VCD, SVCD, DVD abd X(S)VXD comparison

[Ktranmd_99]

My question for this post is for video only - not audio.
Reading a number of posts on this web site regarding the picture quality between different video formats, can some experts out there confirm me with the belows:
1- Is that bit rate = picture quality?
It means that does not really matter what type of video format you select (either VCD, SVCD, DVD, or X(S)VCD). As long as you select a higher bit rate, you will obtain a better quality picture. Is it true?
2- What is the relationship between resolutions and picture quality? Is there any? With a same bit rate, is there any difference in picture quality between 2 video clips: one with SVCD 480x480 and the other of DVD 720x480 (or X(S)VCD 720x480 vs. 480x480)?
3- Some of DVD player have a progressive scan feature?
Will this feature improve picture quality of the DVD versus other formats?

Thanks in advance.

[Kdiddy]

First lemme start by some definitions..
fidelity: The result of a prescribed operation on the signal impressed upon its input.
quality: a degree of excellence.

Now how to to relate to what you asking. Many people misuse the word quality a lot, especially around here. just because something has a higher fidelity does not mean it will be higher in quality as well. Ex, if I eat the healthiest foods around, you eat all junk, but we both sh!t, the sh!t still stinks right, even though mine is probably higher fidelity sh!t. When it comes to this process, overall perceptual quality depends a lot of factors, the encoding process, the media, the dvd player, but most importantly YOUR EYE. So to your questions

1) bitrate = quality: No, higher bitrate is higher fidelity. However, at some point, yes the perceptual quality will get better with higher bitrates. It will be up to you to determine what that point is.

2) Yes there is a relationship. At the same bitrate, the smaller resolution always has a better fidelity. This is where the definitions become so important. Lets say you a clip at 2 mbps at 352x240 and also at 352x480. The smaller resolution has better fidelity, However, most would say the higher resolutions provides better perceptual quality.
"With a same bit rate, is there any difference in picture quality between 2 video clips: one with SVCD 480x480 and the other of DVD 720x480 (or X(S)VCD 720x480 vs. 480x480)?"
Well yes & no, what bitrate are we talking about, at a high bitrate (6+ mbps) on both, the perceptual quality is basically the same. At lower bitrates, then obviously the lower resolution provides better fidelity, which some interpret as better quality.

3)Again, yes & no. The progressive does yeild a better fidelity. However, unless you have a TV that can interpret progressive scan signal, then it is a waste. This feature is most likely found in digital only TVs.
http://www.cnet.com/electronics/0-3219398-8-6226096-1.html?txt




<font size=-1>[ This Message was edited by: Kdiddy on 2001-11-30 10:36:24 ]</font>

[JHebert]

My thoughts on your questions:
1 - Picture quality depends on a combination of both bitrate and resolution. But in general, other things equal higher bitrate = better picture.
2 - Higher resolutions require higher bitates to produce a good picture. For example, at a bitrate of 1150kb/s a resolution of 352x240 looks pretty good but 720x480 would look terrible because 1150kb/s is just not enough bits to support this resolution. On the other hand, at 5000kb/s the 720x480 looks much better than 352x240 because there is much more detail. For any given resolution, you can increase the bitrate to get better quality, but eventually you reach the point of diminishing returns where higher bitrate doesn't improve the quality much more, and moving up to a higher resolution makes sense. My rough estimate of these points is:
352x240 ~2500kb/s max
480x480 ~4500kb/s max
720x480 ~9000kb/s max
3 - The progressive scan dvd players are only better for hdtv sets that support progressive display. Normal tv sets are interlaced display only so there is no advantage. Most Hollywood movies are progressive encoded and the picture is somewhat better on a progressive player and hdtv. I don't think vcd and svcd would gain much if anything in picture quality with a progressive player.


<font size=-1>[ This Message was edited by: JHebert on 2001-11-30 10:44:42 ]</font>