Get Better Clarity And Enhanced Sound With G722 Codec

The ITU-T standard G.722 wideband audio has the ability to operate at 64,56, and 48 kbit/s. Its technology is founded on sub-band ADPCM (SB-ADPCM). G.722 helps providing augmented speech quality thanks to an extended speech bandwidth of 50-7000 Hz, likened to narrowband speech coders as G.711, which are generally created for POTS wireline quality of 300–3400 Hz. Created to be used in ISDN video-conferencing, the G.722 codec had been the first wideband speech codec the ITU-T standardized. With the sampling of the speech signal at 16 kHz, G.722 increased the encoded speech information, and provides better clarity and enhanced sound as compared to the narrowband speech codecs.

Additional ITU-T 7 kHz wideband codecs comprise G.722.1 & G.722.2. Both these codecs aren’t variations of G.722 and they make use of varied patented compression technologies. Where Siren codecs-G.722.1 rendered lower bit-rate compressions (32 kbit/s & 24 kbit/s), the latest ACELP-based G.722.2, which is otherwise called as AMR-WB ("Adaptive Multirate Wideband") provides even lower bit-rate compressions (6.6 kbit/s to 23.85 kbit/s). Besides, the latter can quickly adapt to compressions network topography changes.

Applications of G.722 CodecThe ITU standardG.722 codecproves to be highly useful for voice over IP applications, for example on a local area network, where network bandwidth significantly improves the speech quality, but for doing significant improvement in implementation complexity. The most bitrate-efficient codecs like G.722.1 (Siren7) or G.722.2 (AMR-WB) come useful for environments where bandwidth remains more constrained. Radio broadcasters also make wide use of G.722 to send commentary grade audio over a single 56 or 64 kbit/s ISDN B-channel.

The codec functions by getting the in-bound voice signal passed via a digital filter that does splitting of the audio signal into 4 kHz-to-8 kHz and 0 Hz-to-4 kHz audio bands. Thereafter, these sub-bands are encoded with the use of sub-band ADPCM. Most of the human voice energy remains focused on the lower half of the audio band (0-4kHz), thus 48 kbit/s of the bandwidth goes to the lower sub-band and the remaining 16 kbit/s is provided to the higher sub-band.

There is a gamut of G722 codec specifications and key functional parts of this 64 kbit/s (7 kHz) audio coder. Let’s learn about them below:

64 kbit/s audio encoder

Transmit audio part: This helps in converting an audio signal to a uniform digital signal that’s coded with the use of 14 bits including 16 kHz sampling

SB-ADPCM encoder: This helps in reducing the bit rate to 64 kbit/s (G.722 encoder, makes use of 64 kbit/s at all times regardless of operation mode)

Data Insertion Device: This makes use of the minimal important bit or two minimally essential bits of the encoded signal as additional data channel

64, 56, or 48 kbits audio decoder

Data Extraction Device: This helps in extracting the additional data from the encoded audio data at the receiver side with none, one or two of the minimal important bits

SB-ADPCM decoder: This carries out the reverse operation to the encoder.Receive audio part: This helps in reconstructing the audio signal from the uniform digital signal, which is encoded through 14 bits with 16 kHz sampling

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