Video/pic quality - Bit Rate, Dimensions...?

[tigerb]

Ok, newbie here with few video quality questions :P

I've avi and wmv video files with dimensions ranges from:
320 X 240
480 X 360
480 X 576
512 X 384
640 X 480
720 X 480

and Bit Rate ranges form 96, 128, 320, 1689, 2115,....9360 kbps

Do I take it that in general 720 X 480 with the highest Bit Rate = excellent video/pic quality?

I've a 19'' LCD 8 bits S-IPS panel capable of up to 1280 X 1024, however currently I'm only running it at 1024 X 768 and whenever I play my avi/wmv files using WMP 10 or MPC @ std zoom level 100% or auto zoom 200%, some of my video files have excellent pic quality and some are NOT? (e.g. some with only 320 X 240 after auto zoom 200% = excellent quality and some with 320 X 240 after auto zoom 200% = Not so good quality), how come?

Once a video file (avi/wmv) is made, is there anything you can do to improve the video quality OR IT'S sayonara?

Regards.

[jagabo]

whenever I play my avi/wmv files using WMP 10 or MPC @ std zoom level 100% or auto zoom 200%, some of my video files have excellent pic quality and some are NOT? :? (e.g. some with only 320 X 240 after auto zoom 200% = excellent quality and some with 320 X 240 after auto zoom 200% = Not so good quality), how come?

Because some where well converted and some wheren't? Maybe someone use a very low bitrate to make a very small file and didn't care about the quality? Maybe one was from a nice clean source and the other was from a poor source?

Once a video file (avi/wmv) is made, is there anything you can do to improve the video quality OR IT'S sayonara?

There are some particular problems you can fix -- like color shifts, brightness, and contrast. But most other things cannot be fixed to any real extent.

[redwudz]

You can't really improve it, even by re-encoding at a higher bitrate or changing the framesize. You might be able to make it look a little better with some selective filtering, though.

If you are going to use the video for a DVD or to play on a set top player, you may have to re-encode and resize it. This will result in some quality loss. Re-encoding with a higher bitrate in this case will minimize the loss.

When you are encoding, higher bitrates usually mean higher quality. You do reach a 'saturation point' with a codec, however. This is when more bitrate will make the filesize bigger, but won't increase the quality. This varies with the codec, and the framesize. A larger framesize will require a higher bitrate than the same video in a smaller framesize to keep the same quality.

Some formats like DVD have fixed framesizes and you will have to use them for compliant video. See 'WHAT IS' DVD, SVCD, VCD to the upper left. VCD also requires a set bitrate to be compliant. The others have suggested maximum bitrates.

Hopefully that's not too confusing, and is generally correct.

[tigerb]

Thanks jagabo and redwudz for the explanations 8) ........well, now I know how little I know about video encoding in general , will read up more I guess

Best regards.

[jagabo]

Why are you running a 1280x1024 LCD monitor at 1024x768? Feeding it at its native resolution will give much better picture quality.

[TBoneit]

I used to run the 19" LCD at 1024 by 768 myself and yes I know what you mean but the Acer/Aopen I had it was a minimal hit in quality. at its native resolution the text was just to darn small at my viewing distance.

Here at work where I get closer 1024 by 768 on a 17" trinitron is large enough.

IOWs quality was trumped by being able to read the text. Now I use 1024 by 768 from approx. 5 foot away on a 32" HDTV LCD. Once again not optimal native resolution but pretty sharp anyway.

Cheers