How should we perceive the relationship between bit rates and the synthesis length and between bit rates and sound quality?
Descriptive Answer:
Bit rate and length of synthesis
A bit rate indicates the degree of information compression, and how many bits of data are required for synthesis in one second. Thus, the bit rate depends on the sampling frequency and the amount of data per sample, and is determined by the following formula:
Bit rate (kbps) = sampling frequency (kHz) x amount of data per sample (bits)
Example 1
Sampling frequency: 4 kHz, data: 4-bit ADPCM
Bit rate (kbps) = 4 (kHz) x 4 (bits) = 16 (kbps)
Example
Sampling frequency: 8 kHz, data: 4-bit ADPCM
Bit rate (kbps) = 8 (kHz) x 4 (bits) = 32 (kbps)
The length of synthesis depends on the memory capacity and the bit rate, as shown in the following formula:
Example
Bit rate and sound quality
A lower bit rate results in a longer synthesis length. But the response to a voice waveform becomes lowered, with deteriorated sound quality.
A bit rate indicates the degree of information compression, and how many bits of data are required for synthesis in one second. Thus, the bit rate depends on the sampling frequency and the amount of data per sample, and is determined by the following formula:
Bit rate (kbps) = sampling frequency (kHz) x amount of data per sample (bits)
Example 1
Sampling frequency: 4 kHz, data: 4-bit ADPCM
Bit rate (kbps) = 4 (kHz) x 4 (bits) = 16 (kbps)
Example
Sampling frequency: 8 kHz, data: 4-bit ADPCM
Bit rate (kbps) = 8 (kHz) x 4 (bits) = 32 (kbps)
The length of synthesis depends on the memory capacity and the bit rate, as shown in the following formula:
Example
Bit rate and sound quality
A lower bit rate results in a longer synthesis length. But the response to a voice waveform becomes lowered, with deteriorated sound quality.
Recording/Playback Time Quick Reference Table
The following is a quick reference table for recording/playback times calculated on the basis of each voice synthesis method.
