Yesterday we talked about the fundamental differences between HD, SD 16×9 and SD 4×3. Let’s take it one step further and talk about down-conversion and cross-conversion.

As we talked about yesterday, modern software makes it easy to jump back and forth, but knowing the how/why will make your process and final quality better.

Downconversion

Converting from HD down to SD isn’t a simple, one-step process, although your software might make it seem that way. It’s actually very complex and how your software handles it will directly effect your quality.

First, your software needs to crop the source video down to the format of the output if you are going from 16×9 to 4×3. Then it needs to scale the image to the appropriate dimensions (remember the square vs. non-square differences?) and finally convert to your desired format.

The real complexity comes in the scaling step, which employs an intricate algorithm to take a large source, make it smaller and stretch the pixels so that  it all looks correct. It’s way too technical and boring to get into, but suffice it to say that you need to pay attention to different software packages and how they handle the scaling.

Crossconversion

Converting back and forth between formats in HD or SD is a bit of a tricky proposition as you can really only degrade the final output of your video, so take extra caution here. Every step you take decreases your final output’s integrity.

If you have to make more than two jumps to get to your end product, you should really look around to see about some new software that can do it all in one step or eliminate steps altogether because ever jump you make is only compressing the most recent version, not the original.

Click here to see what happens to a video that you continuously encode into the same format.

Generation Loss

Generation loss is a term you hear that applies mostly to tape and analog source, but you have to be careful about it when it comes to your encoding processes too. The fewer steps you have to take, the better. So review your workflow and see what you can make simpler.