[mythtv] seeking with pvr / usleep

Isaac Richards ijr at po.cwru.edu
Thu Apr 24 11:23:29 EDT 2003


On Thursday 24 April 2003 03:13 am, Jim Paris wrote:
> > Second step (and a much better way to do it) would be to do some quick
> > demuxing on record and store the start locations of the keyframes, much
> > like the nuppelvideo stuff does now when it generates a seektable.
>
> What about building this table as we play?  For jumping into a
> position we've already seen (eg rewinding), we'll have the keyframe
> locations cached.  For jumping into unvisited frames, we go to our
> last known keyframe and scan frames without decoding them.  Fast
> forward would be a bit slower than rewind but I can't imagine it would
> be too bad -- would it?

Well, of course -- that's how it's done in the nuppeldecoder class if no 
preexisting seek table exists.  It's just that you don't want to scan forward 
like that if you're playing remotely, if you can't help it, since it requires 
transferring all the data over the wire.  

> BTW, on an unrelated note, one thing I've noticed throughout the code
> is your use of
>      usleep(50);
>      usleep(500);
>      usleep(5000);
> FYI, those will all actually delay about 20 msec on a stock 2.4
> i386 kernel; 

Yup.  

Isaac


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