Peter, this is fantastic. I can't wait to try to put it to use on, say, 80m!
73, Bruce VE9QRP On Fri, Feb 17, 2012 at 2:06 PM, Peter Lawrence <[email protected]> wrote: > 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 -- http://ve9qrp.blogspot.com ------------------------------------------------------------------------------ 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
