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 difference between the SPDIF RAW and SPDIF PCM audio ... 
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RAW usually means to put out the original bitstream whereas PCM means the decoding of that stream to uncompressed PCM.
What fits best to you depends. If your AV receiver is able to decode most of the common audio codecs (for SPDIF that would mean AC3 and DTS) you can leave it to RAW. When you set to PCM the PlayonHD will decode the supported audio codecs for you. But I'm not sure whether it will also Downmix the audio to Stereo.

Tue Jan 12, 2010 9:34 am
All audio codecs inside of video containers (avi, mkv, mov, mp4, etc..) are encoded with some type of complex digital algorithm (unless it actually is LPCM) and this must be decoded somewhere before it can be sent to a digital to analog converter. They get decoded into a non-complex digital signal known as LPCM (lineal pulse code modulation.) This can be done inside of the PlayOn!HD or in your AVR.

The problem is that things are encoded for a reason. To save space. A raw (encoded) digital audio signal using DTS, AC3 (Dolby Digital), Flak, Vogg, Mp3, etc. uses bandwith in the mega bits per second magnitude. LPCM is in the giga bits per second magnitude. SPDIF will support the bandwidth of 6 channels (aka 5.1) of DTS or AC3 but only 2 channels of LPCM. If you want surround sound to be played through your AVR system then you will want to keep it on Raw if you are using Toslink or Coax SPDIF to connect your PlayOn!HD to your AVR.

HDMI on the other hand can carry 8 channels of high bandwith LPCM sound and even more when the signal is still encoded.

The PlayOn!HD will downmix 5.1 channel encoded audio to stereo if you have SPDIF LPCM selected.

I hope this helps.


Tue Jan 12, 2010 3:35 pm
Thank you for the explanations, as I had the same question.

Tue Jan 12, 2010 8:08 pm
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