SDI is 1920X1080...how is this done when it is a 1440X1080 chip?
3. Are they all giving you an uncompressed HD signal, or are there different levels of compression (I've read that the EX-1 is up-converted after compression)?
4. What are the other options for a sub-$10,000 HDV camera that can output HS-SDI?
5. What is the most cost effective and portable way to capture the HD-SDI signal in the field.
I've only seen the HD-SDI captured footage from a Canon, not the others, so I can't compare the three from an aesthetic standpoint. I have seen the regular old HDV footage from all three, though. Should I assume that the ways in which they compare in HDV are analogous to how they would compare HD-SDI?
Re: Getting a handle on HD-SDI by Mads Nybo Jørgensen on Oct 4, 2008 at 2:30:54 pm
Dear Trip.
HD-SDI is a signal carrier agreed by an international standard committee and should be the same no matter what camera, vtr, mixer or other kit that you use. In essence; if you compare it to a 35mm film that will fit into all 35mm projectors (Not cameras, which can be 3 perm! ;-)), the same goes with HD-SDI. However, like a 35mm film the HD-SID carrier is not a benchmark for the quality of the image - that will be down to the operator and kit used.
In my humble opinion, you shouldn't really spend to much time on considering your sub $10,000 HDV purchase, but instead concentrate on getting clients or projects off the ground that will allow you to spend $40,000 next time around.
All the Best
Mads
London, UK
Mac Million Ltd. - HD Production & Editing
Please watch our latest video on Data Protection at http://www.youtube.com/watch?v=CVyv_lTywwc
Blog: http://blog.myspace.com/bigflopproductions
Re: Getting a handle on HD-SDI by Tim Kolb on Nov 4, 2008 at 6:35:20 pm
The most important factors to understand with HDSDI is that it is uncompressed...if whatever is upstream of the HDSDI stream has compressed video, it must be decompressed or decoded to run on an SDI pipe...it also only understands square pixel PAR...so you either have to take 1440x1080 and convert it to a 4:3 image to run through HDSDI (assuming something on the other end 'knows' it should really be 16:9, 1.333~ PAR and changes it back...), or you need to interpolate the raster up to 1920x1080 so the image is 16:9 square PAR, in which case everything on the other end understands it with no special instructions.
The major factor in the quality of the signal from a lower end camera will lie in whether the signal going out to SDI is upstream from the recording compression process (HDV to tape in the Canon's case), or after the compression takes place. I would suspect that all the smart folks who develop these cameras are grabbing the signal pre-compression...but I don't know this for a fact.
