Apple Lossless
Bit-perfect compression in an M4A container — compatible with iPhone, iPad, and Apple Music.
Pro Audio Converter can convert audio files to and from Apple Lossless (.m4a).
Apple Lossless (also known as ALAC — Apple Lossless Audio Codec — or ALE — Apple Lossless Encoder) is an audio codec developed by Apple Inc. for lossless data compression of digital music. Apple Lossless data is stored within an MP4 container with the filename extension .m4a, which Apple also uses for AAC audio data in an MP4 container. However, Apple Lossless is not a variant of AAC (a lossy format) — it is a distinct lossless format that uses linear prediction similar to other lossless codecs such as FLAC. All current iPods, iPhones, and iPads can play Apple Lossless files from Apple Music or iTunes.
Encoding Options
Sample Rate — The number of samples of audio carried per second, measured in Hz or kHz (1000 Hz). 44.1 kHz is the sampling rate of audio CDs and 48.0 kHz is common for professional video. Higher sample rates result in higher quality audio with larger file sizes. Setting this to Auto creates an output file with the same sample rate as the input file. If the output file does not support the sample rate of the input file, Pro Audio Converter uses the greatest sample rate that is supported.
Bit Depth — The number of bits used to represent each sample. Increasing bit depth reduces quantization noise and improves the signal-to-noise ratio by about 6 dB per bit. 24-bit digital audio has a theoretical maximum S/N of 144 dB, compared to 96 dB for 16-bit. Audio CDs use 16 bits; 24-bit is common in professional audio and video.
Channels — The number of audio channels in the output file. Auto attempts to match the input file's channel count. You can also force Stereo (2 channels) or Mono (1 channel).
Quality — Since Apple Lossless is a lossless format, the quality setting only affects file size, not audio quality. Higher quality settings take longer to encode but produce smaller files.
