Supported Audio Compression Codecs

**Original Audio Compression Codec**
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 subjected to special encoding for HCA-MX playback

Codec-specific features

: ADX is an audio compression codec with super-low load.
Although compression rate is not good compared with HCA etc., since the decoding process is very lightweight, it can play a lot of sound with low load.

: HCA was developed for the purpose of low load, high-quality, and high compression ratio.
Compression ratio comparable to the general-purpose audio codecs such as mp3 or AAC is achieved.

: Since the algorithm of HCA is simple, it needs low-load and uses less memory compared to the general-purpose audio codecs.
Moreover, since it is designed so that rapid load fluctuation may not occur, it will not adversely affect the application at a specific timing.

: When performing HCA encoding, sound quality (compression ratio) can be specified by the five-level value.
Relationship between the encode setting and the compression ratio is described in the ' Compression Ratio of HCA '.

: HCA-MA is a name of playback method that decodes after mixing HCA data.
In ordinary audio compression codecs, CPU load rises ten times when ten sounds are played, but in HCA-MX, load rises as low as two times.

: Its audio data format is the same as HCA codec's, but it is encoded for HCA-MX playback while changing sample rates and loop regions.
If audio data that does not match the HCA-MX playback condition, sample rate or playback pitch may be changed.

: In HCA-MX playback, audio data is decoded after mixing.
Therefore, functions such as filtering or pitch change by sounds or seamless concatenated playback cannot be used in HCA-MX.

**Comparison of Functions In Each\Codec**
Function	ADX	HCA	HCA-MX	Note
Loop playback	Yes	Yes	Partial	In order to use loop playback in HCA-MX, the number of samples in loop interval must be the multiples of 128.
Seek playback	Partial	Yes	Partial	In seek playback in ADX, noise may occur depending on the starting position or loop position. In seek playback in HCA-MX, sound may be distorted at the starting 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 setting	Partial	Partial	No	Whether envelope setting is possible or not depends on the target.
Biquad filter	Yes	Yes	No
Band-pass filter	Yes	Yes	Partial	Band-pass filter in HCA-MX only allows the sound to be changed by 1/256th of the sampling rate.
Bus send level setting	Yes	Yes	No
Bass Effects	Yes	Yes	No