Key takeaways
- Bitstream, sometimes labelled Passthrough, hands the soundbar the original encoded track untouched, object-based metadata included, so the bar itself does the decoding.
- PCM means the television has already decoded the track before sending it onward, which strips out the object placement data that Dolby Atmos and DTS:X depend on.
- PCM exists for the television's own built-in speakers and for basic stereo systems, not for a soundbar or receiver capable of real surround decoding.
- Auto is usually the safer default on a modern TV, since it lets the source and the soundbar negotiate the correct format rather than forcing one manually.
- A soundbar left on PCM by mistake gets blamed for missing Atmos far more often than the actual TV setting does, which is an expensive misdiagnosis.
A customer once called convinced his new soundbar, bought specifically for the height channels, had arrived faulty. Movies played at full volume, dialogue was clear, and nothing overhead ever moved. The unit was fine. The television had been left on PCM since the day it was unboxed, and nothing about that setting announces itself on screen.
That single field, buried under sound or audio output settings on every modern TV, decides whether a soundbar gets the raw material Dolby Atmos or DTS:X actually needs, or a version already stripped down to something plainer. Understanding what it does costs nothing and takes about thirty seconds to fix once you know where to look.
What bitstream and PCM actually mean
Bitstream, sometimes labelled Passthrough on the same menu, hands the soundbar the encoded audio track exactly as the disc or streaming app produced it. Nothing is opened, decoded, or altered along the way. The object-based placement data that Dolby Atmos or DTS:X relies on rides along inside that stream, untouched, all the way to the bar.
PCM is the opposite approach. The television decodes the track itself first, converts it into plain linear channels of audio, and sends that already-processed signal onward. Whatever object metadata the original track carried is gone by the time it reaches the soundbar, because PCM has no way to describe a sound moving independently of a fixed channel.
Some TVs also offer multichannel PCM, up to 5.1, rather than plain stereo PCM. It fills more speakers than stereo PCM does, but it is still the television’s own downmix rather than the original track, so Atmos and DTS:X still lose their object placement data regardless of how many channels PCM happens to spread across.
Why televisions decode audio at all
PCM exists for a reason that has nothing to do with soundbars. Every television has its own built-in speakers, usually a pair of them, and for audio to reach those speakers the TV has to decode it internally regardless of what else is plugged in.
PCM output on the digital connection is really a side effect of that internal decoding path, made available as a convenience. It works fine for the television’s own small speakers, or for an ordinary stereo system with no interest in surround or object-based sound.
The trouble starts when a soundbar or receiver built for real decoding gets fed that same already-processed PCM signal instead of the original stream. It has nothing left to decode, so it plays back exactly what it is given: usually stereo, sometimes a basic multichannel downmix, never Atmos or DTS:X, no matter how capable the hardware actually is.
What actually changes once the setting is switched
| Bitstream or Passthrough | PCM | |
|---|---|---|
| Who decodes the audio | The soundbar or receiver | The television |
| Object-based metadata | Preserved | Lost |
| Works with a plain stereo system | Sometimes not | Always |
| Best choice with a modern soundbar | Yes | No |
Switch a system from PCM to Bitstream and the difference shows up immediately on the soundbar’s own display, not the TV’s. A bar that was quietly showing PCM Stereo or plain Dolby Digital switches to Dolby Digital Plus for a streaming Atmos title, or Dolby TrueHD for a 4K Blu-ray disc, the moment the correct format actually arrives.
I ran exactly this test on a Denon AVR-X1800H last winter, changing only the TV’s output field and touching nothing else. The receiver’s front display read PCM 2.0 for a full minute of test tone, then Dolby Digital Plus the instant Bitstream was selected, with the same cable, the same port, and the same source still in place.
Bitstream alone does not make streaming Atmos identical to disc Atmos, either. Streaming services deliver Atmos as Dolby Digital Plus, a compressed format that passes correctly over plain ARC. A 4K Blu-ray disc carries its Atmos track as Dolby TrueHD, lossless and considerably larger, which needs eARC’s extra bandwidth to get through intact, a distinction covered fully in why streaming Atmos is not Blu-ray Atmos.
The two connections most likely to carry that improved signal are covered in eARC versus ARC, since bandwidth still decides which formats fully make it through. Getting the port right and getting this setting right are two separate fixes, and both need to be correct before Atmos actually reaches the bar.
Where the setting actually hides on your TV
The menu wording differs by brand, which is most of why this setting goes unnoticed for months. Samsung labels it Digital Output Audio Format, LG calls it Digital Sound Output, and Sony tucks it under HDMI signal format or Audio Output.
Whatever the label, look for a choice between Bitstream, sometimes shown as Passthrough or Auto, and PCM. Auto is usually the safest pick on a modern television, since it lets the source and the soundbar negotiate the best format between themselves rather than forcing one manually.
Auto is not infallible, though. A few TVs default to PCM under Auto when they fail to recognise a connected device correctly, which happens more often with a third-party AV receiver than with a name brand soundbar. If Atmos still is not showing up with Auto selected, forcing Bitstream manually is worth trying before assuming the receiver itself is at fault.
TVs sold before around 2015 to 2016 often skip this choice entirely, offering only a fixed PCM output over HDMI with no Bitstream option anywhere in the menu. Those sets usually still have an optical output that carries a genuine bitstream, just capped at Dolby Digital 5.1 or DTS 5.1 and never Atmos or DTS:X, a limit covered fully in optical versus HDMI for TV audio.
The expensive mistake this setting causes
The customer mentioned earlier had already started pricing a soundbar with more height channels, assuming the one he owned simply could not produce the ceiling effect, before the actual fault turned out to be a ten second menu change on the television.
That pattern is common enough to name directly. A missing Atmos badge, flat sounding surround, or effects that never move overhead get blamed on the soundbar, the cable, or the disc, when the television’s own output setting is the real cause in a large share of cases.
Before spending money over missing Atmos, confirm the TV’s digital output is set to Bitstream, Passthrough, or Auto rather than PCM. It is the single cheapest check in the whole chain.
It is worth checking again after any TV software update, since several manufacturers have shipped updates that quietly reset this field back to PCM with no on-screen notice. Related settings that break the same way are covered in TV audio output settings that break your sound, worth a look if more than one symptom shows up at once.
A receiver that shows an Atmos badge but still sounds flat is usually a different fault entirely, one covered in why your receiver says Atmos but sounds flat. A soundbar that never had the chance to decode a track properly cannot be judged on the strength of that track alone, so confirm this one setting first before any cable or piece of hardware takes the blame for something a menu was doing all along.
None of this requires special tools or a technician’s visit. A remote, the TV’s own settings menu, and about a minute of patience are enough to rule this setting in or out, which makes it the first thing worth checking whenever surround sound or Atmos disappears without warning.
Questions readers ask about this
Choose Bitstream or Passthrough if the TV offers it, or Auto if it does not offer a manual Bitstream option. A modern soundbar or receiver is built to decode the original track itself, and PCM only exists as a fallback for the television's own speakers or a basic stereo system with no decoding of its own.
It can on some models, since Bitstream sends the encoded track to the external device rather than decoding it for internal playback. If both the TV speakers and an external soundbar need to work at different times, check whether the TV offers a separate setting for that rather than assuming Bitstream disables one permanently.
In most modern TVs, yes, since Auto simply lets the source and the soundbar agree on Bitstream when both support it. On older or more basic televisions, Auto can sometimes default to PCM for compatibility, so if Atmos still is not appearing, try selecting Bitstream manually instead of relying on Auto.
This usually means the source itself is not sending an Atmos track at all, rather than a setting problem. Not every piece of content carries Atmos, and a receiver correctly set to Bitstream will still show whatever format the original disc or stream actually contains.
Not for any content carrying Dolby Atmos or DTS:X, since PCM removes the object-based data those formats depend on before it reaches the soundbar. For plain stereo material with no surround content at all, the difference is negligible either way.
About the author
Rahul Gupta
Rahul Gupta has spent nearly a decade quietly wiring living rooms, testing soundbars in every awkward apartment layout imaginable, and untangling the kind of HDMI handshake problems that make people give up on Atmos altogether. He writes here about what actually works when you get the boxes home—not what the spec sheet promises. If a piece of gear on this site earns a recommendation, it earned it in a real room with real furniture, not a lab.
