bitrate of source video (Xvid, Divx) VS bitrate of VCD

[F u r u y á]

Suppose I have a movie which is a Xvid, 1100Kbps.

If I make a VCD of this movie with 1100Kbps, the quality will be the same and the best possible right? I mean, is it a waste of bytes if I set bitrates higher than 1100Kbps for the VCD?

[reboot]

You can't make a VCD with that bitrate. It's got to be 1150kbps.
You CAN make a non-standard mpeg-1 or mpeg-2 at any bitrate you want.
XviD avi compression has nothing to do with mpeg compression.
If you want high quality output, and the source is high quality, make a dvd compliant mpeg-2 with it.

[Cornucopia]

You could make an XVCD out of it, but there is no magic to keeping the bitrate the same.

Xvid is one of the varieties of MPEG4 and has MUCH better compression efficiency than MPEG1 (which is what VCD is). Therefore, assuming the same program duration (and not knowing the difficulty of the contents), XVid at 1100kbps would probably be equivalent in quality to MPEG2 at ~3000kbps, and MPEG1 at ~4200kbps.

There is something to be said for maintaining the quality that you have and keeping the bitrate as high as possible is the best way to do that. (That is--you would NOT be wasting bytes)

If you can swing DVD, great. If not, try to do SVCD-which would still give "similar" quality at the usual SVCD rates. Otherwise, VCD will be a noticeable drop in quality. You could try XVCD, but make sure your player can accomodate it. Use RW media to test 1st.

Scott

[Gurm]

To simplify what Cornucopia said a little...

There's always a tradeoff. Good quality in a small filesize can't be achieved by magic. In the case of XVID compression, you're trading processor power for quality. Quite a lot of processor power, in fact - it takes substantially more CPU time to decode a DVD-resolution XVID than to decode a DVD. Your average P3-450 can display DVD's, with full DTS, quite capably. An XVID at 720x480 takes a much more modern chip to render properly.

MPEG1 files render on lowly machines such as Pentium 100's. But they're relatively gigantic.

It's all relative.

[F u r u y á]

Alright, thanks guys, I understood (nice explanation) 8)

Is there any problem making XVCDs with high bitrates? For example, a 2500Kbps XVCD gets same file size and quality as a 2500Kbps XSVCD?

My Standalone DVD Player runs X(S)VCD, no problem with that. And I have a pair of CDRW for tests, yesterday I guess I formated them at least some 5 times

[Gurm]

No, you're a bit confused.

An SVCD will, all things considered, give BETTER quality at the SAME bitrate as a regular VCD, due to the MPEG2 compression.

MPEG2 is more processor intensive, therefore it yields higher quality with lower bitrate.

[reboot]

If you're only making (S)VCD, then encode at whatever bitrate allows you to fit what you want on the CDR.
Encode it to mpeg-2, not mpeg-1 for better quality at the same given bitrate as Gurm has explained.
If you want to fit even more, try the KVCD (KSVCD) templates, or use the XSVCD setting in tmpgenc Xpress 3.

[Nelson37]

It has been quite some time since I have seen this discussed, and I never tested it myself, but I believe it was established that the compression efficiencies for MPG1 and MPG2 were very similar, if not identical.

The main difference was that MPEG-2 added support for more features, most critically interlacing.

Furuya - when you say your player handles XVCD, this is like saying your car goes fast. An XVCD could have a bitrate of 2500, or 5000, or more. If you have tested XVCD with bitrates of 2500, which worked, then you could say your player handles xvcd with bitrate up to 2500. For ANY player, there will be some point at which an XVCD cannot be played.

SVCD sounds like your best conversion choice, for quality.

[F u r u y á]

One more question.

The same ideia for video (example: 1000Kbps in Xvid is not the same as 1000Kbps in XVCD - like Cornucopia explained) applies to the audio too?? I mean, audio behaviors just like video?
If a Xvid audio bitrate is 448Kbps, setting XVCD audio bitrate as 448Kbps too, will I loose some quality?

[ZippyP.]

If a Xvid audio bitrate is 448Kbps, setting XVCD audio bitrate as 448Kbps too, will I loose some quality?

XVID is the video type, the audio could be just about anything but is usually either MP3 or AC3.

VCD audio is mpeg1 layer2, also called MP2.

Bitrates for MP2, MP3 and 2-channel AC3 are similar. 192 kbps and above is the best for maintaining quality

[Gurm]

As Zippy said, audio bitrates are similar regardless of which layer is used. In theory MP3 offers slightly better compression than MP2, but it's negligible. Of course, multichannel AC3 is different, but 2-channel AC3 is also negligibly different from MP3.

So don't sweat the audio so much.

[F u r u y á]

Alright, so I will maintain the original bitrate of source movie for the VCD or whatever I'm going to make.

I just encoded a movie maintaining the 128Kbps audio.


thanks

[Cornucopia]

Depending on the bitrate and format of the audio, you may not even need to re-encode. Might just be a matter of demuxing, and then remuxing with the new video into the new format (MPEG1/MPEG2).

Aside, Gurm--I would say that WRT comparable quality, mp2@224kbps=mp3@192kbps=ac3@128kbps or thereabouts.
Mild difference, but still pertinent if you're watching your weight (aka bit budget).

Scott

[vitualis]

I would not say that the differences between MP2 and MP3 are "negligible". IMHO, at lower bitrates (i.e., < 160 kbit/s), depending on your source audio you can quite easily tell the difference between MP2 and MP3. With MP3, there will be relatively few audible compression artifacts. With MP2, you will hear them.

Regards.

[Gurm]

Ahh yes. I agree with both of you. Everything is relative here. 224 vs 128 is not as big a deal as 800 vs 128 like the original poster was talking about.

And you also have to remember that VCD and DVD are guaranteed supported, SVCD not always as much. So bear that in mind as well.

Also MP3 requires more overhead than MP2. Hence, again, the "cpu power versus file size" equation.