Contents
Compression, resolution and PCM/DSD: three separate criteria
Compression tells you whether information has been discarded or preserved. Resolution describes PCM bit depth and sample rate. PCM and DSD are two representations of the signal. These criteria combine: a FLAC can losslessly preserve either CD-resolution or high-resolution PCM.
Lossy compression
MP3, AAC, Vorbis and Opus reduce size by discarding or approximating some audio information. This is irreversible; its audible effect depends on encoding and listening conditions.
Lossless compression
FLAC and ALAC compress PCM and reproduce exactly the samples supplied to the encoder. WAV and AIFF can store those same samples without compression. Lossless does not necessarily mean CD resolution.
PCM / DSD
PCM uses multi-bit samples; DSD uses a 1-bit stream at a very high rate. High resolution describes parameters above CD resolution, without guaranteeing better audible results.
Lossy compressed formats
Lossy compression reduces storage and bandwidth needs. Results depend on the codec, encoder, chosen bitrate and content. Keep a lossless source if you want to create other compressed versions later.
MPEG-1 Layer 3
MP3 is widely supported by players and devices. It can use a constant or variable bitrate. At 320 kb/s it is still lossy: a high bitrate does not restore discarded information or guarantee inaudible differences for every track.
Advanced Audio Coding
AAC is a lossy codec, often stored in an .m4a file. Do not confuse AAC with ALAC: they can share the same extension, but only ALAC preserves PCM losslessly. Check the codec reported by your player.
Vorbis / Opus
Ogg is a container, not a codec. It can carry Vorbis or Opus, two distinct lossy codecs. RustMusic plays Ogg Vorbis and Opus; for another device, check the supported codec rather than only the file extension.
Lossless formats
Lossless encoding preserves its source’s digital samples. If the source is a correctly extracted CD, the PCM samples are preserved; if it comes from MP3, its losses remain. Metadata and the container can change without changing the samples.
Free Lossless Audio Codec
FLAC compresses PCM losslessly, with an open specification and metadata for titles, artists and artwork. Storage savings depend on the signal and compression settings: there is no fixed 50% reduction. The same decoded content remains identical regardless of compression level.
Waveform Audio
WAV is a container commonly used for uncompressed PCM in audio production. With identical samples, that PCM is not better quality than its FLAC version: it simply takes more space. The container can also hold other encodings; metadata support depends on the software.
Audio Interchange (Apple)
AIFF is commonly used to store uncompressed PCM. At the same rate, bit depth and samples, its audio content can be identical to PCM WAV. The choice then depends on your software and its metadata handling.
Apple Lossless
ALAC (Apple Lossless) also compresses PCM losslessly, usually in an .m4a file. It is used in the Apple ecosystem and supported by RustMusic 0.3.0. Converting FLAC to ALAC without changing PCM parameters preserves the samples, but check metadata transfer.
DSD, a format apart
DSD is a 1-bit audio representation: DSD64 uses 2.8224 MHz per channel. It is not a quality tier above FLAC. DSF or DFF denotes a DSD container; playback capabilities also depend on its encoding and your hardware.
RustMusic plays DSF and uncompressed DSD DFF by converting to a compatible PCM output or using DoP with a compatible DAC. On Windows, DoP requires exclusive output. SACD ISO images and DST-compressed DFF are not read directly. Check the actual mode in the audio chain.
Want to know more about DSD and how to play it? See the complete DSD/SACD guide.
Comparison table: size, signal and playback
Reference values for exactly four minutes of stereo. Numeric sizes cover audio data, excluding headers and metadata; FLAC and ALAC sizes depend on the content.
Swipe the table horizontally to see every column.
| Format | Storage | Size (4 min) | Decoded signal | Playback requirement |
|---|---|---|---|---|
| MP3 320 kb/s | Lossy compression | ≈ 9.6 MB | PCM after lossy decoding | MP3 player |
| AAC 256 kb/s | Lossy compression | ≈ 7.7 MB | PCM after lossy decoding | AAC player |
| FLAC 16 / 44.1 | Lossless compression | Variable | PCM 16-bit / 44.1 kHz | FLAC player |
| FLAC 24 / 96 | Lossless compression | Variable | PCM 24-bit / 96 kHz | FLAC player; 24/96 output to retain this resolution |
| ALAC 16 / 44.1 | Lossless compression | Variable | PCM 16-bit / 44.1 kHz | ALAC player |
| WAV PCM 16 / 44.1 | Uncompressed | ≈ 42.3 MB | PCM 16-bit / 44.1 kHz | PCM WAV player |
| DSD64 | Uncompressed | ≈ 169.3 MB | DSD 1-bit / 2.8224 MHz | PCM conversion or compatible DoP output |
1 MB = 1,000,000 bytes. MP3/AAC: bitrate × duration ÷ 8. Uncompressed PCM/DSD: rate × bits per sample × channels × duration ÷ 8. MP3/AAC values assume the stated average bitrate. Neither size nor format ranks audible quality; compare the master and playback settings.
Which one for your use case?
The best format mostly depends on how and where you listen:
Mobile listening (smartphone)
To save storage or mobile data, create a lossy copy from your lossless source. Choose bitrate and codec according to the device and your listening tests; background noise does not guarantee that every difference is inaudible.
→ AAC, MP3 or Opus depending on the device
Archiving & personal library
Keep an accurate CD extraction or your lossless purchases, with metadata. Preserve the source resolution: artificially increasing its rate or bit depth does not recreate information.
→ FLAC or ALAC at the original resolution
Critical listening on headphones
Use the version of the master you want to hear and check the audio chain. For bit-perfect PCM in RustMusic, use a compatible output at the same rate and channel count, volume at 100% and ReplayGain disabled.
→ Lossless PCM source, without unnecessary conversion
High-end hi-fi system
Compatibility depends on the input, driver and formats accepted by the DAC or network player. System price guarantees neither DoP nor an audible gain from high resolution. First choose a master and a supported playback path.
→ Lossless PCM or DSD depending on master and output
Frequently asked questions
Is FLAC really better than MP3?
FLAC preserves its source’s PCM samples losslessly, while MP3 retains an approximation. An audible difference is not guaranteed and depends on the track, encoder, bitrate and listening conditions. Compare the same master at the same volume; for archiving, FLAC preserves the source data.
Can I convert MP3 to FLAC to improve quality?
No. Decoding MP3 and saving the result as FLAC preserves the decoded samples, but does not restore what MP3 encoding discarded. It usually produces a larger file. To recover a lossless source, return to the CD or available original file.
Does Hi-Res (24-bit / 96 kHz) really make an audible difference?
A higher bit depth allows finer quantization; a higher sample rate allows a wider frequency band to be represented. This does not guarantee an audible difference. The master, volume and playback chain affect the comparison. Converting a CD-resolution file to 24/96 does not recreate information absent from the source.
What format do Spotify, Apple Music and Tidal use?
Spotify Premium now offers lossless FLAC up to 24-bit/44.1 kHz, depending on availability and device. Apple Music offers AAC and ALAC, up to 24-bit/192 kHz for available hi-res tracks. Tidal uses FLAC for stereo audio and removed MQA on July 24, 2024. Enable the quality you want in settings: the plan, track, device and output connection determine the quality actually received.
Sources and verification
Format references and streaming offerings checked on October 8, 2026. RustMusic compatibility checked for version 0.3.0. Table sizes are calculated using the stated assumptions.
Further reading
Your audio formats in RustMusic
RustMusic 0.3.0 plays FLAC, ALAC, WAV, AIFF, MP3, AAC/M4A, Ogg Vorbis, Opus and uncompressed DSF/DFF DSD. Bit-perfect PCM and DoP require a compatible output and appropriate settings. Check the actual path in the audio chain. Free and open source.