This is required if multiple SDP responses are returned. We don't want
to remove a codec with with the first SDP response, which might get
accepted by the second SDP response. Instead we flag the codec as
negotiated or not negotiated.
When early media is received, different codecs may be accepted as when
we receive the actual answer.
A voice message can be sent with a wave file. Pagers that support voice
messages will listen to the wave file on the radio channel.
Use the following command to send a voice message:
$ echo "1709829,v,<wave file>" > /tmp/golay_msg_send
1. Phase is now changed proportional to the time of the bit change, if
it happens somewhere between samples. The amount of phase change per
bit is now the same for all bits, no matter how many samples
currently lay inside this bit.
2. IIR filter is removed, because it causes distortions. A cosine shape
is now used to transit between phase change of F0 to F1 and vice
versa. This limits the spectrum. This filter is optional.
Naming it UPDATE was not a good idea.
Now this is renamed to MODIFY message, related to MNCC (GSM). It is used
to change media coding during a call. It allows new codec negotiation
using SDP protocol and/or changing RTP peer. Also useful for SIP.
Also the dtmf encoder will return less samples, if the digit(+pause)
ends, so that the caller call set the next digit to play seamlessly.
A reset function allows to clear the decoder states, to prevent glitches
when re-attaching to an interrupted stream.