Voice Quality vs Sample Rate
APLUS VOICE IC allow user define different sample rate and encoding algorithm to get the best sound quality.
| IC | Encoding Algorithm | Sample Rate (KHz) |
|||
|---|---|---|---|---|---|
| 4bit (ADPCM) | 5bit (u-Law) | 8bit (PCM) | 16bit (PCM16) | ||
| aP89xxx | V | - | V | - | 6K ~ 22K |
| aIVRxxxx | V | V | V | - | 6K ~ 20K |
| aP23xxx | V | - | V | V | 6K ~ 44K |
| aMTPxxx | - | - | V | V | 6K ~ 44K |
Let's listen the sound quality base on 6KHz, 12KHz and 18KHz/8bit.
Sound quality︰
Obviously 18K Hz > 12K Hz > 6K Hz sound quality. Higher sample rate will have better sound quality. Generally speaking, suggest higher than 12KHz.
How to calculate sample rate ?
Maximum Sample Rate = Memory Size / (voice duration x Data encoding algoritm)
Ex
- Sound total 64sec , use 341sec ic body
- Sample Rate = 8M / ( 64sec X 4bit ) ≒ 32KHz (4bit ADPCM)
- Sample Rate = 8M / ( 64sec X 5bit ) ≒ 25.6KHz (5bit u-Law)
- Sample Rate = 8M / ( 64sec X 8bit ) ≒ 16KHz (8bit PCM)
- Sample Rate = 8M / ( 64sec X 16bit ) ≒ 8KHz (16bit PCM)
Below table show how many seconds we can program for each body In 12KHz.
|
Encoding Memory |
12KHz | ||||
|---|---|---|---|---|---|
| 4bit (ADPCM) | 5bit (u-Law) | 8bit (PCM) | SBC | 16bit (PCM16) | |
| 5sec | 4sec | 2.5sec | - | - | |
| 10sec | 8.5sec | 5sec | - | - | |
| 20sec | 16.5sec | 10sec | - | - | |
| 41sec | 33sec | 21sec | - | 10.5 | |
| 85sec | - | 42sec | - | 21sec | |
| 170sec | 133sec | 85sec | - | 42sec | |
| 341sec | - | 170sec | - | 85sec | |
| - | - | 333sec | - | - | |
| - | - | - | 4474sec | 341sec | |
Note: Sound quality 16bit > SBC > 8bit > 5bit > 4bit