[linux-dvb] Audio Description and multiple audio pids

Monty monty-dvb at bc.cx
Tue May 10 13:05:26 CEST 2005


Hello,

I am hoping that someone on this list may have some ideas on how to help 
me.
I am using a Hauppauge Nova-T PCI card on an AMD64/Debian-AMD64 machine in 
Scotland.

What I am hoping to be able to do is to be able to listen to the standard 
audio-pid of a given channel as well as the audio-pid containing the 
"audio description for the blind".  Effectively mixing the two audio 
streams.  This would be very nice because as you may have guessed, I am 
blind myself!

So far, I have played with the dvbstream and tzap tools and have not been 
successfull.  I can play one or the other audio pid but not both.

Example:

> tzap -r "BBC One Scot" 1>/dev/null 2>/dev/null &
> cat /dev/dvb/adapter0/dvr0 | ts2es 202 | mplayer -

The above pipes a 192 Kbit stereo mp3 stream to mplayer.

The APid=202 above is the standard audio-pid for BBC One Scotland from the 
BlackHill transmitter.  The audio-description Audio-pid for the same 
channel is 206.

That is to say, the above set of commands with 206 substituted for 202 
produces a 64 Kbit mono mp3 stream containing the audio description.

I have tried putting both audio-pids on the ts2es command line but it 
seams to only sepperate one pid-stream at a time.  I have also tried 
running the cat command twice - once for each APid, but the device seams 
to lock on the first read request.

I've also played with dvbstream and although it takes two pids on the 
command line, one seams to have to be a video-pid.

Of course, another potential problem with this is that the 
audio-description APids seam to transmit 64 Kbits mono whereas the 
standard APid's stream at 128/192 Kbits.  It would seam to me that the 
different encoding rates wouldn't mix very easily.

If anyone has any ideas on how I can accomplish listening to both at once 
that would be really great!

Thanks in advance,
   Monty





More information about the linux-dvb mailing list