This system supports the following audio compression codecs:

**Original audio codecs**
Codec	Description
ADX compression	High-quality, low-load codec with a compression ratio of about 1/4
HCA compression	High-quality, high-compression codec with a maximum compression ratio of 1/16
HCA-MX compression	HCA data specially encoded for HCA-MX playback

: ADX is a super-low-load audio compression codec.
Although its compression rate is lower than HCA, it can play a lot of sounds with a light load, because the decoding is very lightweight.

: HCA is designed to achieve a low load, high quality, and high compression.
(Its compression ratio is comparable to general-purpose audio codecs such as mp3 or AAC.)

: Because of its simple algorithm, HCA operates at a lower load and uses less memory than general-purpose audio codecs.
Moreover, since it is designed to avoid fast load fluctuations, it does not disturb the application's processing at a specific timing.

: Concerning the HCA encoding, five levels of sound quality (compression ratio) are available.
For the relations between encoding settings and compression ratios, see the "CRI Atom Tool User Manual."

: HCA-MX is a playback method where HCA data is mixed before decoding.
With an ordinary audio compression codec, the CPU load increases ten times when ten sounds are played, but, with HCA-MX, the load only doubles.

: For HCA-MX playback, the same format of sound data as for the HCA codec is used, but sampling rates and loop sections are fixed when encoding the data.
If you encode some sound data that does not meet the HCA-MX playback conditions, its sampling rate and playback pitch may be changed at encoding.

: For HCA-MX playback, the sound data is mixed before decoding.
It means that it is not possible to use functions such as filtering and pitch change on a per-sound basis (as well as seamless concatenated playback) during HCA-MX playback.

The table below shows the available functions for each codec.

**Available functions for each codec**
Function	ADX	HCA	HCA-MX	Remarks
Loop playback	Yes	Yes	Partially	For loop playback with HCA-MX, the number of samples in a loop section must be a multiple of 128.
Seek playback	Partially	Yes	Partially	During seek playback with ADX, noise may occur at the playback start position and at the loop position. During seek playback with HCA-MX, the sound may be distorted at the playback start position.
Seamless concatenated playback	Yes	Yes	No
Filter callback	Yes	Yes	No
Volume change	Yes	Yes	Yes
Pan change	Yes	Yes	Yes
Pitch change	Yes	Yes	No
Envelope settings	Partially	Partially	No	Whether it is available depends on the target.
Biquad filter	Yes	Yes	No
Band-pass filter	Yes	Yes	Partially	The band-pass filter in HCA-MX can change the sound only by increments of 1/256th of the sampling rate.
Bus send level settings	Yes	Yes	No