On 30. May 2017, at 09:43, Mychaela Falconia mychaela.falconia@gmail.com wrote:
Holger Freyther holger@freyther.de wrote:
Hi
What exactly are the bits which you send and receive every 40 ms? Do you get two 260-bit GSM 06.10 codec frames every 40 ms, with the ability to send your own arbitrary bits into the TCH uplink, including the possibility of passing non-speech data over voice TCH if the network does TFO as in GSM 02.53? The latter is what the Calypso DSP allows.
It is alaw. I assume the Qualcomm DSP will do the transcoding but I didn't look/trace the implementation (and the UC20 doesn't run Linux).
E.g. I used this to play a sine wave on a connected call.
gst-launch-1.0 audiotestsrc wave=sine ! audioconvert ! audioresample ! audio/x-raw, rate=8000, channels=1, format=S16LE ! filesink location=/dev/ttyUSB1 sync=true