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imsd/implementations/media.cpp
Jorijn van der Graaf 649923d36f media: play AMR narrowband and G.711 as well as AMR-WB 
imsd-media spoke exactly one codec, AMR-WB. A landline caller reaches the
IMS core through the PSTN gateway, which offers narrowband — AMR (NB)
and/or G.711 — so with the engine now accepting those offers the media leg
has to play them.

CODEC (set by the daemon from the negotiated SDP) selects AMR-WB (the
default, unchanged), AMR, PCMA or PCMU. AMR narrowband rides the same RFC
4867 payload code as AMR-WB with its own frame-size table (RFC 4867 table
1) and libopencore-amrnb dlopen'd like the wideband pair — same package as
the AMR-WB decoder, no new dependency; AMR_MODE defaults to 7 (12.2 kbit/s)
for it. G.711 is the ITU-T table codec, raw samples in the payload, digital
zero as keepalive. The narrowband path runs pw-record/pw-play at 8 kHz and
steps the RTP clock by 160 per frame.

Two test seams so the leg can be driven against a synthetic RTP peer with
no PipeWire and no network: MIC_SRC=<file> feeds raw PCM through the
encoder in real time instead of pw-record, PCM_DUMP=1 writes the decoded
downlink to <out>.pcm. --selftest now covers both AMR tables (both payload
formats) and G.711 (digital zero, idempotence over the full 16-bit range,
1 kHz sine SNR >= 30 dB for both laws).

Verified on the workstation with a Python gateway stand-in for PCMA, PCMU
and AMR (octet-aligned and bandwidth-efficient): uplink RTP shape (pt, seq,
ts step 160, payload sizes 160 / 33 / 32) and a 440 Hz mic tone recovered
from our packets by an independent decoder; a 1 kHz gateway tone recovered
from our decoded downlink. The AMR-WB default path keeps its legacy
keepalive shape (ts step 320, FT0 payloads 19/18 bytes).
2026-09-02 03:18:58 +02:00

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// SPDX-License-Identifier: GPL-3.0-only
// SPDX-FileCopyrightText: Copyright (C) 2026 Catcrafts®
// lint-disable-file fixed-width-types no-char-pointer
/*
imsd-media — the RTP media leg for a userspace VoLTE call, spawned as its
own process by the daemon (imsd) exactly as the Python prototype spawned
rtpcap.py: one media leg per call, argv-configured, torn down on SIGTERM or
when the downlink dries up. Keeping it a separate process preserves the
far-end-hangup contract (exit code 3 = downlink RTP stopped, which on carriers
whose network BYE never reaches our SAs is the reliable teardown trigger) and
isolates a media crash from the control-plane daemon.
Codecs (CODEC env, set by the daemon from the negotiated SDP): AMR-WB
(16 kHz; the mobile-to-mobile VoLTE codec, the default), AMR narrowband and
G.711 PCMA/PCMU (8 kHz; what a PSTN gateway offers when a landline calls).
AMR frames ride RFC 4867 payloads, octet-aligned or bandwidth-efficient
(OCTET_ALIGN, mirrored from the SDP); G.711 is raw samples. The AMR codecs
are dlopen'd (libvo-amrwbenc + libopencore-amrwb for WB, libopencore-amrnb
for NB) so the binary has no link-time dependency on them; G.711 is a table.
Binds the advertised local RTP port, sends uplink frames toward the media
gateway, captures the downlink, and — with PLAY=1 — reconstructs the media
clock from RTP timestamps so pw-play stays real-time-paced through far-end
DTX silence (every missing 20 ms slot is decoded as a NO_DATA frame for
CNG/PLC; zeros for G.711). MIC=1 feeds live pw-record audio through the
encoder.
Usage: imsd-media <local-ip> <rtp-port> <remote-ip> <remote-port> <pt> <secs> <out-base>
imsd-media --selftest (payload pack/depay roundtrip, both formats,
both AMR codecs; G.711 table roundtrip)
Env: CODEC MIC PLAY GAIN PLAY_GAIN AMR_MODE DTX MEDIA_TIMEOUT RTP_DUMP
OCTET_ALIGN AUDIO_USER MIC_SRC PCM_DUMP
(OCTET_ALIGN=0 selects RFC 4867 bandwidth-efficient payloads both ways; the
daemon sets it from the negotiated SDP — 1 is the default/legacy behavior.
AMR_MODE is the encoder mode of whichever AMR codec is active; default 2
for AMR-WB (12.65 kbit/s), 7 for AMR (12.2 kbit/s). MIC_SRC=<file> feeds
raw s16 PCM at the codec rate through the encoder instead of pw-record,
paced in real time; PCM_DUMP=1 writes the decoded downlink to <out-base>.pcm
— both are test seams for driving the leg against a synthetic RTP peer
with no PipeWire and no network.)
*/
#include <arpa/inet.h>
#include <dlfcn.h>
#include <fcntl.h>
#include <netinet/in.h>
#include <pwd.h>
#include <signal.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <unistd.h>
import std;
namespace {
using Clock = std::chrono::steady_clock;
double Now() {
return std::chrono::duration<double>(Clock::now().time_since_epoch()).count();
}
enum class Codec { AmrWb, AmrNb, Pcma, Pcmu };
Codec ParseCodec(std::string_view name) {
if (name == "AMR") return Codec::AmrNb;
if (name == "PCMA") return Codec::Pcma;
if (name == "PCMU") return Codec::Pcmu;
return Codec::AmrWb;
}
std::string_view CodecName(Codec c) {
switch (c) {
case Codec::AmrWb: return "AMR-WB";
case Codec::AmrNb: return "AMR";
case Codec::Pcma: return "PCMA";
case Codec::Pcmu: return "PCMU";
}
return "AMR-WB";
}
bool IsAmr(Codec c) { return c == Codec::AmrWb || c == Codec::AmrNb; }
// Sample rate = RTP clock rate; one 20 ms frame is 320 or 160 samples.
int CodecRate(Codec c) { return c == Codec::AmrWb ? 16000 : 8000; }
int FrameSamples(Codec c) { return CodecRate(c) / 50; }
// AMR speech bits per frame type — the exact payload bit counts of the
// bandwidth-efficient format. AMR-WB: RFC 4867 table 2 / TS 26.201; AMR:
// RFC 4867 table 1 / TS 26.101 (FT 8 = SID, 9-11 = the other systems' SID
// frames a gateway may forward). FT 14/15 (SPEECH_LOST/NO_DATA) carry 0
// bits; unknown FTs return -1 so a corrupt ToC aborts the packet instead of
// shifting every later bit.
constexpr int AmrBits(Codec c, int ft) {
if (c == Codec::AmrWb) {
switch (ft) {
case 0: return 132; case 1: return 177; case 2: return 253; case 3: return 285;
case 4: return 317; case 5: return 365; case 6: return 397; case 7: return 461;
case 8: return 477; case 9: return 40; case 14: return 0; case 15: return 0;
default: return -1;
}
}
switch (ft) {
case 0: return 95; case 1: return 103; case 2: return 118; case 3: return 134;
case 4: return 148; case 5: return 159; case 6: return 204; case 7: return 244;
case 8: return 39; case 9: return 43; case 10: return 38; case 11: return 37;
case 15: return 0;
default: return -1;
}
}
// octet-aligned speech-frame byte size by frame type: the bits rounded up
// (AMR-WB: 17 23 32 36 40 46 50 58 60, SID 5; AMR: 12 13 15 17 19 20 26 31,
// SID 5). 0 for frame types that carry no speech.
constexpr int AmrBytes(Codec c, int ft) {
int bits = AmrBits(c, ft);
return bits <= 0 ? 0 : (bits + 7) / 8;
}
// ---- G.711 (ITU-T, the classic Sun g711.c formulation) --------------------
// 16-bit linear <-> 8-bit companded. Byte 0xD5 (A-law) / 0xFF (mu-law) is
// digital zero. Idempotent: encoding a decoded sample gives the same byte.
constexpr int UlawBias = 0x84;
constexpr int UlawClip = 8159;
int SegmentOf(int val, std::span<const int> ends) {
for (std::size_t i = 0; i < ends.size(); i++)
if (val <= ends[i]) return static_cast<int>(i);
return static_cast<int>(ends.size());
}
std::uint8_t LinearToAlaw(std::int16_t pcm) {
static constexpr std::array<int, 8> ends = {0x1F, 0x3F, 0x7F, 0xFF, 0x1FF, 0x3FF, 0x7FF, 0xFFF};
int val = pcm >> 3; // 13-bit magnitude space
int mask = 0xD5;
if (val < 0) {
mask = 0x55;
val = -val - 1;
}
int seg = SegmentOf(val, ends);
if (seg >= 8) return static_cast<std::uint8_t>(0x7F ^ mask);
int aval = seg << 4;
aval |= seg < 2 ? (val >> 1) & 0x0F : (val >> seg) & 0x0F;
return static_cast<std::uint8_t>(aval ^ mask);
}
std::int16_t AlawToLinear(std::uint8_t a) {
a ^= 0x55;
int t = (a & 0x0F) << 4;
int seg = (a & 0x70) >> 4;
if (seg == 0) t += 8;
else if (seg == 1) t += 0x108;
else t = (t + 0x108) << (seg - 1);
return static_cast<std::int16_t>((a & 0x80) ? t : -t);
}
std::uint8_t LinearToUlaw(std::int16_t pcm) {
static constexpr std::array<int, 8> ends = {0x3F, 0x7F, 0xFF, 0x1FF, 0x3FF, 0x7FF, 0xFFF, 0x1FFF};
int val = pcm >> 2; // 14-bit magnitude space
int mask = 0xFF;
if (val < 0) {
val = -val;
mask = 0x7F;
}
if (val > UlawClip) val = UlawClip;
val += UlawBias >> 2;
int seg = SegmentOf(val, ends);
if (seg >= 8) return static_cast<std::uint8_t>(0x7F ^ mask);
int uval = (seg << 4) | ((val >> (seg + 1)) & 0x0F);
return static_cast<std::uint8_t>(uval ^ mask);
}
std::int16_t UlawToLinear(std::uint8_t u) {
u = static_cast<std::uint8_t>(~u);
int t = ((u & 0x0F) << 3) + UlawBias;
t <<= (u & 0x70) >> 4;
return static_cast<std::int16_t>((u & 0x80) ? (UlawBias - t) : (t - UlawBias));
}
std::uint8_t G711Encode(Codec c, std::int16_t pcm) { return c == Codec::Pcma ? LinearToAlaw(pcm) : LinearToUlaw(pcm); }
std::int16_t G711Decode(Codec c, std::uint8_t b) { return c == Codec::Pcma ? AlawToLinear(b) : UlawToLinear(b); }
std::uint8_t G711Zero(Codec c) { return c == Codec::Pcma ? 0xD5 : 0xFF; }
std::string EnvOr(const char* k, const char* d) {
const char* v = std::getenv(k);
return v ? std::string(v) : std::string(d);
}
bool EnvBool(const char* k, bool d) {
const char* v = std::getenv(k);
return v ? std::string_view(v) == "1" : d;
}
bool Is6(std::string_view a) { return a.contains(':'); }
// Fill a sockaddr_storage from an IP literal + port; returns its length.
socklen_t MakeAddr(std::string_view ip, int port, sockaddr_storage& ss) {
std::memset(&ss, 0, sizeof ss);
std::string s(ip);
if (Is6(ip)) {
auto* a = reinterpret_cast<sockaddr_in6*>(&ss);
a->sin6_family = AF_INET6;
a->sin6_port = htons(static_cast<uint16_t>(port));
inet_pton(AF_INET6, s.c_str(), &a->sin6_addr);
return sizeof(sockaddr_in6);
}
auto* a = reinterpret_cast<sockaddr_in*>(&ss);
a->sin_family = AF_INET;
a->sin_port = htons(static_cast<uint16_t>(port));
inet_pton(AF_INET, s.c_str(), &a->sin_addr);
return sizeof(sockaddr_in);
}
// ---- AMR codecs via dlopen ------------------------------------------------
// AMR-WB: vo-amrwbenc E_IF_* (encode), opencore-amrwb D_IF_* (decode).
// AMR: opencore-amrnb Encoder_Interface_* / Decoder_Interface_*.
// Both families speak the RFC 4867 §5.3 storage format: [header byte][speech],
// header = (FT << 3) | (Q << 2) — exactly the octet-aligned ToC byte with F=0.
class Encoder {
public:
bool Open(Codec c, int dtx) {
codec_ = c;
if (c == Codec::AmrWb) {
lib_ = dlopen("libvo-amrwbenc.so.0", RTLD_NOW);
if (!lib_) return false;
wbInit_ = reinterpret_cast<WbInitFn>(dlsym(lib_, "E_IF_init"));
wbEnc_ = reinterpret_cast<WbEncFn>(dlsym(lib_, "E_IF_encode"));
exit_ = reinterpret_cast<ExitFn>(dlsym(lib_, "E_IF_exit"));
if (!wbInit_ || !wbEnc_ || !exit_) return false;
st_ = wbInit_();
return st_ != nullptr;
}
lib_ = dlopen("libopencore-amrnb.so.0", RTLD_NOW);
if (!lib_) return false;
nbInit_ = reinterpret_cast<NbInitFn>(dlsym(lib_, "Encoder_Interface_init"));
nbEnc_ = reinterpret_cast<NbEncFn>(dlsym(lib_, "Encoder_Interface_Encode"));
exit_ = reinterpret_cast<ExitFn>(dlsym(lib_, "Encoder_Interface_exit"));
if (!nbInit_ || !nbEnc_ || !exit_) return false;
st_ = nbInit_(dtx); // NB: DTX is an init-time choice
return st_ != nullptr;
}
// one 20 ms frame of s16 samples -> one storage frame (header byte + speech).
std::vector<std::uint8_t> Encode(std::int16_t* samples, int mode, int dtx) {
std::uint8_t out[128];
int n = codec_ == Codec::AmrWb
? wbEnc_(st_, static_cast<std::int16_t>(mode), samples, out, static_cast<std::int16_t>(dtx))
: nbEnc_(st_, mode, samples, out, 0);
if (n <= 0) return {};
return std::vector<std::uint8_t>(out, out + n);
}
~Encoder() {
if (st_ && exit_) exit_(st_);
if (lib_) dlclose(lib_);
}
private:
using WbInitFn = void* (*)();
using WbEncFn = int (*)(void*, std::int16_t, std::int16_t*, std::uint8_t*, std::int16_t);
using NbInitFn = void* (*)(int);
using NbEncFn = int (*)(void*, int, const std::int16_t*, std::uint8_t*, int);
using ExitFn = void (*)(void*);
Codec codec_ = Codec::AmrWb;
void* lib_ = nullptr;
void* st_ = nullptr;
WbInitFn wbInit_ = nullptr;
WbEncFn wbEnc_ = nullptr;
NbInitFn nbInit_ = nullptr;
NbEncFn nbEnc_ = nullptr;
ExitFn exit_ = nullptr;
};
class Decoder {
public:
bool Open(Codec c) {
codec_ = c;
bool wb = c == Codec::AmrWb;
lib_ = dlopen(wb ? "libopencore-amrwb.so.0" : "libopencore-amrnb.so.0", RTLD_NOW);
if (!lib_) return false;
init_ = reinterpret_cast<InitFn>(dlsym(lib_, wb ? "D_IF_init" : "Decoder_Interface_init"));
dec_ = reinterpret_cast<DecFn>(dlsym(lib_, wb ? "D_IF_decode" : "Decoder_Interface_Decode"));
exit_ = reinterpret_cast<ExitFn>(dlsym(lib_, wb ? "D_IF_exit" : "Decoder_Interface_exit"));
if (!init_ || !dec_ || !exit_) return false;
st_ = init_();
return st_ != nullptr;
}
// one storage frame ([header][speech]) -> one 20 ms frame of s16 PCM.
std::vector<std::int16_t> Decode(const std::uint8_t* frame, int len) {
std::vector<std::int16_t> out(static_cast<std::size_t>(FrameSamples(codec_)), 0);
std::vector<std::uint8_t> in(frame, frame + len);
dec_(st_, in.data(), out.data(), 0);
return out;
}
~Decoder() {
if (st_ && exit_) exit_(st_);
if (lib_) dlclose(lib_);
}
private:
using InitFn = void* (*)();
using DecFn = void (*)(void*, const std::uint8_t*, std::int16_t*, int);
using ExitFn = void (*)(void*);
Codec codec_ = Codec::AmrWb;
void* lib_ = nullptr;
void* st_ = nullptr;
InitFn init_ = nullptr;
DecFn dec_ = nullptr;
ExitFn exit_ = nullptr;
};
// MSB-first bit cursor over an RTP payload (bandwidth-efficient AMR-WB is
// bit-packed: 4-bit CMR, 6-bit ToC entries, then the speech bits back to
// back with only the final octet padded — RFC 4867 §4.3).
struct BitReader {
std::span<const std::uint8_t> d;
std::size_t pos = 0;
bool Ok(std::size_t n) const { return pos + n <= d.size() * 8; }
std::uint32_t Take(int n) {
std::uint32_t v = 0;
for (int i = 0; i < n; i++, pos++)
v = (v << 1) | ((d[pos >> 3] >> (7 - (pos & 7))) & 1);
return v;
}
};
// bandwidth-efficient AMR de-payload. Same contract as DepayOctet:
// [(storage-header-byte, speech-bytes)...], speech re-aligned to octets.
std::vector<std::pair<std::uint8_t, std::vector<std::uint8_t>>>
DepayBe(Codec c, std::span<const std::uint8_t> pl) {
std::vector<std::pair<std::uint8_t, std::vector<std::uint8_t>>> out;
BitReader br{pl};
if (!br.Ok(4)) return out;
br.Take(4); // CMR
struct Toc { int ft; int q; };
std::vector<Toc> tocs;
for (;;) {
if (!br.Ok(6)) return out;
int f = static_cast<int>(br.Take(1));
int ft = static_cast<int>(br.Take(4));
int q = static_cast<int>(br.Take(1));
tocs.push_back({ft, q});
if (!f) break;
}
for (auto [ft, q] : tocs) {
int bits = AmrBits(c, ft);
if (bits < 0 || !br.Ok(static_cast<std::size_t>(bits))) break;
std::vector<std::uint8_t> speech(AmrBytes(c, ft), 0);
for (int i = 0; i < bits; i++)
if (br.Take(1)) speech[i >> 3] |= 0x80 >> (i & 7);
out.emplace_back(static_cast<std::uint8_t>((ft << 3) | (q ? 0x04 : 0)), std::move(speech));
}
return out;
}
// storage-format frame (header byte + octet-aligned speech) -> RTP payload.
// Octet-aligned: CMR byte + the frame verbatim (the storage header doubles
// as a ToC byte with F=0). Bandwidth-efficient: 10 header bits + exactly
// AmrBits(ft) speech bits, final octet zero-padded.
std::vector<std::uint8_t> PayloadFromFrame(Codec c, std::span<const std::uint8_t> frame, bool octetAlign) {
if (octetAlign) {
std::vector<std::uint8_t> pl = {0xF0};
pl.insert(pl.end(), frame.begin(), frame.end());
return pl;
}
int ft = (frame[0] >> 3) & 0x0F;
int q = (frame[0] >> 2) & 1;
int bits = AmrBits(c, ft);
if (bits < 0) bits = 0;
std::vector<std::uint8_t> pl((10 + bits + 7) / 8, 0);
auto put = [&](int pos, int n, std::uint32_t v) {
for (int i = 0; i < n; i++)
if ((v >> (n - 1 - i)) & 1) pl[(pos + i) >> 3] |= 0x80 >> ((pos + i) & 7);
};
put(0, 4, 15); // CMR: no mode request
put(4, 1, 0); // F: single frame
put(5, 4, static_cast<std::uint32_t>(ft));
put(9, 1, static_cast<std::uint32_t>(q));
for (int i = 0; i < bits; i++)
if (frame[1 + (i >> 3)] & (0x80 >> (i & 7))) pl[(10 + i) >> 3] |= 0x80 >> ((10 + i) & 7);
return pl;
}
// octet-aligned AMR de-payload: skip CMR, read ToC bytes until F=0, then
// the speech runs. Returns [(storage-header-byte, speech-bytes)...].
std::vector<std::pair<std::uint8_t, std::vector<std::uint8_t>>>
DepayOctet(Codec c, std::span<const std::uint8_t> pl) {
std::vector<std::pair<std::uint8_t, std::vector<std::uint8_t>>> out;
if (pl.empty()) return out;
std::size_t i = 1; // skip CMR
std::vector<std::uint8_t> tocs;
while (i < pl.size()) {
std::uint8_t toc = pl[i++];
tocs.push_back(toc);
if (!(toc & 0x80)) break;
}
for (std::uint8_t toc : tocs) {
int ft = (toc >> 3) & 0x0F;
int n = AmrBytes(c, ft);
std::vector<std::uint8_t> speech;
if (n > 0 && i + n <= pl.size()) speech.assign(pl.begin() + i, pl.begin() + i + n);
out.emplace_back(static_cast<std::uint8_t>(toc & 0x7C), std::move(speech));
i += n;
}
return out;
}
std::size_t RtpPayloadOffset(std::span<const std::uint8_t> pkt) {
int cc = pkt[0] & 0x0F;
int ext = (pkt[0] >> 4) & 1;
std::size_t off = 12 + cc * 4;
if (ext && off + 4 <= pkt.size()) {
std::uint16_t extlen = (pkt[off + 2] << 8) | pkt[off + 3];
off += 4 + extlen * 4;
}
return off;
}
// Spawn pw-record/pw-play in the desktop user's PipeWire session (sudo -u
// when run as root). AUDIO_USER names the session owner; the default "user"
// is postmarketOS's standard account. `toChild` true = we write the child's
// stdin (pw-play); false = we read its stdout (pw-record). Returns {pid, fd}.
struct Child { pid_t pid = -1; int fd = -1; };
Child SpawnPw(bool play, bool toChild, int rate) {
int pipefd[2];
if (pipe(pipefd) != 0) return {};
std::vector<std::string> argv;
if (geteuid() == 0) {
std::string user = EnvOr("AUDIO_USER", "user");
uid_t uid = 0;
if (passwd* pw = getpwnam(user.c_str())) uid = pw->pw_uid;
argv = {"sudo", "-u", user, "env",
std::format("XDG_RUNTIME_DIR=/run/user/{}", uid)};
}
const char* tool = play ? "pw-play" : "pw-record";
const char* lat = play ? "40ms" : "20ms";
std::string rateStr = std::to_string(rate);
for (const char* a : {tool, "--raw", "--rate", rateStr.c_str(), "--channels", "1", "--format", "s16", "--latency", lat, "-"})
argv.emplace_back(a);
pid_t pid = fork();
if (pid == 0) {
if (toChild) { dup2(pipefd[0], STDIN_FILENO); }
else { dup2(pipefd[1], STDOUT_FILENO); }
close(pipefd[0]); close(pipefd[1]);
int devnull = open("/dev/null", O_WRONLY);
if (devnull >= 0) { dup2(devnull, STDERR_FILENO); close(devnull); }
std::vector<char*> cargv;
for (auto& s : argv) cargv.push_back(const_cast<char*>(s.c_str()));
cargv.push_back(nullptr);
execvp(cargv[0], cargv.data());
_exit(127);
}
if (pid < 0) { close(pipefd[0]); close(pipefd[1]); return {}; }
if (toChild) { close(pipefd[0]); return {pid, pipefd[1]}; }
close(pipefd[1]);
return {pid, pipefd[0]};
}
bool ReadExact(int fd, std::uint8_t* buf, std::size_t n) {
std::size_t got = 0;
while (got < n) {
ssize_t r = read(fd, buf + got, n - got);
if (r <= 0) return false;
got += static_cast<std::size_t>(r);
}
return true;
}
// ---- shared RTP tx state (main + mic threads both send) -------------------
struct TxState {
std::mutex lock;
int pt = 0;
std::uint32_t tsStep = 320; // samples per 20 ms frame at the codec's clock
std::uint32_t ssrc = 0x5EED1234;
std::uint32_t seq = 1000;
std::uint32_t ts = 160000;
sockaddr_storage dst{}; socklen_t dstLen = 0;
sockaddr_storage latched{}; socklen_t latchedLen = 0;
std::uint64_t tx = 0;
std::uint64_t txMic = 0;
std::atomic<bool> micOn{false};
};
void RtpSend(int sock, TxState& st, std::span<const std::uint8_t> payload) {
std::uint8_t hdr[12];
sockaddr_storage a1, a2; socklen_t l1, l2;
{
std::scoped_lock g(st.lock);
hdr[0] = 0x80;
hdr[1] = static_cast<std::uint8_t>(st.pt & 0x7F);
hdr[2] = (st.seq >> 8) & 0xFF; hdr[3] = st.seq & 0xFF;
hdr[4] = (st.ts >> 24) & 0xFF; hdr[5] = (st.ts >> 16) & 0xFF;
hdr[6] = (st.ts >> 8) & 0xFF; hdr[7] = st.ts & 0xFF;
hdr[8] = (st.ssrc >> 24) & 0xFF; hdr[9] = (st.ssrc >> 16) & 0xFF;
hdr[10] = (st.ssrc >> 8) & 0xFF; hdr[11] = st.ssrc & 0xFF;
st.seq = (st.seq + 1) & 0xFFFF;
st.ts = (st.ts + st.tsStep) & 0xFFFFFFFF;
a1 = st.dst; l1 = st.dstLen; a2 = st.latched; l2 = st.latchedLen;
}
std::vector<std::uint8_t> pkt(hdr, hdr + 12);
pkt.insert(pkt.end(), payload.begin(), payload.end());
auto sendTo = [&](sockaddr_storage& a, socklen_t l) {
if (l && sendto(sock, pkt.data(), pkt.size(), 0, reinterpret_cast<sockaddr*>(&a), l) >= 0) {
std::scoped_lock g(st.lock);
st.tx++;
}
};
sendTo(a1, l1);
// avoid double-send when latched == dst
if (l2 && (l2 != l1 || std::memcmp(&a1, &a2, l1) != 0)) sendTo(a2, l2);
}
std::vector<std::pair<std::uint8_t, std::vector<std::uint8_t>>>
Depay(Codec c, std::span<const std::uint8_t> pl, bool octetAlign) {
return octetAlign ? DepayOctet(c, pl) : DepayBe(c, pl);
}
// What goes out every 20 ms while the mic is not feeding frames: for AMR a
// storage frame ToC(F=0,FT,Q=1) + zeroed speech, payloaded per mode; for
// G.711 one frame of digital zero.
std::vector<std::uint8_t> SilenceFrame(Codec c, int ft, bool octetAlign) {
if (!IsAmr(c)) return std::vector<std::uint8_t>(static_cast<std::size_t>(FrameSamples(c)), G711Zero(c));
std::vector<std::uint8_t> f = {static_cast<std::uint8_t>((ft << 3) | 0x04)};
f.resize(1 + static_cast<std::size_t>(AmrBytes(c, ft)), 0);
return PayloadFromFrame(c, f, octetAlign);
}
// G.711 uplink: one 20 ms frame of samples -> one payload of companded bytes.
std::vector<std::uint8_t> G711Payload(Codec c, std::span<const std::int16_t> pcm) {
std::vector<std::uint8_t> pl(pcm.size());
for (std::size_t i = 0; i < pcm.size(); i++)
pl[i] = G711Encode(c, pcm[i]);
return pl;
}
// G.711 downlink: one frame's worth of companded bytes -> PCM.
std::vector<std::int16_t> G711DecodeFrame(Codec c, std::span<const std::uint8_t> bytes) {
std::vector<std::int16_t> pcm(bytes.size());
for (std::size_t i = 0; i < bytes.size(); i++)
pcm[i] = G711Decode(c, bytes[i]);
return pcm;
}
std::atomic<bool> Quit{false};
void OnSig(int) { Quit.store(true); }
// playout queue item
struct PktItem { std::uint32_t ts; std::vector<std::uint8_t> payload; };
// --selftest: pack->depay roundtrip of every frame type, both payload
// formats, both AMR codecs; G.711 digital zero, idempotence over the whole
// 16-bit range, and a 1 kHz sine surviving with the codec's nominal SNR.
int SelfTest() {
for (Codec c : {Codec::AmrWb, Codec::AmrNb}) {
for (int ft = 0; ft < 16; ft++) {
int bits = AmrBits(c, ft);
if (bits <= 0) continue;
// BE carries exactly AmrBits(ft) bits, so the pattern's padding
// bits in the last speech byte must be zero for equality to hold.
std::vector<std::uint8_t> frame = {static_cast<std::uint8_t>((ft << 3) | 0x04)};
for (int i = 0; i < AmrBytes(c, ft); i++)
frame.push_back(static_cast<std::uint8_t>(0xA5 + i * 31));
if (bits % 8) frame.back() &= static_cast<std::uint8_t>(0xFF << (8 - bits % 8));
for (bool oa : {true, false}) {
auto got = Depay(c, PayloadFromFrame(c, frame, oa), oa);
if (got.size() != 1 || got[0].first != frame[0] || !std::equal(got[0].second.begin(), got[0].second.end(), frame.begin() + 1, frame.end())) {
std::println(std::cerr, "selftest FAIL {} ft={} oa={}", CodecName(c), ft, oa);
return 1;
}
}
}
}
if (LinearToAlaw(0) != 0xD5 || LinearToUlaw(0) != 0xFF) {
std::println(std::cerr, "selftest FAIL G.711 digital zero");
return 1;
}
for (Codec c : {Codec::Pcma, Codec::Pcmu}) {
for (int v = -32768; v <= 32767; v++) {
std::uint8_t b = G711Encode(c, static_cast<std::int16_t>(v));
if (G711Encode(c, G711Decode(c, b)) != b) {
std::println(std::cerr, "selftest FAIL {} not idempotent at {}", CodecName(c), v);
return 1;
}
}
double sig = 0;
double err = 0;
for (int i = 0; i < 8000; i++) {
double x = 10000.0 * std::sin(2 * std::numbers::pi * 1000.0 * i / 8000.0);
auto sample = static_cast<std::int16_t>(std::lround(x));
std::int16_t d = G711Decode(c, G711Encode(c, sample));
sig += x * x;
err += (x - d) * (x - d);
}
double snr = 10 * std::log10(sig / err);
if (snr < 30) {
std::println(std::cerr, "selftest FAIL {} sine SNR {:.1f} dB", CodecName(c), snr);
return 1;
}
}
std::println("selftest OK");
return 0;
}
} // namespace
int main(int argc, char** argv) {
if (argc == 2 && std::string_view(argv[1]) == "--selftest") return SelfTest();
if (argc < 8) {
std::println(std::cerr, "usage: imsd-media local rtp_port remote_ip remote_port pt secs out");
return 2;
}
std::string local = argv[1];
int rtpPort = std::atoi(argv[2]);
std::string rIp = argv[3];
int rPort = std::atoi(argv[4]);
int pt = std::atoi(argv[5]);
double secs = std::atof(argv[6]);
std::string out = argv[7];
Codec codec = ParseCodec(EnvOr("CODEC", "AMR-WB"));
bool amr = IsAmr(codec);
int rate = CodecRate(codec);
auto frameSamples = static_cast<std::size_t>(FrameSamples(codec));
bool mic = EnvBool("MIC", false);
bool play = EnvBool("PLAY", false);
int amrMode = std::atoi(EnvOr("AMR_MODE", codec == Codec::AmrWb ? "2" : "7").c_str());
double gain = std::atof(EnvOr("GAIN", "1.0").c_str());
double playGain = std::atof(EnvOr("PLAY_GAIN", "1.0").c_str());
int dtx = EnvBool("DTX", false) ? 1 : 0;
bool octetAlign = EnvBool("OCTET_ALIGN", true);
double mediaTimeout = std::atof(EnvOr("MEDIA_TIMEOUT", "6.0").c_str());
bool rtpDump = EnvBool("RTP_DUMP", false);
std::string micSrc = EnvOr("MIC_SRC", "");
bool pcmDump = EnvBool("PCM_DUMP", false);
constexpr int ExitMediaTimeout = 3;
constexpr int PrimeFrames = 8;
constexpr int MaxFill = 25;
constexpr std::size_t PlayqMax = 256;
int sock = socket(Is6(local) ? AF_INET6 : AF_INET, SOCK_DGRAM, 0);
if (sock < 0) {
std::println(std::cerr, "imsd-media: socket failed");
return 1;
}
int one = 1;
setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &one, sizeof one);
sockaddr_storage bindA;
socklen_t bindL = MakeAddr(local, rtpPort, bindA);
if (bind(sock, reinterpret_cast<sockaddr*>(&bindA), bindL) != 0) {
std::println(std::cerr, "imsd-media: bind [{}]:{} failed", local, rtpPort);
return 1;
}
timeval tv{0, 20000}; // 20 ms recv timeout
setsockopt(sock, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof tv);
TxState st;
st.pt = pt;
st.tsStep = static_cast<std::uint32_t>(frameSamples);
st.dstLen = MakeAddr(rIp, rPort, st.dst);
st.latched = st.dst;
st.latchedLen = st.dstLen;
signal(SIGTERM, OnSig);
signal(SIGINT, OnSig);
signal(SIGPIPE, SIG_IGN);
// ---- mic uplink thread: pw-record (or the MIC_SRC file, real-time paced)
// through the codec's encoder, one RTP packet per 20 ms frame
std::atomic<bool> stop{false};
std::jthread micThread;
if (mic) {
micThread = std::jthread([&] {
Encoder enc;
if (amr && !enc.Open(codec, dtx)) {
std::println(std::cerr, "imsd-media: mic: {} encoder unavailable; silence fallback", CodecName(codec));
return;
}
int fd = -1;
pid_t pid = -1;
if (!micSrc.empty()) {
fd = open(micSrc.c_str(), O_RDONLY);
if (fd < 0) {
std::println(std::cerr, "imsd-media: mic: cannot open MIC_SRC {}", micSrc);
return;
}
} else {
Child rec = SpawnPw(false, /*toChild=*/false, rate);
if (rec.pid < 0) return;
fd = rec.fd;
pid = rec.pid;
}
std::vector<std::uint8_t> raw(frameSamples * 2);
std::vector<std::int16_t> samples(frameSamples);
auto next = Clock::now();
while (!stop.load()) {
if (!ReadExact(fd, raw.data(), raw.size())) {
std::println(std::cerr, "imsd-media: mic: {} EOF; silence fallback", pid > 0 ? "pw-record" : "MIC_SRC");
break;
}
if (pid < 0) {
// a file delivers instantly; pace it like a microphone
next += std::chrono::milliseconds(20);
std::this_thread::sleep_until(next);
}
std::memcpy(samples.data(), raw.data(), raw.size());
if (gain != 1.0)
for (auto& sample : samples) {
int v = static_cast<int>(sample * gain);
sample = static_cast<std::int16_t>(v < -32768 ? -32768 : (v > 32767 ? 32767 : v));
}
std::vector<std::uint8_t> payload;
if (amr) {
std::vector<std::uint8_t> frame = enc.Encode(samples.data(), amrMode, dtx);
if (frame.empty()) continue;
payload = PayloadFromFrame(codec, frame, octetAlign);
} else {
payload = G711Payload(codec, samples);
}
st.micOn.store(true);
{ std::scoped_lock g(st.lock); st.txMic++; }
RtpSend(sock, st, payload);
}
st.micOn.store(false);
close(fd);
if (pid > 0) {
kill(pid, SIGKILL);
waitpid(pid, nullptr, 0);
}
});
}
// ---- downlink playout (decode + RTP-timestamp clock reconstruction).
// Runs for pw-play (PLAY=1) and/or the PCM dump (PCM_DUMP=1).
Decoder dec;
Child playCh;
bool playOn = false;
bool decodeOn = false;
if (play || pcmDump) {
if (!amr || dec.Open(codec)) {
if (play) {
playCh = SpawnPw(true, /*toChild=*/true, rate);
playOn = playCh.pid >= 0;
}
decodeOn = playOn || pcmDump;
} else {
std::println(std::cerr, "imsd-media: play: {} decoder unavailable; capture only", CodecName(codec));
}
}
std::FILE* pcmFile = decodeOn && pcmDump ? std::fopen((std::format("{}.pcm", out)).c_str(), "wb") : nullptr;
std::mutex qlock;
std::condition_variable qcv;
std::deque<PktItem> playq;
std::uint64_t rxPlayed = 0;
std::uint64_t cng = 0;
std::uint64_t late = 0;
std::uint64_t qdrop = 0;
std::jthread playThread;
if (decodeOn) {
playThread = std::jthread([&] {
auto writePcm = [&](std::span<const std::int16_t> pcm) {
if (pcmFile) std::fwrite(pcm.data(), 2, pcm.size(), pcmFile);
if (!playOn) return true;
std::size_t bytes = pcm.size() * 2;
const char* p = reinterpret_cast<const char*>(pcm.data());
std::size_t off = 0;
while (off < bytes) {
ssize_t w = write(playCh.fd, p + off, bytes - off);
if (w <= 0) return false;
off += static_cast<std::size_t>(w);
}
return true;
};
auto applyGain = [&](std::vector<std::int16_t>& pcm) {
if (playGain == 1.0) return;
for (auto& sample : pcm) {
int v = static_cast<int>(sample * playGain);
sample = static_cast<std::int16_t>(v < -32768 ? -32768 : (v > 32767 ? 32767 : v));
}
};
// Decoder state is time-ordered: the CNG fill for a gap must be
// decoded BEFORE the frames that follow the gap, so depay first,
// decode in playout order.
auto decodeFrame = [&](std::span<const std::uint8_t> f) {
return amr ? dec.Decode(f.data(), static_cast<int>(f.size())) : G711DecodeFrame(codec, f);
};
std::vector<std::int16_t> zero(frameSamples, 0);
std::optional<std::uint32_t> expect;
for (;;) {
PktItem item;
{
std::unique_lock g(qlock);
qcv.wait(g, [&] { return !playq.empty() || stop.load(); });
if (playq.empty()) return;
item = std::move(playq.front());
playq.pop_front();
}
std::vector<std::vector<std::uint8_t>> frames;
if (amr) {
for (auto& [hdr, speech] : Depay(codec, item.payload, octetAlign)) {
std::vector<std::uint8_t> f = {hdr};
f.insert(f.end(), speech.begin(), speech.end());
frames.push_back(std::move(f));
}
} else {
// whole frames back to back (a gateway may pack 2 at ptime 40)
for (std::size_t off = 0; off + frameSamples <= item.payload.size(); off += frameSamples)
frames.emplace_back(item.payload.begin() + static_cast<std::ptrdiff_t>(off), item.payload.begin() + static_cast<std::ptrdiff_t>(off + frameSamples));
}
if (frames.empty()) continue;
int fill = 0;
if (!expect) {
for (int i = 0; i < PrimeFrames; i++)
if (!writePcm(zero)) return;
} else {
std::uint32_t diff = (item.ts - *expect) & 0xFFFFFFFF;
if (diff >= 0x80000000u) {
late++;
continue;
}
fill = static_cast<int>(diff / frameSamples);
if (fill > MaxFill) fill = 0;
}
for (int i = 0; i < fill; i++) {
cng++;
std::uint8_t nodata = 0x7C;
std::vector<std::int16_t> pcm = amr ? dec.Decode(&nodata, 1) : zero;
applyGain(pcm);
if (!writePcm(pcm)) return;
}
for (auto& f : frames) {
rxPlayed++;
std::vector<std::int16_t> pcm = decodeFrame(f);
applyGain(pcm);
if (!writePcm(pcm)) return;
}
expect = (item.ts + static_cast<std::uint32_t>(frameSamples * frames.size())) & 0xFFFFFFFF;
}
});
}
// ---- main recv loop
std::vector<std::uint8_t> silence = SilenceFrame(codec, 0, octetAlign);
for (int i = 0; i < 5; i++) RtpSend(sock, st, silence); // latch burst
std::FILE* dump = rtpDump ? std::fopen((std::format("{}.rtp", out)).c_str(), "wb") : nullptr;
double t0 = Now();
double lastTx = 0;
double lastRx = Now();
std::uint64_t rx = 0;
std::uint64_t rxBytes = 0;
bool gotMedia = false;
bool mediaEnded = false;
std::string firstSrc;
while (Now() - t0 < secs && !Quit.load()) {
double now = Now();
if (mediaTimeout > 0 && gotMedia && now - lastRx > mediaTimeout) {
mediaEnded = true;
break;
}
if (now - lastTx >= 0.02 && !st.micOn.load()) {
RtpSend(sock, st, silence);
lastTx = now;
}
std::uint8_t buf[65535];
sockaddr_storage src;
socklen_t srcLen = sizeof src;
ssize_t n = recvfrom(sock, buf, sizeof buf, 0, reinterpret_cast<sockaddr*>(&src), &srcLen);
if (n <= 0) continue;
lastRx = Now();
gotMedia = true;
if (firstSrc.empty()) {
char host[INET6_ADDRSTRLEN] = {};
int port = 0;
if (src.ss_family == AF_INET6) {
auto* a = reinterpret_cast<sockaddr_in6*>(&src);
inet_ntop(AF_INET6, &a->sin6_addr, host, sizeof host);
port = ntohs(a->sin6_port);
} else {
auto* a = reinterpret_cast<sockaddr_in*>(&src);
inet_ntop(AF_INET, &a->sin_addr, host, sizeof host);
port = ntohs(a->sin_port);
}
firstSrc = std::format("{}:{}", host, port);
std::scoped_lock g(st.lock);
std::memcpy(&st.latched, &src, srcLen);
st.latchedLen = srcLen; // relatch to the actual media source
}
rx++;
rxBytes += static_cast<std::uint64_t>(n);
if (dump) {
std::uint32_t len = static_cast<std::uint32_t>(n);
std::uint8_t lb[4] = {static_cast<std::uint8_t>((len >> 24) & 0xFF),
static_cast<std::uint8_t>((len >> 16) & 0xFF),
static_cast<std::uint8_t>((len >> 8) & 0xFF),
static_cast<std::uint8_t>(len & 0xFF)};
std::fwrite(lb, 1, 4, dump);
std::fwrite(buf, 1, static_cast<std::size_t>(n), dump);
}
if (playThread.joinable() && n >= 12 && (buf[1] & 0x7F) == pt) {
std::size_t off = RtpPayloadOffset(std::span(buf, static_cast<std::size_t>(n)));
std::uint32_t pktTs = (static_cast<std::uint32_t>(buf[4]) << 24) |
(buf[5] << 16) | (buf[6] << 8) | buf[7];
std::scoped_lock g(qlock);
if (playq.size() >= PlayqMax) {
playq.pop_front();
qdrop++;
}
playq.push_back({pktTs, std::vector<std::uint8_t>(buf + off, buf + n)});
qcv.notify_one();
}
}
stop.store(true);
qcv.notify_all();
if (micThread.joinable()) micThread.join();
if (playThread.joinable()) playThread.join();
if (dump) std::fclose(dump);
if (pcmFile) std::fclose(pcmFile);
if (playOn) {
close(playCh.fd);
int status;
for (int i = 0; i < 20; i++) {
if (waitpid(playCh.pid, &status, WNOHANG) != 0) break;
usleep(100000);
}
kill(playCh.pid, SIGKILL);
waitpid(playCh.pid, nullptr, 0);
}
close(sock);
// .stats sidecar (tiny; always written)
if (std::FILE* sf = std::fopen((std::format("{}.stats", out)).c_str(), "w")) {
std::print(sf,
"{{\"codec\": \"{}\", \"tx\": {}, \"tx_mic\": {}, \"rx\": {}, \"rx_bytes\": {}, "
"\"rx_played\": {}, \"cng\": {}, \"late\": {}, \"qdrop\": {}, "
"\"first_src\": \"{}\", \"dst\": \"{}:{}\", \"pt\": {}, \"mic\": {}, "
"\"play\": {}, \"amr_mode\": {}, \"media_ended\": {}}}",
CodecName(codec), st.tx, st.txMic, rx, rxBytes, rxPlayed, cng, late, qdrop, firstSrc,
rIp, rPort, pt, mic, play, amrMode, mediaEnded);
std::fclose(sf);
}
std::println("imsd-media: codec={} tx={} tx_mic={} rx={} rx_played={} cng={} late={} " "qdrop={} rx_bytes={} first_src={} media_ended={}", CodecName(codec), st.tx, st.txMic, rx, rxPlayed, cng, late, qdrop, rxBytes, firstSrc, mediaEnded);
return mediaEnded ? ExitMediaTimeout : 0;
}
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