Based on the feedback, I've written and uploaded a v0_2 version: http://code.google.com/p/codec2demo/downloads/list
Changes are: - adoption of 48kHz sample rate - use of ALSA API for Linux The .wav files to use at the transmitter were also updated to 48kHz. On Wed, Feb 15, 2012 at 11:08 AM, Peter Lawrence <[email protected]> wrote: > All, I've written proof-of-concept PC software to demonstrate > receiving Codec2-encoded speech over an audio/radio link using a > soundcard. > > It uses a 2500 bps OFDM implementation to convey raw Codec2 data in > about 2.2kHz of audio. > > In the spirit of David's post, there is no FEC and the symbol period > is the same as the Codec2 frame size. The classic 2500bps Codec2 code > is used. > > It is a multi-platform tool (Windows and Linux) and source code and > binaries are provided: > > http://code.google.com/p/codec2demo/ > > The suggested usage is to use one of the provided pre-encoded modem > .wav files (see download section of web page) at the transmitter and > use the tool at the receiver. > > Using the tool, the user picks one soundcard to listen for the modem > signal and one soundcard to playback the speech. (These can be the > same soundcard.) > > As with any soundcard software, some manual tweaking of the audio > levels (both at the transmitter and at the receiver) is needed. I've > provided some instructions in the wiki section on volume controls in > Ubuntu and Windows. > > When the Linux version detects a modem signal, it turns green. On the > Windows version, it displays the word "RECEIVING". > > I've been testing with a simple acoustical coupling of microphone to > speaker. As I increase the distance between microphone and speaker, > the voice quality becomes corrupted and eventually cuts out. > > It would be nice if someone could test it with a real radio link. I > don't claim to know the entire history of Codec2 testing, but you > might literally be the very first person in the world to use a Codec2 > radio link! :) > > Note that because there is no FEC, there will be bit errors; the > Codec2 decoder can misinterpret these errors as loud digital > artifacts. So, please exercise some caution; an open loudspeaker to > listen to the decoded speech seems preferable to using a > headset/handset. > ------------------------------------------------------------------------------ Virtualization & Cloud Management Using Capacity Planning Cloud computing makes use of virtualization - but cloud computing also focuses on allowing computing to be delivered as a service. http://www.accelacomm.com/jaw/sfnl/114/51521223/ _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
