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Scalable Wideband Codec

2nd Workshop on Wideband Speech Quality in Terminals and Networks: Assessment and Prediction 22nd and 23rd June 2005 - Mainz, Germany. Scalable Wideband Codec. Pankaj K.R. rpankaj@ti.com Ajit Rao ajitr@ti.com. Scalable Wideband Codec. Background Current challenges Scalable Architecture

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Scalable Wideband Codec

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  1. 2nd Workshop on Wideband Speech Quality in Terminals and Networks:Assessment and Prediction22nd and 23rd June 2005 - Mainz, Germany 2nd Workshop on Wideband Speech Quality - June 2005

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

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

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

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

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

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

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

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

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