1. Container and codec
The filename first identifies a container or likely codec. FLAC is usually direct; M4A may contain ALAC, AAC, or PCM; Ogg may contain Vorbis, Opus, or FLAC. Nyquist probes the file where possible and presents the detected payload instead of treating the extension as a quality label.
2. Decode or package for transport
For local PCM playback, the codec is decoded into PCM frames. Nyquist streams segments from disk rather than decoding the whole track into memory. For macOS DSD playback, it packages the DSD payload as DSD over PCM for a compatible DAC instead of decoding the DSD signal to PCM.
UPnP/DLNA takes another path: Nyquist sends the original file to a compatible receiver without transcoding. The receiver then owns decoding and subsequent processing.
3. Processing and volume
The PCM engine uses a 32-bit float mixer. Output volume may be a DAC hardware control, software gain, the iPhone or iPad system level, or a network receiver's own level. Any active gain or processing matters to a strict bit-identity claim even when the sample rate is unchanged.
4. Route and output rate
On macOS, Nyquist can bind to a selected CoreAudio device, request a compatible nominal rate, wait for the device clock, and optionally use exclusive mode. Its signal path compares the source and output and reports whether resampling is detected.
On iPhone, iPad, and Apple TV, the operating system controls more of the final route. Bluetooth and AirPlay add transport behavior outside Nyquist's direct control. A signal-path view should distinguish these limits rather than presenting every route as equivalent.
5. Conversion to sound
A DAC eventually converts digital samples to an analog signal. Amplification, speakers or headphones, room acoustics, and hearing then sit beyond the digital path. A transparent software path cannot by itself describe or rank the entire listening result.
See the product-level Nyquist signal-path reference, bit-perfect audio, or sample rate and bit depth.