[vorbis-dev] granulepos start/end revisited

[André Pang]

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.

<p>
-- 
% Andre Pang : trust.in.love.to.save

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