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Topic: AC3filter, SPDIF, and a bit of Confusion (Read 1402 times) previous topic - next topic
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AC3filter, SPDIF, and a bit of Confusion

So I've been trying to get my audio setup finally together.  Now I'm trying to wrap my head around some things that are confusing me. 

I currently have a 2.1 speaker set-up connected to a Pioneer AVR.  My PC is connected to the AVR via toslink.  Now, I know that only PCM stereo or multiplexed multichannel audio can be transmitted over it.  I have AC3filter decoding its supported formats.  Is it considered preferable to set it to output AS-IS as opposed to 2.0?  If I understand correctly,  5.1 audio, for instance, will be downsampled to 2ch PCM via software if I set it to output 2.0, and will then be upsampled later by the soundcard if it isn't 48kHz.  If I set it to output AS-IS, the 5.1 will just pass to the soundcard which would then downsample to stereo and upsample to 48kHz itself.  The two ways look the same to me, save that when I output AS-IS the volume is lower than when I set AC3filter to output 2.0 (with all of the autogain and normalizations turned off) so I'm kinda confused. 

Also, I downloaded a couple of 5.1 audio samples from here:
http://www.diatonis.com/downloads_dts_ac3.html

There are 5.1 wav files there, but unless I use AC3filter for PCM, they are just garble and static when I play them.  Why exactly is that?  I figure that since they are just uncompressed wavs and not DTS, AC3 or anything else, that it wouldn't be problematic to handle normally with DS filters.  Is it because a non-standard codec is still needed to parse the multiple audio channels in the wav?

One last question.  When I upgrade to a 5.1 speaker set-up, would it be better to output ProLogic II or reencode to AC3 for non-passthrough non-stereo sounds?  I imagine PL2, since it's PCM, is less lossy but it doesn't have the discreet channels that AC3 has. 

Sorry if this is simple stuff but I get confused easily.