svcd quality question

[dcapp1]

When I encode to svcd mpeg format, I follow the how to on the right about how to convert to svcd using TMPGEnc and I calculate the bitrate I should use with FitCD in the tools section. My question is how come the quality of the video gets worse? The source is a good quality divx. Shouldn't it at least stay the same. Thanks

[adam]

First off anytime you transcode something you lose at least some quality.

Divx does not transcode well to any other formats. Also, most divx use non-standard resolutions and with SVCD you have to use a relatively high resolution, 480x480. If either your vertical or horizontal resolution of your divx file is smaller than this then it will be stretched, in most cases by quite a bit. Not only does this increase the number of pixels, thereby making your bitrate less effective, but you are also blowing up all the artifacts present in the source, making them much more noticable.

Thats not to say that a svcd can't look just about as good as the divx source, but in most cases it won't.

To ensure that you are getting good quality with svcd, regardless of what your source is, you probably should not put more than 55mins of movie onto a single cdr. 45-50 mins is a good limit to shoot for on most sources.

[dcapp1]

So what your saying is then to get the same quality, make sure the source is the a higer resolution than the svcd format. By the way I only had about 45 min a cd.

[adam]

The source doesn't necessarily have to be higher in resolution, just at least as big. And this is only the most preferable divx source to use. Its just never preferable to increase your resolution so if you can avoid this then by all means do.

45 mins is definitely reasonable. At that playtime you are maxing out SVCD's quality, at least as far as bitrate is concerned. If you are happy with 45 mins per disk then you can use just CBR to encode since VBR will not provide any noticable improvement and it takes much longer to encode.

Just keep experimenting until you find an adequate method to provide acceptable quality. The fact is though that divx is a poor source for any type of encode.

[dcapp1]

if divx is a poor source, what about just a plain avi or mpeg4 v3 source?

[Mirror_Image]

if divx is a poor source, what about just a plain avi or mpeg4 v3 source?

I believe he means that if the source looks shabby, that's about as good as you're going to get, regardless of the codec used. For instance, a 172 mbit/sec uncompressed video would convert to a worse-looking VCD (or SVCD, or whatever) than would a 3mbit/sec divx or mpeg video. To oversimplify, think of it like a painting that looks like it's been stomped on and dragged face-down through an alley. A $10,000 large format camera isn't going to magically snap a picture in which all the damage disappears, any more than a $100 35mm camera will. A teeny bit better, but it's stil going to look like it was dragged down an alley.