`nx_ts_es.nx` source

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1// nx_ts_es.nx -- MPEG-TS -> H.264 elementary-stream helpers, LIFTED VERBATIM from
2// nx_cam_poster.nx (lines 68-152) 2026-07-31 so a second consumer does not copy-paste
3// them (rule 15). Behaviour must stay byte-identical: nx_cam_poster_gate is the oracle.
4//   demux_video_es  -- PAT/PMT walk -> video PID -> ES bytes; codec via nx_ts_nal
5//   find_first_nal  -- first NAL of a given type out of an ES
6//   nal_to_rbsp     -- emulation-prevention-byte removal
7// license_tier: ORIGINAL
8import "nx_syscalls.nx"
9import "nx_ts_nal.nx"
10
11// scan window for the TS->ES pass. Owned HERE because demux_video_es reads it;
12// the compiler rejects a module const used above its declaration (it would
13// silently read 0), so a lib cannot borrow this from its caller.
14const MAXSCAN: i64 = 8388608
15
16func demux_video_es(filebuf: *u8, total: i64, es: *u8, pidout: *i64) -> i64 {
17    var eslen: i64 = 0
18    var pmtpid: i64 = 0 - 1
19    var vidpid: i64 = 0 - 1
20    // HEVC seen in the PMT but deliberately NOT claimed as vidpid (this organ
21    // decodes H.264). Surfaced so the caller can refuse BY NAME instead of
22    // reporting the generic "no video PID", which reads as a corrupt file.
23    var cphevc: i64 = 0
24    var i: i64 = 0
25    while i + 188 <= total {
26        if filebuf[i] != (0x47 as u8) { i = i + 1 } else {
27            let b1: i64 = filebuf[i+1] as i64
28            let pusi: i64 = (b1 >> 6) & 1
29            let pid: i64 = ((b1 & 0x1f) << 8) | (filebuf[i+2] as i64)
30            let afc: i64 = ((filebuf[i+3] as i64) >> 4) & 3
31            var payoff: i64 = i + 4
32            if afc == 2 { payoff = i + 188 } else { if afc == 3 { payoff = i + 5 + (filebuf[i+4] as i64) } }
33            if payoff < i + 188 {
34                if pid == 0 { if pmtpid < 0 {
35                    var p: i64 = payoff
36                    if pusi == 1 { p = p + 1 + (filebuf[p] as i64) }
37                    let sl: i64 = (((filebuf[p+1] as i64) & 0x0f) << 8) | (filebuf[p+2] as i64)
38                    var pp2: i64 = p + 8
39                    let pe: i64 = p + 3 + sl - 4
40                    while pp2 + 4 <= pe { let pr: i64 = ((filebuf[pp2] as i64) << 8) | (filebuf[pp2+1] as i64); let pm: i64 = (((filebuf[pp2+2] as i64) & 0x1f) << 8) | (filebuf[pp2+3] as i64); if pr != 0 { if pmtpid < 0 { pmtpid = pm } } pp2 = pp2 + 4 }
41                } }
42                if pid == pmtpid { if pmtpid >= 0 { if vidpid < 0 {
43                    var p: i64 = payoff
44                    if pusi == 1 { p = p + 1 + (filebuf[p] as i64) }
45                    let sl: i64 = (((filebuf[p+1] as i64) & 0x0f) << 8) | (filebuf[p+2] as i64)
46                    let pil: i64 = (((filebuf[p+10] as i64) & 0x0f) << 8) | (filebuf[p+11] as i64)
47                    var ep: i64 = p + 12 + pil
48                    let pe: i64 = p + 3 + sl - 4
49                    while ep + 5 <= pe { let st: i64 = filebuf[ep] as i64; let ed: i64 = (((filebuf[ep+1] as i64) & 0x1f) << 8) | (filebuf[ep+2] as i64); let el: i64 = (((filebuf[ep+3] as i64) & 0x0f) << 8) | (filebuf[ep+4] as i64); let vc: i64 = tsn_codec_of_stream_type(st); if vc == TSN_H264 { if vidpid < 0 { vidpid = ed } } if vc == TSN_HEVC { cphevc = 1 } ep = ep + 5 + el }
50                } } }
51                if pid == vidpid { if vidpid >= 0 {
52                    var p: i64 = payoff
53                    if pusi == 1 { if filebuf[p] == (0 as u8) { if filebuf[p+1] == (0 as u8) { if filebuf[p+2] == (1 as u8) { p = p + 9 + (filebuf[p+8] as i64) } } } }
54                    var qv: i64 = p
55                    while qv < i + 188 { if eslen < MAXSCAN { es[eslen] = filebuf[qv]; eslen = eslen + 1 } qv = qv + 1 }
56                } }
57            }
58            i = i + 188
59        }
60    }
61    pidout[0] = vidpid
62    pidout[1] = pmtpid
63    pidout[2] = cphevc
64    return eslen
65}
66
67// H.264 ONLY, DELIBERATELY. This organ DECODES the bitstream (nx_h264_parse_pps,
68// CAVLC/CABAC) to render the poster image -- it does not merely demux. Widening
69// the PMT to accept HEVC here would hand H.265 NALs to an H.264 decoder and turn
70// a clean "no video PID" refusal into a MISDECODE. An HEVC poster needs an H.265
71// decoder, which is a separate arc; until then HEVC is REFUSED BY NAME (see the
72// cphevc path) rather than silently producing nothing.
73func find_first_nal(es: *u8, eslen: i64, want: i64, dst: *u8, cap: i64) -> i64 {
74    var k: i64 = 0
75    while k + 3 < eslen {
76        if es[k] == (0 as u8) { if es[k+1] == (0 as u8) { if es[k+2] == (1 as u8) {
77            let ns: i64 = k + 3
78            let nt: i64 = (es[ns] as i64) & 0x1f
79            if nt == want {
80                var m: i64 = ns
81                var ne: i64 = eslen
82                var fnd: i64 = 0
83                while m + 3 < eslen { if fnd == 0 { if es[m] == (0 as u8) { if es[m+1] == (0 as u8) { if es[m+2] == (1 as u8) { ne = m; fnd = 1 } } } if fnd == 0 { m = m + 1 } } else { m = eslen } }
84                if fnd == 1 { if es[ne-1] == (0 as u8) { ne = ne - 1 } }
85                let nl: i64 = ne - ns
86                var c: i64 = 0
87                while c < nl { if c < cap { dst[c] = es[ns+c] } c = c + 1 }
88                return nl
89            }
90            k = ns
91        } else { k = k + 1 } } else { k = k + 1 } } else { k = k + 1 }
92    }
93    return 0
94}
95
96func nal_to_rbsp(nal: *u8, nallen: i64, rbsp: *u8) -> i64 {
97    return nx_h264_unescape_rbsp(((nal as i64) + 1) as *u8, nallen - 1, rbsp)
98}
99
100// YUV420 (cropped region) -> RGB, integer box-average downscale into dst[dstW*dstH*3].
nx_ts_es.nx source

`nx_ts_es.nx` source
