static int get_bit_raw(fsk_data *fskd, short *buffer, int *len)
{
/* This function implements a DPLL to synchronize with the bits */
float x,spb,spb2,ds;
int f;
spb = fskd->spb;
if (fskd->spb == 7)
spb = 8000.0 / 1200.0;
ds = spb/32.;
spb2 = spb/2.;
for (f = 0;;) {
if (demodulator(fskd, &x, GET_SAMPLE))
return -1;
if ((x * fskd->x0) < 0) { /* Transition */
if (!f) {
if (fskd->cont<(spb2))
fskd->cont += ds;
else
fskd->cont -= ds;
f = 1;
}
}
fskd->x0 = x;
fskd->cont += 1.;
if (fskd->cont > spb) {
fskd->cont -= spb;
break;
}
}
f = (x > 0) ? 0x80 : 0;
return f;
}
// 文件测试接收
void File_Rx()
{
av_register_all();
boost::coroutines::asymmetric_coroutine<float>::push_type demodulator(FSK_demodulator<CHIPSIZE/2,CHIPSIZE, SAMPLES_PER_CHIP>);
AVFormatContext * avcontext = avformat_alloc_context();
if(avformat_open_input(&avcontext, "test.wav", NULL, NULL))
{
std::cerr << "can't open test.wav" << std::endl;
exit(0);
}
if( avformat_find_stream_info(avcontext, NULL) )
{
std::cerr << "can't guess test.wav file format" << std::endl;
exit(0);
}
AVCodec * decoder = NULL;
int audio_stream_index = av_find_best_stream(avcontext, AVMEDIA_TYPE_AUDIO, -1, -1, &decoder, 0);
if( avcodec_open2(avcontext->streams[audio_stream_index]->codec, decoder, NULL) )
{
std::cerr << "avcodec_open2 failed" << std::endl;
exit(0);
}
// 循环读取
while(true)
{
AVPacket packet = { 0 };
av_init_packet(&packet);
BOOST_SCOPE_EXIT_ALL(&packet)
{
av_free_packet(&packet);
};
// finished
if( av_read_frame(avcontext, &packet) < 0 )
{
std::cerr << "file EOF" << std::endl;
break;
}
if( packet.stream_index != audio_stream_index)
continue;
AVFrame * avframe = av_frame_alloc();
BOOST_SCOPE_EXIT_ALL(&avframe)
{
av_frame_free(&avframe);
};
while(1)
{
int got_frame = 0;
int ret = avcodec_decode_audio4(avcontext->streams[audio_stream_index]->codec, avframe, &got_frame, &packet);
if( ret < 0 )
{
std::cerr << "error decoding audio file" << std::endl;
exit(1);
}
packet.size -= ret;
packet.data += ret;
if (!got_frame && packet.size > 0)
continue;
/* packet中已经没有数据了, 并且不足一个帧, 丢弃这个音频packet. */
if (packet.size == 0 && !got_frame)
break;
if (avframe->linesize[0] != 0)
{
// 传递给流水线下一步
for(int i=0; i < av_samples_get_buffer_size(NULL,
avcontext->streams[audio_stream_index]->codec->channels, avframe->nb_samples,
avcontext->streams[audio_stream_index]->codec->sample_fmt,1) ; i+=2)
{
// 丢掉一个频道
demodulator( avframe->data[0][i] / 32768.0 );
}
}
}
}
for(int i=0; i < avcontext->nb_streams; i ++)
{
if(avcontext->streams[i]->codec)
avcodec_close(avcontext->streams[i]->codec);
}
avformat_close_input(&avcontext);
// RAII 自动关闭了
}
int fsk_serial(fsk_data *fskd, short *buffer, int *len, int *outbyte)
{
int a;
int i,j,n1,r;
int samples = 0;
int olen;
switch (fskd->state) {
/* Pick up where we left off */
case STATE_SEARCH_STARTBIT2:
goto search_startbit2;
case STATE_SEARCH_STARTBIT3:
goto search_startbit3;
case STATE_GET_BYTE:
goto getbyte;
}
/* We await for start bit */
do {
/* this was jesus's nice, reasonable, working (at least with RTTY) code
to look for the beginning of the start bit. Unfortunately, since TTY/TDD's
just start sending a start bit with nothing preceding it at the beginning
of a transmission (what a LOSING design), we cant do it this elegantly */
/*
if (demodulator(zap,&x1)) return(-1);
for (;;) {
if (demodulator(zap,&x2)) return(-1);
if (x1>0 && x2<0) break;
x1 = x2;
}
*/
/* this is now the imprecise, losing, but functional code to detect the
beginning of a start bit in the TDD sceanario. It just looks for sufficient
level to maybe, perhaps, guess, maybe that its maybe the beginning of
a start bit, perhaps. This whole thing stinks! */
if (demodulator(fskd, &fskd->x1, GET_SAMPLE))
return -1;
samples++;
for (;;) {
search_startbit2:
if (*len <= 0) {
fskd->state = STATE_SEARCH_STARTBIT2;
return 0;
}
samples++;
if (demodulator(fskd, &fskd->x2, GET_SAMPLE))
return(-1);
#if 0
printf("x2 = %5.5f ", fskd->x2);
#endif
if (fskd->x2 < -0.5)
break;
}
search_startbit3:
/* We await for 0.5 bits before using DPLL */
i = fskd->spb/2;
if (*len < i) {
fskd->state = STATE_SEARCH_STARTBIT3;
return 0;
}
for (; i>0; i--) {
if (demodulator(fskd, &fskd->x1, GET_SAMPLE))
return(-1);
#if 0
printf("x1 = %5.5f ", fskd->x1);
#endif
samples++;
}
/* x1 must be negative (start bit confirmation) */
} while (fskd->x1 > 0);
fskd->state = STATE_GET_BYTE;
getbyte:
/* Need at least 80 samples (for 1200) or
1320 (for 45.5) to be sure we'll have a byte */
if (fskd->nbit < 8) {
if (*len < 1320)
return 0;
} else {
if (*len < 80)
return 0;
}
/* Now we read the data bits */
j = fskd->nbit;
for (a = n1 = 0; j; j--) {
olen = *len;
i = get_bit_raw(fskd, buffer, len);
buffer += (olen - *len);
if (i == -1)
return(-1);
if (i)
n1++;
a >>= 1;
a |= i;
}
j = 8-fskd->nbit;
a >>= j;
/* We read parity bit (if exists) and check parity */
if (fskd->parity) {
olen = *len;
i = get_bit_raw(fskd, buffer, len);
buffer += (olen - *len);
if (i == -1)
return(-1);
if (i)
n1++;
if (fskd->parity == 1) { /* parity=1 (even) */
if (n1&1)
a |= 0x100; /* error */
} else { /* parity=2 (odd) */
if (!(n1&1))
a |= 0x100; /* error */
}
}
/* We read STOP bits. All of them must be 1 */
for (j = fskd->nstop;j;j--) {
r = get_bit_raw(fskd, buffer, len);
if (r == -1)
return(-1);
if (!r)
a |= 0x200;
}
/* And finally we return */
/* Bit 8 : Parity error */
/* Bit 9 : Framming error*/
*outbyte = a;
fskd->state = STATE_SEARCH_STARTBIT;
return 1;
}
