You bought the speakers, ran the cables and chose a film with Dolby Atmos on the cover. The receiver's display says PCM. Nothing is broken: somewhere along the chain, a device has decided to open the sound up and pass it on in a simpler form. Finding which one is mostly a matter of following the signal from the source to the speakers.
Follow the signal
Every sound starts in a source: a disc player, a streaming box, a console or an app on the TV itself. It then travels by HDMI to the receiver or soundbar, either directly or through the TV. Each device along the way can either pass the sound on untouched, which is called bitstream or passthrough, or decode it and send it on as PCM.
PCM is not bad sound. Multichannel PCM can be lossless and excellent. But once a device has turned a Dolby Atmos track into ordinary PCM channels, the height information is usually gone. The receiver can only show Dolby Atmos when the original track reaches it untouched.
ARC, eARC and the long way round
When the source is plugged into the TV, the sound has to come back down the cable to the receiver. That return trip is the audio return channel. Plain ARC was designed for stereo and compressed surround. On most TVs it can carry Dolby Digital Plus, which is usually how streaming services deliver Atmos, but not the lossless Dolby TrueHD and DTS-HD Master Audio tracks found on Blu-ray and 4K discs, nor multichannel PCM.
eARC, the enhanced version that arrived with HDMI 2.1, has far more bandwidth and carries all of them. So a common pattern, Atmos from apps but PCM or plain Dolby from discs, usually means the sound is travelling over ARC. The surest fix is the simplest layout: plug every source into the receiver and run a single cable from the receiver to the TV.
The receiver can only show Dolby Atmos when the original track reaches it untouched.
The settings that quietly decode
Most sources have an audio output setting, and several defaults choose PCM. Look for words like Auto, Bitstream or Dolby Atmos rather than PCM or LPCM. On a TV that passes sound on to a receiver, the matching setting is often called digital audio output, with options such as Passthrough, Auto or Bitstream.
Blu-ray players have one more trap: secondary audio, the setting that mixes in menu clicks and commentary. With it switched on, many players decode the soundtrack themselves so they can blend the extra sounds in, and the receiver sees PCM. Switch it off for films.
Read the display like a clue
Dolby Atmos, sometimes shown as TrueHD Atmos or DD+ Atmos, means everything upstream is passing the track on. Dolby Digital Plus or TrueHD without Atmos usually means the title, the app or the subscription has no Atmos version, or the receiver is in a listening mode that ignores the height layer.
PCM 2.0 points to a stereo setting somewhere, or to a TV app sending PCM over plain ARC. Multichannel PCM means a device decoded the surround track for you. Change one thing at a time, play the same scene, and watch the display: it tells you the moment the chain is clear. If you would rather work through it as a checklist, the troubleshooter in our free tools lists the steps by symptom.
