I know this is a very specific topic for this message board, but I’ve already asked it on the Apple, Arcam, and Plex forums without any replies.
I have an M1 Mac mini running Monterey (12.2.1) and am using Plex Media Player (4.75.0) to play video files that are being served from a Synology DiskStation DS918+ (DSM 7.0.1-42218 Update 3) running Plex media Server (1.25.6.5577-7000). The computer is connected via an HDMI cable to the AV port on a Arcam AVR10.
When I play a video with an EAC3 5.1 or TrueHD 5.1 or 7.1 soundtrack, it’s output in stereo and the volume is very low. Is there a fix for this issue? I do not experience the issue with other Dolby Atmos, DTS, or other Dolby digital soundtracks.
Maybe what you should do instead of trying to troubleshoot the specific complicated details is just convert the audio using FFMPEG to a format that works for you – for example, EAC3 to AC3. This is a free open-source command line utility available for both Windows and Mac. The command line syntax may seem daunting but it’s well documented and once you get it right, it works very well. A starter here:
mplayer is also worth a try since it gives verbose output and will complain about any problems with the channel layout (e.g trying to play 5.1 surround sound on 2 channels without mixing)
btw ffprobeing a file gives information about the streams like Audio: eac3, 48000 Hz, 5.1(side), fltp, 640 kb/s (default)
Yes, that’s pretty much integral to how it works. It takes either the video stream and/or the audio stream, converts one or both to a different codec or else copies it unchanged, and re-muxes into a specified output file. Once you figure out the switches and arguments you need, it’s a simple one-step operation that is invoked by a single command line and can be put into a command file.
For example, this command will copy the video codec from infile.mp4 as is, while converting whatever multichannel audio codec there is to AAC at 192Kbps and downmix to two channels, and remux to outfile.mp4: