Local and network playback are different. Locally, Nyquist decodes supported files through its Apple-platform audio path. For UPnP/DLNA playback, it sends the original file without transcoding, so the receiver must support the container and codec itself.
FLAC
.flac files use Free Lossless Audio Codec compression.
Decoding reconstructs the original PCM samples represented by the
file. Nyquist supports local FLAC playback and track analysis on its
Apple platforms. A compatible network receiver can receive the
original FLAC file directly.
ALAC and MPEG-4 Audio
.m4a, .m4b, and .m4r identify
MPEG-4 Audio containers; they may hold lossless ALAC, lossy AAC, or
PCM. The less common .alac extension is also
recognized. Nyquist inspects the payload rather than treating the
extension as a quality promise. Local support is available on Mac,
iPhone, iPad, and Apple TV.
MP3 and AAC
.mp3, .aac, and .adts files
use lossy compression. That is separate from sample rate and bit
depth: a high sample rate does not restore information removed by a
lossy encode. Nyquist plays these files locally and can send the
original file to a network receiver that supports it.
AIFF, WAV, Wave64, CAF, AU, and SND
Nyquist recognizes .aif, .aiff,
.aifc, .wav, .wave,
.w64, .caf, .caff,
.au, and .snd. These containers often hold
uncompressed PCM, though some permit other payloads. Local playback
depends on whether the operating system can decode the payload in
the particular file.
Ogg, Vorbis, and Opus
Ogg is a container. Nyquist recognizes .ogg and
.oga files containing Vorbis, Opus, or FLAC, plus the
.opus extension used for Ogg Opus. Local playback uses
the available Apple decoding path; Vorbis playback is verified on
macOS. Network support depends on the receiver.
DSD in DSF and DFF
.dsf and .dff contain Direct Stream
Digital audio. On macOS, Nyquist packages the DSD payload as DSD
over PCM for a compatible USB DAC. It does not convert that payload
to PCM for this route. For network playback, a compatible receiver
receives the original DSF or DFF file. Local DSD playback is not
available on iPhone, iPad, or Apple TV.
Unsupported formats
MMF/SMAF (.mmf) and WMA/ASF (.wma) are not
indexed because Apple's audio stack does not provide the decoding
path Nyquist uses. SACD ISO (.iso) is also unsupported:
it requires disc-image parsing, virtual tracks, DST decoding, and
separate licensing work. Extracted DSF or DFF files can be used on
supported DSD routes.
Formats do not rank recordings
Lossless compression, sample rate, and bit depth answer different questions. A 24-bit/192 kHz file is not automatically a better master than a 16-bit/44.1 kHz file. Nyquist reports these properties so you can identify the file and understand the active output path, not to assign a score to the music.
Continue with Lossless audio, FLAC vs. ALAC, or Sample rate and bit depth.