Doctoring Tools, chapter generator and audio reencoding

macuser01 · Post by **macuser01** » Thu May 31, 2007 9:36 pm

To be short:

I have a lot of Quicktime video files with two 6 channel aac audio tracks (two languages). Recently I have bought an aTV and as you know, the aTV only does a stereo downmix.

So I think the following 2 feauters would be very useful for aTV users:

1. Reencoding of audio tracks in existing Quicktime movies (from 6-channel aac to Dolby Pro Logic II)

2. Automatic chapter generation for existing movies without chapters.

In this place I would thank the developers for their work on handbrake.

Sincerely

maurj · Post by **maurj** » Sat Jun 02, 2007 10:32 pm

Hi there,

How would feature 2 work? How would you be able to create chapters where no chapter info exists? Or are you after more of a manual chapter editor? If that's what you want, then one option can be found here:

http://www.apple.com/quicktime/tutorial ... racks.html

As for 1, it's a good idea, but I'm not likely to add the code to do it any time soon - as it would be very different from the existing HandBrake approach, which expects an MPEG2-type source input. However, you might be able to take Handbrake and adapt it to something else to do what you need?

- maurj

realityking · Post by **realityking** » Sun Jun 03, 2007 9:48 pm

For No. 2:

I remember seeing that Metadata Hootenanny (I don't have a clue how its spelled correctly) has an option to read the chapter times out of a dvd and put it into a .mov file. However I doesn't seem to support MP$s.

maurj · Post by **maurj** » Sun Jun 03, 2007 10:08 pm

The problem with trying to add in this info for existing, already-ripped files is that the chapter marker positioning is frame-specific, and is rather complex in the way it is passed through HandBrake's decode / encode process. The output movie's frame sync is different from the source, so it's not as simple as copying the time of the chapter markers from the source DVD - this may not quite match up with the previously-ripped HandBrake file. I'm afraid the only option for accuracy is to rip again - which may mean quite a lot of re-ripping

- maurj

Cyander · Post by **Cyander** » Fri Jun 15, 2007 7:17 pm

maurj wrote:The problem with trying to add in this info for existing, already-ripped files is that the chapter marker positioning is frame-specific, and is rather complex in the way it is passed through HandBrake's decode / encode process. The output movie's frame sync is different from the source, so it's not as simple as copying the time of the chapter markers from the source DVD - this may not quite match up with the previously-ripped HandBrake file. I'm afraid the only option for accuracy is to rip again - which may mean quite a lot of re-ripping

- maurj

What he said.

For #1... Handbrake really isn't a great tool for it. Anything that can take an MP4, pass-through the video, and downsample the AAC into Pro Logic would be okay. ffmpeg might even able to do this with a recent build.

#2 is even worse: Metadata Hootenany produces the same chapter markers as HB 0.8.5b1, in the next release HB will have updated chapter marker code as maurj points out. The whole reason for this change is that DVDs are authored funny. The chapter break that the DVD points to is for cells... and the DVD player has to seek for the right type of frame inside the cell which is the real start of the chapter. The updated chapter code emulates this behavior, giving more accurate chapter titles.

After the fact, the best we can do without re-ripping is how Metadata Hootenany does it. There is also another tool which lets you add chapters manually to quicktime files that you can find on MacUpdate. I would recommend one of those tools for after-the-fact chapters.