September 2008
Intermediate to advanced
550 pages
18h 10m
English
Content preview from VoIP Voice and Fax Signal ProcessingBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
20
VoIP VOICE QUALITY
For several decades, telephone users have been experiencing public switched telephone network (PSTN) based voice communication quality. Subjectively, this experience is used as the main reference for comparing the voice quality from other voice communication systems. In PSTN-based systems, voice has good intelligibility, acceptable speaker identification, naturalness, and only minor disturbing impairments. The PSTN uses G.711 μ-law and A-law as compression. Compressed bits are sent on synchronous times-division multiplexed (TDM) interfaces. In VoIP voice communication, a similar G.711 is also used end to end as one of the compression codecs. In VoIP, instead of TDM bits, groups of compressed bytes are sent as a packet on the Internet Protocol (IP) network. The VoIP quality closely matches with PSTN quality under the correct conditions of end-to-end G.711 IP packet transmission. VoIP will also use many high-compression codecs like G.729AB, G.723.1A, and iLBC, which causes VoIP voice quality to be lower than PSTN quality even in best end-to-end packet delivery networks. The goal here is how to reach and finally to exceed PSTN quality through VoIP.
VoIP will have to take care of additional impairments to achieve the quality comparable with the PSTN quality. The four main voice impairment contributors popularly referred for VoIP telephony according to TIA-810A [TIA/EIA-810A (2000)] are delay, echo, voice compression, and packet loss. In a recent upgrade of TIA ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.