Voice UDP to RF conversion, and better sample rate management in codec2

[m17rt] / m17core / src / reflector / convert.rs

diff --git a/m17core/src/reflector/convert.rs b/m17core/src/reflector/convert.rs
new file mode 100644 (file)
index 0000000..8e5a96d
--- /dev/null
+++ b/m17core/src/reflector/convert.rs
@@ -0,0 +1,58 @@
+//! Utilities for converting streams between UDP and RF representations
+
+use crate::protocol::{LsfFrame, StreamFrame};
+
+use super::packet::Voice;
+
+/// Accepts `Voice` packets from a reflector and turns them into LSF and Stream frames.
+///
+/// This is the format required for the voice data to cross the KISS protocol boundary.
+pub struct VoiceToRf {
+    /// Link Setup most recently acquired
+    lsf: Option<LsfFrame>,
+    /// Which LICH part we are going to emit next, 0-5
+    lich_cnt: usize,
+}
+
+impl VoiceToRf {
+    pub fn new() -> Self {
+        Self {
+            lsf: None,
+            lich_cnt: 0,
+        }
+    }
+
+    /// For a Voice packet received from a reflector, return the frames that would be transmitted
+    /// on RF, including by reconstructing the LICH parts of the stream frame.
+    ///
+    /// If this is the start of a new or different stream transmission, this returns the Link Setup
+    /// Frame which comes first, then the first associated Stream frame.
+    ///
+    /// If this is a continuation of a transmission matching the previous LSF, then it returns only
+    /// the Stream frame.
+    pub fn next(&mut self, voice: &Voice) -> (Option<LsfFrame>, StreamFrame) {
+        let this_lsf = voice.link_setup_frame();
+        let emit_lsf = if Some(&this_lsf) != self.lsf.as_ref() {
+            self.lsf = Some(this_lsf.clone());
+            self.lich_cnt = 0;
+            true
+        } else {
+            false
+        };
+        let lsf = self.lsf.as_ref().unwrap();
+        let stream = StreamFrame {
+            lich_idx: self.lich_cnt as u8,
+            lich_part: (&lsf.0[self.lich_cnt * 5..(self.lich_cnt + 1) * 5])
+                .try_into()
+                .unwrap(),
+            frame_number: voice.frame_number(),
+            end_of_stream: voice.is_end_of_stream(),
+            stream_data: voice.payload().try_into().unwrap(),
+        };
+        let lsf = if emit_lsf { self.lsf.clone() } else { None };
+        if voice.is_end_of_stream() {
+            self.lsf = None;
+        }
+        (lsf, stream)
+    }
+}