The Super Video CD FAQ

Contents

1. Video

• 1.1 If SVCD resolution is only 480x480 or 480x576, doesn't the picture look all too tall and squished on my TV?
• 1.2 Does the SVCD spec allow using any other resolution than 480x480 or 480x576?
• 1.3 How should I convert 768, 720, 704, 702 or 640 horizontal pixels to 480 in order to maintain correct aspect ratio? And what about NTSC source material that has more than 480 scanlines?
• 1.4 How can I capture directly to 480x480 or 480x576?

2. Audio

• 2.1 What programs exist for creating MPEG-2 Multichannel 5.1 audio streams?
• 2.2 Are there any utilities for converting Dolby Digital (AC3) streams to MPEG-2 Multichannel 5.1 streams?

3. Playback

• 3.1 Do SVCDs have region codes?
• 3.2 Do SVCDs have Macrovision protection?

4. Availability

• 4.1 Do you have any SVCD test disc images online for me to download?
• 4.2 Where could I buy commercially produced SVCD discs? Are there any online SVCD shops in the Internet?

Recent updates

14-May-2000

• Revamped section 1.2

04-May-2000

• Revamped section 1.3. Check it out.

03-May-2000

• Changed the misleading wording in section 1.3. Also added a link to a resource that explains the aspect ratio issue more thoroughly.

01-May-2000

• Added a link to SVCD test disc images.

Abstract

This document tries to answer the most usual questions about the SVCD format. It is intended to complement the Super Video CD Overview, not replace it.

Feel free to e-mail me any comments, corrections, suggestions, additions or opinions. If you would like to share some tips with others (or recommend some particular software title or a site related to SVCD), I would be happy to hear from you. Should you come across a broken link, please let me know so I can fix it.

Linking to this document

You are free to link to this document anytime. If you do so, please use the URL <http://www.iki.fi/znark/video/svcd/faq/> This ensures that the link will always work, regardless of the actual physical location of this site.

Acknowledgments

I would like to thank Billy, Jari Ketola, Mike Kujbida, Avery Lee, Michael Simmons, Jim Taylor and all the good folks in the rec.video.desktop newsgroup for contributing in to this FAQ.

1. Video

1.1 If SVCD resolution is only 480×480 or 480×576, doesn't the picture look all too tall and squished on my TV?

No. When encoding (or preparing video for encoding), the material will look squished, but at playback time, the player will strech it horizontally to fill the whole 4:3 screen.

Note that even the 720×(480|576) (as used on DVD or MiniDV / Digital8 tapes) or 704×(480|576) aren't exactly 4:3. This is also true for VCD's 352×(240|288). Unlike computers, most digital video storage formats do not use square pixels.

1.2 Does the SVCD spec allow using any other resolution than 480×480 or 480×576?

No. The only allowed resolutions and frame rates are

• 480×480 @ 29.97 fps (for NTSC and PAL-M)
• 480×576 @ 25 fps (for PAL and SECAM)

For still images, it is also possible to use the resolution 704×480 (NTSC) or 704×576 (PAL), but this is for still images only.

You should be aware that if you create an 'SVCD' disc with any other resolution than 480×480 or 480×576, you have created a non-standard variation, not an SVCD. Then don't call it an 'SVCD' either, as it is not.

1.3 How should I convert 768, 720, 704, 702 or 640 horizontal pixels to 480 in order to maintain the correct aspect ratio? And what about NTSC source material that has more than 480 scanlines?

1.3.1 Converting full screen source formats to SVCD resolution

Note: if you have captured NTSC material that has more than 480 scanlines, you should crop (not scale!) the extraneous scanlines off, so that you will only have 480 scanlines. Unfortunately, I do not yet know if this should be done on top or bottom or both. Use common sense: if there are lots of blank lines only at top or only at bottom, try to preserve the actual image information as much as possible and crop accordingly.

1.3.2 Why do I need to add borders?

Contrary to popular belief, the commonly used digital video resolutions do not exactly match an ideal 4:3 image frame. Also the pixel aspect ratio varies: some capture resolutions use square-pixeled resolutions, some don't. If you just blindly resample each "full-screen" format to SVCD resolution, you're likely to get slightly incorrect aspect ratio on your disc.

All the calculations have already been made for you in the table 1.3.1, but the following table clarifies a bit where those figures originally came from:

How do these map to the SVCD resolutions?

• 480×576 is equivalent to 720×576 (at pixel aspect ratio 54/59)
• 480×480 is equivalent to 720×480 (at pixel aspect ratio 11/10)
• The rest has already been calculated for you. See the table 1.3.1.

Explaining the subject in any further depth would easily account for its own web page. Actually, there is one, Square and non-Square Pixels, an excellent article by Chris Pirazzi. It is a part of The Lurker's Guide to Video. Also see EBU (European Broadcasting Union) Technical Recommendation R92-1999, Active picture area and picture centring in analogue and digital 625/50 television systems. If you really want to get your hands dirty with this thing, the final truth can be found from the International Telecommunications Union recommendation ITU-R BT.601: Studio encoding parameters of digital television for standard 4:3 and wide-screen 16:9 aspect ratios.

1.3.3 But I have made hundreds of White Book VCDs and never once added any borders to the source material. Why does SVCD require this?

Sorry to burst your bubble, but if you haven't paid much attention to the source video format resolution and pixel aspect ratio, it is entirely possible that your White Book VCDs have slightly off-the-spec aspect ratios on them.

Before you ask, safe full-screen VCD source resolution is 704×576 for 625-line systems and 640×480 or 704×480 for 525-line systems. You can calculate the rest from the table 1.3.2 if you need to. Note that you can't use the SVCD conversion table 1.3.1 for regular VCDs, since converting captured material to SVCD resolution usually requires padding, while doing the same for VCD requires cropping.

1.3.4 Which interpolation method should I use for downsampling, bilinear or bicubic?

Avery Lee, the author of VirtualDub clarifies this matter from the mathematical viewpoint:

The coefficients for linear (triangle or tent) decimation are all positive, meaning that it is purely a blur. However, some of the bicubic coefficients are negative, so cubic resampling will give you a mild sharpening effect. As a general rule, I choose linear resampling to reduce noise, but use cubic resampling if I have a good source, because it produces sharper output.

Note that VirtualDub's cubic kernel is not the same as a cubic spline, which still contains only positive coefficients.

Obviously, linear decimation will be faster, because the FIR kernel is half the size. The performance difference is lesser if the 2:1 MMX code kicks in.

Right now, I'm using a rather mild bicubic kernel (A=-0.75), and may bring back the old kernel (A=-1.0), which has a stronger sharpening effect.

1.4 How can I capture directly to 480x480 or 480x576?

You could try using Avery Lee's VirtualDub for capturing, instead of the capture program that originally came with your capture card. VirtualDub allows you to set the capture size freely (although this trick will only work if the device driver supports arbitrary capture resolutions.)

2. Audio

2.1 What programs exist for creating MPEG-2 Multichannel 5.1 audio streams?

Read Sven Kölsch's tutorial How to make a multichannel MPEG-2 Audiostream.

2.2 Are there any utilities for converting Dolby Digital (AC3) streams to MPEG-2 Multichannel 5.1?

Read Sven Kölsch's tutorial How to make a multichannel MPEG-2 Audiostream.

3. Playback

3.1 Do SVCDs have region codes?

No. Any SVCD disc will play in any SVCD compatible player, provided that both the player and the tv set used for viewing can handle PAL and NTSC standards.

3.2 Do SVCDs have Macrovision protection?

No, they don't.

4. Availability

4.1 Do you have any SVCD test disc images online for me to download?

Not currently. Even if I did, I could not store them directly on this site.

As I realize many people would like to have a test disc to try out their players (and this is an often requested feature anyway), I'm looking into what I can do about it. Meanwhile, check out the test disc images in the SVCD Overview, Related Links section.

4.2 Where could I buy commercially produced SVCD discs? Are there any online SVCD shops in the Internet?

Good question. I don't currently know of any. If you do, please e-mail me more information about them. If you have any relatives or acquintances visiting Far East, you could try to convince them to buy some for you from the local markets.