Originally Posted by gnicks
This may be a silly question, but I want to make sure I am getting full lossless sound.
I have an older 7.1 receiver, which, for whatever reason, never decodes Dolby Atmos content into full 7.1. Sometimes it puts out 5.1, sometimes even 6.1, but it never shows full 7.1 on Atmos tracks.
I just got a UBK90 and decided to use the PCM Multi-Ch out setting for audio. Am I right in assuming that this simply handles the decoding internally and sends out the lossless audio to the receiver?
My receiver is detecting proper 7.1 now, and I just wanted to make sure that there is no degradation in audio quality by using this setting over the Auto option where my receiver handles the decoding.
Yes, so long as your Receiver is not able to decode an Atmos Bitstream *AS* Atmos audio, you are fine letting the player do the decoding, and getting LPCM 7.1 sent to the Receiver.
I've written this up in my Blog post here:
Digital Audio 101
An Atmos track is a Dolby TrueHD 7.1 track with extra "sprinkles" which differentiate it as Atmos. Only an Atmos-capable decoder will use those sprinkles. The player will not use the sprinkles. And evidently your older Receiver ALSO will not use them.
But that means the decode should be of the underlying Dolby TrueHD 7.1 track. The fact your older Receiver is not decoding that into 7.1 speaker channels may indicate a mistake in your speaker configuration setup in the Receiver.
I recommend you play a calibration track while checking what's actually happening via the settings in your Receiver. You could use the Channel ID TrueHD 7.1 track from AIX Audio Calibration, Blu-ray. I've linked that disc in my Blog post here:
Set the player to produce LPCM output and play that track. You should get individual test tones sent to each of your 7 speakers and the Subwoofer.
Now set the player to produce Bitstream output, play that track again (now with Dolby TrueHD 7.1 going to the Receiver), and compare the result. If you are not getting individual test tones to each of your 7 speakers and the Subwoofer, recheck BOTH your speaker configuration and "Surround Sound" processing options in the Receiver. You may not have configured your speaker setup correctly, or you may have a Surround Sound mode active which is limiting output to 5.1 or 6.1 speakers. Try turning any such Surround Sound Mode OFF so that the audio is sent to the speakers without any down-mixing or any creation of more speakers of output from fewer channels of content.
I've written THIS up in my Blog post here:
Understanding Downmix and Surround Sound Processing
Note that if your Receiver is old enough it may be limited in the type of Bitstreams it can handle. For example, even though it can receive LPCM 7.1, it may be limited to 5.1 for the Lossless Bitstreams (Dolby TrueHD and DTS-HD MA). In such case, the player would automatically send a 5.1 Bitstream instead (perhaps with "matrixed" content for a 6th, Center Rear, speaker). Often this means you will get the "Compatibility" track from the disc instead of the full Lossless track. Check if your Receiver says it is actually receiving Dolby TrueHD 7.1 -- even though it is only decoding that into 5.1 or 6.1 speaker output. The Compatibility track for this would instead show as Dolby Digital 5.1.
If you ARE getting the Compatibility track, and if your Receiver is SUPPOSED TO be able to handle TrueHD 7.1 Bitstream input, double check that you have Blu-ray Secondary Audio Mixing turned OFF in the player.
Secondary Audio Mixing, combined with Bitstream audio output forces the player to output a lossless Bitstream -- DD 5.1 or DTS 5.1 -- whenever you are playing a Blu-ray disc which includes Secondary Audio anywhere in its contents.