Plex transcoding
The server re-encodes audio when it believes the client cannot handle it — spatial metadata is the first thing discarded.
The Passthrough Problem
You hit play on a pristine 4K reference file with TrueHD 7.1 Atmos. Instead of an immersive soundscape, your AVR shows "PCM", the height channels vanish, or the server begins buffering aggressively. The hardware is capable, but the signal path is compromised.
Media Server Diagnostic
4K Reference
TrueHD 7.1
TrueHD 7.1
Reference Cinematic Title
4K HDR10
Dolby Vision
TrueHD Atmos 7.1
Video
4K (HEVC Main 10)
Audio
TrueHD Atmos 7.1 / DTS-HD MA
Bitrate
85.4 Mbps
Illustrative Cinema Machina diagram, not a client application
screenshot.
Signal Diagnostic: Transcode vs Passthrough
Transcode Risk
Source
TrueHD 7.1 Atmos
Output
FLAC / PCM
Metadata
Spatial Data Removed
Direct Play
Source
TrueHD 7.1 Atmos
Output
TrueHD 7.1 Atmos
Metadata
Object-Based Audio Intact
Illustrative Cinema Machina diagram, not a client application
screenshot.
Audit Shield Plex Atmos
Reading the Result
A playback chain either preserves the format or it does not. These are the states we look for.
Pass — chain preserved
- Bitstream handoff from player to AVR or soundbar
- Direct Play confirmed on the server dashboard
- Atmos or DTS:X metadata preserved to the decoder
- AVR reports the expected format, not a fallback
Fail — format lost
- Server transcoded the audio track mid-stream
- Decoded to PCM unexpectedly inside the player
- eARC blocked or negotiated below full rate
- Metadata lost — height layer silently absent
- Endpoint does not support the source format
Where It Breaks
Seven failure points account for nearly every lost lossless track we diagnose.
TV app limitations
Built-in TV apps rarely pass lossless formats, whatever the panel's spec sheet implies.
Player decodes internally
The device converts to PCM before the AVR ever sees the track — the display still says Direct Play.
eARC disabled or downgraded
A return channel negotiated at ARC rates strips high-bitrate audio without any visible error.
HDMI / EDID mismatch
The chain advertises the wrong capabilities, so every device politely agrees to a lesser format.
Reporting mismatch
The AVR or soundbar shows a format label that does not match what is actually being decoded.
Source not as expected
The file never carried the intended track — no configuration can restore what the source lacks.
The Solution
What Cinema Machina Verifies
To experience true lossless audio (Dolby TrueHD Atmos, DTS-HD MA, DTS:X), the client device must send the raw data (bitstream) directly to the AV Receiver without interference. We map the path before making configuration changes.
1. Source Verification
Hardware Capabilities
We verify that your playback client physically supports TrueHD and DTS-HD MA passthrough. Many popular commercial streamers decode internally and cannot be forced into true passthrough mode.
2. Passthrough Checks
Client Configuration
We verify the client path can hand off the raw bitstream. The correct behavior depends on the specific device firmware, receiver model, and display path.
3. Routing Validation
Direct to AVR vs eARC
We map whether the playback device routes directly to the AV Receiver or relies on an eARC return channel from the display. If routing through a display, both the TV and the Receiver must be correctly matched to allow high-bandwidth audio passthrough.
Source format
Player capability
App behavior
HDMI / eARC path
AVR reporting
Direct Play vs transcode
Final room result
Device Route Matrix
The endpoint decides the format. The same file behaves differently on every one of these routes.
| Endpoint | Lossless audio path | Atmos metadata behavior | Direct Play / app behavior | Best use case |
|---|---|---|---|---|
| Nvidia Shield | TrueHD and DTS-HD MA passthrough when configured | Object metadata preserved over bitstream | Strong Direct Play support in server apps | Plex-centric rooms wanting lossless passthrough |
| Zidoo | Purpose-built for full bitstream output | Metadata preserved, including on complex remux files | Local-library players favor untouched playback | Dedicated cinema rooms built around disc-grade files |
| Dune HD | Bitstream-focused local playback | Metadata preserved on supported chains | Local files first; app ecosystem is secondary | Library-first rooms with an AVR-direct route |
| HTPC | Full passthrough with the right software stack | Metadata preserved when configured precisely | Most flexible — and easiest to misconfigure | Owners who want maximum control and verification |
| Apple TV | Decodes internally — no TrueHD bitstream handoff | Re-packaged output rather than original bitstream | Excellent app polish; format ceiling applies | Streaming-first rooms where apps outrank lossless |
| TV apps | Rarely support lossless audio output | Typically limited to lossy Atmos variants | Frequent silent transcoding of local media | Convenience viewing, not reference playback |
| Blu-ray player | Native bitstream directly from the disc | Metadata preserved by design | No server layer — nothing to transcode | Reference playback and chain benchmarking |
What the AVR Should Say
The receiver's front panel is the verdict. These are the kinds of readouts that confirm — or contradict — the intended path.
Dolby TrueHD
Lossless track arriving intact
Dolby Atmos / TrueHD
Object metadata riding the lossless carrier
DTS-HD MSTR
DTS lossless path confirmed
DTS:X
Immersive DTS layer engaged
Multi Ch PCM
Decoded upstream — verify this was intended
DD+ Atmos
Lossy carrier — streaming grade, not disc grade
Text examples of format readouts, not reproductions of any manufacturer's interface.
Frequently Asked Questions
Why is the server transcoding my TrueHD 7.1 Atmos audio?
Transcoding happens if the client device does not support lossless passthrough, or if the TV/AVR chain does not properly negotiate eARC. Most built-in TV apps and certain standalone devices do not support TrueHD passthrough, forcing the audio into FLAC or PCM, which permanently removes the Atmos spatial metadata.
What does a lossless Dolby Atmos path require locally?
To get true lossless Dolby Atmos (TrueHD), you need a playback device that explicitly supports audio passthrough, connected directly to an AVR or soundbar that decodes TrueHD, or routed through a display that reliably handles eARC without internally downmixing the signal.
Why does the player say 'Direct Play' but my receiver says 'PCM'?
If TrueHD is Direct Playing but the receiver shows PCM, the playback device is decoding the audio internally instead of passing the bitstream to the AVR. On an Apple TV, this is by design (it uses MAT 2.0). On other platforms, it indicates that passthrough behavior and content audio resolution are not correctly matched to your display hardware.
Map the Signal Chain
The exact configuration path varies drastically per room. Let Cinema Machina map your audio chain to ensure you're hearing the uncompressed spatial audio you paid for. Starting a library instead? We review the best available legal viewing path, source quality, and playback-chain suitability before recommendation.
Book a lossless audio path audit Request a title for private cinema review