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dvd: route private_stream_1 audio sub-ids by positional stream number

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The private_stream_1 sub-stream id low nibble is the DVD audio-stream
NUMBER (0-7), shared across codecs, not a per-codec ordinal. A DTS (or
LPCM) track that isn't the disc's first audio stream got a sub-id one
too low, so the demux routing key (0xBD00 | sub_id) never matched and
every packet was dropped -> present-but-silent track. AC-3 at position
0 coincidentally worked (ordinal==position). Route by positional index.

Fixes silent DTS 5.0 track on The Punisher (AC-3 5.1 @ pos0 plays,
DTS 5.0 @ pos1 was 0xBD88, real wire id 0xBD89).
This commit is contained in:
Matthew Jackson
2026-07-01 13:49:55 -07:00
parent a93da78621
commit e94319c099
2 changed files with 81 additions and 46 deletions
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src/ifo.rs
+69 -35
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@@ -621,37 +621,34 @@ fn parse_audio_attr(data: &[u8], offset: usize) -> Result<DvdAudioAttr> {
}
/// Assign the on-wire `private_stream_1` sub-stream id to each audio
/// stream by per-codec ordinal, matching DVD authoring convention and the
/// muxer's `dvd_pid()` routing:
/// - AC-3 → `0x80 + n` (n = 0-based index among AC-3 streams)
/// - DTS → `0x88 + n`
/// - LPCM → `0xA0 + n`
/// stream. On DVD-Video the sub-id's **low nibble is the audio-stream
/// *number* (0-7), shared across all codecs** — the single stream index the
/// PGC `audio_control` table / navigation registers select — and the high
/// nibble is the codec base. So the sub-id is `codec_base | position`, where
/// `position` is the stream's index in the IFO audio-attribute table (NOT a
/// per-codec running count):
/// - AC-3 → `0x80 | i`
/// - DTS → `0x88 | i`
/// - LPCM → `0xA0 | i`
/// - MP1/MP2 and anything else → `None` (regular MPEG-audio PES, not a
/// private-stream-1 sub-id).
///
/// Indices saturate at the codec range ceiling (8 AC-3/DTS, 8 LPCM) so a
/// malformed over-count never produces an out-of-range sub-id.
/// A per-codec ordinal was wrong: it only coincides with the wire id when a
/// codec's first stream is also the disc's audio stream #0. Any codec that is
/// not the first audio stream (e.g. a DTS track after an AC-3 track) then got
/// a sub-id one-too-low, so the demux routing key (`0xBD00 | sub_id`) never
/// matched and the track muxed silent. The positional index is the real wire
/// number, so distinct positions still give distinct sub-ids (no collision).
///
/// Position saturates at 7 so a malformed over-count never produces an
/// out-of-range sub-id.
fn assign_audio_sub_stream_ids(streams: &mut [DvdAudioAttr]) {
let mut n_ac3 = 0u8;
let mut n_dts = 0u8;
let mut n_lpcm = 0u8;
for s in streams.iter_mut() {
for (i, s) in streams.iter_mut().enumerate() {
let n = (i as u8).min(7);
s.sub_stream_id = match s.codec {
Codec::Ac3 => {
let id = 0x80 + n_ac3.min(7);
n_ac3 = n_ac3.saturating_add(1);
Some(id)
}
Codec::Dts => {
let id = 0x88 + n_dts.min(7);
n_dts = n_dts.saturating_add(1);
Some(id)
}
Codec::Lpcm => {
let id = 0xA0 + n_lpcm.min(7);
n_lpcm = n_lpcm.saturating_add(1);
Some(id)
}
Codec::Ac3 => Some(0x80 | n),
Codec::Dts => Some(0x88 | n),
Codec::Lpcm => Some(0xA0 | n),
_ => None,
};
}
@@ -1138,9 +1135,10 @@ mod tests {
#[test]
fn mixed_codec_sub_stream_ids_are_distinct() {
// A title mixing AC-3, DTS and LPCM must get per-codec ordinal
// sub-ids (0x80, 0x88, 0xA0...), all distinct — this is the
// routing key that keeps mixed-codec audio from colliding.
// A title mixing AC-3, DTS and LPCM: the sub-id low nibble is the
// POSITIONAL audio-stream number (shared across codecs), OR'd with the
// codec base. So idx 1 (DTS) → 0x89, idx 3 (AC-3) → 0x83 — the real
// wire ids the demux routes on. All distinct (positions are unique).
let mut streams = vec![
DvdAudioAttr {
codec: Codec::Ac3,
@@ -1172,10 +1170,10 @@ mod tests {
},
];
assign_audio_sub_stream_ids(&mut streams);
assert_eq!(streams[0].sub_stream_id, Some(0x80)); // AC-3 #0
assert_eq!(streams[1].sub_stream_id, Some(0x88)); // DTS #0
assert_eq!(streams[2].sub_stream_id, Some(0xA0)); // LPCM #0
assert_eq!(streams[3].sub_stream_id, Some(0x81)); // AC-3 #1
assert_eq!(streams[0].sub_stream_id, Some(0x80)); // AC-3 @ pos 0
assert_eq!(streams[1].sub_stream_id, Some(0x89)); // DTS @ pos 1
assert_eq!(streams[2].sub_stream_id, Some(0xA2)); // LPCM @ pos 2
assert_eq!(streams[3].sub_stream_id, Some(0x83)); // AC-3 @ pos 3
// All sub-ids unique.
let ids: Vec<u8> = streams.iter().filter_map(|s| s.sub_stream_id).collect();
let mut sorted = ids.clone();
@@ -1184,6 +1182,42 @@ mod tests {
assert_eq!(ids.len(), sorted.len(), "sub-stream ids must be unique");
}
/// Regression (The Punisher 2004): audio[0]=AC-3 5.1, audio[1]=DTS 5.0.
/// The DTS track sits at audio position 1, so its wire sub-id is 0x89
/// (0x88 | 1), NOT the per-codec 0x88. With the old per-codec ordinal it
/// got 0x88 → demux routing key 0xBD88 had no match → every DTS packet
/// (which carries 0x89) was dropped → the track muxed present-but-silent
/// while the AC-3 (at position 0, where ordinal and position coincide)
/// played fine. Positional numbering fixes it end-to-end.
#[test]
fn dts_after_ac3_uses_positional_substream_id() {
let mut streams = vec![
DvdAudioAttr {
codec: Codec::Ac3,
channels: 6,
sample_rate: 48000,
language: "en".into(),
sub_stream_id: None,
},
DvdAudioAttr {
codec: Codec::Dts,
channels: 5,
sample_rate: 48000,
language: "en".into(),
sub_stream_id: None,
},
];
assign_audio_sub_stream_ids(&mut streams);
assert_eq!(streams[0].sub_stream_id, Some(0x80));
assert_eq!(
streams[1].sub_stream_id,
Some(0x89),
"DTS at audio position 1 routes to 0x89 on the wire, not 0x88"
);
// The routing key the muxer actually uses must resolve for 0x89.
assert_eq!(crate::mux::ps::dvd_audio_pid(0x89), Some(0xBD89));
}
#[test]
fn audio_attr_dts() {
let mut data = vec![0u8; 16];
@@ -1371,10 +1405,10 @@ mod tests {
];
assign_audio_sub_stream_ids(&mut streams);
assert_eq!(streams[0].sub_stream_id, None); // MP2 → no sub-id
assert_eq!(streams[1].sub_stream_id, Some(0x80)); // AC3 #0
assert_eq!(streams[1].sub_stream_id, Some(0x81)); // AC3 @ pos 1
}
/// assign_audio_sub_stream_ids saturates the per-codec ordinal at the
/// assign_audio_sub_stream_ids saturates the positional index at the
/// range ceiling (min(7)) so a malformed over-count never produces an
/// out-of-range sub-id. 9 AC-3 streams: the 9th still ≤ 0x87.
#[test]