What is a FLAC file?
FLAC (Free Lossless Audio Codec) is a revolutionary lossless audio coding format developed by the Xiph.Org Foundation. As a completely royalty-free and open-source format, identified by the .flac file extension, it offers a significant advantage in digital audio storage and fidelity. The powerful FLAC compression algorithm efficiently reduces the size of digital audio files by an impressive 50 to 70 percent. Most importantly, this compression is entirely lossless, meaning FLAC files can be decompressed into a perfect, bit-for-bit identical copy of the original source, preserving every detail of the audio quality without any degradation.
Key Characteristics of FLAC Files
| Characteristic | Description |
|---|---|
| Official Name | Free Lossless Audio Codec |
| File Extension | .flac |
| File Size | Typically 30-50% smaller than uncompressed WAV |
| Support | Open-source and royalty-free |
| Resolution | Supports standard CD quality (16-bit/44.1kHz) up to ultra-high-resolution audio (24-bit/192kHz+) |
| Ideal For | Audiophiles, music archivists, and high-quality streaming. |
FLAC file Format
This is an overview of the FLAC bitstream.
- fLaC marker: This marker is added to the beginning of the stream. It is followed by one or more metadata blocks.
- Metadata Blocks: 128 kinds of metadata blocks are supported by FLAC; currently the following are defined.
- STREAMINFO: Contains the information about the whole stream.
- APPLICATION: This is used by third-party applications for identification.
- PADDING: It is used to reserve space for metadata if the metadata will be edited after encoding. When the metadata is edited, the padding is replaced by the actual metadata.
- SEEKTABLE: An optional table to store seek points.
- VORBIS_COMMENT: Used to store human-readable key/value pairs.
- CUESHEET: Used to store cue sheet information.
- PICTURE: Used to store pictures.
- FRAME: The audio data is composed of one or more audio frames.
- FRAME_HEADER: Contains the basic information about the stream.
- SUBFRAME: To decrease the complexity, individual subframes are coded separately within a frame (one frame per channel).
- FRAME_FOOTER: Contains the CRC of the complete frame.
Brief History of FLAC File Format
Josh Coalson began the development of FLAC in 2000. The first version of FLAC was released on 20 July 2001. FLAC was incorporated under the Xiph.Org flag on 20 January 2003. The development of FLAC was moved to the Xiph.Org git repository with the release of version 1.3.0 on 26 March 2013.
Composition of FLAC Project
The FLAC project consists of the following:
- Stream formats.
- Simple container format for the stream(FLAC).
- libFLAC: A library of reference encoders, decoders, and metadata interface.
- libFLAC++: An object-oriented wrapper for libFLAC.
- flac: A command-line program to encode and decode FLAC streams.
- metaflac: A command-line metadata editor for FLAC.
- Input plugins for music players like Winamp, XMMX, etc.
- Ogg container format (Ogg FLAC).
FLAC Design
Depending on the density and amplitude of the music, the size of the compressed file can be 80% less than the original file.
Source Encoder
- It only supports integer samples and not floating-point. It can handle PCM bit resolution from 4 to 32 bits per sample and sampling rate from 1Hz to 65,535 Hz. FLAC encoding is limited to 24 bits per sample.
- Channels can be grouped to take advantage of interchannel correlations to increase compression.
- CRC checksums are used to identify corrupted frames.
- For conversion of audio samples, FLAC uses linear prediction.
Metadata
- FLAC supports ReplayGain(used to perceive and normalize loudness in audio).
- FLAC uses the same system used in Vorbis comments for tagging.
- libFLAC is used by most FLAC application for encoding/decoding.
- libFLAC API is organized into streams, seekable streams, and files to increase abstraction from base FLAC bitstream.
Compression
libFLAC uses compression levels from 0 to 8 where 0 is the fastest and 8 is the slowest compression level. The compressed files are always lossless although the tradeoff is between speed and size.
FLAC vs MP3
The MP3 is a lossy compression format mean it may cut some part of the audio to reduce its size after applying compression. Whereas, FLAC is a lossless file format which means that you are able to hear the audio in its purest form. Earlier the lossless file formats were CDA or WAV which were not much space efficient as FLAC. The following table will show the comparison between these two formats for some important terms:
| Term | FLAC | MP3 |
|---|---|---|
| Data Quality | No any loss of audio data | Some data may be lost when compressing audio data |
| Size | Larger file size as compared to lossy formats. So need larger storage capacity | Smaller file size, suitable to play on compact audio devices with little storage space |
| Hardware requirements | Need high-quality audio gear and huge storage capacity | Huge audio libraries can be saved in a smaller storage space. Suitable for handheld devices, such as audio players or mobile phones |
| Distribution over the internet | Can’t be distributed easily over the internet because of massive file size | Compact file size makes it easy to distribute over the internet |
| Compatibility | The most popular music and audio listening codec that pretty much compatible with every device on the planetCompatible with new generation PCs, phones, AV receivers, blu-ray players, streaming devices like Roku or Fire TV |
FAQ
Q1: Is FLAC better than MP3?
A: Yes, in terms of pure audio quality, FLAC is superior to MP3 because it is lossless, while MP3 discards audio data to create a smaller file.
Q2: Can the human ear actually hear the difference between FLAC and MP3?
A: On high-quality audio equipment, many listeners can hear a clear improvement in detail, clarity, and soundstage with FLAC, especially in complex musical passages.
Q3: Does FLAC work in my car or on my phone?
A: Most modern car stereos (via USB) and smartphones can natively play FLAC files, but you should check your device’s specifications to be sure.
Q4: Why would I use WAV if FLAC is smaller and identical?
A: WAV files are slightly more universally compatible with some professional audio and DJ software, but FLAC’s metadata support and smaller size make it better for library management.
Q5: Is FLAC the same quality as a CD?
A: A FLAC file ripped from a CD is the exact same quality as the CD itself, as it is a perfect, lossless copy of the original data.