Movie Audio formats for my Onkyo receiver

[sportflyer]

I am confused what happening with between my Onkyo NR3007 Receiver and WDTV Live. The audio streams are connected via optical between WDTV Live and Onkyo Receiver. I set WDTV Audio to optical pass through.

According to the Receiver specs it does not support AC3 but supports AAC directly.

I downloaded several .mkv movies with an AC3 - 6 ch audio stream . Since my receiver could not handle AC3 , I promptly converted the audio streams to AAC .

Here is the issue:

I get no sound output from the receiver using the converted AAC audio streams . But when I switched to the original AC3 sound streams I do get sound .

Can someone help me to understand whats happening. Tks

[Cornucopia]

That receiver may not explicitly support AC-3 (aka Dolby Digital) FILES, but it certainly implicitly supports both AC-3/DD and DTS (and their better cousins) as STREAMS.

Your WDTVLive is streaming the audio (via the optical port, as well as via HDMI). The receiver sees the AC-3 stream and decodes it. BTW, optical ports can support LPCM stereo, as well as compressed formats which can fit in the LPCM stereo bandwidth (IOW, 2ch * 48kHz * 24bit = 2304kbps). So clearly DSD, LPCM surround, and usually other lossless surround formats cannot fit. Also, some lossy formats that are > 2304kbps cannot fit. Plus, if the receiver doesn't expect the optical/spdif/toslink to provide other formats, it won't decode them.

My guess is that your 6ch AC-3 stream is ~640kbps, so that works great as a streamed output via either HDMI or optical. Since that receiver clearly can decode AC-3/DD, there is no problem with it coming from the WDTVLive box as a stream. Should you try to put it on a USB storage and play it directly from the app in the reciever, you might find it has difficulty there.

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You converted your AC-3 to AAC, but it could have been non-standard in some way, plus it could also have been left as 5.1/6 ch surround, instead of being downmixed. Since ALL the formats on page 124 of your manual that the receiver supports (incl. MP3, FLAC, AAC, OGG Vorbis, WMA/WMALossless, and LPCM) only allow for 2ch/stereo playback, that would explain the AAC not working. Plus, those are again FILES that it supports, not necessarily STREAMS (it isn't clear what streams beyond the standard LPCM/AC-3/DTS... are supported).

Scott

[sportflyer]

Thanks for a good explanation.

Since the Onkyo Receiver can implicitly support AC-3 as streams I will not bother with the extra process of converting to AAC . I reread the manual on Audio formats supported and definitely did not read it properly previously because it states clearly for 2 ch only. How careless of me. Yes I did leave the encoded AAC stream as 5.1/6 ch which is why it did not work.

I may just convert one movie to AAC audio but downmixed to 2 Ch Stereo just to check it out.

Thanks

[Cornucopia]

Good idea (checking it out). Yes, extra conversion means re-encoding and since it is to another lossy format, that means some more (though likely minor) loss of quality. Best to avoid if possible.

Good luck,
Scott