Open speech Codec. Low bitrate 2400 b/s down to 1400 b/s
Applcations for digital radio
Fills <5000 b/s gap
http://rowetel.com/codec2.html
Not a DSP talk
Can send 45 calls inside 64 kb/s chanel
Not useful for VOIP due to IP/UDP overhead of 8kb/s on 1400b/s data
Main use radio spectrum. Less data = less power required since your power gets concentrate on less bits
doesn’t matter too much if odd packet dropped
proprietary codecs slowing digital voice over radio
Proprietary codes: hardware or licensed software form, difficult to distribute, can’t modify
Example g729 license $40k. Doesn’t believe closed source codecs benefit society
Authors of propriety/patented codecs borrowed heavily from public domain. perhaps 5% is original. Good news is only 5% needs to be replaced
Speech coding: eg 16bit samples at 8kHz, comprss to 1400-2400 b/s . What can we thrown away, retain intelligible speech, retain natural speech. Use a model of speech, send model parameters, for effecient than coding waveform
Model: example is pitch, humans 50-500 Hz , can be represented with 7 bits, updated every 20ms 7/0.02 = 350b/s to represent pitch
Bit allocation: 56bits every 40ms. Of these: Amplitude 32 , Frame energy 10 , voicing 4, pitch 10
Developing Codecs: complex DSP algorithms, run codecs in non-realtime, dump values from codecs every “frame” ( 80 samples, 10 ms of speech) . Gnu Octave
Banned exports list includes ” Speech codecs below 2400 b/s ” . Have been advised by DECO that Codec 2 has “assessed as not controlled” but waiting for certificate
UEFI and Linux – Matthew Garrett
Replacement for PC BIOS
BSD licensed core
Adds standardized support for new hardware features
Platform init
EFI image load – loaded drivers
EFI OS loader load – oot from ordered list of EFIOS loaders
