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PCM or Bitstream from Blu-ray Player

Scott Wilkinson  |  Feb 3, 2012

Which is best, PCM or bitstream from a Blu-ray player to the A/V receiver? I have reviewed many posts on various forums, but I have not found a definitive answer. I have an Onkyo TX-SR608 AVR and an LG Blu-ray player capable of decoding DTS-HD Master Audio and Dolby TrueHD lossless audio. I view Blu-ray discs and regular DVDs about 50/50; certainly Blu-ray when available. Should I set the player to output PCM or bitstream? Why one over the other? Do I need to tell the AVR which stream is incoming?

James

In terms of audio quality, it doesn't matter; the results should be identical either way. I suppose there might be a slight difference between the decoder in the player and AVR; to find out, all you have to do is try it both ways and see if you hear a difference. I bet you won't. And you shouldn't have to tell the AVR which stream to expect; it should detect and process the stream automatically.

The main reason to use PCM instead of bitstream is that with PCM, you can hear any secondary audio that might be on the disc—things like commentaries during the movie and sounds when you click on a menu item. In most cases, if you select the bitstream output, the player does not mix the secondary audio with the main soundtrack, so it is not sent to the AVR. Some players offer a "bitstream/re-encode" option that re-encodes everything to standard DTS or Dolby Digital, and you can hear the secondary audio in this case, but I don't recommend it because the lossless audio is converted into lossy audio, lowering the sound quality.

Home Theater reviewer Tom Norton generally uses the bitstream output, because that way, his Integra pre/pro indicates exactly which format he's listening to. If he selects the PCM output, the pre/pro only indicates that it's multichannel. Your Onkyo AVR does something similar as seen in the drawing of its display above, so if you want to be sure of which format you're hearing—and you don't care about the secondary audio—use bitstream. Otherwise, use PCM so you can hear the secondary audio.

If you have an A/V question, please send it to askhometheater@gmail.com.

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