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Draft new Recommendation ITU-T G.711.0 (ex G.711-LLC) Lossless compression of G.711 pulse code modulation AAP Summary ITU-T Recommendation G.711 is the benchmark standard for narrowband PSTN/GSTN telephony encoding and has been so for many decades. Owing to its proven voice quality, ubiquity and utility, G.711 continues to enjoy widespread use in today’s newer packet-based networks – even when neither endpoint interfaces to a telephony network. The rationale for continued use of G.711 over newer and more bandwidth-efficient coders is varied according to use cases and can include: the desire to attain highest telephony voice quality, to provide highest available linearity for effective network echo canceller/suppressor applications, to provide for highest possible FAX/modem connect speeds, and the need for improved interworking with accessibility devices (e.g., text telephony). Many of these use cases require G.711 without the use of silence suppression. To address these needs, G.711.0 (ex G.711-LLC) defines a lossless and stateless compression for G.711 packet payloads typically used in IP networks. The stateless design does not allow for error propagation, as the original G.711 payload can be recreated using only data contained in the compressed payload. The lossless design allows for G.711.0 compression and decompression to be applied multiple times on an end-to-end connection (multiple self-transcodings) with no degradation of voice/audio quality. G.711.0 may be used as a traditional codec with its use negotiated end-to-end. However, its lossless and stateless design also allows its use as a compression mechanism on any link (or combination of links) where G.711 has been negotiated end-to-end. In this case, explicit use of G.711.0 on any intermediate link need not be signaled to or negotiated by the end systems. G.711.0 accommodates both G.711 coding laws (µ-law and A-law) and frame lengths typically used in IP networks (40, 80, 160, 240 and 320 samples). It is lossless for all possible G.711 packet payloads. G.711.0 has been designed to have low complexity (1.0 WMOPS average, less than 1.7 WMOPS worst case) and low memory footprint (less than 5k octets RAM, 5k octets ROM, and 3.6k basic operations) while effectively compressing the dominant use-case of G.711 encoding of zero-mean acoustic signals (e.g., speech and audio). The G.711.0 codec has been characterized to provide over 50% average compression in typical service provider environments and over 65% in typical office environments. Overall compression is primarily a function of the signal type and level, background noise level, and encoding law (µ-law or A-law). ITU-T G.711.0 contains as electronic attachments a reference ANSI-C source code and the associated test vectors.