[vdr] [ANNOUNCE] bitstreamout plugin 0.80 (sound loop through sound card)

Dr. Werner Fink werner at suse.de
Wed Mar 16 17:01:54 CET 2005


On Wed, Mar 16, 2005 at 07:01:51PM +0200, Per Mellander wrote:
> On Wed, 16 Mar 2005 13:39:44 +0100, Roland Praml wrote
> > Long time ago there were so called 'copy-bit killer'
> > Can I set the nonaudio with a similar circuit.
> 
> Yes you can, it's a similar control bit. It was in an Elektor magazine a few 
> years ago. Maybe you can modify the circuit. It was all done in hardware 
> because of the high rate.
> 
> > 
> > As other mentioned this should also be done by a soundcard
> > by reading from spdif-in, set the bit, and writing to spdif-out
> 
> I was thinking the same but it seems that a dsPIC is the only ( reasonable )
> uController that can work in that high speed area. ( Unless the soundcard is 
> equipped with such a feature. )

The speed rate is

     32 bit word per 16 bit PCM sample
     multiplied with 2 for two channels
     multiplied with 2 for the biphase-mark-code
     multiplied with e.g. 48kHz

     which is 6.144MHz

... now you have to read the preamble of each 32 bit
word to catch the starting one and rise the status
bit of the second and third (aka second bit for the
second channel) status bit and maybe the parity bit
is needed.  And this should be switchable by the DVB
driver or firmware via a not used pin of the ARM.


          Werner

-- 
AC3 loop through sound card http://bitstreamout.sourceforge.net/
Howto http://www.vdr-portal.de/board/thread.php?threadid=1958
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