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AC3 Audio Playback Issues ...


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#1 Scrappy

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Posted 10 September 2011 - 06:15 AM

First off, I just spent this evening going through the forums, trying to see if I can't find *something* that works to fix this, and have tried as many solutions as I could find, all getting me nowhere ...

I am running a miniMac from early 2010 ... bought it just before they did the integrated audio/HDMI, of course.

OS: Lion (updated current) ... the problem existed before Lion, so it isn't related to the upgrade.
Plex: Version 0.9.3.4-397e914

I have an optical cable going from the miniMac to my DVD/Sound system (RCA RT317W) ... I've tried with Soundflower, and without, same effect ...

The problem is that when watch certain movies, or shows, I get sound, but not audio ... I can only describe it as 'static' ... I tried to upload an audio clip i recorded on my iphone, but theforum woul allow me to upload a .m4a file, and I don't know how to convert it to something else :(

Now, I watched, in this case, Penn&Teller's Bull#### Season 1&2, no problem, but their audio was recorded as:

Audio Stream #1
Codec.............................................MPEG Audio
Codec (FourCC)....................................55
Codec Profile.....................................Joint stereo
Audio Stream Length...............................29mn 52s 776ms
Audio Stream BitRate..............................128 Kbps
Audio Stream BitRate Mode.........................VBR
Number of Audio Channels..........................2
Sampling Rate.....................................48.0 KHz
Audio Stream Size.................................28.3 MiB (12%)
Audio Encoder.....................................LAME3.90.
Audio Encoder (Settings)..........................-m j -V 4 -q 2 -lowpass 17.6 --abr 128
Audio Stream Language.............................English


The Season 3 files, still AVI, but are AC-3:

Audio Stream #1
Codec.............................................AC-3
Codec (FourCC)....................................2000
Audio Stream Length...............................29mn 39s 796ms
Audio Stream BitRate..............................192 Kbps
Audio Stream BitRate Mode.........................CBR
Number of Audio Channels..........................2
Audio Channel's Positions.........................Front: L R
Sampling Rate.....................................48.0 KHz
Bit Depth.........................................16 bits
Audio Stream Size.................................40.7 MiB (17%)


I get the same audio results whether I use Built-In Output, or Soundflower ...

I've downloaded VLC, and both Season 2 and Season 3 play perfectly fine ...

I have two different movies, with again, same characteristics ... the one that Audio is AC-3 creates the same static as below, the other one works, with the following details:

Audio Stream #1
Codec.............................................MPEG Audio
Codec (FourCC)....................................55
Codec Profile.....................................Joint stereo
Audio Stream Length...............................1h 39mn 33s 0ms
Audio Stream BitRate..............................86.2 Kbps
Audio Stream BitRate (Nominal)....................128 Kbps
Audio Stream BitRate Mode.........................VBR
Number of Audio Channels..........................2
Sampling Rate.....................................48.0 KHz
Audio Stream Size.................................61.3 MiB (9%)
Audio Encoder.....................................LAME3.97
Audio Encoder (Settings)..........................-m j -V 4 -q 2 -lowpass 17 --abr 128
Audio Stream Language.............................English


So the only common thread so far as I can see is AC-3 vs everything else ...

And all of these files play *beautifully* (albeit small) on Plex for iOS, on my iPhone ...

Since VLC does work for both of the AC-3 files, with all the sound going out and through the same receiver as Plex, I *believe* that its something I've got mis-configured on the Plex side of things, but I'm perplexed in figuring out just what it is that I'm missing :(

Ideas / recommendations much appreciated ...

Thx

#2 Chris C

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Posted 10 September 2011 - 02:51 PM

My first recommendation would be to take a look at the audio settings in your Plex client under Preferences > System > Audio. In particular, try adjusting the "Digital Output Support" setting and (if active) the two sub-settings for it. Hopefully, this is just an issue of finding the correct settings.

If that doesn't work... getting some logs would be useful:

1. Close your Plex client and stop/quit the Plex Media Server.

2. Restart Plex, which will get us fresh logs.

3. In the client, first play an item that works correctly for you. Let it run a few seconds and stop.

4. Now, play an item with AC3 audio that causes issues for you. Again, let it run a few seconds and stop.

5. Zip up and attach the "Plex.log" and "Plex Media Server.log" files (see link in signature).

6. Just to make sure we're all on the same page, please let us know which file/library item you played first and second.

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#3 Scrappy

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Posted 10 September 2011 - 07:46 PM

That was it, and it was something obvious I should have tried ... disabled the "AC3 Capable Receiver" setting and now I can watch it all !!

Thank you ...