X-Git-Url: https://code.octet-stream.net/m17rt/blobdiff_plain/4e2358c2ade1278f4835bc263e7df1dd8e74e8c9..d5f46a2d5d294c5a4287780dd609475fa73df9a8:/m17core/src/modem.rs?ds=inline diff --git a/m17core/src/modem.rs b/m17core/src/modem.rs index e07826f..8cbd003 100644 --- a/m17core/src/modem.rs +++ b/m17core/src/modem.rs @@ -27,8 +27,10 @@ pub struct SoftDemodulator { candidate: Option, /// How many samples have we received? sample: u64, - /// Remaining samples to ignore so once we already parse a frame we flush it out in full - suppress: u16, + /// Remaining samples to read in before attempting to decode the current candidate + samples_until_decode: Option, + /// Do we think there is a data carrier, i.e., channel in use? If so, at what sample does it expire? + dcd: Option, } impl SoftDemodulator { @@ -40,7 +42,26 @@ impl SoftDemodulator { rx_cursor: 0, candidate: None, sample: 0, - suppress: 0, + samples_until_decode: None, + dcd: None, + } + } +} + +impl SoftDemodulator { + fn dcd_until(&mut self, end_sample: u64) { + if self.dcd.is_none() { + debug!("SoftDemodulator DCD on"); + } + self.dcd = Some(end_sample); + } + + fn check_dcd(&mut self) { + if let Some(end_sample) = self.dcd { + if self.sample > end_sample { + self.dcd = None; + debug!("SoftDemodulator DCD off"); + } } } } @@ -59,18 +80,67 @@ impl Demodulator for SoftDemodulator { self.rx_cursor = (self.rx_cursor + 1) % 1920; self.sample += 1; + self.check_dcd(); - if self.suppress > 0 { - self.suppress -= 1; - return None; + if let Some(samples_until_decode) = self.samples_until_decode { + let sud = samples_until_decode - 1; + if sud > 0 { + self.samples_until_decode = Some(sud); + return None; + } + self.samples_until_decode = None; + + if let Some(c) = self.candidate.take() { + // we have capacity for 192 symbols * 10 upsamples + // we have calculated that the ideal sample point for 192nd symbol is right on the edge + // so take samples from the 10th slot all the way through. + let start_idx = self.rx_cursor + 1920 + 9; + let mut pkt_samples = [0f32; 192]; + for i in 0..192 { + let rx_idx = (start_idx + i * 10) % 1920; + pkt_samples[i] = (self.rx_win[rx_idx] - c.shift) / c.gain; + } + match c.burst { + SyncBurst::Lsf => { + if let Some(frame) = parse_lsf(&pkt_samples) { + return Some(Frame::Lsf(frame)); + } + } + SyncBurst::Bert => { + // TODO: BERT + } + SyncBurst::Stream => { + if let Some(frame) = parse_stream(&pkt_samples) { + return Some(Frame::Stream(frame)); + } + } + SyncBurst::Packet => { + if let Some(frame) = parse_packet(&pkt_samples) { + return Some(Frame::Packet(frame)); + } + } + SyncBurst::Preamble | SyncBurst::EndOfTransmission => { + // should never be chosen as a candidate + } + } + } } - let mut burst_window = [0f32; 71]; - for i in 0..71 { - let c = (self.rx_cursor + i) % 1920; + let mut burst_window = [0f32; 8]; + for i in 0..8 { + let c = (self.rx_cursor + 1920 - 1 - ((7 - i) * 10)) % 1920; burst_window[i] = self.rx_win[c]; } + for burst in [SyncBurst::Preamble, SyncBurst::EndOfTransmission] { + let (diff, _, _) = sync_burst_correlation(burst.target(), &burst_window); + if diff < SYNC_THRESHOLD { + // arbitrary choice, 240 samples = 5ms + // these bursts keep repeating so it will keep pushing out the DCD end time + self.dcd_until(self.sample + 240); + } + } + for burst in [ SyncBurst::Lsf, SyncBurst::Bert, @@ -103,47 +173,17 @@ impl Demodulator for SoftDemodulator { .map(|c| c.burst == burst) .unwrap_or(false) { - if let Some(c) = self.candidate.take() { - let start_idx = self.rx_cursor + 1920 - (c.age as usize); - let start_sample = self.sample - c.age as u64; - let mut pkt_samples = [0f32; 192]; - for i in 0..192 { - let rx_idx = (start_idx + i * 10) % 1920; - pkt_samples[i] = (self.rx_win[rx_idx] - c.shift) / c.gain; - } - match c.burst { - SyncBurst::Lsf => { - debug!( - "Found LSF at sample {} diff {} max {} shift {}", - start_sample, c.diff, c.gain, c.shift - ); - if let Some(frame) = parse_lsf(&pkt_samples) { - self.suppress = 191 * 10; - return Some(Frame::Lsf(frame)); - } - } - SyncBurst::Bert => { - debug!("Found BERT at sample {} diff {}", start_sample, c.diff); - } - SyncBurst::Stream => { - debug!( - "Found STREAM at sample {} diff {} max {} shift {}", - start_sample, c.diff, c.gain, c.shift - ); - if let Some(frame) = parse_stream(&pkt_samples) { - self.suppress = 191 * 10; - return Some(Frame::Stream(frame)); - } - } - SyncBurst::Packet => { - debug!("Found PACKET at sample {} diff {}", start_sample, c.diff); - if let Some(frame) = parse_packet(&pkt_samples) { - self.suppress = 191 * 10; - return Some(Frame::Packet(frame)); - } - } - } - } + // wait until the rest of the frame is in the buffer + let c = self.candidate.as_ref().unwrap(); + self.samples_until_decode = Some((184 * 10) - (c.age as u16)); + debug!( + "Found {:?} at sample {} diff {}", + c.burst, + self.sample - c.age as u64, + c.diff + ); + // After any of these frame types you would expect to see a full EOT + self.dcd_until(self.sample + 1920 + 1920); } } @@ -184,7 +224,7 @@ pub trait Modulator { ); /// Supply the next frame available from the TNC, if it was requested. - fn next_frame(&mut self, frame: Option); + fn provide_next_frame(&mut self, frame: Option); /// Calculate and write out output samples for the soundcard. /// @@ -244,8 +284,9 @@ pub enum ModulatorFrame { } pub struct SoftModulator { + // TODO: 2000 was overflowing around EOT, track down why /// Next modulated frame to output - 1920 samples for 40ms frame plus 80 for ramp-down - next_transmission: [i16; 2000], + next_transmission: [i16; 4000], /// How much of next_transmission should in fact be transmitted next_len: usize, /// How much of next_transmission has been read out @@ -288,7 +329,7 @@ pub struct SoftModulator { impl SoftModulator { pub fn new() -> Self { Self { - next_transmission: [0i16; 2000], + next_transmission: [0i16; 4000], next_len: 0, next_read: 0, tx_delay_padding: 0, @@ -306,20 +347,27 @@ impl SoftModulator { } fn push_sample(&mut self, dibit: f32) { - // Right now we are encoding everything as 1.0-scaled dibit floats - // This is a bit silly but it will do for a minute - // Max theoretical gain from the RRC filter is 4.328 - // Let's bump everything to a baseline of 16383 / 4.328 = 3785.35 - // This is not particularly high but at least we won't ever hit the top - self.filter_win[self.filter_cursor] = dibit * 3785.0; - self.filter_cursor = (self.filter_cursor + 1) % 81; - let mut out: f32 = 0.0; - for i in 0..81 { - let filter_idx = (self.filter_cursor + i) % 81; - out += RRC_48K[i] * self.filter_win[filter_idx]; + // TODO: 48 kHz assumption again + for i in 0..10 { + // Right now we are encoding everything as 1.0-scaled dibit floats + // This is a bit silly but it will do for a minute + // Max possible gain from the RRC filter with upsampling is about 0.462 + // Let's bump everything to a baseline of 16383 / 0.462 = 35461 + // For normal signals this yields roughly 0.5 magnitude which is plenty + if i == 0 { + self.filter_win[self.filter_cursor] = dibit * 35461.0; + } else { + self.filter_win[self.filter_cursor] = 0.0; + } + self.filter_cursor = (self.filter_cursor + 1) % 81; + let mut out: f32 = 0.0; + for i in 0..81 { + let filter_idx = (self.filter_cursor + i) % 81; + out += RRC_48K[i] * self.filter_win[filter_idx]; + } + self.next_transmission[self.next_len] = out as i16; + self.next_len += 1; } - self.next_transmission[self.next_len] = out as i16; - self.next_len += 1; } fn request_frame_if_space(&mut self) { @@ -336,6 +384,7 @@ impl Modulator for SoftModulator { capacity: usize, output_latency: usize, ) { + //log::debug!("modulator update_output_buffer {samples_to_play} {capacity} {output_latency}"); self.output_latency = output_latency; self.buf_capacity = capacity; self.samples_in_buf = samples_to_play; @@ -350,7 +399,7 @@ impl Modulator for SoftModulator { self.request_frame_if_space(); } - fn next_frame(&mut self, frame: Option) { + fn provide_next_frame(&mut self, frame: Option) { let Some(frame) = frame else { self.try_get_frame = false; return; @@ -410,7 +459,7 @@ impl Modulator for SoftModulator { // if we have pre-TX padding to accommodate TxDelay then expend that first if self.tx_delay_padding > 0 { - let len = out.len().max(self.tx_delay_padding); + let len = out.len().min(self.tx_delay_padding); self.tx_delay_padding -= len; for x in 0..len { out[x] = 0; @@ -421,7 +470,7 @@ impl Modulator for SoftModulator { // then follow it with whatever might be left in next_transmission let next_remaining = self.next_len - self.next_read; if next_remaining > 0 { - let len = (out.len() - written).max(next_remaining); + let len = (out.len() - written).min(next_remaining); out[written..(written + len)] .copy_from_slice(&self.next_transmission[self.next_read..(self.next_read + len)]); self.next_read += len;