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What exactly is a bit-perfect output?
Bit-perfect PCM playback sends the decoded samples of a lossless source to the DAC unchanged. It avoids resampling, volume changes, mixing and other processing that alters those samples.
In shared mode, the system lets several applications use the same output. It can mix sounds, apply effects or convert a stream whose sample rate differs from the output rate. Going through a mixer does not mean every file is always resampled.
Exclusive mode reserves the DAC. Bit-perfect PCM also requires a lossless source, a compatible format without conversion, matching channel counts, volume at 100% and ReplayGain disabled.
Why the system can alter your sound
On each OS, a different audio layer sits between your player and the DAC. Here's how to get bit-perfect on each:
Windows
WASAPI Exclusive lets RustMusic reserve the DAC and bypass the Windows mixer. The DAC must accept the requested format without conversion.
macOS
RustMusic uses CoreAudio exclusive mode (hog mode). Check the DAC’s supported sample rate, channels, volume and absence of processing; shared output alone does not establish bit-perfect playback.
Linux
RustMusic can open the hardware directly through ALSA in exclusive mode. Bit-perfect playback requires a compatible format and no processing. PipeWire or PulseAudio settings also need checking in shared mode.
What to check in a bit-perfect player
To judge a bit-perfect output, check these four points:
- An exclusive mode suited to your system: WASAPI exclusive on Windows, CoreAudio hog mode on macOS, direct ALSA access on Linux.
- Processing you can neutralize: software volume at 100%, ReplayGain disabled, no resampling or effects.
- An indication of the format actually sent to the DAC, so you can check that no conversion takes place.
- For DSD, DoP output to a compatible DAC; otherwise DSD is converted to PCM.
RustMusic brings these points together on Windows, macOS and Linux: exclusive output, a “Bit-perfect” badge and a detailed audio chain, and DSD over DoP for compatible DACs. It is free and open source.
Bit-perfect setup with RustMusic
Configure exclusive output: WASAPI on Windows, CoreAudio on macOS and ALSA on Linux. Bit-perfect playback also depends on the file, the format accepted by the DAC and processing in the player.
Download and install RustMusic
Free, open-source, available for Windows, macOS and Linux. One-click install, no account required.
Open Settings → Audio
In the « Audio output » section, you'll see the list of your devices (USB DAC, built-in sound card, etc.). Select the one you use for critical listening.
Enable exclusive output and disable processing
In Settings → Audio, enable exclusive output for the selected DAC. For bit-perfect PCM, set volume to 100%, disable ReplayGain and use a lossless source whose sample rate and channels are accepted without conversion. For native DSD, enable DoP with a compatible DAC.
Check the « Bit-perfect » badge in the player
Check the “Bit-perfect” badge and the audio chain details. The “Exclusive” badge only means the DAC is reserved. A rejected format, conversion, reduced volume or active ReplayGain can alter the signal; RustMusic explains the reason.
Frequently asked questions
Can you really hear bit-perfect?
Bit-perfect playback guarantees the integrity of samples sent to the DAC. It does not guarantee an audible improvement: that depends on the processing avoided, the recording and the playback system. The format alone cannot predict an audible difference.
How can I check that playback is really bit-perfect?
Check the output mode, the actual sample rate, volume and effects. Shared output can apply processing or resampling. In RustMusic, the “Bit-perfect” badge and the audio chain show whether the conditions are met and, if not, why. Your DAC’s display can confirm the sample rate it receives.
Does bit-perfect work with my computer's headphone output?
Yes, if the built-in output accepts exclusive mode and the source format without conversion. An external DAC is not mandatory. The same requirements for volume, channels and absence of processing apply.
Can I listen to other apps at the same time as a bit-perfect player?
In exclusive mode, the selected DAC is reserved for RustMusic on Windows, macOS and Linux. Other applications can use a different output. To share this same DAC, switch back to shared mode and check processing and the output sample rate.
Sources and verification
RustMusic information checked for version 0.3.0.
Further reading
Ready for bit-perfect sound?
RustMusic offers true bit-perfect output on Windows (WASAPI Exclusive), macOS and Linux, for free and without compromise. Native DSD support, DoP, and all HD formats.