Hi Radek, Am 29.01.2012 um 14:45 schrieb Radek Polak:
> There is still problems with GSM calls that other site hears echo and you > will > need to set silent profile in Qtmoko's settings to have sound in incoming > call. while testing some boards with our arecord | aplay scripts I observed that the ringing tone of the phone being called is transmitted after several seconds. Let me try an explanation: * arecord on the microphone starts immediately filling the pipe * aplay towards the modem does not start before it gets clocked * this is only when the connection is accepted * this may delay up to 5 seconds * arecord on the modem does start at the same moment * and aplay on the phone sees an empty pipe until then So, the filling level of the pipe microphone -> CPU -> pipe -> CPU -> modem is up to 5 seconds with sound - before the phone call is established. This includes recording the ringing tone of my landline phone :) Since supplier and consumer speeds are both 8 kHz, the pipe filling level remains constant, i.e. the same delay. So a solution would be to use a pipe with limited size (does not exist) or write our own daemon to spawn and communicate with all arecord/aplay subprocesses and discard all microphone data until the first byte from the modem arrives. It does not need to be complex, just forking 4 processes and setting up a select(). Maybe, the code of femtocom.c could even be a start. If I find some time before/during FODEM I could give it a try... Hope this gives an idea... Nikolaus _______________________________________________ Openmoko community mailing list [email protected] http://lists.openmoko.org/mailman/listinfo/community
