True definition of the following terms?

[next]

I hear the following terms being used but I tend to think everybody may have their on definition of what they might mean.

1. macroblocks

2. artifacts

3. pixelization

4. glitches on dvd player playback

I ask because I hear of the many comparisions being offered that are 'artifact' free. Or contains no 'glithces' etc. I've seen comments like 'artifact free but I get an occasional glitch' which at least to me seems to be a contradiction.

Anybody have any opinions?

[TOMMO]

I think 1,2 and 3 can all be bundled together as the same. These would refer to large pixel dots all over or in certain places or colours.

Glitches I would assume to mean a hesitation or jump either in picture or sound.

However a Glitch could also perhaps be deemed a suitable word for "has pixelisation" or perhaps correctly - motion artifact - in certain areas of high speed action.

Who knows - but an interesting question which deserves thought. Posting a point using strange terms or improper terminology can lead people down the wrong route in problem solving.

[next]

The reason I posed the question is because I've been able to eliminate all of them. At least as how I define them which is like this:

1. macroblocks - I view these as blocks that appear in dark sceens. Not a breakup of the picture or anything like that. Just a 'roughness' in the picture.

2. artifacts - to me these are when the picture breaks of for a second or two. The picture actually degenerates into a mess of unviewable blocks many times green in color.

3. pixelization - to me this is the degree of intensity of the dots that comprise the picture and how these dots appear. In a picture that is heavely pixelated, say for example a blue screen, you would be able to see the many many dots. In a picture that is not heavely pixelated, the blue dots would blend together better and these dots would be less obvious.

4. glitches - for me this has been another term for a screen breakup like artifacts above.

Not sure if I am right - probably not. It's not a big deal but as far as advise goes it would be nice to pretty much know what everyone is talking about as far as problems go.

<font size=-1>[ This Message was edited by: next on 2001-08-27 12:08:39 ]</font>

[patrickm]

as for macroblocks, this is basically what it sounds like, the pixels are grouped as (usually 8x blocks when encoding. when the edges don't match up, it's real obvious.

arifacts, at least from my background, refers more to compression effects than 'skips' or 'glitches'. for example, if you draw a really smooth curve or circle, and then compress it into JPEG or MPEG, you will see some stepping/squares around it that shouldn't be there. other common artifacts are 'mosquitos' which are generally found near moving objects at their edges (if you don't know what i mean, encode 10 seconds of a football game and watch the players' shoulders/helmet areas). similar JPEG artifacts can be seen if you encode fine font text into JPG (make a bitmap and try it). another way to see JPG artifacts (which appear in MPEG too, since it's extremely similar compression) is to take a picture and encode as a JPG, then as a BMP, then back to JPG, etc, about 10-15 times. you'll see the sharp edges that appear from compression

glitches is a playback skip or encode error that causes one. have you ever seen a frame that was half picture and then half green squares. i'd categorize that here.

the other thing (at least for us ATI owners) is high-spatial-frequency noise. i guess that could fall under either pixelization or macroblocking, since it's some of both. this is what's wrong with the realtime 1150k VCD captures. you'll see slight changes in the picture re-orienting the macroblock from primarily horizontal to primarily vertical components very quickly, giving a fluctuating pattern.

also, next, i think i solved your sync problem for svcd. it's all bitrate. it came up for me this weekend when i did a 2.3 Mbps VBR. it shot as high as 3.4. so i redid as CBR 2.20, and it's perfect (and the avg went up from 1650 to 2100) i posted a quick explanation after another post you made somewhere today

<font size=-1>[ This Message was edited by: patrickm on 2001-08-27 13:41:17 ]</font>