//! M2TS metadata header — embeds title/stream info in raw m2ts files. //! //! Format: [8B magic] [4B json_len] [JSON] [padding to 192B boundary] [BD-TS data...] //! Other tools skip the header during TS sync recovery (scan for 0x47). use crate::disc::{AudioStream, ColorSpace, DiscTitle, Stream, SubtitleStream, VideoStream}; use serde::{Deserialize, Serialize}; use std::io::{self, Read, Seek, SeekFrom, Write}; /// Magic bytes: "FMKV" + version 1 + 2 reserved bytes. const MAGIC: [u8; 8] = [b'F', b'M', b'K', b'V', 0x00, 0x01, 0x00, 0x00]; /// BD-TS packet size (header must be padded to this boundary). const PACKET_SIZE: usize = 192; /// Metadata embedded in an m2ts file. #[derive(Debug, Clone, Serialize, Deserialize)] pub struct M2tsMeta { /// Format version. pub v: u8, /// Title name (e.g. filename stem or disc title). #[serde(default)] pub title: String, /// Duration in seconds. #[serde(default)] pub duration: f64, /// Stream descriptors. pub streams: Vec, } /// A single stream descriptor in the metadata. #[derive(Debug, Clone, Serialize, Deserialize)] #[serde(tag = "type")] pub enum MetaStream { #[serde(rename = "video")] Video { pid: u16, codec: String, #[serde(default)] resolution: String, #[serde(default)] frame_rate: String, #[serde(default)] hdr: String, #[serde(default)] label: String, #[serde(default)] secondary: bool, }, #[serde(rename = "audio")] Audio { pid: u16, codec: String, #[serde(default)] channels: String, #[serde(default)] language: String, #[serde(default)] sample_rate: String, #[serde(default)] label: String, #[serde(default)] secondary: bool, }, #[serde(rename = "subtitle")] Subtitle { pid: u16, codec: String, #[serde(default)] language: String, #[serde(default)] forced: bool, }, } impl M2tsMeta { /// Build metadata from a disc Title. pub fn from_title(title: &DiscTitle) -> Self { let streams = title .streams .iter() .map(|s| match s { Stream::Video(v) => MetaStream::Video { pid: v.pid, codec: v.codec.id().into(), resolution: v.resolution.to_string(), frame_rate: v.frame_rate.to_string(), hdr: v.hdr.id().into(), label: v.label.clone(), secondary: v.secondary, }, Stream::Audio(a) => MetaStream::Audio { pid: a.pid, codec: a.codec.id().into(), channels: a.channels.to_string(), language: a.language.clone(), sample_rate: a.sample_rate.to_string(), label: a.label.clone(), secondary: a.secondary, }, Stream::Subtitle(s) => MetaStream::Subtitle { pid: s.pid, codec: s.codec.id().into(), language: s.language.clone(), forced: s.forced, }, }) .collect(); Self { v: 1, title: title.playlist.clone(), duration: title.duration_secs, streams, } } /// Convert back to a library Title (for remux). pub fn to_title(&self) -> DiscTitle { let streams = self .streams .iter() .map(|s| match s { MetaStream::Video { pid, codec, resolution, frame_rate, hdr, label, secondary, } => Stream::Video(VideoStream { pid: *pid, codec: codec.parse().unwrap(), resolution: resolution.parse().unwrap(), frame_rate: frame_rate.parse().unwrap(), hdr: hdr.parse().unwrap(), color_space: ColorSpace::Bt709, secondary: *secondary, label: label.clone(), }), MetaStream::Audio { pid, codec, channels, language, sample_rate, label, secondary, } => Stream::Audio(AudioStream { pid: *pid, codec: codec.parse().unwrap(), channels: channels.parse().unwrap(), language: language.clone(), sample_rate: sample_rate.parse().unwrap(), secondary: *secondary, label: label.clone(), }), MetaStream::Subtitle { pid, codec, language, forced, } => Stream::Subtitle(SubtitleStream { pid: *pid, codec: codec.parse().unwrap(), language: language.clone(), forced: *forced, codec_data: None, }), }) .collect(); DiscTitle { playlist: self.title.clone(), playlist_id: 0, duration_secs: self.duration, size_bytes: 0, clips: Vec::new(), streams, chapters: Vec::new(), extents: Vec::new(), content_format: crate::disc::ContentFormat::BdTs, } } } /// Write the metadata header to a writer. Padded to 192-byte boundary. pub fn write_header(w: &mut impl Write, meta: &M2tsMeta) -> io::Result<()> { let json = serde_json::to_vec(meta).map_err(io::Error::other)?; let json_len = json.len() as u32; let raw_len = 8 + 4 + json.len(); // magic + len + json let padded_len = raw_len.div_ceil(PACKET_SIZE) * PACKET_SIZE; let padding = padded_len - raw_len; w.write_all(&MAGIC)?; w.write_all(&json_len.to_be_bytes())?; w.write_all(&json)?; if padding > 0 { w.write_all(&vec![0u8; padding])?; } Ok(()) } /// Try to read a metadata header from the start of an m2ts file. /// Returns None for bare m2ts files (no header). /// On success, leaves reader positioned at the first TS packet. /// On failure, seeks back to the start. pub fn read_header(r: &mut R) -> io::Result> { let start = r.stream_position()?; let mut magic = [0u8; 8]; if r.read_exact(&mut magic).is_err() { r.seek(SeekFrom::Start(start))?; return Ok(None); } if magic[..4] != MAGIC[..4] { // Not a freemkv m2ts — seek back r.seek(SeekFrom::Start(start))?; return Ok(None); } let mut len_buf = [0u8; 4]; r.read_exact(&mut len_buf)?; let json_len = u32::from_be_bytes(len_buf) as usize; let mut json_buf = vec![0u8; json_len]; r.read_exact(&mut json_buf)?; let meta: M2tsMeta = serde_json::from_slice(&json_buf) .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?; // Skip padding to next 192-byte boundary let raw_len = 8 + 4 + json_len; let padded_len = raw_len.div_ceil(PACKET_SIZE) * PACKET_SIZE; let padding = padded_len - raw_len; if padding > 0 { r.seek(SeekFrom::Current(padding as i64))?; } Ok(Some(meta)) } /// Read a metadata header from a forward-only stream (no Seek required). /// Returns None if the magic bytes don't match. Consumes the header bytes. pub fn read_header_from_stream(r: &mut impl Read) -> io::Result> { let mut magic = [0u8; 8]; r.read_exact(&mut magic)?; if magic[..4] != MAGIC[..4] { return Ok(None); } let mut len_buf = [0u8; 4]; r.read_exact(&mut len_buf)?; let json_len = u32::from_be_bytes(len_buf) as usize; let mut json_buf = vec![0u8; json_len]; r.read_exact(&mut json_buf)?; let meta: M2tsMeta = serde_json::from_slice(&json_buf) .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?; // Skip padding let raw_len = 8 + 4 + json_len; let padded_len = raw_len.div_ceil(PACKET_SIZE) * PACKET_SIZE; let padding = padded_len - raw_len; if padding > 0 { let mut skip = vec![0u8; padding]; r.read_exact(&mut skip)?; } Ok(Some(meta)) } // Serialization uses Codec::id() / HdrFormat::id() and Display impls. // Deserialization uses FromStr impls (.parse()) on each enum.