voice coding trends

Speech Codec Trends

Robustness

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Robustness

Wideband (HD Voice)

Multi-bitrate

Robustness

• Based on

▫ Better packet loss concealment

▫ Reduced Inter-frame dependency

▫ Built-in FEC


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


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


• 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

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


• Lower delay than standard solutions when combined with NetEQ

• Allows more efficient network provisioning• Use CODEC level FEC

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


� 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)

WideBand Codecs


WideBand Codecs

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


• The algorithmic delay is 40 ms (20 ms frame size + 20 ms look-ahead).

G.722.1(cont)

• Supports all bit rates viz. 16/32 kbps at 16khz sampling rate

• Supports Multi-channel capability • Optimized implementation


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


• 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

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

GIPS Codecs

• Narrowband codecs

▫ GIPS Enhanced G.711TM

▫ iLBC FreewareTM


• Wideband codecs

▫ GIPS iPCM-wbTM

▫ GIPS iSACTM

Test yourself - 2

1. What are the main three voice coding trends?

2. Provide a codec example for each category


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voice coding trends

Education

ms wideband

ms frame size

codec example

ms ultrawideband

packet loss robustness

ms look

gips ipcmwb wideband

rate wideband coder