bitstream vs software decode to AV receiver - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 5 Old 02-16-2015, 06:37 AM - Thread Starter
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bitstream vs software decode to AV receiver

Hi.

Is there a difference between playing an MKV file from my computer, through my XBMC (Kodi) which sends a DTS ES bitstream to my receiver, versus a theoretical situation where the same file is first decoded in software (by eg. ffmpeg) and sent as multi-channel PCM down the same path? Is there any quality difference? Does it matter that the DTS light doesn't turn on?

setup is:
Denon avr-2310
Apple TV 2 jailbroken to run Kodi 14.1
computer that shares movies using NFS to ATV2

File in question is a DVD I ripped LOTR with a DTS ES 6.1 soundtrack. Ripped it using Handbrake. Kodi is setup for passthrough when playing the file.

The reason I ask, is because I was trying out a new PC as a media center, running Kodibuntu. I found out they they rip out Pulse Audio (the audio subsystem in Linux) for the older ALSA subsystem, because of the fact that you cannot bitstream with Pulse Audio.

I then went on the Pulse Audio mailing list and asked why you couldnt do it, and got a response to the effect "we're not going to do it and we might just let ffmpeg decode the bitstream and send out PCM multi channel).

The guy I talked to seemed to think that there would be no difference sending already decoded DTS ES to the receiver in PCM format. I just wanted a second opinion! He did say that there won't be any dialogue normalisation, but from what I can gather, that's a bit irrelevant in a media center anyway (no commercials).
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post #2 of 5 Old 02-17-2015, 02:55 PM
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Quote:
Is there any quality difference? Does it matter that the DTS light doesn't turn on?
No and no.

Quote:
He did say that there won't be any dialogue normalisation
This is a good thing.
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post #3 of 5 Old 02-18-2015, 01:29 AM - Thread Starter
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Quote:
Originally Posted by Alan P View Post
No and no.



This is a good thing.
Do I need to do anything when playing already decoded dts as pcm? Do I need to turn master volume up by +4db to be able to compare? I played the film mkv through Plex Server which transcoded to PCM, and through Kodi, which bitstreamed the audio to the receiver, and the bitstream version was clearer (maybe because it was louder). It seemed like better quality.
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post #4 of 5 Old 02-18-2015, 05:04 AM
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We all share a hearing characteristic that causes us to prefer louder presentations. That is why we match levels exactly when we do bias controlled listening tests.
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post #5 of 5 Old 02-18-2015, 09:29 AM
 
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By default Windows will resample all PCM audio as defined in the advanced properties of your sound device. Whereas bitstream gets passed through directly. So yes, there is a difference unless you use an output scheme that bypasses the processing in the OS.

This is what the UI looks like in the control panel:

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