fix(voip): pick the inbound codec from the negotiation, and never go silent without saying so

scripts/mlow-vectors/mlow_frames.c

@@ -0,0 +1,153 @@
+// Encode a raw PCM file as MLow/smpl packets and decode each one back through the same
+// reference, so a single run produces both halves of a decoder cross-check vector.
+//
+// Output, one line per packet, on stdout:
+//
+//     <hex payload> <hex s16le pcm>
+//
+// Diagnostics (packet index, byte count, TOC, sample count) go to stderr, so stdout can be
+// redirected straight into a fixture builder.
+//
+// Two things are easy to get wrong and cost an afternoon each:
+//
+//   * smpl_CreateCodec() must run before the first encode. Without it every encode fails with
+//     SMPL_ENC_NO_GLOBAL_DATA (-112), which opus_encode flattens into a bare OPUS_INTERNAL_ERROR
+//     (-3) with no hint that global tables were the problem.
+//   * The output buffer handed to opus_encode is a hard bound, not a capacity. Under CBR the
+//     encoder pads to exactly that size, so an oversized buffer fails the pad. Keep it near the
+//     real packet size.
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "opus.h"
+
+// Declared here rather than pulled from a private header: the reference exposes it as a plain
+// symbol and the harness only needs the one entry point.
+extern int smpl_CreateCodec(void);
+
+#define FS 16000
+#define MAX_PACKET 400
+
+static void usage(const char *argv0) {
+    fprintf(stderr,
+            "usage: %s <input.raw> <frame_ms> [packets] [bitrate]\n"
+            "  input.raw  s16le mono @ 16 kHz\n"
+            "  frame_ms   10, 20, 60 or 120\n"
+            "  packets    how many to emit (default: until EOF)\n"
+            "  bitrate    encoder bitrate in bps (default 20000)\n",
+            argv0);
+}
+
+int main(int argc, char **argv) {
+    if (argc < 3) {
+        usage(argv[0]);
+        return 2;
+    }
+    const char *path = argv[1];
+    const int frame_ms = atoi(argv[2]);
+    const int want = argc > 3 ? atoi(argv[3]) : -1;
+    const int bitrate = argc > 4 ? atoi(argv[4]) : 20000;
+
+    if (frame_ms != 10 && frame_ms != 20 && frame_ms != 60 && frame_ms != 120) {
+        fprintf(stderr, "error: frame_ms must be 10, 20, 60 or 120 (got %d)\n", frame_ms);
+        return 2;
+    }
+    const int samps = FS / 1000 * frame_ms;
+
+    if (smpl_CreateCodec() != 0) {
+        fprintf(stderr, "error: smpl_CreateCodec failed\n");
+        return 1;
+    }
+
+    FILE *f = fopen(path, "rb");
+    if (!f) {
+        perror("open input");
+        return 2;
+    }
+
+    int err = 0;
+    OpusEncoder *enc = opus_encoder_create(FS, 1, OPUS_APPLICATION_VOIP, &err);
+    if (err != OPUS_OK || !enc) {
+        fprintf(stderr, "error: encoder create: %s\n", opus_strerror(err));
+        return 1;
+    }
+    opus_encoder_ctl(enc, OPUS_SET_USING_SMPL(1));
+    opus_encoder_ctl(enc, OPUS_SET_BITRATE(bitrate));
+    opus_encoder_ctl(enc, OPUS_SET_FORCE_CHANNELS(1));
+
+    OpusDecoder *dec = opus_decoder_create(FS, 1, &err);
+    if (err != OPUS_OK || !dec) {
+        fprintf(stderr, "error: decoder create: %s\n", opus_strerror(err));
+        return 1;
+    }
+    opus_decoder_ctl(dec, OPUS_SET_USING_SMPL(1));
+
+    opus_int16 *pcm = malloc((size_t)samps * sizeof(opus_int16));
+    opus_int16 *out = malloc((size_t)samps * sizeof(opus_int16));
+    unsigned char packet[MAX_PACKET];
+    if (!pcm || !out) {
+        fprintf(stderr, "error: out of memory\n");
+        return 1;
+    }
+
+    int emitted = 0;
+    int short_read = 0;
+    for (int n = 0; want < 0 || n < want; n++) {
+        if (fread(pcm, sizeof(opus_int16), (size_t)samps, f) != (size_t)samps) {
+            // A partial frame at EOF, or a read error. Either way this run cannot produce the
+            // vector that was asked for, and callers overwrite committed fixtures with whatever
+            // comes out of it -- so remember it and fail below rather than emit a short vector.
+            short_read = 1;
+            if (ferror(f)) {
+                perror("read input");
+            }
+            break;
+        }
+        opus_int32 len = opus_encode(enc, pcm, samps, packet, sizeof(packet));
+        if (len <= 0) {
+            fprintf(stderr, "error: encode packet %d: %s\n", n, opus_strerror(len));
+            return 1;
+        }
+        int ns = opus_decode(dec, packet, len, out, samps, 0);
+        if (ns <= 0) {
+            fprintf(stderr, "error: decode packet %d: %s\n", n, opus_strerror(ns));
+            return 1;
+        }
+        for (opus_int32 i = 0; i < len; i++) {
+            printf("%02x", packet[i]);
+        }
+        printf(" ");
+        for (int i = 0; i < ns; i++) {
+            unsigned short v = (unsigned short)out[i];
+            printf("%02x%02x", v & 0xff, (v >> 8) & 0xff);
+        }
+        printf("\n");
+        fprintf(stderr, "packet %d: %d bytes, TOC 0x%02x, %d samples\n", n, len, packet[0], ns);
+        emitted++;
+    }
+
+    fprintf(stderr, "emitted %d packet(s) of %d ms\n", emitted, frame_ms);
+
+    // Exiting 0 with fewer packets than requested would let a regeneration quietly replace a
+    // fixture with a smaller one: the relative length checks downstream stay satisfied, so the
+    // coverage loss is invisible. A short count is a failure, not a partial success.
+    int ok = 1;
+    if (emitted == 0) {
+        fprintf(stderr, "error: no packets emitted\n");
+        ok = 0;
+    } else if (want >= 0 && emitted != want) {
+        fprintf(stderr,
+                "error: asked for %d packet(s) but the input only yielded %d%s\n",
+                want, emitted, short_read ? " (short read)" : "");
+        ok = 0;
+    }
+
+    free(pcm);
+    free(out);
+    opus_encoder_destroy(enc);
+    opus_decoder_destroy(dec);
+    fclose(f);
+    return ok ? 0 : 1;
+}

scripts/regenerate-mlow-vectors.sh

@@ -0,0 +1,106 @@
+#!/usr/bin/env bash
+# Regenerate the MLow decoder cross-check fixtures from the `smpl` C reference.
+#
+# Consumers never run this — the fixtures are committed and the tests read them directly. It
+# exists so the vectors stop being a documented recipe with a missing binary: everything needed
+# to reproduce them, including the two non-obvious setup steps, lives in
+# `scripts/mlow-vectors/mlow_frames.c`.
+#
+# The committed fixtures were produced with this exact oracle:
+#
+#   https://github.com/edgardmessias/opus_mlow at 84b076e0809412df22e8a0d26f944610c4a3e40f
+#
+# Byte-for-byte reproduction is only claimed against that revision. A different checkout can
+# change the output because the ORACLE changed, which is not the same thing as a decoder change,
+# so the script prints the revision it actually built against and warns when it differs.
+#
+# Requires a built `smpl` reference (the WhatsApp MLow fork of libopus):
+#
+#   cd "$MLOW_REFERENCE" && ./autogen.sh && ./configure --disable-shared --disable-doc \
+#     --disable-extra-programs && make -j"$(nproc)"
+#
+# Then:
+#
+#   MLOW_REFERENCE=/path/to/opus_mlow scripts/regenerate-mlow-vectors.sh
+#
+# Regenerating changes committed fixtures. Re-run the decoder suite afterwards and treat any
+# correlation change as a finding, not as a number to paper over:
+#
+#   cargo test -p wacore --features voip-mlow --lib
+
+set -euo pipefail
+
+repo_root="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+testdata="$repo_root/wacore/src/voip/mlow/testdata"
+harness_src="$repo_root/scripts/mlow-vectors/mlow_frames.c"
+
+ref="${MLOW_REFERENCE:-}"
+if [[ -z "$ref" ]]; then
+  echo "error: set MLOW_REFERENCE to the built smpl/opus reference checkout" >&2
+  exit 1
+fi
+if [[ ! -f "$ref/.libs/libopus.a" ]]; then
+  echo "error: $ref/.libs/libopus.a not found; build the reference first (see the header of this script)" >&2
+  exit 1
+fi
+
+# Recorded so a regeneration says which oracle produced it; see the header.
+expected_rev="84b076e0809412df22e8a0d26f944610c4a3e40f"
+actual_rev="$(git -C "$ref" rev-parse HEAD 2>/dev/null || echo unknown)"
+if [[ "$actual_rev" == "unknown" ]]; then
+  echo "warning: $ref is not a git checkout; cannot confirm the oracle revision" >&2
+else
+  # The revision alone does not identify the build: uncommitted changes still compile into the
+  # static library while rev-parse keeps reporting the pinned commit, so a modified oracle would
+  # silently rewrite the fixtures and look like a legitimate update. Refuse unless told otherwise.
+  if [[ -n "$(git -C "$ref" status --porcelain 2>/dev/null)" ]]; then
+    if [[ "${MLOW_ALLOW_DIRTY_REFERENCE:-}" == "1" ]]; then
+      echo "warning: oracle worktree is DIRTY; output does not correspond to $actual_rev" >&2
+    else
+      echo "error: oracle worktree has uncommitted changes, so the fixtures it produces would not" >&2
+      echo "       correspond to any recorded revision. Commit or stash them, or re-run with" >&2
+      echo "       MLOW_ALLOW_DIRTY_REFERENCE=1 if you mean to generate from a modified oracle." >&2
+      exit 1
+    fi
+  fi
+  if [[ "$actual_rev" != "$expected_rev" ]]; then
+    echo "warning: oracle is $actual_rev, fixtures were generated with $expected_rev" >&2
+    echo "         differences below may come from the reference, not from this repository" >&2
+  fi
+fi
+echo "==> oracle: $ref @ $actual_rev"
+
+work="$(mktemp -d)"
+trap 'rm -rf "$work"' EXIT
+
+echo "==> building the harness against $ref"
+cc -O2 \
+  -I "$ref/include" -I "$ref/src" -I "$ref/celt" -I "$ref" \
+  -o "$work/mlow_frames" "$harness_src" "$ref/.libs/libopus.a" -lm
+
+# One packet per line: "<hex payload> <hex s16le pcm>". Split into the frames fixture and the
+# reference PCM the decoder test compares against.
+emit() {
+  local frame_ms="$1" packets="$2" frames_json="$3" pcm_raw="$4"
+  echo "==> ${frame_ms}ms x ${packets} -> $(basename "$frames_json"), $(basename "$pcm_raw")"
+  "$work/mlow_frames" "$testdata/synth_mic.raw" "$frame_ms" "$packets" > "$work/vectors.txt"
+  python3 - "$work/vectors.txt" "$frames_json" "$pcm_raw" <<'PY'
+import json, sys
+src, frames_path, pcm_path = sys.argv[1:4]
+frames, pcm = [], bytearray()
+for line in open(src):
+    payload, samples = line.split()
+    frames.append(payload)
+    pcm += bytes.fromhex(samples)
+json.dump(frames, open(frames_path, "w"), indent=1)
+open(pcm_path, "wb").write(pcm)
+print(f"   {len(frames)} frames, {len(pcm)//2} samples, TOCs: {sorted({f[:2] for f in frames})}")
+PY
+}
+
+emit 120 8 "$testdata/mlow_120ms_frames.json" "$testdata/ref_120ms_expected.raw"
+# 60 ms with DTX off: the encoder emits VoA=00 frames (TOC 0x10) for the silent stretches of
+# synth_mic.raw, which is the only in-repo coverage of the DTX-off decode path.
+emit 60 110 "$testdata/mlow_dtx_off_frames.json" "$testdata/ref_dtx_off_expected.raw"
+
+echo "==> done; re-run: cargo test -p wacore --features voip-mlow --lib"