AC3 audio stream is silent. And how to set preferred stream?

[Barsk]

When watching TV, and knowing there is a AC3 stream, there is no way to get sound.
For MPEG audio I use either the MPEG decoder or Microsoft bundled standard decoder. My decoder setting for AC3 is disabled. Seems that Win 7 handles it nicely and passes ac3 on the S/PDIF out. It works nicely for MKVs for instance, but not for TV.

It would also be nice to have an option in settings where I can choose a preferred stream. For me whenever AC3 is available, I want that stream by default. That would be on my wishlist for future relseases.
In GB-PVR you could choose this by selecting the "channel" with the AC3-stream in device setup.

[IanJ]

Hi,

I'd like to see it so that when you view a live Tv channel and right click and select the audio stream then that config would be saved for that channel only. That way it would be easy to custom setup the audio (or video) for each and every channel.
If that stream was then disabled under settings then it would revert a custom configured channel back to default.

Just a thought mind you.

Ian.

[johnsonx42]

If you have the AC3 decoder setting disabled, then you will simply not get AC3 audio, period. You need an AC3 decoder set; if you want the AC3 stream to then be passed thru to your SPDIF connection, you'd have to set a passthru option in that decoder (so yes, you're not decoding the AC3 stream at all, but nonetheless you still need *something* to handle the stream and send it on). That's what Win7 is doing - it uses the Microsoft DTV-DVD Audio decoder. Unfortunately that decoder won't handle AC3 for third-party apps, so you need AC3Filter or FFDShow. I'm pretty sure both of those do have a passthru option.

[BigMoose]

They do both have passthru that works well.

[Barsk]

Hi,

I'd like to see it so that when you view a live Tv channel and right click and select the audio stream then that config would be saved for that channel only. That way it would be easy to custom setup the audio (or video) for each and every channel.

I agree setting a default audio stream per channel would be the best alternative. Preferably this would go in the Channels section in Settings

[Barsk]

If you have the AC3 decoder setting disabled, then you will simply not get AC3 audio, period. You need an AC3 decoder set; if you want the AC3 stream to then be passed thru to your SPDIF connection, you'd have to set a passthru option in that decoder (so yes, you're not decoding the AC3 stream at all, but nonetheless you still need *something* to handle the stream and send it on). That's what Win7 is doing - it uses the Microsoft DTV-DVD Audio decoder. Unfortunately that decoder won't handle AC3 for third-party apps, so you need AC3Filter or FFDShow. I'm pretty sure both of those do have a passthru option.

I had some problems getting FFDShow to work. It turns out I had installed the 64-bit version installed when N-PVR is a 32-bit app (see other thread for that). So I will give it a try tonight. Last night there was this football game that took all my time (Sweden got throurohgly spanked by Holland in the European Championships qualifications. A sad story...)
And yes, both of the decoders you mention have a pass-through. It was that setup I had in my previous installation with Win XP.

You mention that Microsoft DTV-DVD Decoder silently passes AC3 to S/PDIF for my MKV's with AC3, and that is how Win 7 magically handles AC3. Did I understand that right? But this option does not work for the TV stream. Funny it work in one case, but not the other then?

[whurlston]

The Microsoft decoder only allows AC3 in Microsoft applications due to Dolby licensing agreements.

[Barsk]

I don't understand. I get AC3 pass-through working fine when I play MKV files in N-PVR. That is with setting AC3 decoder to disabled in settings. If what whurlston says is correct, that would not work.

If, according to johnsonx42, Microsoft's DTV-DVD decoder is used silently to do this pass-through, and it works, why would it not work for TV as well?

And just to get records straight. I use S/PDIF out for all audio. The AV amplifier does the decoding of AC3. MPEG Audio is decoded to PCM on the HTPC before streaming to the AV amp.
So there is no AC3 decoding going on.

[johnsonx42]

The microsoft DTV-DVD decoder works for AC3 when Windows builds the graph; it doesn't work when another app tries to use it directly. When NextPVR wants to play an .MKV file, all it does is hand the file to windows and says "directshow, please play this file for me, k, thanks!" - so at that point Windows is playing the file not NextPVR and the Microsoft DTV-DVD Decoder works fine. When NextPVR plays it's TV files, NextPVR builds a graph using your chosen filter components and various NextPVR bits (like the NPVRTSReader.ax, etc.); so now the Microsoft DTV-DVD Decoder says "nope, sorry, only microsoft apps can use me for AC3" so it just doesn't work.

[Barsk]

Ok, I get it.
Thanks for the thorough explanation.

I have installed ffdshow 32-bit, set it for pass-through and everything works perfectly!

Thanx for all help everybody!