Dolby TrueHD Dolby TrueHD (Lossless Audio Codec)

What Dolby TrueHD is

Dolby TrueHD is a lossless, multi-channel audio codec developed by Dolby Laboratories for home video, used principally in Blu-ray Disc. Its compression layer is Meridian Lossless Packing (MLP) — the same codec family Dolby licensed for DVD-Audio prior to Blu-ray, although the two MLP implementations on DVD-Audio and Blu-ray are not mutually compatible.

Dolby's own positioning is that TrueHD delivers a bit-for-bit identical copy of the studio master — the defining property of a lossless codec, distinguishing it from perceptual (lossy) formats like Dolby Digital or Dolby Digital Plus that discard audio data the encoder predicts will be inaudible. In practice that means a decoded TrueHD track reconstructs exactly the same sample values the mixing engineer signed off on, where lossy codecs only approximate them.

How TrueHD encodes audio

On Blu-ray Disc, a TrueHD track may carry up to 8 discrete channels (7.1) of 24-bit audio at 96 kHz, or up to 6 channels (5.1) at 192 kHz — the underlying TrueHD codec spec itself reaches further (up to 16 channels at up to 192 kHz / 24-bit) but Blu-ray's profile caps it at the 7.1/96 kHz or 5.1/192 kHz ceilings above. TrueHD is variable bitrate, with a peak instantaneous bitrate including metadata of 18 Mbit/s; by comparison, DTS-HD Master Audio — the competing lossless Blu-ray codec — peaks at 24.5 Mbit/s on Blu-ray.

How much disc space TrueHD saves over uncompressed PCM depends on framing. MLP, the codec inside TrueHD, typically delivers about 1.5:1 compression on music material; Dolby's own marketing frames the same idea as 100 percent lossless audio in files half the size of uncompressed PCM — both phrasings describe a typical, not guaranteed, ratio, and actual savings vary with content. The two figures (≈33% reduction vs ≈50% reduction) are different framings of overlapping but not identical claims; a single universal ratio does not exist.

Dolby Atmos on UHD Blu-ray is delivered as a Dolby TrueHD bitstream with the Atmos object metadata layered on top, encapsulated in Dolby's MAT (Metadata-Enhanced Audio Transport) frames over HDMI 1.3 or higher; MAT itself is not a codec — AVPro Global describes it as neither a codec nor a format — it is a transport container that uses the multi-lane HDMI audio pipeline to carry both the lossless TrueHD bed and the Atmos object data to a compatible AVR.

TrueHD vs DD+ JOC, DTS-HD MA, and S/PDIF limits

TrueHD-Atmos and Dolby Digital Plus with Joint Object Coding (DD+ JOC) Atmos carry the same kind of Atmos object metadata, but the underlying audio bed is different: TrueHD is lossless and DD+ is perceptually lossy. UHD Blu-ray uses TrueHD-Atmos; every major streaming service (Netflix, Disney+, Prime Video, Apple TV+) embeds Atmos in DD+, not TrueHD, because DD+ fits inside the bitrate budget streaming infrastructure can deliver.

DTS-HD Master Audio is the competing lossless Blu-ray codec to Dolby TrueHD — both are bit-for-bit lossless and both target Blu-ray and UHD Blu-ray. On UHD Blu-ray, TrueHD has re-emerged as the carrier for Dolby Atmos, while DTS-HD MA remains common on titles with non-Atmos lossless audio (and is the carrier for DTS:X on UHD BD).

Legacy digital audio links cannot move TrueHD. S/PDIF — TOSLINK optical and coaxial digital — does not have sufficient bandwidth to carry a TrueHD bitstream, or more than two channels of PCM audio, so TrueHD pass-through requires HDMI. The same bandwidth gap shows up between HDMI ARC and eARC: standard HDMI ARC carries roughly 1–3 Mbps and cannot bitstream TrueHD, while eARC raises the audio link to roughly 37–38 Mbps and is what enables a TV to pass TrueHD (including TrueHD-Atmos from a UHD Blu-ray player feeding the TV first) to an AVR or soundbar — ARC can still carry DD+ JOC Atmos from streaming apps, which is why streaming-only Atmos works on ARC-only TVs while disc-quality TrueHD-Atmos does not.

Where TrueHD ships

UHD Blu-ray players bitstream TrueHD (and TrueHD-Atmos via MAT) over HDMI to an AVR or processor for decoding; every Blu-ray that carries a TrueHD track must also include a fail-safe Dolby Digital (AC-3) track per Blu-ray spec, so any player that cannot decode TrueHD still gets sound.

Streaming is the opposite story. No major streaming service (Netflix, Disney+, Prime Video, Apple TV+, Max) delivers Dolby TrueHD — all streaming Atmos is encoded in Dolby Digital Plus with JOC, because TrueHD's bitrate ceiling (up to 18 Mbit/s peak for audio alone) is incompatible with streaming bitrate budgets, and DD+ JOC was specifically engineered to carry Atmos object metadata at streaming-friendly bitrates.

Among streaming boxes that can also play local files, behavior diverges. Nvidia Shield (and recent Fire TV Cube/Max generations) support lossless audio pass-through, so they can bitstream TrueHD from local files (e.g., MKV rips) to an AVR; Apple TV 4K historically did NOT pass through bitstream audio — it always re-encoded to Dolby MAT — and only added a passthrough audio API beginning with the tvOS 26 beta surfaced in 2025, enabling future support for Dolby Atmos in TrueHD and DTS:X in DTS-HD MA from local-network sources.