input/AlsaInputPlugin.cxx: use I/O thread to poll for available data
[mk: modified to use MultiSocketMonitor instead of SocketMonitor]
This commit is contained in:
Steven O'Brien
Max Kellermann
parent
08f5b9f1f9
commit
f39a34ccfa
@ -31,59 +31,250 @@
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#include "util/Domain.hxx"
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#include "util/Error.hxx"
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#include "util/StringUtil.hxx"
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#include "util/ReusableArray.hxx"
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#include "util/Cast.hxx"
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#include "Log.hxx"
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#include "event/MultiSocketMonitor.hxx"
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#include "event/DeferredMonitor.hxx"
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#include "event/Call.hxx"
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#include "thread/Mutex.hxx"
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#include "thread/Cond.hxx"
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#include "IOThread.hxx"
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#include <alsa/asoundlib.h>
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#include <assert.h>
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#include <string.h>
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static constexpr Domain alsa_input_domain("alsa");
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static constexpr const char *default_device = "hw:0,0";
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// this value chosen to balance between limiting latency and avoiding stutter
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static constexpr int max_frames_to_buffer = 64;
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// the following defaults are because the PcmDecoderPlugin forces CD format
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static constexpr snd_pcm_format_t default_format = SND_PCM_FORMAT_S16;
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static constexpr int default_channels = 2; // stereo
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static constexpr unsigned int default_rate = 44100; // cd quality
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struct AlsaInputStream {
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/**
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* This value should be the same as the read buffer size defined in
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* PcmDecoderPlugin.cxx:pcm_stream_decode().
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* We use it to calculate how many audio frames to buffer in the alsa driver
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* before reading from the device. snd_pcm_readi() blocks until that many
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* frames are ready.
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*/
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static constexpr size_t read_buffer_size = 4096;
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class AlsaInputStream final : MultiSocketMonitor, DeferredMonitor {
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InputStream base;
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snd_pcm_t *capture_handle;
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size_t frame_size;
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size_t max_bytes_to_read;
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int frames_to_read;
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bool eof;
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AlsaInputStream(const char *uri, Mutex &mutex, Cond &cond,
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snd_pcm_t *handle)
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:base(input_plugin_alsa, uri, mutex, cond),
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capture_handle(handle) {
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frame_size = snd_pcm_format_width(default_format) / 8 * default_channels;
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max_bytes_to_read = max_frames_to_buffer * frame_size;
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/**
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* Is somebody waiting for data? This is set by method
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* Available().
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*/
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std::atomic_bool waiting;
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ReusableArray<pollfd> pfd_buffer;
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public:
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AlsaInputStream(EventLoop &loop,
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const char *uri, Mutex &mutex, Cond &cond,
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snd_pcm_t *_handle, int _frame_size)
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:MultiSocketMonitor(loop),
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DeferredMonitor(loop),
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base(input_plugin_alsa, uri, mutex, cond),
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capture_handle(_handle),
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frame_size(_frame_size),
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eof(false)
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{
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assert(uri != nullptr);
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assert(_handle != nullptr);
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/* this mime type forces use of the PcmDecoderPlugin.
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Needs to be generalised when/if that decoder is
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updated to support other audio formats */
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base.mime = strdup("audio/x-mpd-cdda-pcm");
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base.seekable = false;
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base.size = -1;
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base.ready = true;
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frames_to_read = read_buffer_size / frame_size;
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snd_pcm_start(capture_handle);
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DeferredMonitor::Schedule();
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}
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~AlsaInputStream() {
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snd_pcm_close(capture_handle);
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}
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using DeferredMonitor::GetEventLoop;
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static InputStream *Create(const char *uri, Mutex &mutex, Cond &cond,
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Error &error);
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#if GCC_CHECK_VERSION(4,6) || defined(__clang__)
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#pragma GCC diagnostic push
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#pragma GCC diagnostic ignored "-Winvalid-offsetof"
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#endif
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static constexpr AlsaInputStream *Cast(InputStream *is) {
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return ContainerCast(is, AlsaInputStream, base);
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}
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#if GCC_CHECK_VERSION(4,6) || defined(__clang__)
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#pragma GCC diagnostic pop
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#endif
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bool Available() {
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if (snd_pcm_avail(capture_handle) > frames_to_read)
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return true;
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if (!waiting.exchange(true))
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SafeInvalidateSockets();
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return false;
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}
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size_t Read(void *ptr, size_t size, Error &error);
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bool IsEOF() {
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return eof;
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}
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private:
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static snd_pcm_t *OpenDevice(const char *device, int rate,
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snd_pcm_format_t format, int channels,
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Error &error);
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int Recover(int err);
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void SafeInvalidateSockets() {
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DeferredMonitor::Schedule();
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}
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virtual void RunDeferred() override {
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InvalidateSockets();
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}
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virtual int PrepareSockets() override;
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virtual void DispatchSockets() override;
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};
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static InputStream *
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alsa_input_open(const char *uri, Mutex &mutex, Cond &cond, Error &error)
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inline InputStream *
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AlsaInputStream::Create(const char *uri, Mutex &mutex, Cond &cond,
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Error &error)
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{
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int err;
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// check uri is appropriate for alsa input
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if (!StringStartsWith(uri, "alsa://"))
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const char *const scheme = "alsa://";
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if (!StringStartsWith(uri, scheme))
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return nullptr;
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const char *device = uri + 7;
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if (device[0] == '\0')
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const char *device = uri + strlen(scheme);
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if (strlen(device) == 0)
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device = default_device;
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/* placeholders - eventually user-requested audio format will
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be passed via the URI. For now we just force the
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defaults */
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int rate = default_rate;
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snd_pcm_format_t format = default_format;
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int channels = default_channels;
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snd_pcm_t *handle = OpenDevice(device, rate, format, channels,
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error);
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if (handle == nullptr)
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return nullptr;
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int frame_size = snd_pcm_format_width(format) / 8 * channels;
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AlsaInputStream *stream = new AlsaInputStream(io_thread_get(),
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uri, mutex, cond,
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handle, frame_size);
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return &stream->base;
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}
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inline size_t
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AlsaInputStream::Read(void *ptr, size_t size, Error &error)
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{
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assert(ptr != nullptr);
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int num_frames = size / frame_size;
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int ret;
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while ((ret = snd_pcm_readi(capture_handle, ptr, num_frames)) < 0) {
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if (Recover(ret) < 0) {
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eof = true;
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error.Format(alsa_input_domain,
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"PCM error - stream aborted");
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return 0;
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}
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}
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size_t nbytes = ret * frame_size;
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base.offset += nbytes;
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return nbytes;
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}
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int
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AlsaInputStream::PrepareSockets()
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{
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if (!waiting) {
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ClearSocketList();
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return -1;
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}
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int count = snd_pcm_poll_descriptors_count(capture_handle);
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if (count < 0) {
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ClearSocketList();
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return -1;
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}
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struct pollfd *pfds = pfd_buffer.Get(count);
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count = snd_pcm_poll_descriptors(capture_handle, pfds, count);
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if (count < 0)
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count = 0;
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ReplaceSocketList(pfds, count);
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return -1;
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}
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void
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AlsaInputStream::DispatchSockets()
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{
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waiting = false;
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const ScopeLock protect(base.mutex);
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/* wake up the thread that is waiting for more data */
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base.cond.broadcast();
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}
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inline int
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AlsaInputStream::Recover(int err)
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{
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switch(err) {
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case -EPIPE:
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LogDebug(alsa_input_domain, "Buffer Overrun");
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// drop through
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case -ESTRPIPE:
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case -EINTR:
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err = snd_pcm_recover(capture_handle, err, 1);
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break;
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default:
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// something broken somewhere, give up
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err = -1;
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}
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return err;
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}
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inline snd_pcm_t *
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AlsaInputStream::OpenDevice(const char *device,
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int rate, snd_pcm_format_t format, int channels,
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Error &error)
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{
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snd_pcm_t *capture_handle;
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int err;
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if ((err = snd_pcm_open(&capture_handle, device,
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SND_PCM_STREAM_CAPTURE, 0)) < 0) {
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error.Format(alsa_input_domain, "Failed to open device: %s (%s)", device, snd_strerror(err));
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@ -106,34 +297,52 @@ alsa_input_open(const char *uri, Mutex &mutex, Cond &cond, Error &error)
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if ((err = snd_pcm_hw_params_set_access(capture_handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED)) < 0) {
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error.Format(alsa_input_domain, "Cannot set access type (%s)", snd_strerror (err));
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snd_pcm_hw_params_free (hw_params);
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snd_pcm_hw_params_free(hw_params);
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snd_pcm_close(capture_handle);
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return nullptr;
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}
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if ((err = snd_pcm_hw_params_set_format(capture_handle, hw_params, default_format)) < 0) {
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if ((err = snd_pcm_hw_params_set_format(capture_handle, hw_params, format)) < 0) {
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snd_pcm_hw_params_free(hw_params);
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snd_pcm_close(capture_handle);
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error.Format(alsa_input_domain, "Cannot set sample format (%s)", snd_strerror (err));
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return nullptr;
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}
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if ((err = snd_pcm_hw_params_set_channels(capture_handle, hw_params, default_channels)) < 0) {
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if ((err = snd_pcm_hw_params_set_channels(capture_handle, hw_params, channels)) < 0) {
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snd_pcm_hw_params_free(hw_params);
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snd_pcm_close(capture_handle);
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error.Format(alsa_input_domain, "Cannot set channels (%s)", snd_strerror (err));
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return nullptr;
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}
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if ((err = snd_pcm_hw_params_set_rate(capture_handle, hw_params, default_rate, 0)) < 0) {
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if ((err = snd_pcm_hw_params_set_rate(capture_handle, hw_params, rate, 0)) < 0) {
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snd_pcm_hw_params_free(hw_params);
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snd_pcm_close(capture_handle);
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error.Format(alsa_input_domain, "Cannot set sample rate (%s)", snd_strerror (err));
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return nullptr;
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}
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/* period needs to be big enough so that poll() doesn't fire too often,
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* but small enough that buffer overruns don't occur if Read() is not
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* invoked often enough.
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* the calculation here is empirical; however all measurements were
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* done using 44100:16:2. When we extend this plugin to support
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* other audio formats then this may need to be revisited */
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snd_pcm_uframes_t period = read_buffer_size * 2;
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int direction = -1;
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if ((err = snd_pcm_hw_params_set_period_size_near(capture_handle, hw_params,
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&period, &direction)) < 0) {
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error.Format(alsa_input_domain, "Cannot set period size (%s)",
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snd_strerror(err));
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snd_pcm_hw_params_free(hw_params);
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snd_pcm_close(capture_handle);
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return nullptr;
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}
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if ((err = snd_pcm_hw_params(capture_handle, hw_params)) < 0) {
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error.Format(alsa_input_domain, "Cannot set parameters (%s)", snd_strerror (err));
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error.Format(alsa_input_domain, "Cannot set parameters (%s)",
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snd_strerror(err));
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snd_pcm_hw_params_free(hw_params);
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snd_pcm_close(capture_handle);
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return nullptr;
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@ -141,54 +350,79 @@ alsa_input_open(const char *uri, Mutex &mutex, Cond &cond, Error &error)
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snd_pcm_hw_params_free (hw_params);
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// clear any data already in the PCM buffer
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if ((err = snd_pcm_drop(capture_handle)) < 0) {
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error.Format(alsa_input_domain, "Cannot clear PCM buffer (%s)", snd_strerror (err));
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snd_pcm_hw_params_free(hw_params);
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snd_pcm_sw_params_t *sw_params;
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snd_pcm_sw_params_malloc(&sw_params);
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snd_pcm_sw_params_current(capture_handle, sw_params);
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if ((err = snd_pcm_sw_params_set_start_threshold(capture_handle, sw_params,
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period)) < 0) {
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error.Format(alsa_input_domain,
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"unable to set start threshold (%s)", snd_strerror(err));
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snd_pcm_sw_params_free(sw_params);
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snd_pcm_close(capture_handle);
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return nullptr;
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}
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AlsaInputStream *ais = new AlsaInputStream(uri, mutex, cond, capture_handle);
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return &ais->base;
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if ((err = snd_pcm_sw_params_set_period_event(capture_handle, sw_params,
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1)) < 0) {
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error.Format(alsa_input_domain,
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"unable to set period event (%s)", snd_strerror(err));
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snd_pcm_sw_params_free(sw_params);
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snd_pcm_close(capture_handle);
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return nullptr;
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}
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if ((err = snd_pcm_sw_params(capture_handle, sw_params)) < 0) {
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error.Format(alsa_input_domain,
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"unable to install sw params (%s)", snd_strerror(err));
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snd_pcm_sw_params_free(sw_params);
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snd_pcm_close(capture_handle);
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return nullptr;
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}
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snd_pcm_sw_params_free(sw_params);
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snd_pcm_prepare(capture_handle);
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return capture_handle;
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}
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/*######################### Plugin Functions ##############################*/
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static InputStream *
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alsa_input_open(const char *uri, Mutex &mutex, Cond &cond, Error &error)
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{
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return AlsaInputStream::Create(uri, mutex, cond, error);
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}
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static void
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alsa_input_close(InputStream *is)
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{
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AlsaInputStream *ais = (AlsaInputStream*) is;
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AlsaInputStream *ais = AlsaInputStream::Cast(is);
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delete ais;
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}
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static size_t
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alsa_input_read(InputStream *is, void *ptr, size_t size,
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gcc_unused Error &error)
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static bool
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alsa_input_available(InputStream *is)
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{
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AlsaInputStream *ais = (AlsaInputStream*) is;
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int num_frames = max_frames_to_buffer;
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if (size < ais->max_bytes_to_read)
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// calculate number of whole frames that will fit in size bytes
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num_frames = size / ais->frame_size;
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AlsaInputStream *ais = AlsaInputStream::Cast(is);
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return ais->Available();
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}
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int ret;
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while ((ret = snd_pcm_readi(ais->capture_handle, ptr,
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num_frames)) < 0) {
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snd_pcm_prepare(ais->capture_handle);
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LogDebug(alsa_input_domain, "Buffer Overrun");
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}
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size_t nbytes = ret == max_frames_to_buffer
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? ais->max_bytes_to_read
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: ret * ais->frame_size;
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is->offset += nbytes;
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return nbytes;
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static size_t
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alsa_input_read(InputStream *is, void *ptr, size_t size, Error &error)
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{
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AlsaInputStream *ais = AlsaInputStream::Cast(is);
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return ais->Read(ptr, size, error);
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}
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static bool
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alsa_input_eof(gcc_unused InputStream *is)
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{
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return false;
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};
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AlsaInputStream *ais = AlsaInputStream::Cast(is);
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return ais->IsEOF();
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}
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const struct InputPlugin input_plugin_alsa = {
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"alsa",
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@ -199,7 +433,7 @@ const struct InputPlugin input_plugin_alsa = {
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nullptr,
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nullptr,
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nullptr,
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nullptr,
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alsa_input_available,
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alsa_input_read,
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alsa_input_eof,
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nullptr,
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