Tweaking bitrate calculation for DVD menus / extras

[jknutson2]

I've looked at the various bitrate calculators and guides for calculating bitrates, but most seem to ignore any menus or authoring material that may be included with the encoded streams. It appears that Fit2Disc and FitCD might have some concept of space taken for things other than video and audio, but perhaps only for some authoring tools (I haven't actually tried it yet).

The question is, is there anything more accurate than the what one of the guides suggests of subtracting 50 from the bitrate calculation if you add menus?

This seems to be one area where the integrated tools would have an advantage (knowing how much space for extras will be needed prior to actually doing the encoding).

[Sifaga]

how can you accurately calculate the size the menu will be before its done ?

[adam]

Fitcd has an option to calculate the size of still menu's. Just put in how many still menu's you anticipate you will have and it will take it into consideration when determining your avg bitrate. As for motion menu's, you'd have to factor that in yourself. If you want to use the same bitrate for the menus as the movie, well then just count up the runtime of your menu's and add that in to the length of the movie. The best option is to author everything out but the main movie and then take this filesize and enter it into the extra data option in FitCD.

[jknutson2]

how can you accurately calculate the size the menu will be before its done ?

That's the point I was making earlier about all-in-one tools having an advantage of sorts. You edit and create chapters and menus before you convert. Given that you know what menus are needed, you can adjust for the size they take up. I think this would also cover the case for animated menus and audio background because you will know that size ahead of time too.

The downside is that I'm not sure that chapter definitions generated prior to conversion will ensure the proper frame type at that position. Anyone know that answer?

[adam]

Most encoders support the option to force an I frame at a designated frame number or point in time. If you later set your chapter to this point it will be frame accurate. This is the only way to get frame accurate chapters, since a chapter can only fall at an I frame.

Whenever I author a DVD I always create all of the menu's first. If space is a concern I just tweak the encode of the menu's until they are as small as possible, but still good quality. Then I just take this filesize into account in my bitrate calculator.

[guns1inger]

If you think it will be an issue, create you menu structures but replace your assets with a still image. The stills will take up negligable space. Include this in your bitrate calculations before encoing your main assets. In the case of stills menus, even with some music 25mb or so will usually be enough - unless the music is LPCM, in which case allow 250mb