[mythtv] DVD playback - average length of a VOBU? (related to ticket #4492)
skamithi at gmail.com
Wed Jan 30 04:16:26 UTC 2008
> From my research it seems a VOBU can vary in length from between 0.4
> seconds to 1 second. I haven't found any useful statistics on an
> average VOBU length. My understanding is that there isn't any...it
> will vary from movie to movie, and may even vary significantly from
> place to place within a movie. If this is the case, then I guess
> just have to make a best guess, right?. Does anyone know how the
> current seekSpeedMap rates were arrived at?
DVDs in the vobu search information provide offsets to 0.5, 1.0, 1.5,
2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 10, 30 and 60
backwards and forwards.
Seeking through the dvd using the sticky ff/rew is not 100%, but this is
because mythtv is
not designed to be a dvd player
The seekSpeedMap does the following mapping (and this was trial and error)
3x -> 0.5 seconds behind/forward
5x -> 1 seconds behind/forward
10x -> 2 seconds behind/forward
20x -> 4 seconds behind/forward
30x -> 5 seconds behind/forward
60x -> 7.5 seconds behind/forward
120x ->10 seconds behind/forward
180x -> 30 seconds behind/forward
So if you choose 4x, and send this info to DVDringbuffer Seek function, it
But since i never thought of someone changing the mapping in tv_play.cpp, I
should write in a condition to do nothing if someone enters a speed that is
not in the mapping. I suppose this info is fed to the dvdnav function
and it goes crazy and seeks to some unexpected spot on the dvd.
would also suggest you read dvd_time_search_within_cell() in
and http://dvd.sourceforge.net/dvdinfo/dsi_pkt.html with focus on the
sri_bwda and sri_fwda labels.
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