Will the optical cable’s pure, interference-free notes hit the high mark, or does HDMI’s one-cable-to-rule-them-all approach steal the auditory crown? And what about Dolby Atmos – can this atmospheric sound giant be contained within the fibers of optical technology, or does it demand the broader realms of HDMI? For the curious sound seeker, this isn’t just about connecting tech; it’s about orchestrating an audio experience par excellence.
Pros and Cons of Optical Cable
- Consistency in Audio Quality: Optical cables transmit audio signals via light, ensuring that the signal remains free from any electrical interference that can occur with electrical cables, potentially offering a more consistent audio quality.
- Physical Flexibility: Optical cables are typically more flexible than HDMI cables, making them easier to install in tight spaces.
- Isolation from Electrical Interference: Since optical cables use light to transmit data, they are immune to electromagnetic interference, which can be a significant advantage in areas with a lot of electronic noise.
- Bandwidth Limitations: Optical cables have bandwidth limitations. They can handle standard Dolby Digital and DTS audio, but they lack the capacity for higher-resolution audio formats that are common with Blu-ray and ultra-high-definition content.
- Lack of Audio/Video Sync: Unlike HDMI, which can carry both audio and video signals, optical cables are audio-only. This means that users need a separate cable for video, which can complicate setups and synchronization.
- Fragility: Despite their flexibility, optical cables are made of glass or plastic and can be brittle. They are prone to break if bent too sharply or stepped on.
Bitrates and Frequencies of Optical vs. HDMI Audio
Optical connections typically support:
- PCM: Up to 2 channels with a bitrate of up to 1.5 Mbps and a frequency of up to 96 kHz.
- Dolby Digital: Compressed 5.1 surround sound with bitrates up to 640 kbps.
- DTS: Compressed 5.1 surround sound with bitrates up to 1.5 Mbps.
- Dolby Digital Plus: Although capable, it’s not standard, and often downmixed due to the optical’s maximum bitrate of approximately 1.5 Mbps.
Optical cable’s frequency response usually maxes out at 96 kHz, which is ample for high-quality audio but does not reach the high-definition audio standards that HDMI can support.
In contrast, HDMI supports a far broader and higher quality range of audio formats, with substantially greater bitrates and frequencies:
- PCM: Up to 8 channels with a bitrate as high as 6.144 Mbps (which equates to eight channels of 24-bit/96 kHz audio) or even higher with HDMI versions 1.3 and above.
- Dolby Digital Plus: Bitrates up to 1.7 Mbps for compressed 7.1 surround sound.
- Dolby TrueHD and DTS-HD Master Audio: Lossless formats with bitrates up to 18 Mbps (HDMI 1.3 and above) and frequencies up to 192 kHz.
- Dolby Atmos and DTS:X: Object-based formats do not have a fixed bitrate because they adapt to the complexity of the audio. The total bitrate, including all the audio elements of a Dolby TrueHD with Atmos soundtrack, can be up to 24.5 Mbps on Blu-ray and up to 18 Mbps on streaming platforms.
- PCM Multi-Channel: HDMI 2.0 increases audio resolution support up to 32 audio channels and up to 1536 kHz sample frequency for incredible fidelity.
The advancements in HDMI technology have even pushed these limits further. For example, HDMI 2.1, which supports eARC (Enhanced Audio Return Channel), has a bandwidth capability that allows for up to 37 Mbps for audio alone, accommodating the most sophisticated audio formats available.
While optical audio delivers enough bandwidth for standard digital surround sound formats, it’s the expansive bitrate and frequency capabilities of HDMI that cater to the demands of high-resolution, multi-channel audio formats used in modern home theaters and professional audio setups. HDMI not only surpasses optical in pure audio throughput but also in its ability to seamlessly integrate into the ecosystem of 4K and 8K video, HDR content, and the corresponding audio formats that these advanced visuals demand.
Maximum Audio Quality of Optical Cable
Optical cables (also known as TOSLINK) typically support audio formats up to 24-bit/96kHz in quality. They can deliver 5.1 channels of audio, which is enough for basic home theater setups. However, they fall short when it comes to high-bitrate audio like DTS-HD Master Audio, Dolby TrueHD, and the newer object-based audio formats such as Dolby Atmos or DTS:X, which require greater bandwidth.
Can Optical Cable Carry Dolby Atmos?
No, optical cables cannot carry Dolby Atmos. Dolby Atmos requires the bandwidth and audio return channel (ARC) capabilities that are inherent in HDMI but are not supported by optical cables. Dolby Atmos combines traditional surround sound with additional channels to create a 3D sound experience, and this data-rich audio format exceeds the capacity of optical technology.
Using HDMI and Optical Simultaneously
It is technically possible to use both HDMI and optical cables at the same time. For instance, if you have a gaming console or a Blu-ray player, you can use HDMI to transmit both audio and video to your TV and an optical cable to transmit audio to a separate soundbar or home theater receiver. This setup could be useful if your audio device does not support HDMI ARC or if you want to ensure the most direct audio path to your sound system. However, in most modern setups, HDMI alone would suffice as it can handle both high-definition audio and video, simplifying the system and reducing cable clutter.
Whether optical audio quality is “better” than HDMI is not a straightforward question. Optical audio is capable and reliable within its limitations, providing clear sound quality free from electronic interference. However, HDMI is the more robust solution, capable of delivering the full range of audio data required by the latest high-definition audio formats. For users looking to future-proof their systems or those who demand the pinnacle of audio quality with formats like Dolby Atmos, HDMI is the preferable choice. Optical remains a valid option for setups with less demanding audio requirements or where electrical interference is a concern.