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STB Audio Output - Delay
http://forum.linhes.org/viewtopic.php?f=17&t=17453		 Page 1 of 1
Author:  mattshaw [ Thu Dec 20, 2007 2:36 pm ]
Post subject:  STB Audio Output - Delay
Hi there

I am just trying to set up a knoppmyth pc for my dad.

I have a twinhan anolgue/digital card, with 3 inputs, one for aerial to catch FTA (freeview in the UK), one composite and one s-video.

The DVBT is working fine. I intend to use the composite input to take the output from my dad's Virginmedia Samsung STB. Upon testing at home, without the STB available, I am using a VCR. It is working OK for video. I have audio output from the VCR scart into the Line in on the PC, and am picking up sound, but that sound is permanently on when the VCR is playing. Also, the audio is about 4 seconds behind the video.

Is there any way to mute the audio until the audio/video is required by LiveTV or recording ????

Also is there any way to delay the audio when starting LiveTV or a recording ????
Author:  mattshaw [ Fri Apr 04, 2008 7:54 pm ]
Post subject: 
Can anyone please help with this ????
Author:  manicmike [ Sat Apr 05, 2008 12:41 am ]
Post subject: 
mattshaw wrote:
Can anyone please help with this ????


Yes, although the answer is very easily found with a web search.

The problem is that your sound card is passing the audio straight through to the speakers. You need to mute it. I assume you are also unable to pause the sound when you pause a TV show?

I wrote a howto about this some time ago, but have since lost it.
I think I had to go into alsamixer, mute the sound output, go into the capture menu (press tab) and unmute + increase the input level.

All from memory, which is very broken in my case, but it should get it all back in sync.

Mike
Author:  ChapmanI [ Tue Apr 08, 2008 9:34 pm ]
Post subject: 
I think it is more than that. The delay is the buffering of live television. Because you are passing the audio directly to the sound card, it isn't tired to the video, and hence it isn't buffered.

You don't say which Twinhan card. I looked at some of the PDF manuals on the Twinhan sight, but they were not very helpful. Depending on the card, there seems to be a couple of different methods of connection.

I'm kind of talking through my hat here, as I'm unfamiliar with those cards. I don't know if they are hardware encoding like the Hauppauge x50 cards, or software encoding ala the BT878 cards.

The tuner card should have an audio in jack, so the audio out from the STB/VCR connects to that input - probably by a mini-phono plug. If it is a hardware encoder card, that should be all that is needed.

If it is a software encoding card, you may need to loop an audio out from the tuner card, to the Aux in on your sound card/motherboard sound connectors. In some cases that is a mini-phono out on the tuner card, to a mini-phono in on the sound card/motherboard (usually blue is the Aux In connector) on the back of the case. From the Twinhan manuals I looked at, at least one of their cards requires using a cable inside the case. The concept is the same - tuner card out, to sound card/motherboard Aux In. But the cable is similar to the one used to connect the Audio Out of a CD/DVD drive to the Aux In (or CD In) on the sound card/motherboard.

And if it is software encoding with connections as I described above, then Manicmike's comments about muting the Aux In in the Alsa Mixer also apply.

One more point though. If the STB has an Svideo connector, that would produce a better quality picture than the composite one. But of course, if the STB is being shared by both the TV and the Myth box, the Svideo is probably already going to the TV.

Perhaps in Europe there is no Svideo out on STB's. It looks like the Svideo type signals do come out of the Scart connector though. It looks like some of the Twinhan cards have an Svideo in - so a Scart to Svideo addapter might be needed.
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