On Monday 31 October 2005 11:05, T.J.H. Kluter wrote:
> Hi all,
>
> Just to come back on an already discussed issue. I'm the proud owner
> of as well a PVR-500 as well as a PVR-150. Both cards are working
> excelent with the current 0.4.0 ivtv driver. But as I'm living in
> Switzerland, there are some cable channels with Dual-Language
> transmission. As stated in earlier threads, the detection of
> SAP/Dual-channel is working perfectly. The only thing that is not
> directly working is the dual-channel output of the audio by using
> "ivtvctrl -z 1", as I suppose is only working with the PVR-250/350
> which contain a MSP34xx chip for audio detection. A solution to this
> problem is also already stated in an earlier thread, namely using
> "echo PREF_MODE=7 | cx25840ctl -s -d /dev/video1".
I think that it is a good idea to replace PREF_MODE 4 with 7 as the
default for stereo. I'll test that today. Then the cx25840 acts the
same as the msp3400.
> This gives also the possibility in mythtv to select the different
> audio tracks by using the seperate left/right channel muting.
>
> The only problem which resides in this solution is:
> 1) Would it not be a nice idea to update the PREF_MODE to the correct
> value by the usage of "ivtvctrl -z 1" for the PVR-150/500 cards?
See above.
> 2) By recording the MPEG stream, although the audio is marked as
> DUAL, it still is a single audio stream, and until now I did not find
> any player/editor who could handle this type of stream (hence detects
> that there are actual two languages instead of a stereo audio
> stream).
What do you mean with 'audio marked as dual'? Did you set the codec's
audio parameter? If you set it to 0xd9 (ivtvctl -c audio=0xd9) then the
audio stream in the mpeg file is marked as a dual audio stream. Note
that changes to the codec parameters only become active during the next
capture, they don't modify a capture in progress. Whether there are
programs that recognize such a stream I've no idea. I think such
streams are quite rare.
> As I do not care about the first point that much, the second point
> could be a bit more iffier.
> Please correct me if I'm wrong, but by my understanding the MPEG
> stream is created by the CX25840 chip by usage of the firmware (hence
> not by the driver itself). In case the firmware permits to create two
> audio tracks in the MPEG stream (which should be known to the people
> who have insight in the FW), one could think of a scheme to instruct
> the FW to create a MPEG stream containing one video channel, and two
> separate audio channels, each containing one language. This would
> ease things up for players/editors (as they already support multiple
> audio channel streams, as found on DVD's), and also would provide a
> nice interface to f.e. mythtv to detect the languages.
The firmware and hardware of the MPEG encoder (not the cx25840) is
responsible for creating the MPEG stream. It is not possible to create
two audio streams, but as mentioned above the audio stream can be
marked as a dual audio stream.
> I would be interested in helping testing this feature, as you guys
> think it's feasable and interesting. I also would apreaceate
> feedback.
If marking the audio stream as dual helps then it might be interesting
to investigate if it is possible to do this automatically by the
driver.
Also note that the PVR350 support a firmware command to select the
language of a dual channel audio stream:
Enum 22/0x16
Description Select audio mode
#Params2
Param[0] Dual mono mode action
Param[1] Stereo mode action
0=Stereo, 1=Left, 2=Right, 3=Mono, 4=Swap, -1=Unchanged
I don't think this is current used in the driver, though.
Hans
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