SVCD 480 * 480

[bambam]

Hi
Can anyone tell my why when we are converting an avi file to a SVCD format, it is always in the format 480 * 480. I don't understant why. Every television have either a format of 4:3 or 16:9 so why would you want to have a file in a 1:1 format if it is mainly to be shown on a television that never have this format ?

[teegee420]

480x480 is the standard SVCD resolution for the NTSC system(PAL is 480x576). Just like 352x240 is the standard VCD resolution(again, for NTSC). These incorrectly proportioned sizes will be automaticaly stretched by your DVD player to the correct aspect ratio.

[bambam]

Yeah i realised that when i try a so watch SVCD on my 4:3 tv.
But i was wondering why these value has been chosen to be the standard for SVCD Since no tv have these proportion. To me it make no sence and there is probably an explanation or a reason for that choice ...

[bugster]

Pixels on TV's are not square. In fact they are not really pixels at all as commonly understood.

[adam]

The standard DVD resolution of 720x480/576 doesn't have a 4:3 or 16:9 ratio either. The aspect ratio is something set in a flag contained in the stream. It instructs the DVD decoder to always display it in that aspect ratio, regardless of what the source resolution is (of course its only guaranteed to work if you use a compliant resolution.)

There are a number factors which went into deciding what resolution various formats would use but the most important was simply to find the best compromise between bitrate and resolution. The size of the medium that the format will be stored on sets the maximum amount of bits that can be used, and by that I mean the maximum average bitrate. The resolution used for the format is basically the maximum resolution that will still look acceptable at this max bitrate, and of course we have had a cap on our resolution of 720x480/576 for a long time because of limitations of our tv's, but now with HDTV we are moving forward again.

In backing the SVCD format the Chinese Govt. actually had a very long format war of sorts trying to decide whether 352x480 (CVD) or 480x480 (Super-Video-CD) was better. Of course they went with the latter but the point is that aspect ratio is irrellevant, the only major concern is how high a resolution the format can get away with at the allowable bitrate limit.

[teegee420]

Now that's what I call an answer. Thanks for the clarification, adam.

[bambam]

Thank you for the answer

[bambam]

These incorrectly proportioned sizes will be automaticaly stretched by your DVD player to the correct aspect ratio.

Does that mean that any "standard" resolution for a video does'nt really matter since no matter what resolution (as long as it is not too small) the file will have it will automaticly be streched by the DVD player.

[adam]

It still matters as far as quality is concerned, but the aspect ratio will be correct regardless of what supported resolution you use.

The higher the resolution the more pixels you have representing each frame, and thus the higher the quality.

[teegee420]

It wouldn't surprise me if there are DVD players that can handle even the most outrageous resolutions but generally the answer is no. All of the players I have owned pretty much only played valid DVD, and (S)VCD resolutions.

[bambam]

Thanx for the info