Tip!: We do not recommend enabling passthrough as the first thing you do. Only do that if you are very well informed about what it entails, because it’s probably not what you want here. Plex Media Player has the capability to perfectly decode most “HD audio” formats, and enabling passthrough creates drawbacks that you likely want to avoid. The “Plex Media Player decode of audio vs. Passthrough” section near the bottom of the article has useful information to read before enabling passthrough.
Digital audio can be complicated and there are certainly better places to get a detailed primer on the subject than this article. The text here should just be considered a quick overview. What you need to know is that there are two major ways to handle audio in the digital age, PCM (or direct or LPCM) and passthrough (or encoded).
PCM/Direct means that the audio decoding is done in software (e.g. Plex Media Player and Plex Home Theater does it) and then sent to the receiver that outputs the PCM streams (one stream per channel) to the speakers.
Encoded/Passthrough is what it sounds like: Plex Media Player takes the encoded stream and passes it to the receiver which does the conversion from encoded formats to PCM and then outputs it.
One important difference is where downmixing is done. For example, if you have 2 speakers connected to your receiver and you have source media with 5.1 channels, the audio needs to be downmixed to hear all the sounds. When you are outputting in PCM mode the downmixing happens in Plex Media Player; if you are running passthrough, the downmixing will happen in the receiver.
There are many digital audio formats. The most common are:
- MP3: Only carries 2 channels and is relatively low bitrate. Not that common in more recent files.
- AAC: The closest thing we can get to a universal standard these days. The drawback with AAC is that while it can carry 6-channel sound, not many receivers handle it natively and it’s not designed for it.
- Dolby Digital / AC3: Probably the most common multi-channel format. It handles at most 6 channels (5.1) and has very wide native support in televisions and receivers. However, it’s relatively low bitrate, so it might not give the best fidelity. Most TV shows have AC3 tracks.
- DTS: Most common for movies, handles 6 channels at most, and is widely supported in mid-range equipment and up. Low end equipment usually does not support DTS natively since there are licensing fees involved. The Apple TV, for example, supports AC3 but not DTS.
- TrueHD: TrueHD is Dolby’s successor to AC3. This codec is lossless and supports 8 channels. High end equipment is needed to get native TrueHD support.
- DTS-HD MA: The successor to DTS. It is backwards compatible with DTS. DTS-HD MA is lossless and supports 8 channels.
- Vorbis, FLAC: While these are not as common, both support multiple channels, but few receivers natively support them. FLAC is becoming more popular.
Setting Plex Media Player Preferences
You’ll configure your audio settings under Settings > Audio in Plex Media Player.
Here you set which interface you want to use when sending your audio out from your computer. There are three types to choose from:
- Basic: You connect something to the headphone jack or using built-in speakers on your laptop/computer. This configuration is very simple, but it also does allow you to select multichannel-PCM. Just make sure your setup supports it.
- Optical (S/PDIF): These connections most commonly use a S/PDIF connector. This is built-in to all Macs and most other modern motherboards have it as well. The S/PDIF protocol can play 5.1 with two data formats: Dolby Digital (AC3) or DTS.
- HDMI: This handles both video and audio and is the best choice if you want to have full codec support. HDMI has the most available bandwidth in its current form and handles all formats natively (e.g. AC3, DTS, TrueHD, DTS-HD MA, LPCM (both stereo and multichannel).
This setting can easily lead to misconceptions. Our recommendation is to set this to the amount of speakers you have connected to your receiver, not how many speakers the receiver supports. If you are following our advice and not enabling passthrough, this setting is very important as Plex Media Player can’t know how many speakers you have.
- If you have 6 speakers (5.1), and a 5.1 receiver: choose 5.1.
- If you have a receiver which supports 7.1 but you only have 6 speakers (5.1) connected to the receiver, then you can choose 5.1 or 7.1 (but 5.1 is recommended!). If you play a 5.1 movie in Plex Media Player but have selected 7.1 in the channel settings, Plex Media Player will stream silence to the side speakers.
- If you want to play a 7.1 movie but only have 6 speakers (5.1) connected to a 7.1 receiver, make sure you have selected 5.1 in the dropdown, or your receiver may behave strangely.
Note: The values you choose are only used when not using passthrough.
The actual device used when not playing encoded or passthrough audio. Analog audio (and future sound effects) are output from this device.
Normalize Downmixed Volume
When downmixing from 7.1 or 5.1 to less channels, Plex Media Player will try to level out all channels to make the speech track more audible. If you hear distortion you can try disabling this.
Show Advanced Settings/Exclusive
If you want Plex Media Player to be the sole owner of audio on your machine while Plex Media Player is running, enable this. This will block out all other application sounds that might occur.
Show Advanced Settings/Various audio codecs
If you are using a digital connection (Optical or HDMI) and want to (despite our recommendation not to do it) use passthrough, you will need to set whether or not your receiver supports the audio formats that are listed. You can refer to your receiver/TV manual to find out what formats it supports (see explanation of formats above).
Tip!: If you mistakenly enable something you shouldn’t, it could result either in you receiving no audio at all or stuttering when Plex Media Player tries to send something unsupported to the receiver. If you are unsure, do not enable passthrough at all.
Plex Media Player Decoding of Audio vs. Passthrough
As you might have read at the top of this article we strongly recommend that you use the audio decoder that Plex Media Player is using. The reasons for this are many:
- Plex Media Player handles PCM better. Features like Settings for Plex Media Player can only work with PCM as there is no way to resample encoded data, and the worry about needing exclusive audio access is not there.
- Some operating systems (like Mac OS X) can not passthrough some audio formats, so issues will arise.
- If you enable passthrough for something that is not 100% supported on your device, you may just get noise, or silence.
So in short; when using decoding the only drawbacks are the lack of the extended Atmos data bits, and that your receiver will not light up the TrueHD light. Don’t worry, though: even if the pretty light doesn’t go on, you’re still getting identical sound!
Lastly; if you know what you do, it is absolutely possible to use passthrough. E.g. if you want the Atmos extra bits and you are using an operating system on the client side which supports it (for example Windows), then you can enable it. Just remember that if your TV does not support 23.976hz, or your computer does not support outputting 23.976 hz, you will not be able to enjoy the Sync Mode we call
Display. This mode resamples the audio slightly to allow the 0.1% speedup needed to avoid the 41.6 second judder that is plaguing some setups.
Still having problems? No audio?
Start your testing by unchecking all passthrough formats. If things work, enable options one at a time until you determine which causes problems.
Still having problems after that?
Make sure to screenshot your configuration, collect a debug log file, and create a new thread in our forums.