making xvcd's w/ 2pass VBR

[kidkurrupt]

i guess the xvcd bitrate calculator cannot determine an approx filesize because it all depends on the scenes in the movie, right?
I need to know what avg bitrate i should set in the tmg template to fill up a 74 min cd with a 54min divx. I tried using somebody's XVCD template on here (the one about a 55 min stream) but it only came out to 600 megs. What should I set it to in order to make it 710-720 megs or even 800 megs incase I use a 80 min disc.

[Truman]

http://members.tripod.de/fitcd/
1652+224kbps or 1748+128kbps to fit 54 minutes on 1 74min CD
1805+224kbps or 1901+128kbps to fit 54 minutes on 1 80min CD

[kidkurrupt]

that's great man, but it only shows me CBR.
Is there another program that can scan through the divx movie with a given avg, max, min + audio bitrate and compute an approximate filesize?

thnx

[Vejita-sama]

Just enter the numbe from the calculator as the ave and everything will be ok.

max = DVD players max
ave = from calculator
min = several options, 0 and 300 are popular.

[Truman]

If you encode with 2pass VBR calculate the avg bitrate as you calculate a constant bitrate.
Bitrates of the divx do not matter, only the time.

[kidkurrupt]

vejita: for the minimum rate, is it better if i set that to be higher or what? if i set it to be very low, will it look shittier during those scenes or the same as if i set it to be like 1000 below the max.

[kidkurrupt]

Truman: during the first pass it determines what bitrates to use during certain scenes according to the user-specified values, right, so is there a program that can perform the 2pass vbr scanning and calculate what the size of the outputted mpg will be?

I'm asking because encoding in 2pass vbr takes so long and experimenting with it is a bitch when you have to wait 4 hours just to check the size of the outputted mpg.

[Kdiddy]

Kid: 2 pass lets you set the average bitrate...so your output bitrate will be close to the specified average, provided you give equal tween your min & max values comapred to the average value...IE, min 1000 avg 1300 max 1600...see 300 both above & below range....you would then use a bitrate calculator to determine how big or what size file you wish to have.....

as for as your experiemnt, why dont you enocde just a short clip first until you get your settings just right...then do the whole thing.

[vhelp]

Kid,

Instead of waiting 4 or more hours to just see the
50% mark (you video), why don't you do this:

IN TMPG:
* click the Advanced tab
* [x] Source (double-click this)

Now, in the area just below the video window (see
scralling left/right bar) - just drag that and while doing
so, click the end button on the right (you'll figure it out)
and try and grab about 500 frames. 500 is usually about
1 or so minutes. i.e., if it turns out to be 2 minutes to
encode, then, in 2pass, it'll probably be something like
your 4th minute to 50% viewing. That's way better than
wating for the WHOLE clip to go though it's first pass...
don't you think?? Anyways, if you need to test more
than once scene or somthing, then just re-do the steps
above (pressing the begin and end buttons appropriately).

Have fun (and more time).

[kidkurrupt]

kdiddy & vhelp: sure I could do that method, select a minute to encode and check the size of that small file, but how would that help me determine the file size for the entire clip at the end?

when using 2pass vbr, doesn't the file size change depending on the amount of fast and slow motion scenes in the movie?

[Kdiddy]

no you are missing the point...do you understand how to use a bitrate calculator????....very simple, specified bitrate multiplied with time of movie, gives file size in terms of bits, divide that by 8 gives file size in terms of bytes....simple math....

file size is affected by time & bitrate...now the motion in the movie (ONLY IN VBR MODE) will determine how close your bitrate is to the specified avg....IE, if you choose 1200 as your avg...1000 min, 1400 max....a lot of high motion may cause it to be like 1275 bitrate, a lot of low motion may cause 1189.....it will get closer to 1200, with more # of passes, but popular opinion states that anything beyond 4 passes doesnt improve quality that much.

[Yeshi]

<TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD><font size=-1>Quote:</font><HR size=1 color=black></TD></TR><TR><TD><FONT SIZE=-1><BLOCKQUOTE>
On 2001-10-14 15:40:33, kidkurrupt wrote:
vejita: for the minimum rate, is it better if i set that to be higher or what? if i set it to be very low, will it look shittier during those scenes or the same as if i set it to be like 1000 below the max.
</BLOCKQUOTE></FONT></TD></TR><TR><TD><HR size=1 color=black></TD></TR></TABLE>

if you set it too high, then you will have the encoder alloctaing a high bitrate in scenes like the credits. Set it low, like 500, and the encoder will allocate the 500 bitrate to non-motion scenes, so the low bitrate doesnt matter, if you set it high, you will end up with a larger file size without any quality improvement.

<font size=-1>[ This Message was edited by: Yeshi on 2001-10-14 19:54:55 ]</font>

[Yeshi]

<TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD><font size=-1>Quote:</font><HR size=1 color=black></TD></TR><TR><TD><FONT SIZE=-1><BLOCKQUOTE>
On 2001-10-14 18:29:40, kidkurrupt wrote:
kdiddy & vhelp: sure I could do that method, select a minute to encode and check the size of that small file, but how would that help me determine the file size for the entire clip at the end?

when using 2pass vbr, doesn't the file size change depending on the amount of fast and slow motion scenes in the movie?

</BLOCKQUOTE></FONT></TD></TR><TR><TD><HR size=1 color=black></TD></TR></TABLE>

The file size changes depending on your bitrate settings. So inputting the AVG bitrate into a calculator should give you an accurate measurement, because its the AVERAGE bitrate! Think about it, its an easy concept to follow

[kidkurrupt]

yeshi: i dunno man, it's wierd.

I encoded at 1900 CBR and the file size turned out to be 582MB. I then encoded the same source at 2650 avg VBR min2100 max3000 and it turned out to be 615MB.

does the vbr one have the same quality as a 2650 CBR encoded mpg? if that's true, that means the only disadvantage of two pass VBR is extra time, right?


btw, at the time i didn't know that the MIN value doesn't have to be so high, that's why i did 2100.

[Kdiddy]

"I encoded at 1900 CBR and the file size turned out to be 582MB. I then encoded the same source at 2650 avg VBR min2100 max3000 and it turned out to be 615MB."

Again man, brush up on your math skillz, OF COURSE the file at avg 2650 is going to larger in size than 1900 CBR because 2650 is a higher bitrate...obviously more bits of info leads to a bigger file..

"btw, at the time i didn't know that the MIN value doesn't have to be so high, that's why i did 2100."

well it doesnt have to be, but you want an EVEN range on both sides of your average value..DO NOT DO THIS: "300 min - 2650 avg, 3000 max" this leads to more lowend bitrate because your range below your average is far greater than the range above your average...keep it equal

"does the vbr one have the same quality as a 2650 CBR encoded mpg? if that's true, that means the only disadvantage of two pass VBR is extra time, right?"

YES, however, when it comes to overall quality, its a matter of opinion, IMO, at that bitrate, you probably wont see a GREAT noticiable difference...all VBR does is allow for a more efficient allocation of the bits.

[kidkurrupt]

kdiddy: hmm, ok. also, do you know what bitrate i should use to maximize the resolution? meaning, i'm using a 352x288 resolution, what bitrate would be superfluous?
5000, 6000?
i know it depends on the source's quality as well, but for a good quality divx what would you think?

thanks

[Yeshi]

For 352x288 you do NOT need an average bitrate higher than 1500. You are using low resolution video. Such a high bitrate for such a low res. video is useless, especially because your source is good quality divX. i think even the standard bitrate of 1150 would be sufficient.

<font size=-1>[ This Message was edited by: Yeshi on 2001-10-14 22:02:00 ]</font>

[Yeshi]

<TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD><font size=-1>Quote:</font><HR size=1 color=black></TD></TR><TR><TD><FONT SIZE=-1><BLOCKQUOTE>
5000, 6000?
</BLOCKQUOTE></FONT></TD></TR><TR><TD><HR size=1 color=black></TD></TR></TABLE>

That would just be ridiculous. You'd be adding tons of extra space to the video, without ANY quality increase. I think for a MPEG video, a bitrate of 5000-6000 would be sufficient if your video was of resolution 1280x960 or something like that, NOT 352x288.

[kidkurrupt]

yeshi: if what you're saying is true, then why do people make templates for xvcd's with bitrates higher than 1500 at the standard vcd resolutions? for example, the XVCD 2PASS VBR(PAL) one in the Tools section, you're saying that there's not much of a gain in doing that?


<font size=-1>[ This Message was edited by: kidkurrupt on 2001-10-14 22:13:16 ]</font>

[Yeshi]

The only gain is the gain in size of your MPEG file. Why dont you do a test. OK? load up your divX file, and load a template for VCD with constant bitrate of say, 1150. Encode say 100 frames, and take a screen shot of the 1st frame of the movie. Now do the same with bitrate of 4000. take a screen shot. You will have 2 screen shots, one of bitrate 4000 and one of 1150 both of the same movie, now open them up in photoshop and magnifiy them 5x and compare, and you wont see ANY difference. Now for another test. Open your video again, and select a VCD template bitrate 1150. Select a very fast action scene to encode. Now encode the same scene at bitrate 4000, and watch the both in your VCD player, you might see slightly less blocks in the 4000 bitrate picture than the 1150 picture, but 1500 will look the same as 4000. Try it.

[Yeshi]

Most of the time, your source divX file will be in a bitrate of about 1100, which is about 1250 MPEG bitrate. so there is no use in increasing it way above that value. There is use in increasing a small amount above that value (ie:1400) because that increase will help to get rid of block noise that is induced will encoding. Same for resizing. When you are resizing to a higher size then you will need to put in MORE bits, to counter block noise induced by resizing. a VCD file in resolution 352x288 with a bitrate of 5000-6000 is put simply a joke.