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mux: reset MPEG-2 field pairing at GOP and sequence headers

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This commit is contained in:
Matthew Jackson
2026-09-29 19:19:50 -07:00
parent 2eb33647bd
commit f754fa12d0
1 changed files with 39 additions and 3 deletions
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src/mux/codec/mpeg2.rs
+39 -3
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@@ -204,6 +204,10 @@ impl Mpeg2Parser {
// datum into one codec-agnostic `PictureInfo`; `nb_fields()`, `keyframe()`,
// and `field_order()` all derive from it, so nothing re-parses the stream.
let (mut tff, rff, progressive_frame, frame_picture) = picture_coding_flags(&data);
// A GOP or sequence header always starts a new pair; drop a stale lone field.
if gop_boundary {
self.pending_first_field = None;
}
if frame_picture {
self.pending_first_field = None;
} else if let Some(first_top) = self.pending_first_field.take()
@@ -510,9 +514,8 @@ mod tests {
use crate::mux::codec::coding::FieldOrder;
let mut p = Mpeg2Parser::new();
let mut frames = Vec::new();
let mut fields = [(1u8, 0x01u8), (2, 0x02), (1, 0x01), (2, 0x02)].into_iter();
let mut first = true;
for (i, (ct, e2)) in fields.by_ref().enumerate() {
for (ct, e2) in [(1u8, 0x01u8), (2, 0x02), (1, 0x01), (2, 0x02)] {
let mut au = Vec::new();
if first {
au.extend_from_slice(&make_seq_header(720, 576, 3, 3));
@@ -530,7 +533,6 @@ mod tests {
data: au,
discontinuity: false,
}));
let _ = i;
}
frames.extend(p.flush());
assert_eq!(frames.len(), 4);
@@ -539,6 +541,40 @@ mod tests {
}
}
#[test]
fn gop_header_resets_stale_lone_field() {
use crate::mux::codec::coding::FieldOrder;
let mut p = Mpeg2Parser::new();
let mut frames = Vec::new();
let feed = |p: &mut Mpeg2Parser, prefix: Vec<u8>, ct: u8, e2: u8| {
let mut au = prefix;
au.extend_from_slice(&make_picture_header(ct));
let mut ext = pic_coding_ext(0, 0, 0, false);
ext[6] = e2;
au.extend_from_slice(&ext);
p.parse(&PesPacket {
source: None,
pid: 0x1011,
pts: None,
dts: None,
data: au,
discontinuity: false,
})
};
// Stray lone top field, then a new GOP coded BFF (bottom, top) x2.
frames.extend(feed(&mut p, make_seq_header(720, 576, 3, 3), 1, 0x01));
let gop = vec![0x00, 0x00, 0x01, GOP_CODE, 0, 0, 0, 0];
frames.extend(feed(&mut p, gop, 1, 0x02));
frames.extend(feed(&mut p, Vec::new(), 2, 0x01));
frames.extend(feed(&mut p, Vec::new(), 2, 0x02));
frames.extend(feed(&mut p, Vec::new(), 2, 0x01));
frames.extend(p.flush());
assert_eq!(frames.len(), 5);
for f in &frames[1..] {
assert_eq!(f.coding.unwrap().field_order(), Some(FieldOrder::Bff));
}
}
#[test]
fn parser_populates_full_pictureinfo_and_source() {
use crate::mux::codec::coding::FieldOrder;