HDMI ARC vs Optical: Which Cable Should Carry TV Audio
Quick answer / TL;DR: Optical carries two-channel LPCM, Dolby Digital 5.1 and DTS 5.1 as light, and it has no control channel. HDMI ARC carries the same formats plus Dolby Digital Plus, and it uses CEC so the television remote can adjust the sound system and switch it on. eARC adds lossless LPCM, TrueHD, Atmos and DTS:X. For a new system eARC wins, then ARC, then optical; for a 5.1 system or an older receiver, optical is still correct.
Both connections exist to get audio out of a television, and they approach the job from opposite directions. Optical carries the stream away from the set as light, one way, with no return path and no control channel. HDMI ARC carries audio back up the cable that already feeds video into the set, which is why it is called an audio return channel. One is a dedicated pipe, the other a shared one with a lane reserved for the return trip.
This is the comparison: what each format carries, what each one lets you control, where optical still wins and which cable suits which pair of devices.
Two Sockets, One Job
The two ports sit within a few centimeters of each other on the back of most televisions, and they compete for the same task. Optical was designed as a dedicated audio output and does nothing else, which makes it predictable: whatever the set sends down the fiber arrives at the other end without negotiation. ARC was designed to save a cable, sending audio back along the HDMI link that already carries video into the television. The saving is real, and it comes with a dependency on the HDMI handshake that optical never has.
What Each One Carries
| Format | Optical | HDMI ARC | HDMI eARC |
|---|---|---|---|
| Stereo LPCM | Yes | Yes | Yes |
| Dolby Digital 5.1 | Yes | Yes | Yes |
| DTS 5.1 | Yes | Yes | Yes |
| Dolby Digital Plus | No | Yes | Yes |
| Dolby TrueHD and Atmos | No | No | Yes |
| DTS-HD Master Audio and DTS:X | No | No | Yes |
| Multichannel LPCM 5.1 | No | Limited | Yes |
The table is the argument in miniature. Optical and ARC overlap on everything S/PDIF was designed for: stereo, Dolby Digital 5.1 and DTS 5.1. ARC adds Dolby Digital Plus, which is what streaming apps actually send, and a limited form of multichannel PCM. eARC removes the ceiling and passes lossless object formats at full quality. If the question is only about a 5.1 soundtrack from a disc, both sockets answer it and the choice comes down to convenience.
Why the bandwidth gap exists
S/PDIF was specified for a two-channel stream at 48 kHz with room for compressed surround, and its frame carries roughly 6 to 8 Mbps at most. ARC borrows bandwidth from the HDMI link and manages about 1 Mbps of audio in practice, enough for compressed 5.1 and Dolby Digital Plus but not for lossless. eARC uses the dedicated Ethernet and Audio Return Channel pair in the HDMI cable to reach tens of Mbps. The numbers explain why a soundbar with only an optical input cannot be fed Atmos, whatever the television offers.
The Control Difference
The second difference is not about sound at all. HDMI carries CEC, the control protocol that lets one remote switch several devices and pass volume commands along the chain. With ARC, the television remote adjusts the soundbar's volume and the bar wakes when the set does. Optical has no control channel whatsoever: the television can send audio down the fiber but cannot ask the bar to raise its volume, so a second remote stays on the table and the bar does not switch on with the set.
CEC in practice
CEC is useful and temperamental. Brands implement it under different names, and a chain of three devices can produce a set that switches itself off when you only wanted the disc player to stop. When it misbehaves, the usual fix is to disable it on the offending device and go back to two remotes, which is the arrangement optical imposes from the start. That predictability is why some installers still prefer the fiber.
When Optical Still Wins
- The television has no ARC port at all, common on sets from before about 2015
- The receiver predates HDMI and has optical inputs only
- A ground loop hums through the HDMI or coaxial path and fiber removes it
- The chain is long and CEC keeps switching the wrong device on
- The source is a console or player with an optical out and the sound is 5.1 at most
Two of those cases are the important ones. A ground loop is a physical problem with an electrical solution: fiber breaks the circuit between two boxes on different outlets, and the hum disappears without a cheater plug or an isolation transformer. A system built around an older receiver has no reason to be replaced to gain a format it cannot use. Optical is not the better format in either case, only the one that fits the hardware already in the room.
Matching the Cable to the Gear Pair
- New television and new eARC soundbar – one HDMI cable, eARC, no optical needed
- New television and older ARC bar – HDMI for convenience, optical as the fallback if CEC fights
- Television and HDMI-era AV receiver – eARC for lossless, optical for legacy sources
- Television and stereo amplifier or DAC – optical, since there is no video return to bother with
- Console to a DAC or soundbar – optical where the console still has the port
The pattern in that list is that optical wins where there is no video to return and the audio is 5.1 or stereo, while HDMI wins wherever the television is the source and the sound system understands the return channel. Owning both cords is not waste: the optical cord is the diagnostic tool that shows whether a fault sits in the HDMI chain or in the television settings, and it costs less than a service call.
The Verdict
For a system assembled now, the order of preference is eARC, then ARC, then optical. eARC carries every consumer format including the object audio mixes and keeps the remote count at one. ARC is the same convenience with a lower ceiling, which is fine for a soundbar that cannot reproduce height channels anyway. Optical is the reliable floor: it carries Dolby Digital 5.1 and DTS 5.1 perfectly, it never suffers from CEC surprises, and it is electrically isolated from everything.
For the older system
If the receiver has no HDMI inputs, optical is not a compromise but the correct answer, and the television menu should be set to bitstream Dolby Digital rather than PCM so the surround reaches the decoder intact. If the receiver has ARC but the television predates it, the same advice holds. The one case where spending on an upgrade is justified is a soundbar that supports Atmos paired with a television that supports eARC, because there the HDMI path unlocks formats the fiber physically cannot carry.
Optical cords and HDMI cables are stocked as separate lines for exactly this decision: the fiber for legacy receivers, soundbars and DACs, and certified HDMI cables for ARC and eARC returns; the catalog lists the connector, the length and the certification per part number.
Related reading: The socket behind the fiber side of this choice: the optical port explained — optical-port
Related reading: The surround question in detail: does optical support 5.1 — does-optical-support-5-1
Frequently Asked Questions
Is optical better than HDMI ARC?
Not in format terms. ARC carries everything optical does plus Dolby Digital Plus, and it adds CEC volume control, so on a modern system ARC is the more capable socket. Optical is better in two narrower ways: it is electrically isolated, which kills ground loop hum, and it has no handshake, which makes it predictable when CEC misbehaves.
Can optical carry Dolby Atmos?
No. Atmos in the home travels as metadata inside a Dolby TrueHD or Dolby Digital Plus stream, and both sit beyond the S/PDIF bandwidth of roughly 6 to 8 Mbps. A television set to Atmos over optical will downconvert or output nothing. Atmos needs eARC, or an HDMI connection direct to the sound system.
Does optical support volume control from the TV remote?
No. The fiber carries audio only, with no control channel, so the television cannot change the volume on the receiving device. You use the sound system's own remote, or program a universal remote. This is the practical cost of the format, and it is the main reason ARC replaced it for everyday living room use.
Which should I use with an older receiver?
Optical. A receiver without HDMI inputs cannot accept ARC, and its decoder was built around Dolby Digital and DTS, which is exactly what the fiber carries. Set the television to bitstream Dolby Digital, plug into any optical input, select that input on the receiver, and the surround works without further configuration.
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