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https://github.com/freemkv/libfreemkv.git
synced 2026-10-07 18:13:10 +00:00
dvd: play a title the way its navigation packs say
A cell in an interleaved block shares its sectors with another program's units (a second language version), and each VOB runs its own clock. The mux read every sector of a cell and inferred joins from timestamp jumps, so a title mixed in the other version's video, froze at the jumps, and lost about half a second of audio at each VOB join. Each VOBU's navigation pack names its cell and its start/end time: keep only the VOBUs of the cell each extent opens with, and shift each new VOB's clock to start where the last kept VOBU ended, on every track at once.
This commit is contained in:
Matthew Jackson
@@ -43,6 +43,8 @@ pub struct PipelinedPesStream {
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/// are expected on every disc; instead of a per-packet WARN they're tallied
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/// and summarised once at EOF.
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dropped_nav_packets: u64,
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/// DVD: keeps each cell's own VOBUs and joins the VOBs' clocks into one timeline.
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vobu_nav: Option<super::ps::VobuNav>,
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/// Packets of MPEG-2 audio extension streams (`0xD0|n`) with no declared extension track,
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/// reported once at EOF (see `ps::warn_undeclared_extensions`).
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mpeg_extension_packets: [u64; 8],
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@@ -120,6 +122,9 @@ impl PipelinedPesStream {
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.then(super::au_assembly::SecondFieldMerge::default)
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})
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.collect();
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let vobu_nav = (title.content_format == crate::disc::ContentFormat::MpegPs
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&& !title.extents.is_empty())
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.then(|| super::ps::VobuNav::new(&title.extents));
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Self {
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title,
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parsers,
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@@ -131,6 +136,7 @@ impl PipelinedPesStream {
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failed: None,
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skip_parse: false,
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dropped_nav_packets: 0,
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vobu_nav,
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mpeg_extension_packets: [0; 8],
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dropped_ps: Default::default(),
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resync,
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@@ -274,7 +280,12 @@ impl PipelinedPesStream {
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}
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fn consume_ps(&mut self, packets: Vec<super::ps::PsPacket>) {
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for ps in packets {
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for mut ps in packets {
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if let Some(nav) = self.vobu_nav.as_mut()
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&& !nav.admit(&mut ps)
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{
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continue;
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}
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if let Some(id) = self.video_stream_id
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&& (0xE0..=0xEF).contains(&ps.stream_id)
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&& ps.stream_id != id
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@@ -382,6 +393,14 @@ impl PipelinedPesStream {
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self.dropped_nav_packets
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);
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}
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if let Some(n) = self
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.vobu_nav
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.as_ref()
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.map(|g| g.dropped_vobus)
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.filter(|&n| n > 0)
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{
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tracing::info!(target: "mux", vobus = n, "left out VOBUs interleaved from another program");
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}
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super::ps::warn_undeclared_extensions(&self.mpeg_extension_packets);
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self.dropped_ps.report();
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// Drain any AU a parser buffered past the last PES (DTS-HD tail, MPEG-2
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+222
@@ -144,6 +144,122 @@ impl DroppedPs {
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}
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}
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/// Reads a DVD title the way its navigation packs say to play it.
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///
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/// A DVD cell is a sector range, and in an interleaved block that range also holds the units of
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/// another program (a second language version, say). Every VOBU opens with a navigation pack
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/// naming its VOB and cell; a cell's first sector is its own first VOBU, so the first one read
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/// in each extent names the cell, and any later VOBU naming another belongs to the other program.
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///
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/// The same pack gives the VOBU's start and end time. Each VOB runs its own clock, so where a
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/// kept VOBU does not start where the last one ended, every later packet is shifted to close
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/// the jump: the title plays as one timeline, on every track at once.
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#[derive(Debug, Default)]
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pub(crate) struct VobuNav {
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// Feed byte offset at which each extent ends, in read order.
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ends: Vec<u64>,
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extent: usize,
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cell: Option<(u16, u8)>,
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keep: bool,
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// The current VOBU's start/end time from its PCI packet, until its DSI decides it is kept.
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pci: Option<(i64, i64)>,
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// Where the last kept VOBU ended, in shifted time, and the shift in force (90 kHz).
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end: Option<i64>,
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shift: i64,
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pub(crate) dropped_vobus: u64,
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pub(crate) joins: u64,
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}
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// A jump smaller than this (1 ms) is rounding, not a new clock.
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const JOIN_SLACK_TICKS: i64 = 90;
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impl VobuNav {
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/// Navigation for a title read as `extents`, back to back.
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pub(crate) fn new(extents: &[crate::disc::Extent]) -> Self {
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let mut end = 0u64;
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let ends = extents
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.iter()
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.map(|e| {
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end += e.sector_count as u64 * 2048;
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end
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})
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.collect();
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VobuNav {
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ends,
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keep: true,
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..Default::default()
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}
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}
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/// Whether `ps` belongs to the cell being read; a kept packet is moved onto the title's
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/// timeline. Packets without a source position pass untouched.
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pub(crate) fn admit(&mut self, ps: &mut PsPacket) -> bool {
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let Some(at) = ps.source.map(|s| s.byte) else {
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return true;
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};
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while self.ends.get(self.extent).is_some_and(|&end| at >= end) {
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self.extent += 1;
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self.cell = None;
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self.keep = true;
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}
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if ps.is_nav() {
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match ps.data.first() {
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Some(0x00) => self.pci = pci_times(&ps.data),
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Some(0x01) => self.on_dsi(&ps.data),
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_ => {}
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}
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return self.keep;
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}
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if self.keep && self.shift != 0 {
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let moved = |t: u64| (t as i64).saturating_add(self.shift).max(0) as u64;
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ps.pts = ps.pts.map(moved);
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ps.dts = ps.dts.map(moved);
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}
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self.keep
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}
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fn on_dsi(&mut self, dsi: &[u8]) {
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let Some(id) = dsi_cell(dsi) else {
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return;
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};
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let cell = *self.cell.get_or_insert(id);
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self.keep = id == cell;
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if !self.keep {
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self.dropped_vobus += 1;
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return;
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}
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let Some((start, end)) = self.pci.take() else {
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return;
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};
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if let Some(prev) = self.end
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&& (start + self.shift - prev).abs() > JOIN_SLACK_TICKS
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{
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self.shift = prev - start;
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self.joins += 1;
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}
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self.end = Some(end + self.shift);
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}
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}
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// The VOBU start and end presentation times a PCI packet gives (90 kHz).
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fn pci_times(payload: &[u8]) -> Option<(i64, i64)> {
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// Substream 0x00, then PCI_GI: LBN (4), category (2), reserved (2), UOP control (4),
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// start time (4), end time (4).
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let word = |o: usize| Some(u32::from_be_bytes(payload.get(o..o + 4)?.try_into().ok()?) as i64);
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let (start, end) = (word(13)?, word(17)?);
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(end > start).then_some((start, end))
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}
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// The (VOB id, cell id) a DSI packet's general information names.
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fn dsi_cell(payload: &[u8]) -> Option<(u16, u8)> {
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// Substream 0x01, then DSI_GI: SCR, LBN, VOBU end and three reference ends (4 bytes each),
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// VOB id (2), a reserved byte and the cell id.
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if payload.first() != Some(&0x01) || payload.len() < 29 {
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return None;
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}
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Some((u16::from_be_bytes([payload[25], payload[26]]), payload[28]))
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}
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/// Reports, once at end of stream, MPEG-2 audio extension packets (`0xD0|n`, index `n`) that
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/// had no declared extension track (the IFO did not say coding mode 3) and were left out.
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pub(crate) fn warn_undeclared_extensions(packets: &[u64; 8]) {
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@@ -1238,6 +1354,112 @@ mod tests {
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}
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}
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// A video packet at feed byte `at` with presentation time `pts` (90 kHz).
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fn video(at: u64, pts: u64) -> PsPacket {
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let mut p = mk(0xE0, None);
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p.pts = Some(pts);
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p.source = Some(crate::pes::SourcePos::at_byte(at));
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p
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}
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// The PCI and DSI packets of a navigation pack at `at`, for a VOBU of `cell` timed
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// `start..end`.
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fn nav_pack(at: u64, cell: (u16, u8), start: u32, end: u32) -> [PsPacket; 2] {
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let mut pci = mk(PRIVATE_STREAM_2, None);
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pci.data = vec![0u8; 21];
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pci.data[13..17].copy_from_slice(&start.to_be_bytes());
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pci.data[17..21].copy_from_slice(&end.to_be_bytes());
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let mut dsi = mk(PRIVATE_STREAM_2, None);
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dsi.data = vec![0u8; 29];
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dsi.data[0] = 0x01;
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dsi.data[25..27].copy_from_slice(&cell.0.to_be_bytes());
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dsi.data[28] = cell.1;
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for p in [&mut pci, &mut dsi] {
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p.source = Some(crate::pes::SourcePos::at_byte(at));
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}
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[pci, dsi]
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}
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// Feed `packets` through `nav`, returning the PTS of each kept non-navigation packet.
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fn kept(nav: &mut VobuNav, packets: Vec<PsPacket>) -> Vec<u64> {
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let mut out = Vec::new();
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for mut p in packets {
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if nav.admit(&mut p) && !p.is_nav() {
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out.extend(p.pts);
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}
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}
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out
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}
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const SECTOR: u64 = 2048;
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#[test]
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fn vobu_nav_keeps_only_the_cell_each_extent_opens_with() {
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let extents = [
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crate::disc::Extent {
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start_lba: 0,
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sector_count: 10,
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},
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crate::disc::Extent {
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start_lba: 50,
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sector_count: 10,
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},
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];
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let mut nav = VobuNav::new(&extents);
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let s = |n: u64| n * SECTOR;
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let mut packets = Vec::new();
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// Extent 1 is cell (7, 2), with a unit of (8, 1) woven in.
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packets.extend(nav_pack(s(0), (7, 2), 0, 900));
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packets.push(video(s(1), 100));
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packets.extend(nav_pack(s(3), (8, 1), 50_000, 50_900));
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packets.push(video(s(4), 50_100));
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packets.extend(nav_pack(s(6), (7, 2), 900, 1_800));
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packets.push(video(s(7), 1_000));
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// Extent 2 opens with (8, 1): that is now the cell being read.
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packets.extend(nav_pack(s(10), (8, 1), 1_800, 2_700));
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packets.push(video(s(11), 1_900));
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packets.extend(nav_pack(s(12), (7, 2), 2_700, 3_600));
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packets.push(video(s(13), 2_800));
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assert_eq!(kept(&mut nav, packets), vec![100, 1_000, 1_900]);
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assert_eq!(nav.dropped_vobus, 2);
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assert_eq!(nav.joins, 0);
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// A packet the demuxer could not place passes untouched.
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let mut loose = mk(0xE0, None);
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assert!(nav.admit(&mut loose));
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}
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#[test]
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fn vobu_nav_joins_each_vob_clock_onto_the_last() {
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// One cell per extent, as a title is read: VOB 4's cell, then VOB 5's.
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let cells = [
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crate::disc::Extent {
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start_lba: 0,
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sector_count: 2,
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},
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crate::disc::Extent {
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start_lba: 2,
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sector_count: 10,
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},
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];
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let mut nav = VobuNav::new(&cells);
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let s = |n: u64| n * SECTOR;
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let mut packets = Vec::new();
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// VOB 4 runs 0.1 s .. 126.6 s; VOB 5 restarts its clock at 0.07 s.
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packets.extend(nav_pack(s(0), (4, 1), 9_000, 11_394_000));
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packets.push(video(s(1), 11_390_000));
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packets.extend(nav_pack(s(2), (5, 1), 6_300, 60_300));
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packets.push(video(s(3), 6_300));
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packets.push(video(s(4), 1_000)); // audio that leads its video in the new VOB
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packets.extend(nav_pack(s(5), (5, 1), 60_300, 114_300));
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packets.push(video(s(6), 60_300));
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let shift = 11_394_000 - 6_300;
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assert_eq!(
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kept(&mut nav, packets),
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vec![11_390_000, 6_300 + shift, 1_000 + shift, 60_300 + shift]
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);
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assert_eq!(nav.joins, 1);
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}
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#[test]
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fn parse_extended_stream_id_extracts_stream_id_extension() {
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// SHAUN's VC-1 video PES: stream_id 0xFD, flags2=0x01 (PES_extension only),
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