[vdr] MP3 playback speed (was Re: MP3 Plugin Problems)

[s.huelswitt@gmx.de (Stefan Huelswitt)]

On 03 Jan 2003 Clemens Kirchgatterer <clemens@thf.ath.cx> wrote:
> "Dr. J. Neumann-Zdralek" <neumann-zdralek@web.de> wrote:
> 
>> i also observed a problem with the speed adjustment. If I tell the
>> driver to use 44.1kHz the playback speed is ok for some seconds, and
>> then the mp3-code switch to 48 kHz even if I use a dvb-driver from
>> december.
> 
> same here. i have also a slow machine (P100) and after starting mp3
> playback the drift detection kicks in, and playback speed slows down.
> i had to disable the speed detection completely to get it work:

Well, obviously there is a problem with that. I don't know how to
cure, but I'm going to say what I know:

- The driver cannot dynamically switch the playback sample rate,
e.g. if your are listening a song with 44.1kHz and the next song
has 48kHz, the second will play too slow (even if the correct
samplerate is passed to the driver) -> speed detection kicks in.
You have to stop playback completely to switch the samplerate.

- In a system with more than one card, playback speed is
sometimes off by 5-6% when recording on another card. This
causes the speed detection to kick in, which changes from
(mostly used) 44.1kHz to resampled 48kHz. Due to problem #1 this
change causes more problems.

- OSD usage disturbes the playback. This may confuse the speed
detection, too.

To eliminate some causes, I suggest to enable the 48kHz mode in
the setup menu and see what happens. At least problem #1 should
vanish.

-- 
Stefan Huelswitt
huels@iname.com  | http://home.pages.de/~nathan


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