The document discusses trends in speech codecs, including robustness against packet loss through improved concealment techniques and reduced inter-frame dependency, wideband codecs that support higher quality HD voice, and multi-bitrate codecs that can adapt to available bandwidth. It provides examples of specific codecs, including iLBC for robustness, G.722.1 and iSAC for wideband, and discusses their features.

1. Speech Codec Trends
Robustness
Wideband (HD Voice)
Multi-bitrate
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2. Robustness
• Based on
▫ Better packet loss concealment
▫ Reduced Inter-frame dependency
▫ Built-in FEC
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3. iLBC
• Internet Low Bit rate Codec
• Packet loss robust CODEC by GlobalIPSound
• CELP based CODEC
• 13.3/15.6 kb/s for 20/30ms Frames
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4. iLBC (internet Low Bitrate Codec)
• Speech sampled at 8 kHZ,
• using a block-independent linear-predictive
coding (LPC) algorithm.
• Bandwidth 13.867 kbps (52 bytes per 30 ms)
• Frame size 20/30
• Complexity and memory requirements are
similar to ITU G.729A
• Basic Quality is equal to or better than G.729.
• Packet loss robustness is significantly better than
G.729.
• Packet loss concealment - Integrated
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5. GIPS Enhanced G.711
• Enhancement of existing standard (G.711)
• Enables speech quality equal to PSTN/G.711 on
impacted networks
• Superior packet-loss robustness compared to
G.711
• Lower delay than standard solutions when
combined with NetEQ
• Allows more efficient network provisioning
• Use CODEC level FEC
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6. Speex
• Open-source patent-free speech codec
• CELP (code-excited linear prediction) codec
• operating modes:
▫ narrowband (8 kHz sampling rate)
2.15 – 24.6 kb/s
delay of 30 ms
▫ wideband (16 kHz sampling rate)
4-44.2 kb/s
delay of 34 ms
▫ ultra-wideband (32 kHz sampling rate)
• intensity stereo encoding
• variable bit rate (VBR) possible
• voice activity detection (VAD)
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7. WideBand Codecs
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8. G.722.1
• G.722.1 is a low-bit-rate wideband coder,
which codes speech at 24 kbps or 32 kbps.
• G.722.1 uses a transform-coding scheme called
Modulated Lapped Transform (MLT), with a 20
ms frame size.
• The algorithmic delay is 40 ms (20 ms frame size
+ 20 ms look-ahead).
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9. G.722.1(cont)
• Supports all bit rates viz. 16/32 kbps at 16khz
sampling rate
• Supports Multi-channel capability
• Optimized implementation
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10. GIPS iSAC™
• Packet size is 30 or 60 ms, look-ahead 3 ms
• No inter-frame dependency => improved
robustness
• Variable bit rate codec with source control
adaptation as well as external control
• The user can set a target bit rate or iSAC can
adapt itself using a bandwidth estimator and
in-band signaling to utilize the available
bandwidth.
• Complexity similar to G.722.2
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11. GIPS iPCM-wb
• Wideband codec enabling better-than PSTN voice quality
▫ Supports increasing adaption of 16 kHz sampled voice
communications for richer voice communication experience
Benefits
• Higher basic speech quality than current standards, such as
G.722.1 and G.722.2
• Packet-loss robustness that exceeds current standards
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12. GIPS Codecs
• Narrowband codecs
▫ GIPS Enhanced G.711 TM
▫ iLBC Freeware TM
• Wideband codecs
▫ GIPS iPCM-wb TM
▫ GIPS iSAC TM
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13. Test yourself - 2
1. What are the main three voice coding trends?
2. Provide a codec example for each category
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14. DSP-IP Contact information
For Course materials licensing & lecture request contact:
Adi Yakov
Training and Courses Manager
adi@dsp-
adi@dsp-ip.com
+972-9-8651933
972-
For projects development services contact:
Alona Ashkenazi
Technology Management Services :
alona@dsp-
alona@dsp-ip.com
+972-9-8850956
972- www.dsp-ip.
www.dsp-ip.com
Mail : info@dsp-ip.com
info@dsp-ip.
Phone: 972- 8850956,
Phone: +972-9-8850956,
Fax : +972-50- 8962910
972-50-
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