[linux-dvb] New samplerates in CVS driver

[<mocm@convergence.de>]

Stefan Huelswitt writes:
 > Hi,
 > from the CVS changes I see that there was added support for 44 &
 > 32 kHz audio. Does this mean that I'm able to play PCM audio with
 > these samplerates now? If yes, how is this done from application
 > level?

The LPCM header, which follows in the PES payload right after the
PES header, is as follows:

   id                                                     8 bit
   number of frames                                       8 bit
   first acces unit pointer, i.e. start of audio frame   16 bit
   audio emphasis on-off                                  1 bit
   audio mute on-off                                      1 bit
   reserved                                               1 bit
   audio frame number                                     5 bit
   quantization word length                               2 bit
   audio sampling frequency (48khz = 0, 96khz = 1)        2 bit  <---
   reserved                                               1 bit
   number of audio channels - 1 (e.g. stereo = 1)         3 bit
   dynamic range control (0x80 if off)                    8 bit

The driver for the DVB card ignores all but the sample frequency
bits.
We added the new frequencies to the header as 44kHz = 2 and 32kHz = 3.
I added support for that to ntuxplayer. You can find a routine called
pcm_play in apps/tuxzap/src/dvb_formats.c in the driver package.
The LPCM PES cannot be larger than 2048 bytes right now.

Marcus

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Dr. Marcus Metzler                             
mocm@netcologne.de                     http://www.metzlerbros.de
mocm@convergence.de                    http://www.convergence.de

Convergence Integrated Media GmbH          
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