initial conversion to double buffering inside DiskReader

Second buffer is not used (or allocated) yet.

4 files changed, 60 insertions, 33 deletions

diff --git a/libs/ardour/ardour/disk_io.h b/libs/ardour/ardour/disk_io.h
index 1c60a19fc2..43898551a8 100644
--- a/libs/ardour/ardour/disk_io.h
+++ b/libs/ardour/ardour/disk_io.h
@@ -151,10 +151,19 @@ protected:
 		ChannelInfo (samplecnt_t buffer_size);
 		virtual ~ChannelInfo ();
 
-		/** A random-access ringbuffer for data to be played back.
-		 * written to in the butler thread, read from in the process thread.
+		/** A pair of random-access ringbuffers for data to be played back.
+		 * written to in the butler thread, read from in the process
+		 * thread.
+		 *
+		 * 
 		 */
-		PBD::PlaybackBuffer<Sample>* rbuf;
+		PBD::PlaybackBuffer<Sample>* _rbuf[2];
+		/* This returns a pointer to the correct PlaybackBuffer to use
+		   for reading from within process context.
+		*/
+		PBD::PlaybackBuffer<Sample>* rbuf();
+		gint current_rbuf;
+		gint read_switch_rbuf;
 
 		/** A ringbuffer for data to be recorded back, written to in the
 		 * process thread, read from in the butler thread.
diff --git a/libs/ardour/disk_io.cc b/libs/ardour/disk_io.cc
index a55e2c559b..cd41f78505 100644
--- a/libs/ardour/disk_io.cc
+++ b/libs/ardour/disk_io.cc
@@ -324,23 +324,34 @@ DiskIOProcessor::use_playlist (DataType dt, boost::shared_ptr<Playlist> playlist
 }
 
 DiskIOProcessor::ChannelInfo::ChannelInfo (samplecnt_t bufsize)
-	: rbuf (0)
+	: current_rbuf (0)
+	, read_switch_rbuf (0)
 	, wbuf (0)
 	, capture_transition_buf (0)
 	, curr_capture_cnt (0)
 {
+	_rbuf[0] = 0;
+	_rbuf[1] = 0;
 }
 
 DiskIOProcessor::ChannelInfo::~ChannelInfo ()
 {
-	delete rbuf;
+	delete _rbuf[0];
+	delete _rbuf[1];
 	delete wbuf;
 	delete capture_transition_buf;
-	rbuf = 0;
+	_rbuf[0] = 0;
+	_rbuf[1] = 0;
 	wbuf = 0;
 	capture_transition_buf = 0;
 }
 
+PlaybackBuffer<Sample>*
+DiskIOProcessor::ChannelInfo::rbuf()
+{
+	return _rbuf[0];
+}
+
 void
 DiskIOProcessor::drop_track ()
 {
diff --git a/libs/ardour/disk_reader.cc b/libs/ardour/disk_reader.cc
index f97f9f3fc3..3e1db0e94f 100644
--- a/libs/ardour/disk_reader.cc
+++ b/libs/ardour/disk_reader.cc
@@ -79,10 +79,16 @@ DiskReader::~DiskReader ()
 void
 DiskReader::ReaderChannelInfo::resize (samplecnt_t bufsize)
 {
-	delete rbuf;
-	rbuf = new PlaybackBuffer<Sample> (bufsize);
+	delete _rbuf[0]; _rbuf[0] = 0;
+	delete _rbuf[1]; _rbuf[1] = 0;
+
+	_rbuf[0] = new PlaybackBuffer<Sample> (bufsize);
 	/* touch memory to lock it */
-	memset (rbuf->buffer(), 0, sizeof (Sample) * rbuf->bufsize());
+	memset (_rbuf[0]->buffer(), 0, sizeof (Sample) * _rbuf[0]->bufsize());
+	g_atomic_int_set (&current_rbuf, 0);
+	g_atomic_int_set (&read_switch_rbuf, 0);
+
+	/* the alternate rbuf is lazily allocated in ::overwrite_existing_buffers() */
 }
 
 void
@@ -106,8 +112,8 @@ DiskReader::add_channel_to (boost::shared_ptr<ChannelList> c, uint32_t how_many)
 		c->push_back (new ReaderChannelInfo (_session.butler()->audio_diskstream_playback_buffer_size(), loop_fade_length));
 		DEBUG_TRACE (DEBUG::DiskIO, string_compose ("%1: new reader channel, write space = %2 read = %3\n",
 		                                            name(),
-		                                            c->back()->rbuf->write_space(),
-		                                            c->back()->rbuf->read_space()));
+		                                            c->back()->rbuf()->write_space(),
+		                                            c->back()->rbuf()->read_space()));
 	}
 
 	return 0;
@@ -216,7 +222,7 @@ DiskReader::buffer_load () const
 		return 1.0;
 	}
 
-	PBD::PlaybackBuffer<Sample>* b = c->front()->rbuf;
+	PBD::PlaybackBuffer<Sample>* b = c->front()->rbuf();
 	return (float) ((double) b->read_space() / (double) b->bufsize());
 }
 
@@ -337,7 +343,7 @@ DiskReader::run (BufferSet& bufs, samplepos_t start_sample, samplepos_t end_samp
 
 		if (!still_locating || _no_disk_output) {
 			for (ChannelList::iterator chan = c->begin(); chan != c->end(); ++chan) {
-				(*chan)->rbuf->increment_read_ptr (disk_samples_to_consume);
+				(*chan)->rbuf()->increment_read_ptr (disk_samples_to_consume);
 			}
 		}
 
@@ -386,7 +392,7 @@ DiskReader::run (BufferSet& bufs, samplepos_t start_sample, samplepos_t end_samp
 
 			if (!declick_out) {
 
-				const samplecnt_t total = chaninfo->rbuf->read (disk_buf.data(), disk_samples_to_consume);
+				const samplecnt_t total = chaninfo->rbuf()->read (disk_buf.data(), disk_samples_to_consume);
 
 				if (disk_samples_to_consume > total) {
 					cerr << _name << " Need " << total << " have only " << disk_samples_to_consume << endl;
@@ -410,7 +416,7 @@ DiskReader::run (BufferSet& bufs, samplepos_t start_sample, samplepos_t end_samp
 				   to ::run()
 				*/
 
-				const samplecnt_t total = chaninfo->rbuf->read (disk_buf.data(), nframes, false, declick_offs);
+				const samplecnt_t total = chaninfo->rbuf()->read (disk_buf.data(), nframes, false, declick_offs);
 
 				if (n == 0) {
 					_declick_offs += total;
@@ -470,13 +476,13 @@ DiskReader::run (BufferSet& bufs, samplepos_t start_sample, samplepos_t end_samp
 		if (_playlists[DataType::AUDIO]) {
 			if (!c->empty()) {
 				if (_slaved) {
-					if (c->front()->rbuf->write_space() >= c->front()->rbuf->bufsize() / 2) {
-						DEBUG_TRACE (DEBUG::Butler, string_compose ("%1: slaved, write space = %2 of %3\n", name(), c->front()->rbuf->write_space(), c->front()->rbuf->bufsize()));
+					if (c->front()->rbuf()->write_space() >= c->front()->rbuf()->bufsize() / 2) {
+						DEBUG_TRACE (DEBUG::Butler, string_compose ("%1: slaved, write space = %2 of %3\n", name(), c->front()->rbuf()->write_space(), c->front()->rbuf()->bufsize()));
 						butler_required = true;
 					}
 				} else {
-					if ((samplecnt_t) c->front()->rbuf->write_space() >= _chunk_samples) {
-						DEBUG_TRACE (DEBUG::Butler, string_compose ("%1: write space = %2 of %3\n", name(), c->front()->rbuf->write_space(),
+					if ((samplecnt_t) c->front()->rbuf()->write_space() >= _chunk_samples) {
+						DEBUG_TRACE (DEBUG::Butler, string_compose ("%1: write space = %2 of %3\n", name(), c->front()->rbuf()->write_space(),
 						                                            _chunk_samples));
 						butler_required = true;
 					}
@@ -515,7 +521,7 @@ DiskReader::set_pending_overwrite ()
 
 	boost::shared_ptr<ChannelList> c = channels.reader ();
 	for (ChannelList::iterator chan = c->begin(); chan != c->end(); ++chan) {
-		(*chan)->rbuf->read_flush ();
+		(*chan)->rbuf()->read_flush ();
 	}
 
 	g_atomic_int_set (&_pending_overwrite, 1);
@@ -538,7 +544,7 @@ DiskReader::overwrite_existing_buffers ()
 		const bool reversed = _session.transport_speed() < 0.0f;
 
 		/* assume all are the same size */
-		samplecnt_t size = c->front()->rbuf->write_space ();
+		samplecnt_t size = c->front()->rbuf()->write_space ();
 		assert (size > 0);
 
 		boost::scoped_array<Sample> sum_buffer (new Sample[size]);
@@ -559,7 +565,7 @@ DiskReader::overwrite_existing_buffers ()
 
 			ReaderChannelInfo* rci = dynamic_cast<ReaderChannelInfo*> (*chan);
 
-			if (audio_read ((*chan)->rbuf, sum_buffer.get(), mixdown_buffer.get(), gain_buffer.get(), start, to_read, rci, n, reversed)) {
+			if (audio_read ((*chan)->rbuf(), sum_buffer.get(), mixdown_buffer.get(), gain_buffer.get(), start, to_read, rci, n, reversed)) {
 				error << string_compose(_("DiskReader %1: when refilling, cannot read %2 from playlist at sample %3"), id(), size, overwrite_sample) << endmsg;
 				goto midi;
 			}
@@ -614,7 +620,7 @@ DiskReader::seek (samplepos_t sample, bool complete_refill)
 	}
 
 	for (n = 0, chan = c->begin(); chan != c->end(); ++chan, ++n) {
-		(*chan)->rbuf->reset ();
+		(*chan)->rbuf()->reset ();
 	}
 
 	playback_sample = sample;
@@ -645,7 +651,7 @@ DiskReader::can_internal_playback_seek (sampleoffset_t distance)
 	boost::shared_ptr<ChannelList> c = channels.reader();
 
 	for (chan = c->begin(); chan != c->end(); ++chan) {
-		if (!(*chan)->rbuf->can_seek (distance)) {
+		if (!(*chan)->rbuf()->can_seek (distance)) {
 			return false;
 		}
 	}
@@ -668,9 +674,9 @@ DiskReader::internal_playback_seek (sampleoffset_t distance)
 	boost::shared_ptr<ChannelList> c = channels.reader();
 	for (chan = c->begin(); chan != c->end(); ++chan) {
 		if (distance < 0) {
-			off = 0 - (sampleoffset_t) (*chan)->rbuf->decrement_read_ptr (::llabs (distance));
+			off = 0 - (sampleoffset_t) (*chan)->rbuf()->decrement_read_ptr (::llabs (distance));
 		} else {
-			off = (*chan)->rbuf->increment_read_ptr (distance);
+			off = (*chan)->rbuf()->increment_read_ptr (distance);
 		}
 	}
 
@@ -890,7 +896,7 @@ DiskReader::refill_audio (Sample* sum_buffer, Sample* mixdown_buffer, float* gai
 	assert(mixdown_buffer);
 	assert(gain_buffer);
 
-	samplecnt_t total_space = c->front()->rbuf->write_space();
+	samplecnt_t total_space = c->front()->rbuf()->write_space();
 
 	if (total_space == 0) {
 		DEBUG_TRACE (DEBUG::DiskIO, string_compose ("%1: no space to refill\n", name()));
@@ -928,7 +934,7 @@ DiskReader::refill_audio (Sample* sum_buffer, Sample* mixdown_buffer, float* gai
 	   work with.
 	*/
 
-	if (_slaved && total_space < (samplecnt_t) (c->front()->rbuf->bufsize() / 2)) {
+	if (_slaved && total_space < (samplecnt_t) (c->front()->rbuf()->bufsize() / 2)) {
 		DEBUG_TRACE (DEBUG::DiskIO, string_compose ("%1: not enough to refill while slaved\n", this));
 		return 0;
 	}
@@ -941,7 +947,7 @@ DiskReader::refill_audio (Sample* sum_buffer, Sample* mixdown_buffer, float* gai
 			/* at start: nothing to do but fill with silence */
 			for (chan_n = 0, i = c->begin(); i != c->end(); ++i, ++chan_n) {
 				ChannelInfo* chan (*i);
-				chan->rbuf->write_zero (chan->rbuf->write_space ());
+				chan->rbuf()->write_zero (chan->rbuf()->write_space ());
 			}
 			return 0;
 		}
@@ -960,7 +966,7 @@ DiskReader::refill_audio (Sample* sum_buffer, Sample* mixdown_buffer, float* gai
 			/* at end: nothing to do but fill with silence */
 			for (chan_n = 0, i = c->begin(); i != c->end(); ++i, ++chan_n) {
 				ChannelInfo* chan (*i);
-				chan->rbuf->write_zero (chan->rbuf->write_space ());
+				chan->rbuf()->write_zero (chan->rbuf()->write_space ());
 			}
 			return 0;
 		}
@@ -998,7 +1004,7 @@ DiskReader::refill_audio (Sample* sum_buffer, Sample* mixdown_buffer, float* gai
 		file_sample_tmp = ffa;
 		samplecnt_t ts = total_space;
 
-		samplecnt_t to_read = min (ts, (samplecnt_t) chan->rbuf->write_space ());
+		samplecnt_t to_read = min (ts, (samplecnt_t) chan->rbuf()->write_space ());
 		to_read = min (to_read, samples_to_read);
 		assert (to_read >= 0);
 
@@ -1006,7 +1012,7 @@ DiskReader::refill_audio (Sample* sum_buffer, Sample* mixdown_buffer, float* gai
 
 		if (to_read) {
 			ReaderChannelInfo* rci = dynamic_cast<ReaderChannelInfo*> (chan);
-			if (audio_read (chan->rbuf, sum_buffer, mixdown_buffer, gain_buffer, file_sample_tmp, to_read, rci, chan_n, reversed)) {
+			if (audio_read (chan->rbuf(), sum_buffer, mixdown_buffer, gain_buffer, file_sample_tmp, to_read, rci, chan_n, reversed)) {
 				error << string_compose(_("DiskReader %1: when refilling, cannot read %2 from playlist at sample %3"), id(), to_read, ffa) << endmsg;
 				ret = -1;
 				goto out;
@@ -1017,7 +1023,7 @@ DiskReader::refill_audio (Sample* sum_buffer, Sample* mixdown_buffer, float* gai
 			/* not sure if action is needed,
 			 * we'll later hit the "to close to the end" case
 			 */
-			//chan->rbuf->write_zero (zero_fill);
+			//chan->rbuf()->write_zero (zero_fill);
 		}
 	}
 
diff --git a/libs/pbd/pbd/debug.h b/libs/pbd/pbd/debug.h
index 7d3a901a11..d82e646582 100644
--- a/libs/pbd/pbd/debug.h
+++ b/libs/pbd/pbd/debug.h
@@ -72,6 +72,7 @@ namespace PBD {
 }
 
 #ifndef NDEBUG
+
 #define DEBUG_TRACE(bits,str) if (((bits) & PBD::debug_bits).any()) { PBD::debug_print (# bits, str); }
 #define DEBUG_STR_DECL(id) std::stringstream __debug_str ## id;
 #define DEBUG_STR(id) __debug_str ## id