[linux-dvb] Re: Fw: DVB audio/video decoder API

[Dennis Noordsij <dennis.noordsij@wiral.com>]

> One thing the driver does which I think it shouldn't is emulating
> demux features in software that the hardware doesn't have.
> E.g. the AV7110 does not give us the TS, thus the output for
> the dvr device must be recreated in software from PES packets.
> IOW, there's a complete TS multiplexer implementation in the
> driver.

So when you want to record multiple PID's, the driver will multiplex a TS 
stream together for you containing those streams ?

Then VDR (for example) demuxes it, and creates its own multiplex PES streams 
for the individual channels.

So say you want to record
Video 512, Audio 650
Video 516, Audio 690

The driver multiplexes these into a TS stream with these 4 streams embedded, 
VDR demultiplexes this TS, and creates 2 multiplexed PES streams, i.e.
512+650
516+690

No wonder 30-40% of CPU is spent in system (TS multiplexing) on my VDR machine 
:-)

Would it speed up things to not create a TS stream in the driver, but simply 
allow the app (VDR is a popular example :) to receive all the PES streams it 
wants (as long as they are available on that transponder of course) and then 
save them however it likes?

Is it already possible to just ask for a(ny) number of PES streams?

And if you are receiving say an audio and video PES stream, independantly, can 
they be combined into a synchronized audio/video stream? (i.e. do these 
streams have the proper timestamps or markers to re-sync them later?).

I hate to keep inquiring about this, and I am sorry for those who are sick of 
it :-) But I don't understand why a low powered machine could not timeshift 
properly if the card supplies the right data directly and accepts the same 
data (i.e. without any real processing). I figured the host machine just 
routes the streams between cards/disks without needing to do any "real" work.

PS - I am very happy to experiment for myself but so far I can only tell you 
how most of the frontend stuff works, not really the demuxer side yet, I'm 
still learning about the guts of the driver, so any pointers are appreciated 
:)


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