Transparent frequency domain coding of speech, a possible candidate for audio coding in the videophone

Considering the need for synchronisation of audio and video an increased delay subband or adaptive transform coder could be a useful alternative for lower rate speech coding in the videophone. It is recognized that with practical implementations a bandwidth of 7 kHz is probably not attainable at rates of 16 kb/s. The authors have achieved transparent frequency domain coding of 4 kHz bandwidth speech at 16 kb/s and are currently working on extending the transparency bandwidth. The normal telephony bandwidth is 300-3400 Hz. Perceptually, 4 kHz bandwidth speech is superior to normal telephony quality not only because of the extended high frequency content but also because of the inclusion of the bass frequencies in the region 125-300 Hz which give the speech a more life like tint