XVCD and Resizing

[Entropy_Controller]

I have questions about creating a XVCD and resizing in TMPG. Why is it that you always resize to 352x240, why do you not make the output video size 708x480 or 720x480. Will making the output video the same size as the input video increase file size???? or decrease quality??? Also what exactly is the 1500 bitrate?? I tried making a xvcd with a bitrate of 2500 and size 708x480 and it was far worse quality than a regular VCD with 320x240 and 1500.

Please help me if you can.

Thanks

[Conquest10]

you need to go into the extras folder and load unlock. then you can change the resolution. the file size doesn't change unless you change the bitrate. you need to read some more before posting.

[Entropy_Controller]

I have read a fair bit already, but I can't find specifically anywhere what exactly the bitrate controls. It seems that it should control the quality as the bitrate of a SVCD is higher than a VCD, and a DVD is higher than both. But it doesnt make sense to me why the quality would be more blocky when I burned my XVCD with a bitrate of 2500.

[Conquest10]

what's your source? judging by how you sound, i'd say you're using avi files you downloaded off the net. most of them are of decent to poor quality. if the source if crap, there is no way to make it better. garbage in garbage out. now if you had a dvd rip, it would be a completely different situation. an xvcd at 2500 should not look blocky. unless its a fast action movie. and that is unless you used motion search set on fastest. but i have done movies such as crouching tiger, hidden dragon at 1600 and it does not look blocky. not even in the fight scenes.

[hwoodwar]

"XVCD...Why is it that you always resize to 352x240" That is not true, the whole basic definition of an XVCD is that you take one or more of the fixed parameters of the VCD specification and increase, decrease, or somehow change it so it is no longer within the parameter limits for the VCD specification. Since NTSC VCD resolution is fixed at 352 x 240 if I cange that to any other resolution I am making a XVCD, and/or I could change bitrate.

"Will making the output video the same size as the input video increase file size????" By "same size" I assume you mean resolution. I have not actually compared specific file sizes, but I can tell you, from working with it but not looking at the "specific" file sizes, it is not significant.

Note: resizing from one resolution to another does add to the encoding time.

"I tried making a xvcd with a bitrate of 2500 and size 708x480 and it was far worse quality than a regular VCD with 320x240 and 1500. " Technically by these values you made two different XVCDs. In both cases the resolution and the bitrate is outside of the VCD standard. Now, I suspect you used a "constant bitrate" of 2500 and 1500. Other "rate control modes, such as 2-Pass VBR will improve quality on both, but you should see a greater improvement on the higher bitrate one. Something else that "may" be coming into play, you made the higher resolution XVCD approximately four times the resolution of the lower res video, and yet you did not even double the bitrate. Also, what is the resolution of your original source, if it is TV or videotape it is less than 708 x 480.

With a higher video bitrate you see a much more dramatic increase in quality when comparing files of the same resolution.

A comparison you may want to try is to make a "standard" VCD including the 1150kbits/sec constant video bitrate and the 352 x 240 (NTSC) resolution. Try to find a high quality original with lots of fast-action and dark scenes. Then from that same original and the same template, change the resolution to 352 x 480, 2-Pass VBR, Minimum 500, average 2000 and maximum bitrate 2500. You should definitely see a quality improvement with the latter one.

Remember with most CD-burning programs you need to turn off VCD compliance before you burn XVCDs.

[Entropy_Controller]

Thanks for your help!!! What it was that I was testing the XVCD on was the Metallica video off the Mission Impossible DVD, so my source is of good quality. I didnt really realize that in going from the standard resolution of 320x240 to 708x480 it was more than double quality. I understand now that by doubling just one of the resolution parameters you double what the bitrate should be. So if I tried creating a XVCD of standard VCD resolution with a higher bitrate, I would see an increase in quality.

The one other question I had, and I have seen a few different guides that have different settings for this, is the motion search precision. What exactly does this do? In TMPG you have a choice from lowest quality (fastest) to highest quality (slowest), does this quality represent the video itself and the speed represent the encoding time??? In other words if I want best quality in my XVCD should I choose the high quality???

[Entropy_Controller]

One more thing, you say that using 2 pass VBR will result in the best quality on a VCD??? is this correct?

[Gazorgan]

320x240 has less than 1/4 the data of the 708x480.

So XvcD at 320x240 at 1500Kbps would tanslate to a 708x480 at over 6000Kbps. That's why the 708x480 at 2500 Kbps looked so bad, it the equivalent of a 320x240 at 600 Kbps.

in a nutshell