Server Version#: 1.26.2.5797
Player Version#: 9.3.0.32977
Hi guys. I recently had to factory reset my Android OTT box which I used to run the Plex Media player. Regarding Audio I was using the Passthrough mode to send 5.1 streams to my audio subsystem over an optical fibre (toslink)
It was working before the factory reset, it is no longer working now. I am not sure what was the version of the Plex Media PLayer before the reset but now I cannot make it work anymore and I see that 5.1 audio streams are transcoded (on the server) into MP3 streams which probably explains why (as far as I understand MP3 is a max of 2 channels)
In another thread I saw that someone at plex said that Optical S/PDIF could only carry 2 PCM uncompressed channel. Which is not true (see wikipedia for example) but may explain the regression
The box is a Formuler Z8. The input audio stream being AAC 5.1 or EAC3 5.1 I configured the Plex app with Passthrough → Optical → DTS. As suggested by @anon18523487 I tried all possible settings with the surround output (Always, Never, Auto). The server always performs a transcoding operation of the input audio stream to MP3 regardless.
I tried the same with Passthrough → Optical → AC3. the server performs an AC3 transcodage but the movie does not play (no progress, black screen, I can move forward but will get a steady picture and no sound). In this configuration the box freezes occasionally.
In the Android "Sound"settings I also have “SPDIF output” set to “RAW”. I believe Raw is the correct setting but I am little at lost here . I tried also LPCM with no better luck (did not try all possible combination though)
Set passthrough = optical and enable both codecs.
EDIT: Set the SPDIF output to RAW, not LPCM.
Set your server for debug level logs: Settings → Server_Name → General (show advanced).
Play a video with AC3 5.1 audio for ~20 seconds.
Repeat with dts 5.1 audio (not dts-HD).
Wait 2 minutes for server to settle.
Pull logs & post to thread.
If you need some test files, go to The Digital Theater. They’ve Dolby and DTS trailers in the Audio/Video Format Trailers section. Ex: Amaze AC3 5.1 in the Dolby section and Animated Logo in the DTS section. Put them in an Other Videos library so Plex will not try to match them with any movies or shows.
Those do not set the output, they enable passthrough of that specific codec. i.e. allow AC3 and/or DTS passthrough. If your input in AAC 5.1 or EAC 5.1, that passthrough setting won’t do anything. Optical only allow 2.0 AAC and does not support EAC3.
someone at plex said that Optical S/PDIF could only carry 2 PCM uncompressed channel. Which is not true (see wikipedia for example)
“S/PDIF can carry two channels of uncompressed PCM audio”
Try playing something with 5.1 AC3 audio and see if passthrough works. If this doesn’t send me the android logs from the playback attempt so I can check what is going on.
OK I understand the semantic now. What I don’t understand, and actually got me confused, is that the server starts a transcoding operation of the audio to mp3. Why not a conversion to “something 5.1” supported by the optical wire ?
Anyway I will try to find something with 5.1 AC3 audio and see what happens. Thanks
It can, but it depends on what your box supports and what your receiver supports.
I found this on the specs for your Z8. formuler | Z8
Audio Format : MPEG-1 Layer 1,2 , AAC-LC , HE AAC V1/V2
It looks like your box only supports MP3 and AAC audio. The only way to get multi channel would be to use the HDMI out with AAC audio and not optical. If your receiver doesn’t support HDMI, then you are out of luck.
Well I am pretty sure I managed to have 5 channels in the past. There is a “raw” mode in the configuration of the audio output which I believe will just pass the audio stream to the home cinema as-is. I will try to produce a log. Thank you for your help.
I am sure I was using optical output. I must be wrong somewhere else.
Now If I forget the passthru mode shouldn’t the server be able to transcode the source to AAC 5.1 ? If yes how do I tell the server (or the client) that my audio system supports AAC 5.1 ?
. I tried also LPCM with no better luck (did not try all possible combination though)
