A couple of SVCD and XSVCD questions...

[jnms]

Just got a few questions...would be grateful for any answers...

1) If I use a resolution on a XSVCD of 720x480 with a bitrate of 2400 and then create a SVCD of 480x480 with a bitrate of 2400. Would the SVCD be better quality in that it would have less artifacts…and less high motion break-up. I understand that the quality resolution wise would be sharper…but for this question it is the artifacts and break-up difference I am more interested in.

2) When encoding with a variable bitrate, if I set the minimum rate to 0, will the bitrate drop too low on the encoded film? Would I be better of setting the minimum bitrate to 2000…or would that defeat the idea of using VBR?

3) Using multiple passes on the encoding…when using VBR. I did a test file last night with 4 passes, and the results really were very good. So…if I kept using a higher pass rate…at what point would I not really see any difference? Am I better of sticking to 2 passes…or is 4 better or perhaps 6? Also, generally…what is the time difference this can make to encoding?

The software I am using is TMPEnc, with DVD2SCVD.

Thanks...

[mats.hogberg]

1) Yes. 720*480=345600 pixels, 480*480=230400 pixels. At least in theory, you'd have to raise the bitrate from 2400 to 3600 to get an equal amount of "bits per pixel" at 720*480, and bits/pixel is what determines the amount of artifacts.

2) The more "room" the encoder has, the better. Take the extreme: If you have a still picture sequence, what use woult it be to throw 2000 kbps at it, when it needs 0? They would be better used during high motion sequences.

3) TMPGEnc seems to take about the same time for each pass, regardless of if it's just figuring out the motion between frames, or rendering the MPEG. So for encoding time, just multiply time with # of passes.
As to where it stops getting better - beats me - I never go beyond 2 pass VBR.

/Mats

[jnms]

Thanks for the info. That helps a lot...

(Aside from the fact that I have left a video encoding in VBR at min 2000 max 2350 )