Bitrate Calculator?

[ApacheWraith]

Does the BR calculator in the tools section automatically adjust for resolution? What I mean is, doesn't resolution affect the final file size? I was messing around with different TMPGEnc templates trying to see what would fit on an 80 min cdr. I had been experimenting with different resolutions and I got a little better picture with 480X480 even at the same 1150 bitrate. So when the calculator is set to SVCD or whatever does it already know 480X480?

Thanks in advance.

[Truman]

Resolution does not affect the file size.

[ApacheWraith]

Truman, I see. But it does effect the overall quality of the video right? The reason being is that I was using Sefy's template for SxVCD, which is really good, and I changed the resolution in the encoding to 480X480, and I got a slightly better picture in the end. Not a whole lot, but enough to notice. Now, I want to obviously use his template to fit a 92 minute movie on a disk. Does this mean I can use a 720 X 480 resolution as long as the A/V bitrate doesn't go to high and get the same size file?

[vitualis]

When you go up in resolution, it does not affect the final file size.

However, what it means is that for each frame, you have more information to encode. MPEG-1/2 is a lossy compression system and if it doesn't have enough bitrate to work with, you start seeing artifacts.

Thus, when you go from say 352x240 --> 704x480, you've increased your resolution by 4x. This inherently also means that you have 4 times the information to encode.

Now, if there aren't any MPEG artificing, 704x480 will look sharper and thus "better" than 352x240. However, if 704x480 breaks out into blocking anytime there is signficant movement, this will usually be interpreted as "poorer" quality.

IMHO, you can't get a framesize of 480x480 to, on overall, look "better" than 352x240 at VCD bitrates (1150 kbps average) for the majority of films (because of artificing). At 720x480, your XVCD would probably be unwatchable at VCD bitrates.

Regards.

_________________
Michael Tam

<font size=-1>[ This Message was edited by: vitualis on 2002-01-17 06:46:04 ]</font>

[Truman]

Of course you can choose any resolution. But the quality (is subjectiv I know) will get worse at that low bitrate.
Higher resolution=more macroblocks / pixels to encode.
If you don't increase the bitrate, the compression will get higher, the quality will get worse (you will see the blocks).

[ApacheWraith]

vitualis>> Cool, I just posted another question for you in my other post. Ok I see now, so at 720 X 480 I would have to have a seriously high bitrate to keep up? So what would be the biggest reloution to go, if your bitrate is around 1150 like in Sefy's templates? 480X480 looked better than 352X240 to me. It was a noticable difference. A/V sync seemed good, and the picture was not jerky at all, motion was good. Obviously I can only go to 640X480 from 480X480, what do you think?

[vitualis]

I personally don't really dabble with XVCDs and quality is subjective.

Whether 480x480 looks better than standard VCD framesize at VCD bitrates I think is debatable (in terms of sharpness vs. artifacts). I tend towards the side that thinks that it does not look as good as standard VCD because of artifacts.

Also, if you use multipass VBR encoding with a suitably high max. bitrate, you may be able to prevent most of the artifacts from being perceptable.

However, it will depend on the movie you encode. If you movie doesn't have much complex action, then at such a low bitrate there may be only minimal artifacts. However, I doubt you will be able to do a movie with a lot of action without those scenes looking bad.

Regards.

_________________
Michael Tam

<font size=-1>[ This Message was edited by: vitualis on 2002-01-17 07:14:32 ]</font>

[ApacheWraith]

I happened to be experimenting last night and KingViper's template is pretty awesome, In my opinion. I would have to rank Sefy's and KV's my two favorites. I wonder if I can combine the two to make an eclectic masterpiece.

LOL

Wraith