New ifoedit guide: formula to calculate video size

[rui]

Hi all,

I consider myself a newbie about CCE usage, so i hope i am not asking something stupid, or that has been asked a lot. I searched the forum about this, and read the guides, but, in spite they mentioned how to calculate the size of the video file, none is too explicit on this, and i just wanted to know if this formula of mine is correct.
If the mod feels that i am breaking rules, please don’t hesitate in acting :)

VideoSize=((4.700.000.000 bytes – (AudioSize+SubSize)*1,05)/1,05)

I reached this formula starting here: (Video+Audio+Subs)*1,05=4.700.000.000 bytes, because i saw in doom9’s guides that one has to multiply his audio plus video by 1,05 to get the true size in the dvd-r.
And since the new ifoedit guide mentions also subs, i thought one should include them in the calculation.
I think that, if the formula is correct, it would be helpfull to other newbies like me in calculating the correct video size. It would be only a matter of making a simple Excel formula.

[FamousPerson]

If your subs are ripped by SubRip, and are in .bmp files, I've found that authoring them into a DVD only uses 5% of their size as bitmaps.

So, this is how I calculate it:

DVD Size: 4700000000
Authoring overhead, providing your doing movie only: 100MB or 104857600 bytes

This leaves you with 4595142400 bytes of room for your subs, audio, and video.

So, from that number, subtract your exact audio size and 5% of your subtitle size.

Whatever you have left over, you can use for video.

Incidentally, if you take that result, divide by 125, and then divide by the number of seconds your movie is long, you get the bitrate you need to encode at (I use 125 instead of 128 because that's how CCE works out. I don't know why).



Example:

Audio = 314572800
Subs = 209715200
Movie Length: 7200 seconds

Calculation:

Videosize = (4595142400 - 314572800 - (209715200 * 5%)) = 4270083840

Bitrate at which to encode = 4270083840 / 125 / 7200 = 4745

[rui]

Thanks for the tips :)

I am extracting the subs with the new vobedit, so they come in a SUP format. Don't know if it can be as compressed as BMP.
Indeed, it's strange the 125 thing. A byte still has 8 bits, right? :D

[FamousPerson]

I found out why 125 instead of 128. According to the CCE manual, one kilobit is regarded as 1000 bits. It does not say why.

(one kilobit is really 1024 bits)

Must have been the same guy who claimed that a DVD-R can hold 4.7 GB...

[PartyBeast]

Is there a way to calculate the overhead when creating the vobs? I have been simply assuming about 100MB for a single AC3 audio track, which usually works fine, but when adding additional audio tracks, assuming 100MB per audio track seems to be over kill. But then DTS tracks seem to require more overhead then AC3 audio tracks. I have been experimenting with the idea of taking a percentage of the size of the audio track, and then subtracting this from the amount of available space. However, I have not burned enough DVD's yet to determine if this is accurate, or a precise percentage amount to use. Has anyone figured an accurate means to calculate this overhead?

Thanks,

PB

[FamousPerson]

From all I've seen, video+audio together, menus or not, usually always require about 120 MB overhead. If you, for example, add another audio track, you do not need to figure any additional overhead. Same with menus. They may add a little, but it's negligible. I always figure 130MB to be safe.