[linux-dvb] Couple of MPEG structures related questions

Andrew de Quincey adq_dvb at lidskialf.net
Wed Jul 13 18:58:39 CEST 2005


On Wednesday 13 July 2005 16:10, Johannes Stezenbach wrote:
> Andrew de Quincey wrote:
> > 2) mpeg_multiplex_buffer_utilization descriptors...
> >
> > They're defined to be:
> > bound_valid_flag		: 1;
> > ltw_offset_lower_bound		: 15;
> > reserved			: 1;
> > ltw_offset_upper_bound		: 15;
> >
> > The problem is ltw_offset_upper_bound is defined to be 14 bits in the
> > structure in ISO13818-1, but in the accompanying text, it is said to be
> > 15 bits... does anyone know which is right?
>
> I would guess 15 is right (how can the upper bound be smaller
> than the lower bound?). But I'm curious what this descriptor
> is good for, and if anyone has ever seen a stream which contains it.

According to the docs: The multiplex buffer utilization descriptor provides 
bounds on the occupancy of the STD multiplex buffer. This information is 
intended for devices such as remultiplexers, which may use this information 
to support a desired re-multiplexing strategy (see Table 2-55).

Never seen it myself - it was easier just to implement all descriptors than to 
pick and choose.




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