I have a Rasplex 1.6.1 PI3 connected to an HDMI/SPDIF splitter, which goes off to an optical-only AV receiver plugged into a 5.1 speaker setup and the TV gets the HDMI.
AC3 and DTS 5.1 surround sound works perfectly fine (I guess it is passed through directly to the receiver). However, on files where the 5.1 audio is encoded with AAC, the central channel is extremely quiet (it was inaudible completely with 1.0.3, so something has changed for the better). Choosing 4.1 output in the audio preferences makes move the dialogues to the front LR speakers, but at least it’s audible.
What am I supposed to change to make this behave correctly? Dowing a central channel boost on downmixing doesn’t do anything, since I suppose I am not downmixing.
Non-surround audio works perfectly fine.
Thanks for any help!
Doing a tvservice -a gives me:
AC3 supported: Max channels: 6, Max samplerate: 48kHz, Max rate 640 kb/s.
DTS supported: Max channels: 7, Max samplerate: 48kHz, Max rate 1536 kb/s.
so it is missing the PCM, which I guess is a funny feature of the audio splitter.
An example mediainfo of a file that is problematic:
Media
Video Resolution 1080p
Duration 21:58
Bitrate 1734 kbps
Width 1920
Height 1080
Aspect Ratio 1.78
Container MKV
Video Frame Rate 24p
Audio Profile lc
Video Profile high
Part
Duration 21:58
File Movie.mkv
Size 272.47 MB
Audio Profile lc
Container MKV
Indexes sd
Video Profile high
Codec H264
Bitrate 1734 kbps
Language English
Bit Depth 8
CABAC true
Chroma Subsampling 4:2:0
Color Range tv
Color Space bt709
Duration 21:58
Frame Rate 23.976 fps
Frame Rate Mode cfr
Height 1080
Level 4.1
Pixel Format yuv420p
Profile high
Ref Frames 4
Scan Type progressive
Width 1920
Codec AAC
Channels 5.1
Audio Channel Layout 5.1
Duration 21:58
Profile lc
Sampling Rate 48000 Hz
Codec SRT
Format SRT
I’ve only just realised that the issue is that SPDIF, which is how I connect to the AV receiver, only has enough bandwidth to carry 2 channels of PCM. So whenever the audio is not AC3 or DTS, Rasplex decodes it to PCM and only the LR channels are passed on the optical fibre.
So maybe this is a PMS question more than Rasplex but is there some way of forcing of transcoding the audio to be AC3/DTS if it has more than 2 channels (in particular for my 5.1 AAC files).
[Edit]
I see some references being made to rasplex 1.6 experimental option to transcode audio to AC3, but this is probably for the DTS streams? I’d like to leave the DTS alone and only do it for AAC etc.
If it can’t be done, is there some utility which would do it on my library?
@Wigster said:
I see some references being made to rasplex 1.6 experimental option to transcode audio to AC3, but this is probably for the DTS streams? I’d like to leave the DTS alone and only do it for AAC etc.
Hi: this is exactly what I am trying to avoid, since it kills the surround sound I have in my 5.1 AAC files. I would love to be able to transcode these to 5.1 AC3/DTS on the fly which my AV receive understands.
In fact from the OpenPHT 1.6.0 release notes:
…
•OpenPHT: Direct play of HEVC and other codecs ffmpeg 2.8 supports
•Transcode audio to AC3 for use with optical out <======
…
How do I turn this on? Or is it not in rasplex because of the CPU limitations?
The RPi has no optical out, however, in Audio Output, set Number of channels to 2.0, enable Passthrough, check Dolby Digital (AC3) capable receiver, check Enable Dolby Digital (AC3) transcoding, enable DTS capable receiver.
This is the same as kwiboo outlined, did you actually try it?
If you have tried everything suggested by the Rasplex guys then you’re kinda stuck.
It does beg a question though, if you knew that your setup didn’t support LPCM then why did you rip your media with AAC5.1 audio, surely AC3 would have been a better option. Suggest that you re-rip your media using an audio format that your setup supports.
In you ‘acquired’ your media from dubious sources then the only option is to remux the audio from AAC5.1 to AC3 5.1. Plenty of tools on the Internet to perform this task.
I had no idea about any of the surround-sound things until last month when I moved to a new apartment where the landlord left his ancient 5.1 AV setup. So now I’m learning of my past errors.
Anyway, I apologise: I completely missed the fact that a new item appears in the AC3 menu to enable transcoding when you select 2.0 speakers. Indeed now it seems that all my non-DTS media is being received by the AV receiver as AC3, so exactly what I wanted.
But is this AC3 5.1 when the original is 5.1 or is it just 2.0? The AV receiver seems to spread the audio to all 5 speakers for both 2.0 and 5.1 sources, so it’s hard to tell. If it’s just 2.0 (which would make sense from the menu selections), is it because it’s impossible to transcode AAC 5.1 > AC3 5.1 on the Pi?
Just used this thread to fix some audio problems with some users. Thanks! AC3 Transcode functionality works great.
Question: If DTS is disabled and AC3 Passthrough support exists, can you enable DTS-HD decode and AC3 transcode so all of the transcoding is done on the Pi? I have a user setup this way and I see it transcoding DTS twice. PMS transcodes DTS to AAC, then the rPI2 trancodes AAC to AC3.
Disable Passthrough and enable Support 8 channel DTS-HD audio decoding, this is done on the RPi. The receiver might not show the right label but the sound is correct for all audio types. (Although the option says 8 channel, if you only have 5.1 (6 channels) then that is what’s supported).
I tend to use this setting on one of my RPi’s connected to an older amp and AAC5.1, AC3, EAC3, DTS and DTS-HD play fine.
