SPR Vocoders 2400 bps
Classic | Robust
SPR Classic ™ 2400 bps vocoder is based on Sinusoidal Pulsed Representation (SPR) model, where excitation signal includes mixture of pitch-harmonics, noisy and aperiodic impulses.
It allows to synthesize correctly any speech sounds, including mixed voiced+unvoiced and complex transients.
Additionally, choice of optimal quantization schemes and high algorithmic optimization provided superior characteristics of this vocoder in comparison with others for the same bit rate
We used ITU-T P.50 multilanguage speech base and ITU-T P.862 utility to estimate speech quality.
SPR 2400 bps vocoder doesn't concede practically MELPe 2400 bps standard vocoder. Average PESQ is: 3.25 vs 3.30.
However, all other characteristics of the SPR 2400 vocoder excel considerably appropriate characteristics of the standard vocoder.
We passed encoded bit streams through AWGN channel simulator with various SNR and estimated quality of decoded speech.
SPR 2400 shows superiority over MELPe 2400.
Time delay is very important characteristic of communication system. Algorithmic delay of vocoder does play determinative role in total delay. Large delay complicates normal conversation.
SPR 2400 provides 40 ms delay, MELPe - 42.5 ms.
Frame size is 20 ms (160 speech samples).
SPR 2400 requires almost two times lower computing resources and shows strong superiority over MELPe 2400.
Only 22 MIPS versus 36 MIPS for TI's C55xx.
We have estimated and compared resources of SPR 2400 bps vocoder for TI's C55xx DSP.
SPR 2400 shows strong superiority over MELPe 2400.
SPR 2400 bps is available right now for TI's C55xx DSP and for PC (Win32) platforms and also is available for any other DSP, RISC or general-purpose platform during two-three months.
- SPEECH QUALITY
- ALGORITHMIC DELAY
- COMPUTING COMPLEXITY
- MEMORY USAGE