For the last few weeks I have been working on integrating the new LPC post filter into Codec 2 as part of some paid Codec 2 work to develop higher quality, higher bit rate modes for VOIP. Although I actually had a budget of up to 6400 bit/s, much to my embarrasment I couldn’t work out a way to effectively use more than 3200 bit/s!
Anyway I am quite happy with the quality improvement, and the new 3200 bit/s mode. See what you think:
|Previous Codec 2 2400 bit/s||New Codec 2 2400 bit/s||Codec 2 3200 bit/s||AMR-NB 4750 bit/s||8000 bit/s Codec|
See the Codec 2 page for some other samples.
I think Codec 2 at 3200 bit/s holds up OK next to AMR-NB at 4750 bit/s. AMR is a heavily patented, license encumbered Codec, running at a 50% higher bit rate, which was developed with the resources of several multi-national corporations. According to the Wikipedia page you need to pay $6,500 for a license, then a minimum of $10,000 a year in royalties.
More quality improvements to Codec 2 are possible in future. I am not a multi-national corporation, just some guy hacking on a kitchen table. Now I better go and make dinner!