Can't extract DVD subtitles

[idrougge]

I've finished translating a movie, but since I don't feel like spending over two hours punching in time codes, I thought I could "borrow" the timing from the existing subtitles.

I've tried both working with a VIDEO_TS folder copied from the DVD and a big VOB file ripped with 0SEx, to no avail.

Using ffmpegX, I load the file as usual, go to "Filters" and check "VOB subtitles" and a number. I then press "Extract", and nothing happens at all. I've tried choosing both .idx and .srt, but still nothing happens.

What am I doing wrong?

[Case]

I've tried both working with a VIDEO_TS folder copied from the DVD and a big VOB file ripped with 0SEx, to no avail.

Using a VIDEO_TS folder would be easier, as the subtitles will be identified by language (en, fr, de, ...). This should help selecting the correct one better than using just a number with big VOB source files.
For 0SEx, make sure to select at least one subtile stream to include in the rip.

Using ffmpegX, I load the file as usual ...

Correct.

... go to "Filters" ...

Correct.

... and check "VOB subtitles" ...

Not important, as this checkbox is not used for only extracting subtitles.

... and a number.

Correct. Keep in mind that "0" may or may not be used as a number for subtitles.

I've tried choosing both .idx and .srt,

'.srt' is the correct setting. I don't think ".idx" will give you usable time codes.

I then press "Extract", and nothing happens at all.

The "Extract" buuton should stay activated (darkened?) and a striped activity circle should appear somewhere in the Subtitles section of the window, while ffmpegX reads the VOB(s). It will extract the subtitles from the VOB(s) into many (possibly 1000+) temporary ".pgm" image files in the Save As location. After that it tries OCR until it finds characters that it can't identify (a Terminal window will ask about it).
If no subtitles are found, the Terminal will give an error that the OCR module finds no ".pgm" files to process.