[linux-dvb] Re: converting PES to TS while reading from (multiple)/dev/ost/demux0

[Ralph Metzler <rjkm@metzlerbros.de>]

Felix Domke writes:
 > > Which is AFAIK a rather nasty limitation of the current API.
 > > As far as I know there is no way to find out where exactly
 > > payload_unit_start_indicator bits were set when you read from
 > > a demux device. You need to read TS packets from dvr if you want
 > > to have the payload_unit_start_indicator bits. But dvr
 > > only supports one concurrent opener...
 > It *IS* a nasty limitation.
 > 
 > I would prefer:
 > 
 > DMX_SET_PES_FILTER
 > 
 > with two new options:
 > 
 > a.) type, like "TRANSPORT" (all 188 bytes), "PAYLOAD" (like the deafault)

This should not be too much work to add.


 > and maybe a "read one payload unit as once", maybe with a header (with the
 > size and - maybe - things like the adaption field, but maybe this is exactly
 > what AV_PES did.. i don't know. so maybe just "PAYLOAD" and if you want to
 > get the PUSI-flag "TRANSPORT")


To get the size would be a problem, because then the whole PES would
have to be buffered additionally to the normal buffering until the
size can be determined. And those PES packets can get quite large.

AV_PES also did not deliver adaptation fields. You will not be 
able to get the original adaptation fields (or TS packets) with 
the AV7110 cards anyway. 


 > b.) the estimated datarate, or more low-level, the amount of data which
 > should be available until an interrupt occurs.
 >
 > The absence of b.) leads to high system load if you break up a fast stream
 > (Video/Audio, EIT) into many small packets, or, if you use a big "buffer
 > size" (or "interrupt threshold") to the problem that you cannot read ONE
 > small packet (for low datarate streams, like PAT/PMT or even NIT).

OK, but influencing such an interrupt threshold is not possible with
all hardware. 

 
 > A huge company did a nice api for using their chipset with Linux, it very
 > much like the OST-Api, but has this new options. I really miss them in the
 > OST.


Which company is that and is the API description available?



Ralph


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