With a new public release due out shortly and lots of problems relating to sound on the forum I thought I'd take the time to explain DScaler's support for sound both now and going forward.
The bt848 chip is very flexible in terms of what it can do for video and there is very little leeway for card hardware designers to muck about with the video end. This is why it is usually very easy to add support for new cards based on the bt8x8 chips.
For sound things get much more complicated.
The Different ways sound is supported
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Mono sound from the tuner is passed to the bt chip. If you have a mono card then this way should work. I will try and resolve issues related to sound on mono cards.
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NICAM Stereo (Europe) MSP Chip. These cards have an MSP chip and some support is in DScaler for these cards. I have no test setup for this but accept patches for changes to get NICAM working. I have reports that it works on some European NICAM broadcasts. I think it doesn't work on UK NICAM.
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BTSC Stereo (US) MSP Chip. There is currently no support for these cards. After a bit of research it seems that these cards will only play stereo when in a mode that is not implemented in the bttv code that the sound support was taken from. This will be addressed in later versions. There is already a large backlog of changes required but this is on the list.
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Other. Some hardware manufacturers have used other chips and ways of supporting sound. These are not supported now and probably won't be unless someone else writes or ports the code. Patches to support specific cards will be accepted once I have implemented a new design for sound support. This should make it easier to add support for new cards.
Workarounds
The most basic workaround is not to use the onboard tuner :-))
This is one used by most of the users of DScaler and explains why sound tends to take a back seat in priority.
Sometimes running the supplied TV tuner application before or after DScaler can help. Note that if you are using an Hauppague card then Dscaler 3.1.0 will include a card type of "Standard bt848 (No init MSP)" that will not touch the MSP on startup which should make the card behave as it did in version 2.3.0.
Using the Mixer
DScaler now also supports controlling the mixer and can mute lines when channels are changed or when DScaler exits.
The mixer set dialog can be accessed from Hardware/Audio Mixer Setup.
It allows you to specify which mixer lines are to be controlled by DScaler and which ones are to be unmuted when a given input is selected.
If "Reset Mixer to Initial Settings on Exit" is selected then it returns the mixer to the state it was when Dscaler started, if off then all the mixers lines that have been selected are muted on exit.
Known Issues
The STB TV cards have a different sound chip which means that they fall into category 4 in board design and that support for them will not be added by the main DScaler team. We would welcome any developers who want to add support for these cards. The code for the support of these cards is in the bttv driver but porting that code to DScaler is not trivial.
Still got a problem
See this Sound Issues post on AVS for an up to date picture of sound issues.