Talk:Super Video CD
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I thought the only method for encoding 5.1 surround sound on a S-VCD was with the MPEG Multichannel format? - Anon
- I'm not sure of the details; my source was the VideoHelp.com SVCD page, which says that 5.1 is supported through an mpeg extension. This information is reflected in the article. Please feel free to clarify it if you know more about it! -- Wapcaplet 23:50, 1 Nov 2004 (UTC)
I have some doubts about the SVCD resolutions.
- Why does SVCD uses 480 lines if, for example, NTSC supports 525 ?
- It's stretched to fit, but it also depends on the aspect ratio. That's why you sometimes see lines flicker.
- How a 4:3 or 16:9 screen is supposed to use a 480x480 / 480x576 resolution, that is, the horizontal resolution lower than the vertical resolution (or, what are the horizontal resolutions of a TV) ?
- The aspect ratio stretches the image (new_width = height*aspect_ratio, height stays the same) and then is rescaled again (zoomed while keeping new width and height proportional) to fit your screen so that the new width fills the screen (this is done in one step by your DVD player). If the height is less than 525 (16:9 ratio), it will fill the empty space with black bars. This is otherwise known as anamorphic. EX: Take a 480x480 SVCD with aspect ratio 4:3, the image will be rescaled to 480*4/3=640. So 640x480 is your image size. Aspect ratio of 16:9 gives 480*16/9 = 854, image size = 854x480.
--200.208.45.2 14:40, 8 Mar 2005 (UTC)
I'm afraid I don't know the technical details of how TVs work, but I know the info in this article is correct because I've worked with SVCDs a lot. According to the NTSC article, the extra scanlines (up to 525) in NTSC are used for sync, vertical retrace, and stuff like closed-captioning, but only 480 lines of picture are actually used (which is in keeping with the 480-pixel height of SVCD and DVD). PAL has more scanlines, and thus more vertical resolution (576 for SVCD and DVD), but a lower screen refresh rate.
At any rate, your question about aspect ratio: a TV can have those funky resolutions simply because the "pixels" in a TV are not square. The image (regardless of how many pixels it has) is just stretched to fit 4:3 or 16:9 (usually by the DVD player, but sometimes by the TV). I don't think standard (non hi-def) TV screens have a defined horizontal resolution; it's just a question of how many pixels you want to stuff in there. VCD resolution is only 352 pixels wide, while full-width DVD resolution is 720 pixels - more than twice as wide (and the difference is noticeable). I suspect that for most non-HDTVs, more than 720 pixels of width would be wasted. I've often seen normal NTSC TVs classified as 640x480 (which happens to also give you square pixels at a 4:3 aspect, making it nice for video production om a computer; computer monitor resolutions usually have ~1:1 pixels).
I hope that helped answer your questions! -- Wapcaplet 15:42, 8 Mar 2005 (UTC)
[edit] Article cleanup
I've made a first attempt at improving the narrative flow of the "Technical specifications" section. I brutally summarized a couple things; the Laserdisc comparison has been condensed to "...at a picture quality roughly comparable to Laserdisc."" The lengthy explanation of why MPEG Multichannel isn't practical was condensed to "...though space constraints and poor hardware support make it somewhat impractical." I removed the bit about why SVCD is tricky to convert to DVD (and how to hack around it), since I don't think it's relevant; I also removed the part about why DTS and Dolby Digital are unsupported. Comments welcome. -- Wapcaplet 16:02, 5 November 2005 (UTC)
