[linux-dvb] Re: Streaming from hard disk

["Gert-Jan van Dijk" <aka_mr_zapper@hotmail.com>]

So, finally got the change to write my first (small) device driver, after 
having to do lot's of other jobs....

Okay, so I'm able to load/unload, open/close, write to the device (for me as 
a Linux nitwit already an achievment...). Now I want to make use of the 
dvb_dmx_swfilter() call, and thus copied that one into my source (as it's 
static in dvb_demux.c). Looking at the code, I see that I have to fill the 
dvb_demux struct (Am I right?). But, I haven't got the faintest idea of how 
to proceed.

Questions:
1) Can I just call the dvb_dmx_swfilter() from the write, after setting up 
the dvb_demux structure?
2) If so, can somebody point me into the right diection of how to set-up the 
struct?
3) To control the playout speed, can I "simply" use kernel timers, and make 
sure that in between triggers enough data is sent to the sw filter? Or is 
this totally the wrong approach?

Thanks a lot,

Gert-Jan van Dijk

> > > > to switch between different streams from network streaming servers) and
> > > > some code that registers a software demux and calls the
> > dvb_dmx_swfilter()
> >
> > > > callback with the data read from disk or a network connection. Since
> > > > multiple people asked for a solution like this we highly welcome patches
> > > > implementing such a debugging driver.
> >
> > That's a good idea. I just took a glance at the dummy code, and I'll start
> > from there. Thanks, and rest asure that I'll share the stuff I make when I
> > get it to work, no worries.
> feel free to ask on this list if you need help understanding or 
> implementing the internal driver API, this is unfortunally not too well 
> documented, sorry.
>
> > > The tricky part is the timing of the TS playback. For the
> > > av7110 driver the dvr device slurps data as fast as the
> > > disk can deliver it, unless you set a video and/or audio PID
> > > with DMX_OUT_DECODER in which case the MPEG decoder controls
> > > the timing.
> >
> > That seems logical, so we need to control the speed by also giving it a
> > symbolrate. That's also what you do on most of the streamers (some 
> > determine
> > this by parsing the tables, others don't). So have to look into the 
> > decoder
> > to see how it controls timing, and then make it configurable via 
> > symbolrate.
> > Thanks, this is grand....
> You can guess/calculate the stream rate either by parsing the stream 
> headers (to keep the deltaPCR/deltaTime rate or deltaPTS/deltaTime rate 
> constant or even more sophisticated use the mux rates encoded in the 
> headers) or simpler use the symbolrate passed to the frontend device -- 
> then you can easily adjust this from userspace according to your needs.
>
> Holger
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