Big difference in sound when decoding 7.1 to 5.1 by Infuse Pro and Plex

Hi,

I recently purchased an Apple TV 4K and decided to try out Infuse again, after favoring Plex over Infuse in the past. Playback of every video file is smooth. Even full 4K Bluray rips.

However I do notice a big difference between Infuse and Plex in volume/dynamic when playing a video with Dolby TrueHD 7.1 / DTS-HD MA 7.1. It seems to be a 7.1 to 5.1 problem only.

First a little information about my setup:

  • Samsung UHD 4K TV capable of passing through Dolby Digital 5.1
  • Sonos Playbar connected to TV with optical cable.
  • Apple TV 4K connected to TV with premium high speed HDMI cable.
  • Audio setting Infuse set to Automatic
  • Apple TV audio setting set to “Best Available”.
  • Reduce loud sounds Apple TV is set to “off”

Naturally I am aware that the 7.1 stream is downsampled to Dolby Digital 5.1 in both cases and that is just fine (I really like my Playbar, so don’t suggest upgrading to a different sound system) but when this is done by Plex (on my laptop) the sound is much more dynamic (louder/clearer if you will) than the same file being decoded by Infuse on Apple TV 4K. It really lacks “volume” or “punch” in a lot of scenes.

I have tested this with a lot of recent movies like Avengers and Tomb Raider, as well as speaker check files from Dolby Itself. Playing the speaker check files confirms both Infuse and Plex are decoding the channels the same. Infuse is just a lot less dynamic/loud. I don’t want to use the volume boost to compensate for volume. My opinion is that both Infuse and Plex should decode and encode 7.1 the same, or am I wrong. Any help is appreciated.

Welcome to the forum!

One thing you may try is switching to a different audio track, if present in your videos. In many cases, this will result in better quality and avoid some of the side effects introduced when the Apple TV converts the 7.1 lossless PCM audio to lossy Dolby Digital 5.1.

I would also suggestion switching the Apple TV’s audio output setting to Dolby Digital, as this will ensure the audio is not getting converted again by your TV before it goes to your Sonos.

Thanks for your reply! Selecting a different audio stream whenever possible is something I do for obvious reasons. Does this mean the conversion to 5.1 is strictly done by the Apple TV and not by Infuse? So from 7.1 Dolby TrueHD to 7.1 LPCM by infuse and from 7.1 LPCM to Dolby Digital 5.1 by Apple TV?

In essence, Infuse will losslessly convert the 7.1 TrueHD to 7.1 PCM and send that to the Apple TV. If the device connected to the Apple TV supports 7.1 PCM, then the Apple TV will send that without changing it. If it does not support 7.1 PCM, the Apple TV will drop the 2 extra channels and send it as 5.1 AC3 or downmix it to 2.0 PCM.

So, in your case since an optical cable is involved, the best you can do is 5.1 AC3. However, depending on how the Apple TV is detecting your TV, it could potentially be sending 2.0 stereo instead of 5.1. Changing the Apple TV setting to Dolby Digital would force the Apple TV to send 5.1, which may help.

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I can tell I’m getting 5.1 Dolby Digital in the Sonos App, so that is not the problem. Perhaps the Apple TV is indeed simply dropping the extra channels instead of down sampling them into the 5.1 channels. I’ll experiment some more. Thanks for your help!

It’s worth noting that by using an optical cable, you’re already limited to lossy multi-channel audio. You’re not really losing anything by switching the Apple TV to DD 5.1 output. I suppose you’ll get lower bitrates from films with a DTS track, but eh, lossy is lossy. Difference probably won’t be noticeable on your setup.

So I am testing this out now since I noticed a HUGE difference in Plex decoding versus Infuse decoding and absolutely hear a difference with dynamics and volume being better through Plex-infuse instead of SMB-Infuse.

Now I have a Sonos 5.1 using the HDMI based Beam. My TV is capable of DD 5.1. Wondering what settings or configuration would be best.