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Dual channel sound
http://forums.linhes.org/viewtopic.php?f=2&t=891		 Page 1 of 1
Author:  saruman [ Wed Mar 03, 2004 11:45 am ]
Post subject:  Dual channel sound
(Sorry, this might be more appropriate for the ivtv list, but I am more familiar with this one, so I thought I would start here)

Has anybody (probably in Europe) managed to get dual channel shows recorded and played correctly?

In some countries (Switzerland for example), some shows are broadcasted using "dual channel" sound. It is then possible to switch between two different language (and typically, get the original soundtrack). The feature is implemented on most TVs.

I have a PVR-350, PAL country.

Poking around in the ivtv documents, I have found a flag that seems to address this:
from http://ivtv.sourceforge.net/firmware-api.html:
Code:
9:8  '00'=Stereo
      '01'=JointStereo
      '10'=Dual
      '11'=Mono


Running the command: "test_ioctl -C", I get:
Code:
root@mythtv:~ # test_ioctl -C
ioctl: IVTV_IOC_G_CODEC
Codec parameters
aspect      : 2
audio       : 0x00e9
bframes     : 3
bitrate_mode: 0
bitrate     : 4500000
bitrate_peak: 6000000
dnr_mode    : 0
dnr_spatial : 0
dnr_temporal: 0
dnr_type    : 0
framerate   : 1
framespergop: 12
gop_closure : 0
pulldown    : 0
stream_type : 0


so, the audio is currently set to:
0xe9: 00 1110 10 01
stereo 384 kbps LayerII 48kHz

I am thinking that by switching to:
0x2e9:10 1110 10 01
dual 384 kbps LayerII 48kHz

I would get the "dual" mode.

1) Before I f*** everything up, has anybody experimented with this before? I am afraid to disrupt my otherwise finally working setup... :)

2) What's the best way to set this up permanently? I guess I would add a line in /etc/mythtv/modules/ivtv:
test_ioctl --set-codec-params="audio=0x2e9"

3) Once it is set up, does anybody know how to switch between channel 1 and 2 (left/right)?

I know the card can do it, because it did switch over one day as I was messing around with the params. I don't know how it got there, however.

Laurent
Author:  saruman [ Tue Mar 30, 2004 9:43 am ]
Post subject: 
Following up on my own thread:

- Yes, the PVR-350 supports dual channels, and the driver is written so that it will detect and switch modes accordingly.

- Unfortunately, if it's a show in dual sound, you will by default get the LANG1 channel, which is not what I wanted. So, I patched the msp3400.c code to switch over to LANG2 by default. Contact me if you are interested.

- Additionally, I have been working with Stephane Zermatten on a "cleaner" solution, which would allow recording LANG1, LANG2 or both languages, then selecting when you play. Some details are under:
http://www.geocities.com/szermatt/bilingual.html
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