[vlc-devel] Block access/demux?

Laurent Aimar fenrir at via.ecp.fr
Fri Jul 20 21:13:13 CEST 2007

On Fri, Jul 20, 2007, Rémi Denis-Courmont wrote:
> Is there a way a demux can pick blocks from the input stream so that 
> they retain the same boundaries as those coming from the (block) 
> access? Using stream_Block does not seem to work (blocks are merged). 
 No there is no way.

> That's problematic if the mux format uses block boundaries from lower 
> layers...
> Also, is it normal that stream_t.pf_block is just always under any 
> circumstances, NULL ??
 Yes, pf_block is a left over from stream_t design, it was there for
reading block with their natural boundaries. But later I changed
stream_Block to read arbitrary block size.

 Such block reading was not usefull anymore with the concept of
access_demux_t (at least at that time).

  What exactly is your situation ?

  In the case the demux need the block boundaries from the access, it
means the demuxer and the access are really bound to each other, and thus
an access_demux_t may be the best solution.
  If you can reuse an existing access (the only one I see is udp) it is easy
to implement an access_demux_t that instantiate such access for itself (bypassing
stream_t layer).

 If it isn't possible or too complicated to use access_demux I could modify
stream_Block to allow it (like using zero/negative size). But it might be tricky
to make stream_Read/Seek coexist with that.


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