can someone explain difference between Encoding and cutting?

[tim73]

I use VideoRedeo or Womble MPEG Editor to cut and trim MPEGS captured from my old Video Cassettes, or to edit Adverts out of films recorded on my DVD recorder. These programs are extremely quick at cutting and joining, and as far as I can see there is no loss in quality. when I've tried programs such as TMPenc express, these programs seem to take forever, as I presume they are 're-encoding' the data. I use this term without actually knowing what it means. I've aked a similar question to this before, and was told that cutting does not involve re-encoding, and hence the reason it is so quick. So can someone tell me why you would re-encode data at all when you can edit in a jiffy with Videoredo or Womble etc?

[skebenin]

If you're talking about cutting or splitting tools in TMPGEnc, I don't think they encode the video. It's just a really bad implementation. I think it copies all the data (minus the stuff that was cut out) to a new file.

Videoredo and Womble probably work on the file system directly to effectively exclude the cut-out data from the existing file in-place, with no (or little) copying of data.

TMPGEnc's tools are nice if that's all you have, but I don't think I'd use them if I had an alternative.

[thecoalman]

Encoding in layman's terms.... I don't know the technicalities anyway.

I'm going to use two images for an example, ther not from video but it's the same concept.

Example 1-Saved at a low compression 15k


Example 2-Saved at a high compression 4 k



As you can see the bottom picture is much less sharp and crisp but has a much smaller file size. Compression works by removing colors. When you take for example a DV-AVI and convert it to MPEG it removes like colors and makes them one producing a smaller file size. Creating say 4 pixels of single grey as opposed to 4 greys of varying shades. If you examine the helmet in example 2 you can see the blocks of color. The change is suttle at low compression so you won't notice it unless you use a really high compression.

Where the quality/fiole size loss comes in is if compress it twice. Lets say you take file 1 and save it at low compression then open it up and save it at no compression then do it again ,again ,again. Eventually it will begin to look like file 2 but you haven't saved any file space. The reason for this is each time you save it the colors become more and more alike expanding producign a less crisp image.

If you just cut or trim a video all your doing is removing the frames you don't want your not changing the ones you keep.

Clear enough I hope.