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authorSteven O'Brien <steven_obrien1@yahoo.co.uk>2014-01-02 17:54:18 +0000
committerMax Kellermann <max@duempel.org>2014-01-06 18:27:44 +0100
commitf39a34ccfa10e10ca4e71db52a5b5fb540b98fb1 (patch)
treecce896fac57824db734f9a4e4ffbc3c1f925a163 /src
parent08f5b9f1f9292a6e9e4a6ede16bb61b38bbae89d (diff)
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input/AlsaInputPlugin.cxx: use I/O thread to poll for available data
[mk: modified to use MultiSocketMonitor instead of SocketMonitor]
Diffstat (limited to 'src')
-rw-r--r--src/input/AlsaInputPlugin.cxx344
1 files changed, 289 insertions, 55 deletions
diff --git a/src/input/AlsaInputPlugin.cxx b/src/input/AlsaInputPlugin.cxx
index c910ae340..5aa0a69b5 100644
--- a/src/input/AlsaInputPlugin.cxx
+++ b/src/input/AlsaInputPlugin.cxx
@@ -31,59 +31,250 @@
#include "util/Domain.hxx"
#include "util/Error.hxx"
#include "util/StringUtil.hxx"
+#include "util/ReusableArray.hxx"
+#include "util/Cast.hxx"
#include "Log.hxx"
+#include "event/MultiSocketMonitor.hxx"
+#include "event/DeferredMonitor.hxx"
+#include "event/Call.hxx"
+#include "thread/Mutex.hxx"
+#include "thread/Cond.hxx"
+#include "IOThread.hxx"
#include <alsa/asoundlib.h>
+#include <assert.h>
+#include <string.h>
+
static constexpr Domain alsa_input_domain("alsa");
static constexpr const char *default_device = "hw:0,0";
-// this value chosen to balance between limiting latency and avoiding stutter
-static constexpr int max_frames_to_buffer = 64;
-
// the following defaults are because the PcmDecoderPlugin forces CD format
static constexpr snd_pcm_format_t default_format = SND_PCM_FORMAT_S16;
static constexpr int default_channels = 2; // stereo
static constexpr unsigned int default_rate = 44100; // cd quality
-struct AlsaInputStream {
+/**
+ * This value should be the same as the read buffer size defined in
+ * PcmDecoderPlugin.cxx:pcm_stream_decode().
+ * We use it to calculate how many audio frames to buffer in the alsa driver
+ * before reading from the device. snd_pcm_readi() blocks until that many
+ * frames are ready.
+ */
+static constexpr size_t read_buffer_size = 4096;
+
+class AlsaInputStream final : MultiSocketMonitor, DeferredMonitor {
InputStream base;
snd_pcm_t *capture_handle;
size_t frame_size;
- size_t max_bytes_to_read;
-
- AlsaInputStream(const char *uri, Mutex &mutex, Cond &cond,
- snd_pcm_t *handle)
- :base(input_plugin_alsa, uri, mutex, cond),
- capture_handle(handle) {
- frame_size = snd_pcm_format_width(default_format) / 8 * default_channels;
- max_bytes_to_read = max_frames_to_buffer * frame_size;
+ int frames_to_read;
+ bool eof;
+
+ /**
+ * Is somebody waiting for data? This is set by method
+ * Available().
+ */
+ std::atomic_bool waiting;
+
+ ReusableArray<pollfd> pfd_buffer;
+
+public:
+ AlsaInputStream(EventLoop &loop,
+ const char *uri, Mutex &mutex, Cond &cond,
+ snd_pcm_t *_handle, int _frame_size)
+ :MultiSocketMonitor(loop),
+ DeferredMonitor(loop),
+ base(input_plugin_alsa, uri, mutex, cond),
+ capture_handle(_handle),
+ frame_size(_frame_size),
+ eof(false)
+ {
+ assert(uri != nullptr);
+ assert(_handle != nullptr);
+
+ /* this mime type forces use of the PcmDecoderPlugin.
+ Needs to be generalised when/if that decoder is
+ updated to support other audio formats */
base.mime = strdup("audio/x-mpd-cdda-pcm");
base.seekable = false;
base.size = -1;
base.ready = true;
+ frames_to_read = read_buffer_size / frame_size;
+
+ snd_pcm_start(capture_handle);
+
+ DeferredMonitor::Schedule();
}
~AlsaInputStream() {
snd_pcm_close(capture_handle);
}
+
+ using DeferredMonitor::GetEventLoop;
+
+ static InputStream *Create(const char *uri, Mutex &mutex, Cond &cond,
+ Error &error);
+
+#if GCC_CHECK_VERSION(4,6) || defined(__clang__)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Winvalid-offsetof"
+#endif
+
+ static constexpr AlsaInputStream *Cast(InputStream *is) {
+ return ContainerCast(is, AlsaInputStream, base);
+ }
+
+#if GCC_CHECK_VERSION(4,6) || defined(__clang__)
+#pragma GCC diagnostic pop
+#endif
+
+ bool Available() {
+ if (snd_pcm_avail(capture_handle) > frames_to_read)
+ return true;
+
+ if (!waiting.exchange(true))
+ SafeInvalidateSockets();
+
+ return false;
+ }
+
+ size_t Read(void *ptr, size_t size, Error &error);
+
+ bool IsEOF() {
+ return eof;
+ }
+
+private:
+ static snd_pcm_t *OpenDevice(const char *device, int rate,
+ snd_pcm_format_t format, int channels,
+ Error &error);
+
+ int Recover(int err);
+
+ void SafeInvalidateSockets() {
+ DeferredMonitor::Schedule();
+ }
+
+ virtual void RunDeferred() override {
+ InvalidateSockets();
+ }
+
+ virtual int PrepareSockets() override;
+ virtual void DispatchSockets() override;
};
-static InputStream *
-alsa_input_open(const char *uri, Mutex &mutex, Cond &cond, Error &error)
+inline InputStream *
+AlsaInputStream::Create(const char *uri, Mutex &mutex, Cond &cond,
+ Error &error)
{
- int err;
-
- // check uri is appropriate for alsa input
- if (!StringStartsWith(uri, "alsa://"))
+ const char *const scheme = "alsa://";
+ if (!StringStartsWith(uri, scheme))
return nullptr;
- const char *device = uri + 7;
- if (device[0] == '\0')
+ const char *device = uri + strlen(scheme);
+ if (strlen(device) == 0)
device = default_device;
+ /* placeholders - eventually user-requested audio format will
+ be passed via the URI. For now we just force the
+ defaults */
+ int rate = default_rate;
+ snd_pcm_format_t format = default_format;
+ int channels = default_channels;
+
+ snd_pcm_t *handle = OpenDevice(device, rate, format, channels,
+ error);
+ if (handle == nullptr)
+ return nullptr;
+
+ int frame_size = snd_pcm_format_width(format) / 8 * channels;
+ AlsaInputStream *stream = new AlsaInputStream(io_thread_get(),
+ uri, mutex, cond,
+ handle, frame_size);
+ return &stream->base;
+}
+
+inline size_t
+AlsaInputStream::Read(void *ptr, size_t size, Error &error)
+{
+ assert(ptr != nullptr);
+
+ int num_frames = size / frame_size;
+ int ret;
+ while ((ret = snd_pcm_readi(capture_handle, ptr, num_frames)) < 0) {
+ if (Recover(ret) < 0) {
+ eof = true;
+ error.Format(alsa_input_domain,
+ "PCM error - stream aborted");
+ return 0;
+ }
+ }
+
+ size_t nbytes = ret * frame_size;
+ base.offset += nbytes;
+ return nbytes;
+}
+
+int
+AlsaInputStream::PrepareSockets()
+{
+ if (!waiting) {
+ ClearSocketList();
+ return -1;
+ }
+
+ int count = snd_pcm_poll_descriptors_count(capture_handle);
+ if (count < 0) {
+ ClearSocketList();
+ return -1;
+ }
+
+ struct pollfd *pfds = pfd_buffer.Get(count);
+
+ count = snd_pcm_poll_descriptors(capture_handle, pfds, count);
+ if (count < 0)
+ count = 0;
+
+ ReplaceSocketList(pfds, count);
+ return -1;
+}
+
+void
+AlsaInputStream::DispatchSockets()
+{
+ waiting = false;
+
+ const ScopeLock protect(base.mutex);
+ /* wake up the thread that is waiting for more data */
+ base.cond.broadcast();
+}
+
+inline int
+AlsaInputStream::Recover(int err)
+{
+ switch(err) {
+ case -EPIPE:
+ LogDebug(alsa_input_domain, "Buffer Overrun");
+ // drop through
+ case -ESTRPIPE:
+ case -EINTR:
+ err = snd_pcm_recover(capture_handle, err, 1);
+ break;
+ default:
+ // something broken somewhere, give up
+ err = -1;
+ }
+ return err;
+}
+
+inline snd_pcm_t *
+AlsaInputStream::OpenDevice(const char *device,
+ int rate, snd_pcm_format_t format, int channels,
+ Error &error)
+{
snd_pcm_t *capture_handle;
+ int err;
if ((err = snd_pcm_open(&capture_handle, device,
SND_PCM_STREAM_CAPTURE, 0)) < 0) {
error.Format(alsa_input_domain, "Failed to open device: %s (%s)", device, snd_strerror(err));
@@ -106,34 +297,52 @@ alsa_input_open(const char *uri, Mutex &mutex, Cond &cond, Error &error)
if ((err = snd_pcm_hw_params_set_access(capture_handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED)) < 0) {
error.Format(alsa_input_domain, "Cannot set access type (%s)", snd_strerror (err));
- snd_pcm_hw_params_free (hw_params);
+ snd_pcm_hw_params_free(hw_params);
snd_pcm_close(capture_handle);
return nullptr;
}
- if ((err = snd_pcm_hw_params_set_format(capture_handle, hw_params, default_format)) < 0) {
+ if ((err = snd_pcm_hw_params_set_format(capture_handle, hw_params, format)) < 0) {
snd_pcm_hw_params_free(hw_params);
snd_pcm_close(capture_handle);
error.Format(alsa_input_domain, "Cannot set sample format (%s)", snd_strerror (err));
return nullptr;
}
- if ((err = snd_pcm_hw_params_set_channels(capture_handle, hw_params, default_channels)) < 0) {
+ if ((err = snd_pcm_hw_params_set_channels(capture_handle, hw_params, channels)) < 0) {
snd_pcm_hw_params_free(hw_params);
snd_pcm_close(capture_handle);
error.Format(alsa_input_domain, "Cannot set channels (%s)", snd_strerror (err));
return nullptr;
}
- if ((err = snd_pcm_hw_params_set_rate(capture_handle, hw_params, default_rate, 0)) < 0) {
+ if ((err = snd_pcm_hw_params_set_rate(capture_handle, hw_params, rate, 0)) < 0) {
snd_pcm_hw_params_free(hw_params);
snd_pcm_close(capture_handle);
error.Format(alsa_input_domain, "Cannot set sample rate (%s)", snd_strerror (err));
return nullptr;
}
+ /* period needs to be big enough so that poll() doesn't fire too often,
+ * but small enough that buffer overruns don't occur if Read() is not
+ * invoked often enough.
+ * the calculation here is empirical; however all measurements were
+ * done using 44100:16:2. When we extend this plugin to support
+ * other audio formats then this may need to be revisited */
+ snd_pcm_uframes_t period = read_buffer_size * 2;
+ int direction = -1;
+ if ((err = snd_pcm_hw_params_set_period_size_near(capture_handle, hw_params,
+ &period, &direction)) < 0) {
+ error.Format(alsa_input_domain, "Cannot set period size (%s)",
+ snd_strerror(err));
+ snd_pcm_hw_params_free(hw_params);
+ snd_pcm_close(capture_handle);
+ return nullptr;
+ }
+
if ((err = snd_pcm_hw_params(capture_handle, hw_params)) < 0) {
- error.Format(alsa_input_domain, "Cannot set parameters (%s)", snd_strerror (err));
+ error.Format(alsa_input_domain, "Cannot set parameters (%s)",
+ snd_strerror(err));
snd_pcm_hw_params_free(hw_params);
snd_pcm_close(capture_handle);
return nullptr;
@@ -141,54 +350,79 @@ alsa_input_open(const char *uri, Mutex &mutex, Cond &cond, Error &error)
snd_pcm_hw_params_free (hw_params);
- // clear any data already in the PCM buffer
- if ((err = snd_pcm_drop(capture_handle)) < 0) {
- error.Format(alsa_input_domain, "Cannot clear PCM buffer (%s)", snd_strerror (err));
- snd_pcm_hw_params_free(hw_params);
+ snd_pcm_sw_params_t *sw_params;
+
+ snd_pcm_sw_params_malloc(&sw_params);
+ snd_pcm_sw_params_current(capture_handle, sw_params);
+
+ if ((err = snd_pcm_sw_params_set_start_threshold(capture_handle, sw_params,
+ period)) < 0) {
+ error.Format(alsa_input_domain,
+ "unable to set start threshold (%s)", snd_strerror(err));
+ snd_pcm_sw_params_free(sw_params);
+ snd_pcm_close(capture_handle);
+ return nullptr;
+ }
+
+ if ((err = snd_pcm_sw_params_set_period_event(capture_handle, sw_params,
+ 1)) < 0) {
+ error.Format(alsa_input_domain,
+ "unable to set period event (%s)", snd_strerror(err));
+ snd_pcm_sw_params_free(sw_params);
snd_pcm_close(capture_handle);
return nullptr;
}
- AlsaInputStream *ais = new AlsaInputStream(uri, mutex, cond, capture_handle);
- return &ais->base;
+ if ((err = snd_pcm_sw_params(capture_handle, sw_params)) < 0) {
+ error.Format(alsa_input_domain,
+ "unable to install sw params (%s)", snd_strerror(err));
+ snd_pcm_sw_params_free(sw_params);
+ snd_pcm_close(capture_handle);
+ return nullptr;
+ }
+
+ snd_pcm_sw_params_free(sw_params);
+
+ snd_pcm_prepare(capture_handle);
+
+ return capture_handle;
+}
+
+/*######################### Plugin Functions ##############################*/
+
+static InputStream *
+alsa_input_open(const char *uri, Mutex &mutex, Cond &cond, Error &error)
+{
+ return AlsaInputStream::Create(uri, mutex, cond, error);
}
static void
alsa_input_close(InputStream *is)
{
- AlsaInputStream *ais = (AlsaInputStream*) is;
+ AlsaInputStream *ais = AlsaInputStream::Cast(is);
delete ais;
}
-static size_t
-alsa_input_read(InputStream *is, void *ptr, size_t size,
- gcc_unused Error &error)
+static bool
+alsa_input_available(InputStream *is)
{
- AlsaInputStream *ais = (AlsaInputStream*) is;
- int num_frames = max_frames_to_buffer;
- if (size < ais->max_bytes_to_read)
- // calculate number of whole frames that will fit in size bytes
- num_frames = size / ais->frame_size;
-
- int ret;
- while ((ret = snd_pcm_readi(ais->capture_handle, ptr,
- num_frames)) < 0) {
- snd_pcm_prepare(ais->capture_handle);
- LogDebug(alsa_input_domain, "Buffer Overrun");
- }
+ AlsaInputStream *ais = AlsaInputStream::Cast(is);
+ return ais->Available();
+}
- size_t nbytes = ret == max_frames_to_buffer
- ? ais->max_bytes_to_read
- : ret * ais->frame_size;
- is->offset += nbytes;
- return nbytes;
+static size_t
+alsa_input_read(InputStream *is, void *ptr, size_t size, Error &error)
+{
+ AlsaInputStream *ais = AlsaInputStream::Cast(is);
+ return ais->Read(ptr, size, error);
}
static bool
alsa_input_eof(gcc_unused InputStream *is)
{
- return false;
-};
+ AlsaInputStream *ais = AlsaInputStream::Cast(is);
+ return ais->IsEOF();
+}
const struct InputPlugin input_plugin_alsa = {
"alsa",
@@ -199,7 +433,7 @@ const struct InputPlugin input_plugin_alsa = {
nullptr,
nullptr,
nullptr,
- nullptr,
+ alsa_input_available,
alsa_input_read,
alsa_input_eof,
nullptr,