[linux-dvb] Re: VDR Playback not smooth ?

[Klaus Schmidinger <Klaus.Schmidinger@cadsoft.de>]

Peter Funk wrote:
> 
> > > The problem ist in the bad multiplexing of the data delivered from the driver.
> > > VDR merely stores what the driver delivers.
> >
> > I don't agree fully with you here, because I found out that if you
> > increase buffersize the intervall between the stutter increases
> > correspondingly. In my opinion the reason for the problem is the buffer
> > code in VDR. During replay you have to feed the card constantly and fast
> > enough with frames. As I understood the buffering code the next data
> > from the file is read just then when you have to feed the data into the
> > driver. As reading may cause disk I/O and therefor additional delay, you
> > may not be able to feed the driver fast enough and cause the stutter.
> [...]
> 
> If Emils analysis is right, it might make sense to use the select
> system call and a simple ring buffer of some size.  This allows to
> handle this situation within the same thread, which simplifies the design
> considerably compared to having to use two threads or processes.

I have already implemented a new ring buffer that uses two separate threads
(one for filling the buffer and another one for emptying it) in the recording
facility of VDR and I believe that part works a lot better now.

This new threaded ring buffer will also be used in the replay facility later,
but I wanted to complete the new API adaptation first. So I suggest we
concentrate on making VDR run with the new API for now, and once that works
I'll switch replaying to the new ring buffer.

Klaus
-- 
_______________________________________________________________

Klaus Schmidinger                       Phone: +49-8635-6989-10
CadSoft Computer GmbH                   Fax:   +49-8635-6989-40
Hofmark 2                               Email:   kls@cadsoft.de
D-84568 Pleiskirchen, Germany           URL:     www.cadsoft.de
_______________________________________________________________


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