[mythtv] DVD playback - average length of a VOBU? (related to ticket #4492)

Ronald Frazier ron at ronfrazier.net
Wed Jan 30 01:23:49 UTC 2008


A few weeks ago I submitted an enhancement: Ticket #4492 -
Configurable fast forward / rewind / slowmo speeds + variable
reposition amount

In the process, I've uncovered a bug thats been in myth for a while,
but was probably never exposed because there was no gui option to
change the settings. If you have ffw/rew configured to a speed other
than one of the defaults (3x, 5x, 10x, etc), lets say 4x for example,
then you run into a problem when playing back DVDs with the internal
player. Instead of seeking at 4x, the DVD player will seek at some
insanely fast speed.

I've found the cause. In DVDRingBuffer.cpp, there is a variable called
seekSpeedMap that is used to calculate how many VOBU's to jump at a
time based on the current seek speed. All I need to do is come up with
the proper mapping from seek speed to VOBUs. The code in
libmythdvdnav/searching.c seems to imply that a VOBU is 1/2 a second.
I tried using that, but when I tested the seek rates weren't accurate.



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