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-rw-r--r--libs/ardour/ardour/transport_master.h148
1 files changed, 83 insertions, 65 deletions
diff --git a/libs/ardour/ardour/transport_master.h b/libs/ardour/ardour/transport_master.h
index 81d250dda9..f6dae4bff1 100644
--- a/libs/ardour/ardour/transport_master.h
+++ b/libs/ardour/ardour/transport_master.h
@@ -66,6 +66,80 @@ namespace Properties {
LIBARDOUR_API extern PBD::PropertyDescriptor<ARDOUR::TransportRequestType> allowed_transport_requests;
};
+struct LIBARDOUR_API SafeTime {
+
+ /* This object uses memory fences to provide psuedo-atomic updating of
+ * non-atomic data. If after reading guard1 and guard2 with correct
+ * memory fencing they have the same value, then we know that the other
+ * members are all internally consistent.
+ *
+ * Traditionally, one might do this with a mutex, but this object
+ * provides lock-free write update. The reader might block while
+ * waiting for consistency, but this is extraordinarily unlikely. In
+ * this sense, the design is similar to a spinlock.
+ *
+ * any update starts by incrementing guard1, with a memory fence to
+ * ensure no reordering of this w.r.t later operations.
+ *
+ * then we update the "non-atomic" data members.
+ *
+ * then we update guard2, with another memory fence to prevent
+ * reordering.
+ *
+ * ergo, if guard1 == guard2, the update of the non-atomic members is
+ * complete and the values stored there are consistent.
+ */
+
+ boost::atomic<int> guard1;
+ samplepos_t position;
+ samplepos_t timestamp;
+ double speed;
+ boost::atomic<int> guard2;
+
+ SafeTime() {
+ guard1.store (0);
+ position = 0;
+ timestamp = 0;
+ speed = 0;
+ guard2.store (0);
+ }
+
+ void reset () {
+ guard1.store (0);
+ position = 0;
+ timestamp = 0;
+ speed = 0;
+ guard2.store (0);
+ }
+
+ void update (samplepos_t p, samplepos_t t, double s) {
+ guard1.fetch_add (1, boost::memory_order_acquire);
+ position = p;
+ timestamp = t;
+ speed = s;
+ guard2.fetch_add (1, boost::memory_order_acquire);
+ }
+
+ void safe_read (SafeTime& dst) const {
+ int tries = 0;
+
+ do {
+ if (tries == 10) {
+ std::cerr << X_("SafeTime: atomic read of current time failed, sleeping!") << std::endl;
+ Glib::usleep (20);
+ tries = 0;
+ }
+ dst.guard1.store (guard1.load (boost::memory_order_seq_cst), boost::memory_order_seq_cst);
+ dst.position = position;
+ dst.timestamp = timestamp;
+ dst.speed = speed;
+ dst.guard2.store (guard2.load (boost::memory_order_seq_cst), boost::memory_order_seq_cst);
+ tries++;
+
+ } while (dst.guard1.load (boost::memory_order_seq_cst) != dst.guard2.load (boost::memory_order_seq_cst));
+ }
+};
+
/**
* @class TransportMaster
*
@@ -138,7 +212,7 @@ class LIBARDOUR_API TransportMaster : public PBD::Stateful {
* @param position - The transport position requested
* @return - The return value is currently ignored (see Session::follow_slave)
*/
- virtual bool speed_and_position (double& speed, samplepos_t& position, samplepos_t now) = 0;
+ virtual bool speed_and_position (double& speed, samplepos_t& position, samplepos_t & lp, samplepos_t & when, samplepos_t now);
/**
* reports to ARDOUR whether the TransportMaster is currently synced to its external
@@ -252,6 +326,9 @@ class LIBARDOUR_API TransportMaster : public PBD::Stateful {
TransportRequestType request_mask() const { return _request_mask; }
void set_request_mask (TransportRequestType);
+
+ void get_current (double&, samplepos_t&, samplepos_t);
+
protected:
SyncSource _type;
PBD::Property<std::string> _name;
@@ -264,6 +341,8 @@ class LIBARDOUR_API TransportMaster : public PBD::Stateful {
PBD::Property<bool> _collect;
PBD::Property<bool> _connected;
+ SafeTime current;
+
/* DLL - chase incoming data */
int transport_direction;
@@ -284,57 +363,6 @@ class LIBARDOUR_API TransportMaster : public PBD::Stateful {
virtual void register_properties ();
};
-struct LIBARDOUR_API SafeTime {
- boost::atomic<int> guard1;
- samplepos_t position;
- samplepos_t timestamp;
- double speed;
- boost::atomic<int> guard2;
-
- SafeTime() {
- guard1.store (0);
- position = 0;
- timestamp = 0;
- speed = 0;
- guard2.store (0);
- }
-
- SafeTime (SafeTime const & other)
- : guard1 (other.guard1.load (boost::memory_order_acquire))
- , position (other.position)
- , timestamp (other.timestamp)
- , speed (other.speed)
- , guard2 (other.guard2.load (boost::memory_order_acquire))
- {}
-
- void update (samplepos_t p, samplepos_t t, double s) {
- guard1.fetch_add (1, boost::memory_order_acquire);
- position = p;
- timestamp = t;
- speed = s;
- guard2.fetch_add (1, boost::memory_order_acquire);
- }
-
- void safe_read (SafeTime& dst) const {
- int tries = 0;
-
- do {
- if (tries == 10) {
- std::cerr << X_("SafeTime: atomic read of current time failed, sleeping!") << std::endl;
- Glib::usleep (20);
- tries = 0;
- }
- dst.guard1.store (guard1.load (boost::memory_order_seq_cst), boost::memory_order_seq_cst);
- dst.position = position;
- dst.timestamp = timestamp;
- dst.speed = speed;
- dst.guard2.store (guard2.load (boost::memory_order_seq_cst), boost::memory_order_seq_cst);
- tries++;
-
- } while (dst.guard1.load (boost::memory_order_seq_cst) != dst.guard2.load (boost::memory_order_seq_cst));
- }
-};
-
/** a helper class for any TransportMaster that receives its input via a MIDI
* port
*/
@@ -377,8 +405,6 @@ class LIBARDOUR_API MTC_TransportMaster : public TimecodeTransportMaster, public
void pre_process (pframes_t nframes, samplepos_t now, boost::optional<samplepos_t>);
- bool speed_and_position (double&, samplepos_t&, samplepos_t);
-
bool locked() const;
bool ok() const;
void handle_locate (const MIDI::byte*);
@@ -399,7 +425,6 @@ class LIBARDOUR_API MTC_TransportMaster : public TimecodeTransportMaster, public
static const int sample_tolerance;
- SafeTime current;
samplepos_t mtc_frame; /* current time */
double mtc_frame_dll;
samplepos_t last_inbound_frame; /* when we got it; audio clocked */
@@ -430,7 +455,6 @@ class LIBARDOUR_API MTC_TransportMaster : public TimecodeTransportMaster, public
void update_mtc_qtr (MIDI::Parser&, int, samplepos_t);
void update_mtc_time (const MIDI::byte *, bool, samplepos_t);
void update_mtc_status (MIDI::MTC_Status);
- void read_current (SafeTime *) const;
void reset_window (samplepos_t);
bool outside_window (samplepos_t) const;
void init_mtc_dll(samplepos_t, double);
@@ -446,7 +470,6 @@ public:
void set_session (Session*);
void pre_process (pframes_t nframes, samplepos_t now, boost::optional<samplepos_t>);
- bool speed_and_position (double&, samplepos_t&, samplepos_t);
bool locked() const;
bool ok() const;
@@ -482,10 +505,7 @@ public:
LTCFrameExt prev_sample;
bool fps_detected;
- samplecnt_t monotonic_cnt;
- samplecnt_t last_timestamp;
- samplecnt_t last_ltc_sample;
- double ltc_speed;
+ samplecnt_t monotonic_cnt;
int delayedlocked;
int ltc_detect_fps_cnt;
@@ -513,7 +533,6 @@ class LIBARDOUR_API MIDIClock_TransportMaster : public TransportMaster, public T
void pre_process (pframes_t nframes, samplepos_t now, boost::optional<samplepos_t>);
void rebind (MidiPort&);
- bool speed_and_position (double&, samplepos_t&, samplepos_t);
bool locked() const;
bool ok() const;
@@ -558,13 +577,12 @@ class LIBARDOUR_API MIDIClock_TransportMaster : public TransportMaster, public T
void start (MIDI::Parser& parser, samplepos_t timestamp);
void contineu (MIDI::Parser& parser, samplepos_t timestamp);
void stop (MIDI::Parser& parser, samplepos_t timestamp);
- void position (MIDI::Parser& parser, MIDI::byte* message, size_t size);
+ void position (MIDI::Parser& parser, MIDI::byte* message, size_t size, samplepos_t timestamp);
// we can't use continue because it is a C++ keyword
void calculate_one_ppqn_in_samples_at(samplepos_t time);
samplepos_t calculate_song_position(uint16_t song_position_in_sixteenth_notes);
void calculate_filter_coefficients (double qpm);
void update_midi_clock (MIDI::Parser& parser, samplepos_t timestamp);
- void read_current (SafeTime *) const;
};
class LIBARDOUR_API Engine_TransportMaster : public TransportMaster
@@ -574,7 +592,7 @@ class LIBARDOUR_API Engine_TransportMaster : public TransportMaster
~Engine_TransportMaster ();
void pre_process (pframes_t nframes, samplepos_t now, boost::optional<samplepos_t>);
- bool speed_and_position (double& speed, samplepos_t& pos, samplepos_t);
+ bool speed_and_position (double& speed, samplepos_t& pos, samplepos_t &, samplepos_t &, samplepos_t);
bool starting() const { return _starting; }
bool locked() const;
generated by cgit v1.2.3 (git 2.39.1) at 2024-05-18 21:20:27 +0000