[Vorbis] Question About syncing

[devel]

On Friday 15 May 2009 11:55:01 am devel wrote:
> On Tuesday 12 May 2009 12:16:08 pm you wrote:
> > On Tue, May 12, 2009 at 10:02 AM, devel <engineering at wwrn.net> wrote:
> > >  What exactly does it mean when, in the decoder_example.c file, you try
> > > to extract the information from the comments and codebook headers and
> > > you loose sync? What is actually being check to determine when sync is
> > > lost?. I known one part of it is that there is a gaps in the stream. Is
> > > the CRC value  the determining factor? Please detail! I read a lot of
> > > the documents. I still am a little fuzzy.
> >
> > "Losing sync" in the context of the vorbis code usually means
> > synchronization between the libogg read position and the beginning of
> > the next Ogg page in the stream. This is verified two ways: presence
> > of the 'OggS' magic sequence at the current read position, correct CRC
> > value for the subsequent page data. Normally, there will be a page
> > right where the code expects it to be. If the 'OggS' or CRC check
> > fail, then the file is corrupt, and it tries to find a place where
> > decoding can begin again by searching forward for the next 'OggS'
> > marking a new page and they trying the CRC from that point. When that
> > happens, the reader is said to have "regained sync" after "hole in
> > data".
>
> As I indicate in a previous post  "Help with old to new sources" I am
> trying to upgrade and learn how the decode method is achieve. The biggest
> problem I am having is chaining at the moment. The code will play the first
> stream successfully but the second stream in the chain fails in the
> CodeBookAndPreMetaData function. I was encourage to write a simplified
> tutorial but I would like all of the code to work. I want to understand how
> to fix this but use it as a good problem solving exercise.  attach is a
> file (HowToCodeOggVorbis.tar.gz).
>
> w3rn
> -rr
 Finally I got chaining working  after recoding!!!
w3rn
-rr