Rendering vs. Recording

[Stephen Mann]

Well, last first – Sony has lumped rendering and encoding into the “Render As” menu. I would guess that it’s easier than explaining the difference. (Because to encode, you first have to render).

Render: Each frame of a video is rendered. In Vegas the render engine takes the one frame of the media and the editing instructions for that frame from memory (when you save the project the editing instructions become the veg file). I don’t know the flow but levels, compositing, color, f/x, etc, get applied to one frame at a time. This is rendering.

Encoding: When you encode video, you start with one rendered frame (called the I-frame) then the encoder looks at the next rendered frame and decides how much has changed from the prior frame. If it’s not too much then it creates a P-frame which just contains the changes from the I-frame. (If it’s a scene change then the encoder will create a new I-frame.)

But few, if any of us stop with rendering. Even uncompressed formats like MOV go through the encoder and every frame is an I-frame. All of the delivery formats are compressed (encoded) including AVC, MPEG and just about everything but AVI.

Since encoding needs a GOP of rendered frames to work from, Vegas stores the uncompressed, rendered frames in the TMP folder. After there’s a GOP (Group of Pictures) rendered, the encoder takes over.

So, since every compressed output requires rendered frames, “Render” is technically correct, but “As” is almost always an encoded product.

Steve Mann
MannMade Digital Video
http://www.mmdv.com