[FFmpeg-devel] [PATCH] rmdec.c: parse INDX chunk

[Kostya]

On Wed, Mar 11, 2009 at 11:17:50AM -0400, Ronald S. Bultje wrote:
> Hi Kostya,
> 
> so now on to the patch:
> 
> On Wed, Mar 11, 2009 at 1:40 AM, Kostya <kostya.shishkov at gmail.com> wrote:
> > On Wed, Mar 11, 2009 at 01:00:45AM -0400, Ronald S. Bultje wrote:
> >> + ? ? ? ?if (size > 20)
> >> + ? ? ? ? ? ?url_fskip(pb, size - 20);
> >
> > err, what happens when somebody decides to follow spec and include size of index
> > entries into header size?
> 
> Oops, old code. I removed these two lines, they're useless.
> 
> >> +skip:
> >> + ? ? ? ?if (url_ftell(pb) != next_off &&
> >> + ? ? ? ? ? ?url_fseek(pb, next_off, SEEK_SET) < 0)
> >> + ? ? ? ? ? ?return -1;
> >
> > this condition should be changed since it does not take into account streamed
> > data, for which we should read or skip only this index chunk
> 
> I've honestly never seen files with an index at the beginning, so I'm
> assuming this code wouldn't ever be reached for non-seekable sources,
> unless someone implements massive data-read-skips in place of
> url_fseek() (please god no). See also this chunk:
> 
> >> @@ -400,6 +446,14 @@
> >> ? ? ?if (!rm->nb_packets && (flags & 4))
> >> ? ? ? ? ?rm->nb_packets = 3600 * 25;
> >> ? ? ?get_be32(pb); /* next data header */
> >> +
> >> + ? ?if (!data_off)
> >> + ? ? ? ?data_off = url_ftell(pb) - 14;
> >> + ? ?if (indx_off && url_fseek(pb, indx_off, SEEK_SET) >= 0) {
> >> + ? ? ? ?rm_read_index(s);
> >> + ? ? ? ?url_fseek(pb, data_off + 14, SEEK_SET);
> >> + ? ?}
> >> +
> >> ? ? ?return 0;
> >> ?}
> 
> I don't think (hope) that rm_read_index() would be called for
> non-seekable sources, am I wrong?

who knows. Please try with some streaming file.
 
> Also, note that a rm_read_seek() isn't strictly necessary, with this
> code, seeking already works for most files, just not for old_format
> files or multirate files, and if there's cached data that is returned
> first before we continue with the after-seek, see my other patch later
> on in this thread.