Bitstreaming & Passthrough

Passthrough (or bitstreaming) tells UMedia to stop decoding the audio and instead send the raw, compressed 1s and 0s directly over HDMI. Your AV Receiver (AVR) or Soundbar then decodes it.

Why use Passthrough?

Dolby Atmos / DTS:X require it. Software decoders can extract the base 7.1 track, but the 3D object metadata (which tells sounds to come from the ceiling speakers) can only be decoded by a licensed hardware receiver.
The AVR display lights up. Seeing "Dolby TrueHD" on your receiver's screen is the only way to know for sure you are getting the untouched signal.
Offloads CPU processing. Though audio decoding is trivial for modern CPUs.

How to configure umedia.conf

# Enable WASAPI exclusive mode (Windows)
audio-exclusive=yes

# Define which formats your receiver supports.
# UMedia will pass these through and decode everything else.
audio-spdif=ac3,dts,dts-hd,eac3,truehd

Common Mistakes & Troubleshooting

Optical / TOSLINK Limitations

Optical audio cables do not have enough bandwidth for lossless audio. If you use optical, you can only passthrough standard Dolby Digital (AC3) or standard DTS. TrueHD and DTS-HD MA require HDMI.

Volume Control Breaks

When passthrough is active, the UMedia volume slider (and Windows volume) will stop working. This is normal. You are sending raw data; you must use your receiver's remote to change the volume.

ARC vs eARC

If your PC is plugged into your TV, and your TV sends audio to a soundbar via ARC, lossless passthrough (TrueHD) will fail. Standard ARC only supports lossy audio. You need eARC on both the TV and Soundbar for lossless passthrough, or plug the PC directly into the Soundbar.