[vorbis-dev] granulepos start/end revisited
ozone at algorithm.com.au
Sun May 23 08:40:29 PDT 2004
On 23/05/2004, at 5:54 PM, Arc Riley wrote:
> I don't believe the start-stop method does anything to solve it. It
> only makes it worse, by not being able to use any subtitle directly
> after seek, even if it knew about it before the seek, while adding
> additional overhead. Extra overhead would be fine, of course, if it
> actually improved the situation, but I can't see a single case where it
> helps us in any way.
The case where it helps you is in implementation. As I said before,
I'll take a bet that if you implement subtitles with a duration field,
you'll find it a lot more painful than implementing it if they were
state changes. I've done both, and while I'm rather far from winning
the world's most kickass programmer title, I found it much harder and
more complex to do the former -- I suspect (and hope) that people who
have implemented similar code would agree. IMHO, I think it's
significantly harder that implementing it as state change rather than
duration is worth the effort (although I don't think there's much
effort involved -- it's a spec change).
BTW, don't take this as an attack on start-time granulepos: I think
there's fairly good arguments for why it's needed, or where it
simplifies stuff greatly, so that all the extra implementation hassles
associated with it are justified. (Mind you, I only say this before I
don't have to write all the code to implement start-time granulepos
support!) But, I think for your particular case of subtitles, using
durations rather than state-change for handling them is a bad idea: it
seems like a good idea now, but when it comes to implementation, you
will feel the pain ...
> I think people who use images
> for subtitles are a-moral spawns of the netherworld. See the crew who
> put together the DVD subtitle format for a good example of this. :-)
On the contrary, I think the DVD method of using images for subtitles
was very clever. As Jan said, expecting a DVD player to have
font-rendering capabilities is a lot more complex than just overlaying
an image on-screen. It's a better solution for its target market than
using text & fonts.
% Andre Pang : trust.in.love.to.save
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