Bitrate tab confusion

[krajyk]

I'm a bit confused with the bitrate tab. First of all, I have 700MB/80minute CDs so I set all of the CD size to 800. Now there are six different boxes where you can determine the minutes range for a particular CD. I have a 180 minute DVD that I want to burn on 3 CDs. What that means is, if I set each minute range to be 30 minutes long, I can evenly distribute the minutes over the CDs (CD 1: 0-30, CD 1: 31-60, CD 2:61-90, CD 2:91-120, CD 3:121-150, CD 3:151-99999). The confusion comes from this; why is it that the bitrate between each of these are not the same? Why is it that in 31-60 the range ends at 2530 and between 91-120, it goes down to 1900 (these aren't exact numbers but the point is, shouldn't the bitrate values be the same since they all use the same minute range)?

[Turbinator]

The bitrate tab also confused me for a very long time. Your specific question is actually quite simple - if the movie ends up to be only 60 minutes, you have 800 MB per CD with which to fit 60 minutes of content. The result is that you get a higher quality SVCD. If your movie is 120 minutes, the bitrate goes down (quality goes down) because you are fitting 120 minutes of content on 800MB per CD.

Does that make sense?

Here's an analogy.. You have a whole CD to fit a single image, say, if you were using Photoshop. You've got 800 MB of space. You might as well make 1 big 800 MB file, very high quality and very high resolution. Now, try to fit 400 pictures on that same CD. There's no way you can fit 400 pictures of 800 MB each, so you're going to have to turn down the quality level and the resolution.

Hope this helps?

Turby

[Labersack]

DVD2SVCD just check in which line of your 'beetween'-lines the _whole_movie fits. After is just uses _this single_ line for conversion, the other 'betweens' are completely ignored for this run.
Many people misunderstood this tab in the beginning. If it's not clear to you than try a search, it was often explained in detail.

[Abond]

@krajyk
Here, some calculations:
0-30 min, 1CD(800 total), bitrate ?-2530
31-60 min, 1CD(800 total), bitrate 2530-1864
....
91-120 min, 2CD(1600 total), bitrate 2458-1864
These values are if you disable audio (= 0 Kbps)
2530 - in fact for 31 min on 1CD 800 the bitrate should be 3608 Kbps but DVD2SVCD will not allow higher than 2530 (Max Avg) to keep it in SVCD specs.

@Turbinator
The bitrate tab also confused me for a very long time. Your specific question is actually quite simple - if the movie ends up to be only 60 minutes, you have 800 MB per CD with which to fit 60 minutes of content. The result is that you get a higher quality SVCD. If your movie is 120 minutes, the bitrate goes down (quality goes down) because you are fitting 120 minutes of content on 800MB per CD.
I think you are not right. 60 min for 800MB (1CD)= 120 min (2 X 60 minutes!) for 1600MB (2CD, 2 X 800MB).

[markrb]

I will try to explain this.
Everything is based on defaults, except all cd sizes have changed to 800 and the audio will be set to 224 for this example.

The bitrate tab is written like this:

Between 0 and 50 mins. Use 1 CD size 800 ?-1950
Between 50 and 76 mins. Use 1 CD size 800 1950-1200
Between 76 and 100 mins. Use 2 CD size 800 2636-1946
Between 100 and 125 mins. Use 2 CD size 800 1946-1509
Between 125 and 163 mins. Use 3 CD size 800 2380-1770

Lets break this down point by point.

Between 0 and 50 mins. section is the total movie length. Not the minutes you want on a cd.

Use 1 cd. This is the number of cd's you wish to use for the total movie length.

CD Size 800. This is the size of the cd in video megabytes. 740 for 74 minute, 800 for 80 minute and 900 for 90 minute cd's

1950-1200. This is the calculated average bitrate for the specified range. The first number is for the lowest number of minutes, the last number is for the highest number of minutes in that range for the number of cd's. If you wish to get a more accurate picture of what your actual bitrate will be simply check the actual length of your video and change the number to match it. Make sure to return the length back above what you changed it to just in case the video is slightly longer then you expected. If this happens then DVD2SVCD will move to the next section.

To raise this calculated bitrate you can add a disc, lower the audio bitrate or increase the size of the disc.

0-30 min, 1CD(800 total), bitrate ?-2530
31-60 min, 1CD(800 total), bitrate 2530-1864
....
91-120 min, 2CD(1600 total), bitrate 2458-1864
These values are if you disable audio (= 0 Kbps)
2530 - in fact for 31 min on 1CD 800 the bitrate should be 3608 Kbps but DVD2SVCD will not allow higher than 2530 (Max Avg) to keep it in SVCD specs.


The reason why the original explantion was a bad example was simply because of the number of cd's used. If they were both 1 cd then the example would have been accurate.

DVD2SVCD will allow the bitrate to go higher if you uncheck warn if above 2756 on the bitrate tab. Unchecking this is not a good idea unless you know that your DVD player can handle out of spec SVCD's.

Mark

[krajyk]

Markrb,

You're explanation clears a bit more but I'm still not sure.
Here is your example.

Between 0 and 50 mins. Use 1 CD size 800 ?-1950
Between 50 and 76 mins. Use 1 CD size 800 1950-1200
Between 76 and 100 mins. Use 2 CD size 800 2636-1946
Between 100 and 125 mins. Use 2 CD size 800 1946-1509
Between 125 and 163 mins. Use 3 CD size 800 2380-1770

First of all, you say that the 0-50 range is not the minutes range you want on the disk but the entire movie. If that is the case, then what is the 50-76 range mean? Also I understand that you can raise the avg. bit rate by setting the first range to lets say 0-40. But if the movie is 82 minutes for instance, who do I specify it to use 1 CD vs. 2 CD vs. 3 CD? Tell me if this is right. If I want to use only 1 CD for an 82 min. DVD, do I make sure that first two ranges (0-50, 50-76) contains the number 82? So maybe something like 0-41 CD 1, 41-82 CD 1, would that work? And if I wanted to use 2 CDs, would I set it the following 0-20 CD 1, 20-40 CD1, 40-60 CD2, 60-82 CD 2 or would I do it like 0-40 CD1 (to keep the bit rate reasonable) 40-60 CD 1, 60-82 CD 2. Does that seem ok? I guess the reason there is confusion is that my inclination is to use all 6 entries divding the mintues evenly based on the number of CDs you want. If I wanted to use 1 CD for a 120 min DVD, I would set the ranges to have 20 mins each and set 1, 1, 1, 1, 1, 1 all the way down. If I wanted 2 CDs, I would set the ranges same; 20 min each and set 1, 1, 1, 2, 2, 2 and for three 1, 1, 2, 2, 3, 3. If you could give me an example of how you would do a 120 min. DVD into 1, 2, 3 CDs, I would be able to understand from it.

Thanks,
krajy

[Labersack]

Between 0 and 50 mins. Use 1 CD size 800 ?-1950
Between 50 and 76 mins. Use 1 CD size 800 1950-1200
Between 76 and 100 mins. Use 2 CD size 800 2636-1946
Between 100 and 125 mins. Use 2 CD size 800 1946-1509
Between 125 and 163 mins. Use 3 CD size 800 2380-1770

The confusing first two lines are because some time ago they were this way:
Between 0 and 50 mins. Use 1 CD size 740
Between 50 and 76 mins. Use 1 CD size 800

This means: For a movie between 0-50min use one 74min-CDR and for a movie between 50-76min use one 80min-CDR. But today almost everywhere are 80min-CDRs in the shop, so there is almost no need for a setting with this kind of media.
You can also set the first line to
Between 0 and 76 mins. Use 1 CD size 800 ?-1200 and this would exactly do the same as the two lines in the first example together did.


Lets explain the way of DVD2SVCD in the example

Between 0 and 50 mins. Use 1 CD size 800 ?-1950
Between 50 and 76 mins. Use 1 CD size 800 1950-1200
Between 76 and 100 mins. Use 2 CD size 800 2636-1946
Between 100 and 125 mins. Use 2 CD size 800 1946-1509
Between 125 and 163 mins. Use 3 CD size 800 2380-1770

DVD2SVCD does the Audio and subtitle stuff. After it has finished, it starts CCE to count the real numer of frames in the movie, because the info in the IFO isn't always correct.
So lets say it finds out the movie is 99 min long.
It goes to the first line and asks: 'Is 99 between 0 and 50?' The answer is no, so it ignores this line.
Next it asks: 'Is 99 between 50 and 76?' Again the answers is no.
Third question: 'Is 99 between 76 and 100?' This time the answer is yes. Now it looks at the rest of the line. The line says: 'Calculate a bitrate that this entire movie will fit on 2 CDs of 800MB each!' So it calculates a bitrate that will be 1600MB-(Audio+subtitle+titlepic+..)
The last two lines
Between 100 and 125 mins. Use 2 CD size 800 1946-1509
Between 125 and 163 mins. Use 3 CD size 800 2380-1770
will be also ignored, because if it has fit in the third line, it can't fit into any other line, as the minutes-values always have to be increasing.

[mrbass]

Between 0 and 50 mins. Use 1 CD size 800 ?-1950
Between 50 and 76 mins. Use 1 CD size 800 1950-1200

to me that is the same as
Between 0 and 76 mins. Use 1 CD size 800 ?-1950

That's why I always use 1CD, 2CD, 3CD, 4CD, 5CD, 6CD.
I've never hit 5CD or 6CD though.

you can see screenshot of of my bitrate settings here.
http://www.mrbass.org/dvd2svcd/svcd/

[markrb]

If the movie is say 120 minutes it simply skips over the other sections until it gets a match. Then once the total length of the movie is between the the minutes in the "Between" section it uses that and only that data to calculate your SVCD.

So in the case of a 120 minute movie.

All sections are ignored except for the one that reads.

Between 100 and 125 mins. Use 2 CD size 800 1946-1509

Then in this case it will make a 2CD SVCD with an average bitrate closer to 1509, but not 1509 exactly since that is what 125 would use. So your bitrate for a 120 minute movie would be very slightly higher.

Mark

[Turbinator]

@Turbinator

I think you are not right. 60 min for 800MB (1CD)= 120 min (2 X 60 minutes!) for 1600MB (2CD, 2 X 800MB).

I guess my explanation wasn't clear. I was simply trying to say that if you fit 60 min onto 1 CD, you'll get some bitrate. If you try to squeeze 120 min on 1 CD, you'll get some gawd awful low bitrate.

Therefore, you get highest quality when you spread out a movie over several CD's. The more CD's you use for a given length movie, the higher the bitrates you can get for that movie.

Turby

[krajyk]

Thanks everyone for your speedy explanations. I understand now. The confusion came from thinking that 0-76 vs. 0-50, 50-76 were two different things, but in actuality , its the same.

Thanks,
krajyk