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Discussion Starter · #1 · (Edited)
Hi,

I have a Sony STRDH550 receiver. Lately it keeps defaulting to "Linear PCM 480kHz" when I play blu rays. Not sure why, I keep going into settings, all looks good

This is when I have it in "Auto Format Decode" mode. I can manually switch it to dolby digital 5.1, but it does not sound like 5.1. It sounds like crap.

Any idea why this is happening and what linear PCM is? I looked at all of the documents it came with and they were not helpful.

When I play movies on netflix or watch them on tv the auto format decode plays them in dolby digital 5.1 and they sound great. The blu rays have sounded like crap though.
 

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The receiver is just telling you what is being sent to it by your Blu-ray disc player. You need to change the audio decoding settings in the player in order for it to send multichannel surround sound to your receiver. In particular, you need to set it to "bitstream" and to "disable secondary audio mix". You need to make both of those settings. Only one of them is insufficient. Also, those are the generic names for those settings. Your player might call them something else.

LPCM is the acronym for "Linear Pulse Code Modulation". It's essentially the same type of audio signal as is used on CDs. LPCM is the audio data type which is output by the player when it is configured to decode a Blu-ray disc's audio in the player. Most current Blu-ray players cannot decode Dolby or DTS high definition 5.1 surround sound tracks to 5.1 channel LPCM audio. They can only decode to 2.0 channel LPCM due to their manufacturers penny-pinching when paying the decoder license fees to Dolby and DTS.
 

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Discussion Starter · #3 ·
Hey,

Thanks for the input and clarification. Now I understand.

I actually googled it at the same time I was posting, and found similar answers, but not as in -depth. So once, again, thanks!!

Last night I changed the blu ray output to "pass through" or something along those lines. I couldn't find exactly what you wrote in the settings.

Once I did that, I popped in Inception, and the AVR now says DTS, and the sound is much better.

Great stuff!!
 

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Just to be clear, there should be no difference in sound quality between bitstream and LPCM. The settings only determine where the audio is decoded (in the player vs. in the AVR).

Most folks like the pretty DTS light to come on on their AVRs though, so they use bitstream. ;)
 

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Discussion Starter · #5 ·
Just to be clear, there should be no difference in sound quality between bitstream and LPCM. The settings only determine where the audio is decoded (in the player vs. in the AVR).

Most folks like the pretty DTS light to come on on their AVRs though, so they use bitstream. ;)

Alan, when my receiver was switching to Linear PCM for Blu Rays, the sound quality was good, but in stereo. When I pushed the "dolby digital" or "dolby pro logic" buttons, it tried taking the stereo sound and changing it to 5.1, so it sounded like crap. Almost all of the sound was coming out of the center channel.

When I switched the Blu Ray to "pass through" the audio to the AVR, the AVR then decoded it properly to 5.1 and the sound was great.

That's what my problem was, maybe I didnt explain it correctly. I am having the same problem now playing some 5.1 videos from my phone to the tv, but not sure to change that. When I play Netflix from my phone the AVR automatically decodes as 5.1
 
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