Add MKV muxer and event system

- Add event.rs: structured event system for progress reporting
- Add mux/: MKV muxer pipeline (EBML writer, TS demuxer, stream assembly)
  - Codec parsers: H.264, HEVC, AC-3, DTS, TrueHD, PGS, VC-1
  - Lookahead buffer for codec private data extraction
  - Direct m2ts-to-MKV streaming without intermediate files

src/mux/codec/hevc.rs

@@ -0,0 +1,170 @@
+//! HEVC (H.265) elementary stream parser.
+//!
+//! Extracts VPS, SPS, PPS NAL units for MKV codecPrivate.
+//! Detects keyframes (IRAP pictures: IDR, CRA, BLA).
+//! Each PES packet = one access unit = one frame.
+
+use super::{CodecParser, Frame, PesPacket, pts_to_ns};
+use super::h264::{find_start_code, skip_start_code};
+
+// HEVC NAL unit types
+const NAL_VPS: u8 = 32;
+const NAL_SPS: u8 = 33;
+const NAL_PPS: u8 = 34;
+const NAL_AUD: u8 = 35;
+// IRAP types (keyframes): BLA, IDR, CRA
+const NAL_BLA_W_LP: u8 = 16;
+const NAL_RSV_IRAP_VCL23: u8 = 23;
+
+pub struct HevcParser {
+    vps: Option<Vec<u8>>,
+    sps: Option<Vec<u8>>,
+    pps: Option<Vec<u8>>,
+}
+
+impl HevcParser {
+    pub fn new() -> Self {
+        Self { vps: None, sps: None, pps: None }
+    }
+}
+
+impl CodecParser for HevcParser {
+    fn parse(&mut self, pes: &PesPacket) -> Vec<Frame> {
+        if pes.data.is_empty() {
+            return Vec::new();
+        }
+
+        let pts_ns = pes.pts.map(pts_to_ns).unwrap_or(0);
+        let data = &pes.data;
+        let mut keyframe = false;
+
+        // Scan NAL units
+        let mut pos = 0;
+        while let Some(sc_pos) = find_start_code(data, pos) {
+            if let Some(nal_start) = skip_start_code(data, sc_pos) {
+                let next = find_start_code(data, nal_start).unwrap_or(data.len());
+                let mut end = next;
+                while end > nal_start && data[end - 1] == 0x00 { end -= 1; }
+
+                if nal_start < data.len() {
+                    // HEVC NAL header: 2 bytes. Type is bits 1-6 of first byte.
+                    let nal_type = (data[nal_start] >> 1) & 0x3F;
+
+                    match nal_type {
+                        NAL_VPS => self.vps = Some(data[nal_start..end].to_vec()),
+                        NAL_SPS => self.sps = Some(data[nal_start..end].to_vec()),
+                        NAL_PPS => self.pps = Some(data[nal_start..end].to_vec()),
+                        t if t >= NAL_BLA_W_LP && t <= NAL_RSV_IRAP_VCL23 => {
+                            keyframe = true;
+                        }
+                        _ => {}
+                    }
+                }
+                pos = next;
+            } else {
+                break;
+            }
+        }
+
+        // Convert Annex B to length-prefixed NALUs.
+        // Skip VPS/SPS/PPS/AUD — they're in codecPrivate.
+        let mut frame_data = Vec::new();
+        let mut pos = 0;
+        while let Some(sc_pos) = find_start_code(&pes.data, pos) {
+            if let Some(nal_start) = skip_start_code(&pes.data, sc_pos) {
+                let next = find_start_code(&pes.data, nal_start).unwrap_or(pes.data.len());
+                let mut end = next;
+                while end > nal_start && pes.data[end - 1] == 0x00 { end -= 1; }
+
+                if nal_start < pes.data.len() {
+                    let nal_type = (pes.data[nal_start] >> 1) & 0x3F;
+                    // Skip parameter sets and AUD
+                    if nal_type != NAL_VPS && nal_type != NAL_SPS && nal_type != NAL_PPS && nal_type != NAL_AUD {
+                        let nal = &pes.data[nal_start..end];
+                        let len = nal.len() as u32;
+                        frame_data.extend_from_slice(&len.to_be_bytes());
+                        frame_data.extend_from_slice(nal);
+                    }
+                }
+                pos = next;
+            } else {
+                break;
+            }
+        }
+
+        if frame_data.is_empty() {
+            return Vec::new();
+        }
+
+        vec![Frame {
+            pts_ns,
+            keyframe,
+            data: frame_data,
+        }]
+    }
+
+    fn codec_private(&self) -> Option<Vec<u8>> {
+        // HEVCDecoderConfigurationRecord (ISO 14496-15)
+        let vps = self.vps.as_ref()?;
+        let sps = self.sps.as_ref()?;
+        let pps = self.pps.as_ref()?;
+
+        // Simplified: store as arrays in Annex B format
+        // Full HEVCDecoderConfigurationRecord is complex — for now, concatenate
+        let mut record = Vec::new();
+
+        // Minimal HEVCDecoderConfigurationRecord header
+        record.push(1);  // configurationVersion
+        // General profile space, tier flag, profile IDC from SPS
+        if sps.len() > 3 {
+            record.push(sps[1]); // general_profile_space + general_tier_flag + general_profile_idc
+        } else {
+            record.push(0);
+        }
+        // general_profile_compatibility_flags (4 bytes)
+        record.extend_from_slice(&[0, 0, 0, 0]);
+        // general_constraint_indicator_flags (6 bytes)
+        record.extend_from_slice(&[0, 0, 0, 0, 0, 0]);
+        // general_level_idc
+        record.push(if sps.len() > 12 { sps[12] } else { 0 });
+        // min_spatial_segmentation_idc (4 + 12 bits)
+        record.extend_from_slice(&[0xF0, 0x00]);
+        // parallelismType (6 + 2 bits)
+        record.push(0xFC);
+        // chromaFormat (6 + 2 bits)
+        record.push(0xFC | 1); // 4:2:0
+        // bitDepthLumaMinus8 (5 + 3 bits)
+        record.push(0xF8);
+        // bitDepthChromaMinus8 (5 + 3 bits)
+        record.push(0xF8);
+        // avgFrameRate
+        record.extend_from_slice(&[0, 0]);
+        // constantFrameRate + numTemporalLayers + temporalIdNested + lengthSizeMinusOne
+        record.push(0x03); // lengthSizeMinusOne = 3 (4 bytes)
+        // numOfArrays
+        record.push(3); // VPS, SPS, PPS
+
+        // VPS array
+        record.push(0x20 | (NAL_VPS & 0x3F)); // array_completeness + NAL type
+        record.extend_from_slice(&[0, 1]); // numNalus = 1
+        record.push((vps.len() >> 8) as u8);
+        record.push(vps.len() as u8);
+        record.extend_from_slice(vps);
+
+        // SPS array
+        record.push(0x20 | (NAL_SPS & 0x3F));
+        record.extend_from_slice(&[0, 1]);
+        record.push((sps.len() >> 8) as u8);
+        record.push(sps.len() as u8);
+        record.extend_from_slice(sps);
+
+        // PPS array
+        record.push(0x20 | (NAL_PPS & 0x3F));
+        record.extend_from_slice(&[0, 1]);
+        record.push((pps.len() >> 8) as u8);
+        record.push(pps.len() as u8);
+        record.extend_from_slice(pps);
+
+        Some(record)
+    }
+}