*/
#define BUFFER_SECONDS 5
-#define FRAMES 4096 /* Frame batch size */
+/** @brief Frame batch size
+ *
+ * This controls how many frames are written in one go.
+ *
+ * For ALSA we request a buffer of three times this size and set the low
+ * watermark to this amount. The goal is then to keep between 1 and 3 times
+ * this many frames in play.
+ *
+ * For all backends we attempt to play up to three times this many frames per
+ * shot. In practice we will often only send much less than this.
+ */
+#define FRAMES 4096
/** @brief Bytes to send per network packet
*
*/
static int ready;
-static int forceplay; /* frames to force play */
-static int cmdfd = -1; /* child process input */
-static int bfd = -1; /* broadcast FD */
+/** @brief Frames to force-play
+ *
+ * If this is nonzero, and playing is enabled, then the main loop will attempt
+ * to play this many frames without checking whether the output device is
+ * ready.
+ */
+static int forceplay;
+
+/** @brief Pipe to subprocess
+ *
+ * This is the file descriptor to write to for @ref BACKEND_COMMAND.
+ */
+static int cmdfd = -1;
+
+/** @brief Network socket
+ *
+ * This is the file descriptor to write to for @ref BACKEND_NETWORK.
+ */
+static int bfd = -1;
/** @brief RTP timestamp
*
*/
static struct timeval rtp_time_0;
-static uint16_t rtp_seq; /* frame sequence number */
-static uint32_t rtp_id; /* RTP SSRC */
+/** @brief RTP packet sequence number */
+static uint16_t rtp_seq;
+
+/** @brief RTP SSRC */
+static uint32_t rtp_id;
+
+/** @brief Set when idled
+ *
+ * This is set when the sound device is deliberately closed by idle().
+ * @ref ready is set to 0 at the same time.
+ */
static int idled; /* set when idled */
-static int audio_errors; /* audio error counter */
+
+/** @brief Error counter */
+static int audio_errors;
/** @brief Structure of a backend */
struct speaker_backend {
* @param t Pointer to track
* @return 0 on success, -1 on EOF
*
- * This is effectively the read callback on @c t->fd.
+ * This is effectively the read callback on @c t->fd. It is called from the
+ * main loop whenever the track's file descriptor is readable, assuming the
+ * buffer has not reached the maximum allowed occupancy.
*/
static int fill(struct track *t) {
size_t where, left;
return 0;
}
-/** @brief Close the sound device */
+/** @brief Close the sound device
+ *
+ * This is called to deactivate the output device when pausing, and also by the
+ * ALSA backend when changing encoding (in which case the sound device will be
+ * immediately reactivated).
+ */
static void idle(void) {
D(("idle"));
if(backend->deactivate)
return backend->activate();
}
-/* Check to see whether the current track has finished playing */
+/** @brief Check whether the current track has finished
+ *
+ * The current track is determined to have finished either if the input stream
+ * eded before the format could be determined (i.e. it is malformed) or the
+ * input is at end of file and there is less than a frame left unplayed. (So
+ * it copes with decoders that crash mid-frame.)
+ */
static void maybe_finished(void) {
if(playing
&& playing->eof
abandon();
}
+/** @brief Start the subprocess for @ref BACKEND_COMMAND */
static void fork_cmd(void) {
pid_t cmdpid;
int pfd[2];
D(("forked cmd %d, fd = %d", cmdpid, cmdfd));
}
+/** @brief Play up to @p frames frames of audio */
static void play(size_t frames) {
size_t avail_frames, avail_bytes, written_frames;
ssize_t written_bytes;
{ -1, 0, 0, 0, 0, 0, 0, 0 } /* end of list */
};
-int main(int argc, char **argv) {
- int n, fd, stdin_slot, poke, timeout;
+/** @brief Main event loop
+ *
+ * This has grown in a rather bizarre and ad-hoc way is very sensitive to
+ * changes...
+ *
+ * Firstly the loop is terminated when the parent process exits. Therefore the
+ * speaker process has the same lifetime as the main server. This and the
+ * reading of data from decoders is comprehensible enough.
+ *
+ * The playing of audio is more complicated however.
+ *
+ * On the first run through when a track is ready to be played, @c ready and
+ * @ref forceplay will both be zero. Therefore @c beforepoll is not called.
+ *
+ * @c afterpoll on the other hand @b is called and will return nonzero. The
+ * result is that we call @c play(0). This will call activate(), setting
+ * @c ready nonzero, but otherwise has no immediate effect.
+ *
+ * We then deal with stdin and the decoders.
+ *
+ * We then reach the second place we might play some audio. @ref forceplay is
+ * 0 so nothing happens here again.
+ *
+ * On the next iteration through however @c ready is nonzero, and @ref
+ * forceplay is 0, so we call @c beforepoll. After the @c poll() we call @c
+ * afterpoll and actually get some audio played.
+ *
+ * This is surely @b far more complicated than it needs to be!
+ *
+ * If at any call to play(), activate() fails, or if there aren't enough bytes
+ * in the buffer to satisfy the request, then @ref forceplay is set non-0. On
+ * the next pass through the event loop @c beforepoll is not called. This
+ * means that (if none of the other FDs trigger) the @c poll() call will block
+ * for up to a second. @c afterpoll will return nonzero, since @c beforepoll
+ * wasn't called, and consequently play() is called with @ref forceplay as its
+ * argument.
+ *
+ * The effect is to attempt to restart playing audio - including the activate()
+ * step, which may have failed at the previous attempt - at least once a second
+ * after an error has disabled it. The delay prevents busy-waiting on whatever
+ * condition has rendered the audio device uncooperative.
+ */
+static void mainloop(void) {
struct track *t;
struct speaker_message sm;
+ int n, fd, stdin_slot, poke, timeout;
- set_progname(argv);
- if(!setlocale(LC_CTYPE, "")) fatal(errno, "error calling setlocale");
- while((n = getopt_long(argc, argv, "hVc:dD", options, 0)) >= 0) {
- switch(n) {
- case 'h': help();
- case 'V': version();
- case 'c': configfile = optarg; break;
- case 'd': debugging = 1; break;
- case 'D': debugging = 0; break;
- default: fatal(0, "invalid option");
- }
- }
- if(getenv("DISORDER_DEBUG_SPEAKER")) debugging = 1;
- /* If stderr is a TTY then log there, otherwise to syslog. */
- if(!isatty(2)) {
- openlog(progname, LOG_PID, LOG_DAEMON);
- log_default = &log_syslog;
- }
- if(config_read()) fatal(0, "cannot read configuration");
- /* ignore SIGPIPE */
- signal(SIGPIPE, SIG_IGN);
- /* reap kids */
- signal(SIGCHLD, reap);
- /* set nice value */
- xnice(config->nice_speaker);
- /* change user */
- become_mortal();
- /* make sure we're not root, whatever the config says */
- if(getuid() == 0 || geteuid() == 0) fatal(0, "do not run as root");
- /* identify the backend used to play */
- for(n = 0; backends[n].backend != -1; ++n)
- if(backends[n].backend == config->speaker_backend)
- break;
- if(backends[n].backend == -1)
- fatal(0, "unsupported backend %d", config->speaker_backend);
- backend = &backends[n];
- /* backend-specific initialization */
- backend->init();
while(getppid() != 1) {
fdno = 0;
/* Always ready for commands from the main server. */
playing->slot = -1;
/* If forceplay is set then wait until it succeeds before waiting on the
* sound device. */
+#if API_ALSA
alsa_slots = -1;
+#endif
cmdfd_slot = -1;
bfd_slot = -1;
/* By default we will wait up to a second before thinking about current
if(time(0) > last_report)
report();
}
+}
+
+int main(int argc, char **argv) {
+ int n;
+
+ set_progname(argv);
+ if(!setlocale(LC_CTYPE, "")) fatal(errno, "error calling setlocale");
+ while((n = getopt_long(argc, argv, "hVc:dD", options, 0)) >= 0) {
+ switch(n) {
+ case 'h': help();
+ case 'V': version();
+ case 'c': configfile = optarg; break;
+ case 'd': debugging = 1; break;
+ case 'D': debugging = 0; break;
+ default: fatal(0, "invalid option");
+ }
+ }
+ if(getenv("DISORDER_DEBUG_SPEAKER")) debugging = 1;
+ /* If stderr is a TTY then log there, otherwise to syslog. */
+ if(!isatty(2)) {
+ openlog(progname, LOG_PID, LOG_DAEMON);
+ log_default = &log_syslog;
+ }
+ if(config_read()) fatal(0, "cannot read configuration");
+ /* ignore SIGPIPE */
+ signal(SIGPIPE, SIG_IGN);
+ /* reap kids */
+ signal(SIGCHLD, reap);
+ /* set nice value */
+ xnice(config->nice_speaker);
+ /* change user */
+ become_mortal();
+ /* make sure we're not root, whatever the config says */
+ if(getuid() == 0 || geteuid() == 0) fatal(0, "do not run as root");
+ /* identify the backend used to play */
+ for(n = 0; backends[n].backend != -1; ++n)
+ if(backends[n].backend == config->speaker_backend)
+ break;
+ if(backends[n].backend == -1)
+ fatal(0, "unsupported backend %d", config->speaker_backend);
+ backend = &backends[n];
+ /* backend-specific initialization */
+ backend->init();
+ mainloop();
info("stopped (parent terminated)");
exit(0);
}
~mdw / disorder / commitdiff