Low-data-rate Speech Coder (LSC)

LSC is useful for long-duration or small-storage digital speech recording and playback such as for handheld and portable audio/visual devices. It is also useful for bandwidth-efficient wireless voice communication.

LSC is available for 4- and 5-kHz signal bandwidth, with corresponding sample rate at 8 and 11.025 kHz, respectively. LSC-4 achieves 64:1 compression ratio (from the original speech data rate at 128 kbit/s to the compressed rate at 2.0 kbit/s), while LSC-5 achieves 80:1 compression ratio (from the original speech data rate at 176.4 kbit/s to the compressed rate at 2.21 kbit/s).

LSC-5 offers wider-bandwidth voice for applications which require significantly enhanced speech intelligibility such as electronic dictionary.

 

LSC/VX: Combined Voice Compression and Voice Changing - LSC/VX integrates two useful functions into LSC: Voice changing (among male, female, children and robot voices) and speaking speed control. LSC/VX is useful for voice chat for on-line games, language learning devices, e-dictionary, toys, children books, text-to-speech, and many other applications. Importantly, the two added functions require negligible increase in DSP resources (MIPS, RAM and ROM).

 

 

Integrated Voice Compression and Channel Error Protection - For technical description and performance demonstartion, please visit the Voice Communication Moduel page and the Demos page. Voice Communication Module
 

FEATURES

• User-selectable multiple data rates:

  - LSC-4: 0.8/0.9/1.0/1.2/1.4/1.6/1.8/2.0/2.4/2.8 kbit/s; with 2.0 kbit/s as normal operating data rate.

  - LSC-5: 1.66/2.21/3.3 kbit/s; with 2.21 kbit/s as normal operating data rate.

• Robust speech quality even with acoustic background noise.
• I/O format: 16 bit/sample linear PCM. 8 kHz (LSC-4) and 11.025 kHz (LSC-5) sample rate.