[gst-devel] seeking

[David I. Lehn]

* vishnu at pobox.com <vishnu at pobox.com> [20010917 04:12]:
> i'm trying to seek around an mpeg2 vob file.  Video works great, but
> audio tends to get messed up after about 20-30 seeks.
> 
> i'm not talking about the obvious lack of good a/v sync.  This is
> worse.  i get lots of these:
> 
> a52dec a52_block error 4
> a52dec a52_block error 5
> a52dec a52_block error 1
> a52dec a52_block error 2
> a52dec a52_block error 3
> a52dec a52_block error 4
> a52dec a52_block error 5
> a52dec a52_block error 1
> ...
> 
> There must be a way to do a reliable seek.  Can you speculate on
> the cause here?
> 

In theory the code should be able to resync to proper frame boundries.
It does this by a simple check byte-by-byte until it finds what looks
like the proper header.  I don't know if the format bans those sync
codes in the rest of the data stream or not.  If not then I guess it
could be seeking to some location, not finding a proper header, doing a
search, and stopping at the wrong spot.  That error message is cause the
block call is working for the first block and failing for the other 5.
(in a frame).  I'm going to take a guess here: in the loop func reset
(memset to 0) the state struct on every frame rather than just once.  I
was getting those errors before due to not setting the state struct to 0
(g_new0) at the beginning (some bug in a52dec).

-dave
-- 
David I. Lehn <dlehn at vt.edu>  | http://www.lehn.org/~dlehn/
Computer Engineering Graduate @ Virginia Tech in sunny Blacksburg, VA