1. 2nd Workshop on Wideband Speech Quality - June 2005 1 2nd Workshop on Wideband Speech Quality in Terminals and Networks: Assessment and Prediction 22nd and 23rd June 2005 - Mainz, Germany

2. 2nd Workshop on Wideband Speech Quality - June 2005 2 Scalable Wideband Codec Pankaj K.R. rpankaj@ti.com Ajit Rao ajitr@ti.com

3. 2nd Workshop on Wideband Speech Quality - June 2005 3 Scalable Wideband Codec  Background  Current challenges  Scalable Architecture  Open scalable architecture  Results  Discussion

4. 2nd Workshop on Wideband Speech Quality - June 2005 4 Background  A large number of narrow-band and wide-band codecs like G.729, G.729ab, EVRC, BV16, G.722, WB- AMR etc  No interoperability of narrow band and wideband codecs  A large number of narrowband terminals are in use  Possible to enhance the voice quality by using additional bandwidth available in new networks such as cable  Digital Cable Channels Support Dynamic QoS (DQoS) channel – probability of packet loss is pre-negotiated Best effort channel – no guarantee of delivery

5. 2nd Workshop on Wideband Speech Quality - June 2005 5 Current Challenges  Wide-band Features  Attracting POTS customers to migrate to Cable-Voice  Interoperability between Wide-band & Narrow-band terminals  Value added services  High quality packet-loss concealment  High Quality for Speech & Music etc  Pay more for higher quality

6. 2nd Workshop on Wideband Speech Quality - June 2005 6 Scalable Architecture Standard Narrowband Encoder Enhancement Layer 1 Enhancement Layer 2 Enhancement Layer N Standard Bit Stream Enhanced Bit Streams

7. 2nd Workshop on Wideband Speech Quality - June 2005 7 Scalable Architecture Standard Narrowband Decoder Optional Enhancement Layers Standard Bit Stream Enhanced Bit Stream High Quality Speech

8. 2nd Workshop on Wideband Speech Quality - June 2005 8 Open Scalable Architecture  Base layer is Standards Compliant  Define the format of the enhancement bit stream.  The enhancement layers and base layers are transmitted separately.  Base Layer in DQOS (Dynamic Quality of Service).  Enhancement Layer in Best Effort  Decoder or Network may choose to discard the enhancement layers  Voice Quality changes must be smooth

9. 2nd Workshop on Wideband Speech Quality - June 2005 9 Scalable Architecture Standard Narrowband Encoder Filter Bank Wideband Speech Higher band Encoder Bit stream 1 C1[n] Bit stream 2 C2[n] Wideband Transmitter  Uses a split band approach

10. 2nd Workshop on Wideband Speech Quality - June 2005 10 Scalable Wideband Codec  Uses a split band approach  Lower sub-band  Coded using a proprietary 16 kbps narrow-band codec  Upper sub-band  LPC + noise excitation  Additional parameters transmitted Sub-band Frame Energy LPC – reuse of low-band LSF quantizer  Synthesis: Additional long-term pitch filtering derived from the lower sub-band.

11. 2nd Workshop on Wideband Speech Quality - June 2005 11 LSP Quantization  Uses the same lower band quantizer  Not designed for higher sub-band.  Higher band LSPs are in the reverse order.  Uses 1-LSP(i) for quantization. Uses the lower sub-band quantizer very effectively. Matches the LPC spectrum smoothly.

12. 2nd Workshop on Wideband Speech Quality - June 2005 12 Scalable Architecture 1/B(z) Noise Generator Receiver C2’[n] Narrowband Decoder C1’[n] G 1/A(z) FILTERFILTER Wideband speech

13. 2nd Workshop on Wideband Speech Quality - June 2005 13 Scalable Architecture Wideband speech Receiver Narrowband Decoder C1’[n] FILTERFILTER Bandwidth Extension

14. 2nd Workshop on Wideband Speech Quality - June 2005 14 Scalable Wideband Codec  Results  Narrow-band codec: 16 Kbps LPC based  The higher sub-band rate is 3.6 Kbps  The results are comparable with 48Kbps G.722  The codecs are compared using NTT database consisting of British and American English.  The PESQ scores for the codecs are as G.722TI-SW-Codec 3.974.08

15. 2nd Workshop on Wideband Speech Quality - June 2005 15 Discussion