feat: Phase 2 — relay daemon and client library with integration pipelines

wzp-relay:
- RelayPipeline: ingest → FEC decode → jitter buffer → FEC encode → send
- SessionManager: tracks active calls, idle expiry
- RelayConfig: TOML-based configuration
- Binary: accepts QUIC connections, receives media packets

wzp-client:
- CallEncoder: mic PCM → Opus encode → FEC → MediaPackets
- CallDecoder: MediaPackets → FEC decode → jitter → Opus decode → PCM
- CLI binary: connects to relay, sends test silence frames

99 tests passing across all 7 crates.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/wzp-client/src/call.rs

@@ -0,0 +1,293 @@
+//! Call session — manages the end-to-end pipeline for a single voice call.
+//!
+//! Pipeline: mic → encode → FEC → encrypt → send / recv → decrypt → FEC → decode → speaker
+
+use bytes::Bytes;
+use tracing::{debug, warn};
+
+use wzp_fec::{RaptorQFecDecoder, RaptorQFecEncoder};
+use wzp_proto::jitter::{JitterBuffer, PlayoutResult};
+use wzp_proto::packet::{MediaHeader, MediaPacket};
+use wzp_proto::quality::AdaptiveQualityController;
+use wzp_proto::traits::{
+    AudioDecoder, AudioEncoder, FecDecoder, FecEncoder,
+};
+use wzp_proto::QualityProfile;
+
+/// Configuration for a call session.
+pub struct CallConfig {
+    /// Initial quality profile.
+    pub profile: QualityProfile,
+    /// Jitter buffer target depth.
+    pub jitter_target: usize,
+    /// Jitter buffer max depth.
+    pub jitter_max: usize,
+    /// Jitter buffer min depth before playout.
+    pub jitter_min: usize,
+}
+
+impl Default for CallConfig {
+    fn default() -> Self {
+        Self {
+            profile: QualityProfile::GOOD,
+            jitter_target: 50,
+            jitter_max: 250,
+            jitter_min: 25,
+        }
+    }
+}
+
+/// Manages the encode/send side of a call.
+pub struct CallEncoder {
+    /// Audio encoder (Opus or Codec2).
+    audio_enc: Box<dyn AudioEncoder>,
+    /// FEC encoder.
+    fec_enc: RaptorQFecEncoder,
+    /// Current profile.
+    profile: QualityProfile,
+    /// Outbound sequence counter.
+    seq: u16,
+    /// Current FEC block.
+    block_id: u8,
+    /// Frame index within current block.
+    frame_in_block: u8,
+    /// Timestamp counter (ms).
+    timestamp_ms: u32,
+}
+
+impl CallEncoder {
+    pub fn new(config: &CallConfig) -> Self {
+        Self {
+            audio_enc: wzp_codec::create_encoder(config.profile),
+            fec_enc: wzp_fec::create_encoder(&config.profile),
+            profile: config.profile,
+            seq: 0,
+            block_id: 0,
+            frame_in_block: 0,
+            timestamp_ms: 0,
+        }
+    }
+
+    /// Encode a PCM frame and produce media packets (source + repair when block is full).
+    ///
+    /// Input: 48kHz mono PCM, frame size depends on profile (960 for 20ms, 1920 for 40ms).
+    /// Output: one or more MediaPackets to send.
+    pub fn encode_frame(&mut self, pcm: &[i16]) -> Result<Vec<MediaPacket>, anyhow::Error> {
+        // Encode audio
+        let mut encoded = vec![0u8; self.audio_enc.max_frame_bytes()];
+        let enc_len = self.audio_enc.encode(pcm, &mut encoded)?;
+        encoded.truncate(enc_len);
+
+        // Build source media packet
+        let source_pkt = MediaPacket {
+            header: MediaHeader {
+                version: 0,
+                is_repair: false,
+                codec_id: self.profile.codec,
+                has_quality_report: false,
+                fec_ratio_encoded: MediaHeader::encode_fec_ratio(self.profile.fec_ratio),
+                seq: self.seq,
+                timestamp: self.timestamp_ms,
+                fec_block: self.block_id,
+                fec_symbol: self.frame_in_block,
+                reserved: 0,
+                csrc_count: 0,
+            },
+            payload: Bytes::from(encoded.clone()),
+            quality_report: None,
+        };
+
+        self.seq = self.seq.wrapping_add(1);
+        self.timestamp_ms = self
+            .timestamp_ms
+            .wrapping_add(self.profile.frame_duration_ms as u32);
+
+        let mut output = vec![source_pkt];
+
+        // Add to FEC encoder
+        self.fec_enc.add_source_symbol(&encoded)?;
+        self.frame_in_block += 1;
+
+        // If block is full, generate repair and finalize
+        if self.frame_in_block >= self.profile.frames_per_block {
+            if let Ok(repairs) = self.fec_enc.generate_repair(self.profile.fec_ratio) {
+                for (sym_idx, repair_data) in repairs {
+                    output.push(MediaPacket {
+                        header: MediaHeader {
+                            version: 0,
+                            is_repair: true,
+                            codec_id: self.profile.codec,
+                            has_quality_report: false,
+                            fec_ratio_encoded: MediaHeader::encode_fec_ratio(
+                                self.profile.fec_ratio,
+                            ),
+                            seq: self.seq,
+                            timestamp: self.timestamp_ms,
+                            fec_block: self.block_id,
+                            fec_symbol: sym_idx,
+                            reserved: 0,
+                            csrc_count: 0,
+                        },
+                        payload: Bytes::from(repair_data),
+                        quality_report: None,
+                    });
+                    self.seq = self.seq.wrapping_add(1);
+                }
+            }
+            let _ = self.fec_enc.finalize_block();
+            self.block_id = self.block_id.wrapping_add(1);
+            self.frame_in_block = 0;
+        }
+
+        Ok(output)
+    }
+
+    /// Update the quality profile (codec switch, FEC ratio change).
+    pub fn set_profile(&mut self, profile: QualityProfile) -> Result<(), anyhow::Error> {
+        self.audio_enc.set_profile(profile)?;
+        self.fec_enc = wzp_fec::create_encoder(&profile);
+        self.profile = profile;
+        self.frame_in_block = 0;
+        Ok(())
+    }
+}
+
+/// Manages the recv/decode side of a call.
+pub struct CallDecoder {
+    /// Audio decoder.
+    audio_dec: Box<dyn AudioDecoder>,
+    /// FEC decoder.
+    fec_dec: RaptorQFecDecoder,
+    /// Jitter buffer.
+    jitter: JitterBuffer,
+    /// Quality controller.
+    quality: AdaptiveQualityController,
+    /// Current profile.
+    profile: QualityProfile,
+}
+
+impl CallDecoder {
+    pub fn new(config: &CallConfig) -> Self {
+        Self {
+            audio_dec: wzp_codec::create_decoder(config.profile),
+            fec_dec: wzp_fec::create_decoder(&config.profile),
+            jitter: JitterBuffer::new(config.jitter_target, config.jitter_max, config.jitter_min),
+            quality: AdaptiveQualityController::new(),
+            profile: config.profile,
+        }
+    }
+
+    /// Feed a received media packet into the decode pipeline.
+    pub fn ingest(&mut self, packet: MediaPacket) {
+        // Feed to FEC decoder
+        let _ = self.fec_dec.add_symbol(
+            packet.header.fec_block,
+            packet.header.fec_symbol,
+            packet.header.is_repair,
+            &packet.payload,
+        );
+
+        // If not a repair packet, also feed directly to jitter buffer
+        if !packet.header.is_repair {
+            self.jitter.push(packet);
+        }
+    }
+
+    /// Decode the next audio frame from the jitter buffer.
+    ///
+    /// Returns PCM samples (48kHz mono) or None if not ready.
+    pub fn decode_next(&mut self, pcm: &mut [i16]) -> Option<usize> {
+        match self.jitter.pop() {
+            PlayoutResult::Packet(pkt) => {
+                match self.audio_dec.decode(&pkt.payload, pcm) {
+                    Ok(n) => Some(n),
+                    Err(e) => {
+                        warn!("decode error: {e}, using PLC");
+                        self.audio_dec.decode_lost(pcm).ok()
+                    }
+                }
+            }
+            PlayoutResult::Missing { seq } => {
+                debug!(seq, "packet loss, generating PLC");
+                self.audio_dec.decode_lost(pcm).ok()
+            }
+            PlayoutResult::NotReady => None,
+        }
+    }
+
+    /// Get the current quality profile.
+    pub fn profile(&self) -> QualityProfile {
+        self.profile
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use wzp_proto::CodecId;
+
+    #[test]
+    fn encoder_produces_packets() {
+        let config = CallConfig::default();
+        let mut enc = CallEncoder::new(&config);
+
+        // 20ms at 48kHz = 960 samples
+        let pcm = vec![0i16; 960];
+        let packets = enc.encode_frame(&pcm).unwrap();
+        assert!(!packets.is_empty());
+        assert_eq!(packets[0].header.seq, 0);
+        assert!(!packets[0].header.is_repair);
+    }
+
+    #[test]
+    fn encoder_generates_repair_on_full_block() {
+        let config = CallConfig {
+            profile: QualityProfile::GOOD, // 5 frames/block
+            ..Default::default()
+        };
+        let mut enc = CallEncoder::new(&config);
+        let pcm = vec![0i16; 960];
+
+        let mut total_packets = 0;
+        let mut repair_count = 0;
+        for _ in 0..5 {
+            let packets = enc.encode_frame(&pcm).unwrap();
+            for p in &packets {
+                if p.header.is_repair {
+                    repair_count += 1;
+                }
+            }
+            total_packets += packets.len();
+        }
+        assert!(repair_count > 0, "should have repair packets after full block");
+        assert!(total_packets > 5, "total {total_packets} should exceed 5 source");
+    }
+
+    #[test]
+    fn decoder_handles_ingest() {
+        let config = CallConfig::default();
+        let mut dec = CallDecoder::new(&config);
+
+        let pkt = MediaPacket {
+            header: MediaHeader {
+                version: 0,
+                is_repair: false,
+                codec_id: CodecId::Opus24k,
+                has_quality_report: false,
+                fec_ratio_encoded: 0,
+                seq: 0,
+                timestamp: 0,
+                fec_block: 0,
+                fec_symbol: 0,
+                reserved: 0,
+                csrc_count: 0,
+            },
+            payload: Bytes::from(vec![0u8; 60]),
+            quality_report: None,
+        };
+        dec.ingest(pkt);
+        // Not enough buffered yet (min_depth = 25)
+        let mut pcm = vec![0i16; 960];
+        assert!(dec.decode_next(&mut pcm).is_none());
+    }
+}