The following table shows the relationship between the encoding quality and the compression ratio in HCA.
Relationship Between Encoding Quality and Compression Ratio
| Quality | Monaural | Stereo |
|---|---|---|
| Highest quality | 1/4 | 1/4 |
| High quality | 1/6 | 1/6 |
| Medium quality | 1/8 | 1/8 |
| Low quality (high compression) | 1/10 | 1/12 |
| Lowest quality (highest compression) | 1/12 | 1/16 |
The compression ratio is the ratio between the encoded size and the size of the 16-bit non-compressed PCM data.
For example, if the compression ratio is 1/6, it means that the 16-bit non-compressed PCM data is 6 times bigger than its encoded version.
The compression ratio is only a guideline.
The actual file size may slightly differ from the size calculated using the ratio due to the addition of the file header, the rounding of samples to frames, or truncation due to other boundaries.
In order to avoid significant degradation in sound quality, the lowest acceptable bit rate is defined:
- Monaural: 42kbps
- Stereo: 64kbps
For example, when encoding 24 kHz monaural audio data, even if the quality is set to the lowest setting, the 42 kbps bit rate is used to encode the data.
- Attention
- When encoding stereo sounds with a quality equal to or worse than the medium quality, part of the stereo sound is converted to monaural to raise the compression ratio.
For audio data which needs to avoid cross-talk between channels (an issue where the audio of other channels is heard) such as multilingual data or Dolby Pro Logic II-encoded audio data, use at least the high quality setting.
Setting the Target Config
