#include "freedv_api_internal.h"
#include "comp_prim.h"
-#define VERSION 10 /* The API version number. The first version is 10. Increment if the API changes
- in a way that would require changes by the API user. */
+#define VERSION 10 /* The API version number. The first version
+ is 10. Increment if the API changes in a
+ way that would require changes by the API
+ user. */
/*
* Version 10 Initial version August 2, 2015.
* Version 11 September
AUTHOR......: David Rowe
DATE CREATED: 3 August 2014
- Takes a frame of input speech samples, encodes and modulates them to produce
- a frame of modem samples that can be sent to the transmitter.
+ Takes a frame of input speech samples, encodes and modulates them to
+ produce a frame of modem samples that can be sent to the
+ transmitter. See freedv_tx.c for an example.
- speech_in[] is sampled at 8 kHz, the user must supply
- f->n_speech_samples. The speech_in[] level should be such that the
- peak speech level is between +/16384 and +/- 32767.
+ speech_in[] is sampled at 8000 Hz, and the user must supply a block
+ of exactly freedv_get_n_speech_samples(). The speech_in[] level
+ should be such that the peak speech level is between +/- 16384 and
+ +/- 32767.
- The FDM modem signal mod_out[] is sampled at f->modem_sample_rate
- and is f->n_modem_samples long. mod_out[] will be scaled such that
- the peak level is just less than +/-32767.
+ The FDM modem signal mod_out[] is sampled at
+ freedv_get_modem_sample_rate() Hz and is
+ freedv_get_n_nom_modem_samples() long. mod_out[] will be scaled
+ such that the peak level is just less than +/-32767.
+
+ Note that freedv_get_modem_sample_rate() is 8000 Hz for 1600 mode
+ but 7500 Hz for 700 and 700B mode. You must convert sample rates as
+ required.
+
+ The complex-valued output can directly drive an I/Q modulator to
+ produce a single sideband signal. To generate the other sideband,
+ take the complex conjugate of mod_out[].
The FreeDV 1600 modem has a high crest factor (around 12dB), however
the energy and duration of the peaks is small. FreeDV 1600 is
- usually operated at a "backoff" of 8dB. Adjust the power
- amplifier drive so that the average power is 8dB less than the
- peak power of the PA. For example, on a radio rated at 100W PEP for
- SSB, the average FreeDV power is typically 20W.
+ usually operated at a "backoff" of 8dB. Adjust the power amplifier
+ drive so that the average power is 8dB less than the peak power of
+ the PA. For example, on a radio rated at 100W PEP for SSB, the
+ average FreeDV power is typically 20W.
- The FreeDV 900 modem has a crest factor of about 5dB (with f->clip=1, the
- default), so if your PA can handle it, it can be driven harder than
- FreeDV 1600. Caution - some PAs cannot handle a high continuous
- power. A conservative level is 20W average for a 100W PEP rated PA.
+ The FreeDV 700 modem has a crest factor of about 8dB (with
+ f->clip=1, the default), so if your PA can handle it, it can be
+ driven harder than FreeDV 1600. Caution - some PAs cannot handle a
+ high continuous power. A conservative level is 20W average for a
+ 100W PEP rated PA.
\*---------------------------------------------------------------------------*/
AUTHOR......: David Rowe
DATE CREATED: 3 August 2014
- Takes a frame of samples from the radio receiver, demodulates them,
- then decodes them, producing a frame of decoded speech samples.
+ Takes a frame of samples from the radio receiver, demodulates and
+ decodes them, producing a frame of decoded speech samples. See
+ freedv_rx.c for an example.
- Both demod_in[] and speech_out[] are 16 bit shorts sampled at 8 kHz.
- The peak level of demod_in[] is not critical, as the demod works
- well over a wide range of amplitude scaling. However it is best to
- avoid clipping (overload, or samples pinned to +/- 32767). Suggest
- scaling so the peak (modem signal plus noise) is between +/-16384
- and +/-32767. speech_out[] will peak at just less than +/-32767.
+ demod_in[] is a variable length block of received samples at the
+ modem sample rate given by freedv_get_n_max_modem_samples(). To
+ account for difference in the transmit and receive sample clock
+ frequencies, the number of demod_in[] samples is time varying. You
+ MUST call freedv_nin() BEFORE each call to freedv_rx() and pass
+ exactly that many samples to this function.
- To account for difference in the transmit and receive sample clock
- frequencies, the number of demod_in[] samples is time varying. It
- is the responsibility of the caller to supply the correct number of
- samples. Call freedv_nin() before each call to freedv_rx() to
- determine how many samples to pass to this function (see example).
+ To help set your buffer sizes, The maximum value of freedv_nin() is
+ freedv_get_n_max_modem_samples().
- The maximum vlaue of freedv_nin is set by f->n_max_modem_samples,
- allocate this much storage to your buffers.
+ freedv_rx() returns the number of output speech samples available in
+ speech_out[], which is sampled at 8000 Hz. You should ALWAYS check
+ the return value of freedv_rx(), and read EXACTLY that number of
+ speech samples from speech_out[].
- Returns the number of output speech samples available in
- speech_out[]. When in sync this will typically alternate between 0
- and f->n_speech_samples. When out of sync, this will be f->nin.
+ 1600 mode: When out of sync, it the number of output speech samples
+ returned will be freedv_nin(). When in sync to a valid FreeDV 1600
+ signal, the number of output speech samples will alternate between
+ freedv_get_n_speech_samples() and 0.
+
+ 700 and 700B mode: The number of output speech samples returned will
+ is always be freedv_get_n_speech_samples(), regardless of sync.
+
+ The peak level of demod_in[] is not critical, as the demod works
+ well over a wide range of amplitude scaling. However avoid clipping
+ (overload, or samples pinned to +/- 32767). speech_out[] will peak
+ at just less than +/-32767.
When out of sync, this function echoes the demod_in[] samples to
speech_out[]. This allows the user to listen to the channel, which
is useful for tuning FreeDV signals or reception of non-FreeDV
- signals.
+ signals. Setting the squelch with freedv_set_squelch_en(1) will
+ return zero-valued samples instead.
\*---------------------------------------------------------------------------*/
// Get integers
int freedv_get_test_frames (struct freedv *f) {return f->test_frames;}
int freedv_get_n_speech_samples (struct freedv *f) {return f->n_speech_samples;}
+int freedv_get_modem_sample_rate (struct freedv *f) {return f->modem_sample_rate;}
int freedv_get_n_max_modem_samples (struct freedv *f) {return f->n_max_modem_samples;}
int freedv_get_n_nom_modem_samples (struct freedv *f) {return f->n_nom_modem_samples;}
int freedv_get_total_bits (struct freedv *f) {return f->total_bits;}
projects / freetel-svn-tracking.git / commitdiff