Key takeaways
- Optical is the single biggest reason for an outright rejection rather than a quiet downgrade, since TOSLINK cannot carry anything past Dolby Digital 5.1 or DTS 5.1.
- A source fixed to a specific PCM or bitstream setting instead of Auto is the second most common cause, and switching back to Auto resolves most of these without touching anything else.
- Only one HDMI input on most TVs is wired for eARC, and formats like Dolby TrueHD and DTS-HD Master Audio get rejected outright on any other port.
- If firmware, ports, and settings all check out and the error still appears, it usually means one specific title used a newer codec revision the hardware genuinely cannot decode yet.
The message on screen is blunt: format not supported, or something close to it, right in the middle of an episode that played fine last week. No audio at all, sometimes a jarring beep tone the receiver uses for a signal it does not recognize.
Five causes explain nearly every version of this error, worth checking in the order they most often turn out to be the answer, starting with the physical connection rather than assuming a broken app or a broken soundbar.
This is a different fault from a dropout or a stutter. A dropout usually means the format is being received and rendered, just interrupted for a moment by something upstream. A rejection means the receiver looked at what arrived, decided it could not handle it, and said so outright, which points the troubleshooting in a completely different direction from the start.
Optical asked to carry a format it was never built for
This is the single most common cause of a flat rejection rather than a quieter downgrade. TOSLINK optical was designed years before object based formats existed, and it physically tops out at Dolby Digital 5.1 or DTS 5.1, both channel based with no spare capacity for anything more.
If a soundbar connects to the TV by optical alone and a source hands it Dolby Atmos, DTS:X, or even a plain 7.1 signal, plenty of receivers reject the signal outright rather than quietly downmixing it, which produces exactly this error instead of a silent stereo fallback.
The test is simple: check the physical connection. If it is optical, and the error appears specifically on Atmos or DTS:X titles while stereo content plays fine, that is the entire explanation, and no menu setting will fix it. Optical versus HDMI for TV audio covers exactly what each cable type can and cannot carry, worth confirming before anything else.
Bitstream and PCM set to disagree with each other
Past the optical case, a mismatched bitstream or PCM setting is the next most common cause. A source fixed to a specific multichannel PCM format, or pinned to one bitstream codec the receiver was not expecting for that title, produces a rejection rather than a graceful fallback on plenty of hardware.
A concrete case: a Denon AVR-X1800H paired with an Apple TV kept rejecting one particular 7.1 title with a format not supported message, while every 5.1 title on the same app played normally. The Apple TV’s audio output had been fixed to a specific format rather than left on Auto, so it kept offering the receiver a channel count it had not negotiated for that source. Switching the setting back to Auto let the two devices negotiate correctly, and the error did not return.
Bitstream versus PCM and which one to choose covers this setting in full, including why Auto is usually the safer default over a fixed selection unless one specific fault calls for pinning it.
An HDMI port that looks right but is not the eARC one
Many TVs carry several HDMI inputs, but typically only one is wired for eARC, usually labeled as such, and formats needing that extra bandwidth, DTS-HD Master Audio and Dolby TrueHD from a connected disc player in particular, get rejected outright on a plain ARC or standard HDMI port rather than just quietly downgrading. The HDMI specification’s own documentation on eARC explains why that bandwidth gap exists between the two.
Check the TV’s manual or the port labeling itself for the specific eARC input, and confirm the soundbar or receiver plugs into that exact port rather than one nearby that looks identical. Which HDMI port to use for your soundbar covers how to identify it on TVs where the labeling is not obvious.
| Connection or setting | Formats it typically rejects outright | Fix |
|---|---|---|
| Optical (TOSLINK) | Atmos, DTS:X, most 7.1 tracks | Switch to HDMI ARC or eARC |
| Fixed PCM output | Any bitstream-only codec | Set the source to Auto or Bitstream |
| Standard ARC port | Dolby TrueHD, DTS-HD Master Audio | Move to the labeled eARC port |
Firmware that predates the format entirely
Occasionally the receiver or soundbar is simply too old in software terms to recognize a newer codec revision, even where the hardware could technically decode it. A firmware update adds support for edge cases like this more often than shoppers expect from what looks like a mature, finished product category.
Check the manufacturer’s own support site for the exact model and look specifically for an audio codec entry in the changelog, not just a general bug fix note. Firmware updates: benefits and risks covers how to check this without installing an update that quietly breaks something else that was working fine.
This cause is more common with newer object based extensions to existing formats than with the core formats themselves. A soundbar bought three or four years ago almost certainly handles plain Dolby Atmos and DTS:X fine, but a later revision of either format aimed at a specific streaming partner can sit just outside what an older decoder chip was built to parse, even with every other setting correct.
A channel count mismatch between source and speaker layout
A source outputting 7.1 PCM to a soundbar physically wired for 5.1 or fewer channels sometimes triggers an outright rejection rather than a silent downmix, particularly on soundbars with a fixed internal channel mapping instead of flexible decoding.
Dropping the source’s audio output setting to match the actual speaker count connected, rather than the maximum the source device is capable of producing, usually clears this within a menu or two. What matters here is simply that the number of channels the source thinks it is sending has to match what the speakers can actually accept. DTS’s own overview of its object based format is worth a read if the rejected title specifically carries DTS:X.
- Confirm the physical connection is HDMI, not optical, if Atmos or DTS:X is involved
- Set the source device’s audio output to Auto rather than a fixed format
- Confirm the soundbar or receiver uses the TV’s labeled eARC port specifically
- Check the manufacturer’s site for a firmware update mentioning audio codecs
- Match the source’s channel output to the number of speakers actually connected
A native smart TV app and the same service running on a separate streaming stick plugged into the same TV can behave differently for this exact error, since each device negotiates the handshake independently. Smart TV apps versus a streaming stick covers why swapping the source device is a legitimate troubleshooting step here, not just a preference.
When the error persists after all of this
If optical is not the connection, the source is set to Auto, the eARC port is confirmed, firmware is current, and the channel count matches the speakers, the fault is likely a genuinely unsupported codec revision unique to one specific title, which does happen with newer object based extensions on older hardware. What streaming audio formats actually deliver covers how service-side encoding choices occasionally sit just ahead of what older hardware was built to decode.
At that point, the practical fix is waiting on a firmware release, or trying an alternate output setting for that one title only, rather than repeating the same five checks. If the error is limited to one title while everything else plays normally, note the specific app and title for the manufacturer’s support line, since a compatibility bug affecting a narrow slice of content is exactly the kind of report that gets resolved in a future update rather than by replacing hardware.
One more thing worth ruling out before giving up: a temporary app glitch rather than a hardware or setting problem at all. Force closing the streaming app, or power cycling the streaming stick or smart TV entirely rather than just returning to the home screen, clears a surprising number of one-off rejections that never recur once the app restarts cleanly. It costs two minutes and rules out the cheapest possible explanation before anything gets swapped or reconfigured.
Questions readers ask about this
Different titles are frequently encoded with different audio tracks, some in plain 5.1, others in Atmos or DTS:X. If your setup can only handle the simpler tracks, only the more demanding titles trigger the error, which is why the fault looks selective rather than constant.
Rarely. It almost always means a mismatch between what the source is sending and what the connection or the receiver's current setting expects, most commonly an optical cable, a fixed PCM setting, or the wrong HDMI port. Genuine hardware failure is well down the list of causes.
Sometimes, particularly for a newer codec revision the hardware was not originally built to recognize. Check the manufacturer's changelog for a specific mention of audio codec support before assuming an update will help, since general firmware updates do not always touch audio decoding.
Casting from a phone routes the audio handshake through a different device entirely, bypassing whatever setting or app behaviour was causing the rejection on the smart TV itself. It is a useful diagnostic step for isolating whether the fault is the app, the TV, or the receiver.
No. A format not supported error is an active rejection, usually with an on-screen message or a warning tone, while no sound at all with no error message points at a muted output, a wrong input selection, or a disconnected cable rather than a codec mismatch.
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.
