Cast param for std::time to a pointer of time_t
[ardour.git] / libs / ardour / audiosource.cc
index 8a367f32a7f766614db41da807f9b1e7f20a896f..84a5b687f969a84bbcfee89ac4fcafe82ab450de 100644 (file)
 #include <glibmm/miscutils.h>
 
 #include "pbd/xml++.h"
-#include "pbd/pthread_utils.h"
 
 #include "ardour/audiosource.h"
-#include "ardour/cycle_timer.h"
-#include "ardour/session.h"
-#include "ardour/transient_detector.h"
+#include "ardour/rc_configuration.h"
 #include "ardour/runtime_functions.h"
 
 #include "i18n.h"
 using namespace std;
 using namespace ARDOUR;
 using namespace PBD;
-using Glib::ustring;
 
+Glib::Threads::Mutex AudioSource::_level_buffer_lock;
+vector<boost::shared_array<Sample> > AudioSource::_mixdown_buffers;
+vector<boost::shared_array<gain_t> > AudioSource::_gain_buffers;
+size_t AudioSource::_working_buffers_size = 0;
 bool AudioSource::_build_missing_peakfiles = false;
 
 /** true if we want peakfiles (e.g. if we are displaying a GUI) */
@@ -57,15 +57,13 @@ bool AudioSource::_build_peakfiles = false;
 
 #define _FPP 256
 
-AudioSource::AudioSource (Session& s, ustring name)
+AudioSource::AudioSource (Session& s, string name)
        : Source (s, DataType::AUDIO, name)
        , _length (0)
 {
        _peaks_built = false;
        _peak_byte_max = 0;
-       peakfile = -1;
-       _read_data_count = 0;
-       _write_data_count = 0;
+       _peakfile_descriptor = 0;
        peak_leftover_cnt = 0;
        peak_leftover_size = 0;
        peak_leftovers = 0;
@@ -78,9 +76,7 @@ AudioSource::AudioSource (Session& s, const XMLNode& node)
 
        _peaks_built = false;
        _peak_byte_max = 0;
-       peakfile = -1;
-       _read_data_count = 0;
-       _write_data_count = 0;
+       _peakfile_descriptor = 0;
        peak_leftover_cnt = 0;
        peak_leftover_size = 0;
        peak_leftovers = 0;
@@ -98,10 +94,7 @@ AudioSource::~AudioSource ()
                cerr << "AudioSource destroyed with leftover peak data pending" << endl;
        }
 
-       if (peakfile >= 0) {
-               ::close (peakfile);
-       }
-
+       delete _peakfile_descriptor;
        delete [] peak_leftovers;
 }
 
@@ -129,17 +122,23 @@ AudioSource::set_state (const XMLNode& node, int /*version*/)
        return 0;
 }
 
-sframes_t
-AudioSource::length (sframes_t /*pos*/) const
+bool
+AudioSource::empty () const
+{
+        return _length == 0;
+}
+
+framecnt_t
+AudioSource::length (framepos_t /*pos*/) const
 {
        return _length;
 }
 
 void
-AudioSource::update_length (sframes_t pos, sframes_t cnt)
+AudioSource::update_length (framecnt_t len)
 {
-       if (pos + cnt > _length) {
-               _length = pos + cnt;
+       if (len > _length) {
+               _length = len;
        }
 }
 
@@ -148,18 +147,24 @@ AudioSource::update_length (sframes_t pos, sframes_t cnt)
   PEAK FILE STUFF
  ***********************************************************************/
 
+/** Checks to see if peaks are ready.  If so, we return true.  If not, we return false, and
+ *  things are set up so that doThisWhenReady is called when the peaks are ready.
+ *  A new PBD::ScopedConnection is created for the associated connection and written to
+ *  *connect_here_if_not.
+ *
+ *  @param doThisWhenReady Function to call when peaks are ready (if they are not already).
+ *  @param connect_here_if_not Address to write new ScopedConnection to.
+ *  @param event_loop Event loop for doThisWhenReady to be called in.
+ */
 bool
-AudioSource::peaks_ready (boost::function<void()> doThisWhenReady, ScopedConnection& connect_here_if_not, EventLoop* event_loop) const
+AudioSource::peaks_ready (boost::function<void()> doThisWhenReady, ScopedConnection** connect_here_if_not, EventLoop* event_loop) const
 {
        bool ret;
-       Glib::Mutex::Lock lm (_peaks_ready_lock);
-
-       /* check to see if the peak data is ready. if not
-          connect the slot while still holding the lock.
-       */
+       Glib::Threads::Mutex::Lock lm (_peaks_ready_lock);
 
        if (!(ret = _peaks_built)) {
-               PeaksReady.connect (connect_here_if_not, MISSING_INVALIDATOR, doThisWhenReady, event_loop);
+               *connect_here_if_not = new ScopedConnection;
+               PeaksReady.connect (**connect_here_if_not, MISSING_INVALIDATOR, doThisWhenReady, event_loop);
        }
 
        return ret;
@@ -177,19 +182,19 @@ AudioSource::touch_peakfile ()
        struct utimbuf tbuf;
 
        tbuf.actime = statbuf.st_atime;
-       tbuf.modtime = time ((time_t) 0);
+       tbuf.modtime = time ((time_t*) 0);
 
        utime (peakpath.c_str(), &tbuf);
 }
 
 int
-AudioSource::rename_peakfile (ustring newpath)
+AudioSource::rename_peakfile (string newpath)
 {
        /* caller must hold _lock */
 
-       ustring oldpath = peakpath;
+       string oldpath = peakpath;
 
-       if (access (oldpath.c_str(), F_OK) == 0) {
+       if (Glib::file_test (oldpath, Glib::FILE_TEST_EXISTS)) {
                if (rename (oldpath.c_str(), newpath.c_str()) != 0) {
                        error << string_compose (_("cannot rename peakfile for %1 from %2 to %3 (%4)"), _name, oldpath, newpath, strerror (errno)) << endmsg;
                        return -1;
@@ -202,7 +207,7 @@ AudioSource::rename_peakfile (ustring newpath)
 }
 
 int
-AudioSource::initialize_peakfile (bool newfile, ustring audio_path)
+AudioSource::initialize_peakfile (string audio_path)
 {
        struct stat statbuf;
 
@@ -210,7 +215,7 @@ AudioSource::initialize_peakfile (bool newfile, ustring audio_path)
 
        /* if the peak file should be there, but isn't .... */
 
-       if (!newfile && !Glib::file_test (peakpath.c_str(), Glib::FILE_TEST_EXISTS)) {
+       if (!empty() && !Glib::file_test (peakpath.c_str(), Glib::FILE_TEST_EXISTS)) {
                peakpath = find_broken_peakfile (peakpath, audio_path);
        }
 
@@ -230,7 +235,7 @@ AudioSource::initialize_peakfile (bool newfile, ustring audio_path)
 
                /* we found it in the peaks dir, so check it out */
 
-               if (statbuf.st_size == 0 || ((nframes_t) statbuf.st_size < ((length(_timeline_position) / _FPP) * sizeof (PeakData)))) {
+               if (statbuf.st_size == 0 || (statbuf.st_size < (off_t) ((length(_timeline_position) / _FPP) * sizeof (PeakData)))) {
                        // empty
                        _peaks_built = false;
                } else {
@@ -239,8 +244,14 @@ AudioSource::initialize_peakfile (bool newfile, ustring audio_path)
                        int err = stat (audio_path.c_str(), &stat_file);
 
                        if (err) {
-                               _peaks_built = false;
-                               _peak_byte_max = 0;
+
+                               /* no audio path - nested source or we can't
+                                  read it or ... whatever, use the peakfile as-is.
+                               */
+
+                               _peaks_built = true;
+                               _peak_byte_max = statbuf.st_size;
+
                        } else {
 
                                /* allow 6 seconds slop on checking peak vs. file times because of various
@@ -258,7 +269,7 @@ AudioSource::initialize_peakfile (bool newfile, ustring audio_path)
                }
        }
 
-       if (!newfile && !_peaks_built && _build_missing_peakfiles && _build_peakfiles) {
+       if (!empty() && !_peaks_built && _build_missing_peakfiles && _build_peakfiles) {
                build_peaks_from_scratch ();
        }
 
@@ -268,14 +279,16 @@ AudioSource::initialize_peakfile (bool newfile, ustring audio_path)
 framecnt_t
 AudioSource::read (Sample *dst, framepos_t start, framecnt_t cnt, int /*channel*/) const
 {
-       Glib::Mutex::Lock lm (_lock);
+       assert (cnt >= 0);
+       
+       Glib::Threads::Mutex::Lock lm (_lock);
        return read_unlocked (dst, start, cnt);
 }
 
 framecnt_t
 AudioSource::write (Sample *dst, framecnt_t cnt)
 {
-       Glib::Mutex::Lock lm (_lock);
+       Glib::Threads::Mutex::Lock lm (_lock);
        /* any write makes the fill not removable */
        _flags = Flag (_flags & ~Removable);
        return write_unlocked (dst, cnt);
@@ -295,7 +308,7 @@ int
 AudioSource::read_peaks_with_fpp (PeakData *peaks, framecnt_t npeaks, framepos_t start, framecnt_t cnt,
                                  double samples_per_visual_peak, framecnt_t samples_per_file_peak) const
 {
-       Glib::Mutex::Lock lm (_lock);
+       Glib::Threads::Mutex::Lock lm (_lock);
        double scale;
        double expected_peaks;
        PeakData::PeakDatum xmax;
@@ -306,7 +319,9 @@ AudioSource::read_peaks_with_fpp (PeakData *peaks, framecnt_t npeaks, framepos_t
        int ret = -1;
        PeakData* staging = 0;
        Sample* raw_staging = 0;
-       int _peakfile = -1;
+
+       FdFileDescriptor* peakfile_descriptor = new FdFileDescriptor (peakpath, false, 0664);
+       int peakfile_fd = -1;
 
        expected_peaks = (cnt / (double) samples_per_file_peak);
        scale = npeaks/expected_peaks;
@@ -357,6 +372,7 @@ AudioSource::read_peaks_with_fpp (PeakData *peaks, framecnt_t npeaks, framepos_t
                        peaks[i].min = raw_staging[i];
                }
 
+               delete peakfile_descriptor;
                delete [] raw_staging;
                return 0;
        }
@@ -367,8 +383,9 @@ AudioSource::read_peaks_with_fpp (PeakData *peaks, framecnt_t npeaks, framepos_t
 
                /* open, read, close */
 
-               if ((_peakfile = ::open (peakpath.c_str(), O_RDONLY, 0664)) < 0) {
+               if ((peakfile_fd = peakfile_descriptor->allocate ()) < 0) {
                        error << string_compose(_("AudioSource: cannot open peakpath (a) \"%1\" (%2)"), peakpath, strerror (errno)) << endmsg;
+                       delete peakfile_descriptor;
                        return -1;
                }
 
@@ -376,8 +393,7 @@ AudioSource::read_peaks_with_fpp (PeakData *peaks, framecnt_t npeaks, framepos_t
                cerr << "DIRECT PEAKS\n";
 #endif
 
-               nread = ::pread (_peakfile, peaks, sizeof (PeakData)* npeaks, first_peak_byte);
-               close (_peakfile);
+               nread = ::pread (peakfile_fd, peaks, sizeof (PeakData)* npeaks, first_peak_byte);
 
                if (nread != sizeof (PeakData) * npeaks) {
                        cerr << "AudioSource["
@@ -392,6 +408,7 @@ AudioSource::read_peaks_with_fpp (PeakData *peaks, framecnt_t npeaks, framepos_t
                             << first_peak_byte
                             << ')'
                             << endl;
+                       delete peakfile_descriptor;
                        return -1;
                }
 
@@ -399,6 +416,7 @@ AudioSource::read_peaks_with_fpp (PeakData *peaks, framecnt_t npeaks, framepos_t
                        memset (&peaks[npeaks], 0, sizeof (PeakData) * zero_fill);
                }
 
+               delete peakfile_descriptor;
                return 0;
        }
 
@@ -421,7 +439,7 @@ AudioSource::read_peaks_with_fpp (PeakData *peaks, framecnt_t npeaks, framepos_t
                */
 
                const framecnt_t chunksize = (framecnt_t) min (expected_peaks, 65536.0);
-               
+
                staging = new PeakData[chunksize];
 
                /* compute the rounded up frame position  */
@@ -441,8 +459,9 @@ AudioSource::read_peaks_with_fpp (PeakData *peaks, framecnt_t npeaks, framepos_t
 
                /* open ... close during out: handling */
 
-               if ((_peakfile = ::open (peakpath.c_str(), O_RDONLY, 0664)) < 0) {
+               if ((peakfile_fd = peakfile_descriptor->allocate ()) < 0) {
                        error << string_compose(_("AudioSource: cannot open peakpath (b) \"%1\" (%2)"), peakpath, strerror (errno)) << endmsg;
+                       delete peakfile_descriptor;
                        delete [] staging;
                        return 0;
                }
@@ -459,10 +478,10 @@ AudioSource::read_peaks_with_fpp (PeakData *peaks, framecnt_t npeaks, framepos_t
                                cerr << "read " << sizeof (PeakData) * to_read << " from peakfile @ " << start_byte << endl;
 #endif
 
-                               if ((nread = ::pread (_peakfile, staging, sizeof (PeakData) * to_read, start_byte))
+                               if ((nread = ::pread (peakfile_fd, staging, sizeof (PeakData) * to_read, start_byte))
                                    != sizeof (PeakData) * to_read) {
 
-                                       off_t fend = lseek (_peakfile, 0, SEEK_END);
+                                       off_t fend = lseek (peakfile_fd, 0, SEEK_END);
 
                                        cerr << "AudioSource["
                                             << _name
@@ -548,21 +567,29 @@ AudioSource::read_peaks_with_fpp (PeakData *peaks, framecnt_t npeaks, framepos_t
 
                                to_read = min (chunksize, (framecnt_t)(_length - current_frame));
 
-                               if (to_read == 0) {
-                                       /* XXX ARGH .. out by one error ... need to figure out why this happens
-                                          and fix it rather than do this band-aid move.
+                               if (current_frame >= _length) {
+
+                                        /* hmm, error condition - we've reached the end of the file
+                                           without generating all the peak data. cook up a zero-filled
+                                           data buffer and then use it. this is simpler than
+                                           adjusting zero_fill and npeaks and then breaking out of
+                                           this loop early
                                        */
-                                       zero_fill = npeaks - nvisual_peaks;
-                                       npeaks -= zero_fill;
-                                       break;
-                               }
 
-                               if ((frames_read = read_unlocked (raw_staging, current_frame, to_read)) == 0) {
-                                       error << string_compose(_("AudioSource[%1]: peak read - cannot read %2 samples at offset %3 of %4 (%5)"),
-                                                               _name, to_read, current_frame, _length, strerror (errno))
-                                             << endmsg;
-                                       goto out;
-                               }
+                                        memset (raw_staging, 0, sizeof (Sample) * chunksize);
+
+                                } else {
+
+                                        to_read = min (chunksize, (_length - current_frame));
+
+
+                                        if ((frames_read = read_unlocked (raw_staging, current_frame, to_read)) == 0) {
+                                                error << string_compose(_("AudioSource[%1]: peak read - cannot read %2 samples at offset %3 of %4 (%5)"),
+                                                                        _name, to_read, current_frame, _length, strerror (errno))
+                                                      << endmsg;
+                                                goto out;
+                                        }
+                                }
 
                                i = 0;
                        }
@@ -593,9 +620,7 @@ AudioSource::read_peaks_with_fpp (PeakData *peaks, framecnt_t npeaks, framepos_t
        }
 
   out:
-       if (_peakfile >= 0) {
-               close (_peakfile);
-       }
+       delete peakfile_descriptor;
 
        delete [] staging;
        delete [] raw_staging;
@@ -621,13 +646,13 @@ AudioSource::build_peaks_from_scratch ()
        {
                /* hold lock while building peaks */
 
-               Glib::Mutex::Lock lp (_lock);
+               Glib::Threads::Mutex::Lock lp (_lock);
 
                if (prepare_for_peakfile_writes ()) {
                        goto out;
                }
 
-               framepos_t current_frame = 0;
+               framecnt_t current_frame = 0;
                framecnt_t cnt = _length;
 
                _peaks_built = false;
@@ -637,7 +662,7 @@ AudioSource::build_peaks_from_scratch ()
 
                        framecnt_t frames_to_read = min (bufsize, cnt);
                        framecnt_t frames_read;
-
+                       
                        if ((frames_read = read_unlocked (buf, current_frame, frames_to_read)) != frames_to_read) {
                                error << string_compose(_("%1: could not write read raw data for peak computation (%2)"), _name, strerror (errno)) << endmsg;
                                done_with_peakfile_writes (false);
@@ -658,13 +683,7 @@ AudioSource::build_peaks_from_scratch ()
                }
 
                done_with_peakfile_writes ((cnt == 0));
-       }
-
-       {
-               Glib::Mutex::Lock lm (_peaks_ready_lock);
-
-               if (_peaks_built) {
-                       PeaksReady (); /* EMIT SIGNAL */
+               if (cnt == 0) {
                        ret = 0;
                }
        }
@@ -682,7 +701,8 @@ AudioSource::build_peaks_from_scratch ()
 int
 AudioSource::prepare_for_peakfile_writes ()
 {
-       if ((peakfile = ::open (peakpath.c_str(), O_RDWR|O_CREAT, 0664)) < 0) {
+       _peakfile_descriptor = new FdFileDescriptor (peakpath, true, 0664);
+       if ((_peakfile_fd = _peakfile_descriptor->allocate()) < 0) {
                error << string_compose(_("AudioSource: cannot open peakpath (c) \"%1\" (%2)"), peakpath, strerror (errno)) << endmsg;
                return -1;
        }
@@ -697,24 +717,25 @@ AudioSource::done_with_peakfile_writes (bool done)
        }
 
        if (done) {
+               Glib::Threads::Mutex::Lock lm (_peaks_ready_lock);
                _peaks_built = true;
+               PeaksReady (); /* EMIT SIGNAL */
        }
 
-       if (peakfile >= 0) {
-               close (peakfile);
-               peakfile = -1;
-       }
+       delete _peakfile_descriptor;
+       _peakfile_descriptor = 0;
 }
 
+/** @param first_frame Offset from the source start of the first frame to process */
 int
-AudioSource::compute_and_write_peaks (Sample* buf, framepos_t first_frame, framecnt_t cnt,
+AudioSource::compute_and_write_peaks (Sample* buf, framecnt_t first_frame, framecnt_t cnt,
                                      bool force, bool intermediate_peaks_ready)
 {
        return compute_and_write_peaks (buf, first_frame, cnt, force, intermediate_peaks_ready, _FPP);
 }
 
 int
-AudioSource::compute_and_write_peaks (Sample* buf, framepos_t first_frame, framecnt_t cnt,
+AudioSource::compute_and_write_peaks (Sample* buf, framecnt_t first_frame, framecnt_t cnt,
                                      bool force, bool intermediate_peaks_ready, framecnt_t fpp)
 {
        Sample* buf2 = 0;
@@ -727,7 +748,7 @@ AudioSource::compute_and_write_peaks (Sample* buf, framepos_t first_frame, frame
        const size_t blocksize = (128 * 1024);
        off_t first_peak_byte;
 
-       if (peakfile < 0) {
+       if (_peakfile_descriptor == 0) {
                prepare_for_peakfile_writes ();
        }
 
@@ -748,7 +769,7 @@ AudioSource::compute_and_write_peaks (Sample* buf, framepos_t first_frame, frame
 
                        off_t byte = (peak_leftover_frame / fpp) * sizeof (PeakData);
 
-                       if (::pwrite (peakfile, &x, sizeof (PeakData), byte) != sizeof (PeakData)) {
+                       if (::pwrite (_peakfile_fd, &x, sizeof (PeakData), byte) != sizeof (PeakData)) {
                                error << string_compose(_("%1: could not write peak file data (%2)"), _name, strerror (errno)) << endmsg;
                                goto out;
                        }
@@ -756,7 +777,7 @@ AudioSource::compute_and_write_peaks (Sample* buf, framepos_t first_frame, frame
                        _peak_byte_max = max (_peak_byte_max, (off_t) (byte + sizeof(PeakData)));
 
                        {
-                               Glib::Mutex::Lock lm (_peaks_ready_lock);
+                               Glib::Threads::Mutex::Lock lm (_peaks_ready_lock);
                                PeakRangeReady (peak_leftover_frame, peak_leftover_cnt); /* EMIT SIGNAL */
                                if (intermediate_peaks_ready) {
                                        PeaksReady (); /* EMIT SIGNAL */
@@ -851,16 +872,17 @@ AudioSource::compute_and_write_peaks (Sample* buf, framepos_t first_frame, frame
                   less than BLOCKSIZE bytes.  only call ftruncate if we'll make the file larger.
                */
 
-               off_t endpos = lseek (peakfile, 0, SEEK_END);
+               off_t endpos = lseek (_peakfile_fd, 0, SEEK_END);
                off_t target_length = blocksize * ((first_peak_byte + blocksize + 1) / blocksize);
 
                if (endpos < target_length) {
-                       ftruncate (peakfile, target_length);
-                       /* error doesn't actually matter though, so continue on without testing */
+                       if (ftruncate (_peakfile_fd, target_length)) {
+                               /* error doesn't actually matter so continue on without testing */
+                       }
                }
        }
 
-       if (::pwrite (peakfile, peakbuf, sizeof (PeakData) * peaks_computed, first_peak_byte) != (ssize_t) (sizeof (PeakData) * peaks_computed)) {
+       if (::pwrite (_peakfile_fd, peakbuf, sizeof (PeakData) * peaks_computed, first_peak_byte) != (ssize_t) (sizeof (PeakData) * peaks_computed)) {
                error << string_compose(_("%1: could not write peak file data (%2)"), _name, strerror (errno)) << endmsg;
                goto out;
        }
@@ -868,7 +890,7 @@ AudioSource::compute_and_write_peaks (Sample* buf, framepos_t first_frame, frame
        _peak_byte_max = max (_peak_byte_max, (off_t) (first_peak_byte + sizeof(PeakData)*peaks_computed));
 
        if (frames_done) {
-               Glib::Mutex::Lock lm (_peaks_ready_lock);
+               Glib::Threads::Mutex::Lock lm (_peaks_ready_lock);
                PeakRangeReady (first_frame, frames_done); /* EMIT SIGNAL */
                if (intermediate_peaks_ready) {
                        PeaksReady (); /* EMIT SIGNAL */
@@ -887,7 +909,7 @@ AudioSource::compute_and_write_peaks (Sample* buf, framepos_t first_frame, frame
 void
 AudioSource::truncate_peakfile ()
 {
-       if (peakfile < 0) {
+       if (_peakfile_descriptor == 0) {
                error << string_compose (_("programming error: %1"), "AudioSource::truncate_peakfile() called without open peakfile descriptor")
                      << endmsg;
                return;
@@ -895,10 +917,13 @@ AudioSource::truncate_peakfile ()
 
        /* truncate the peakfile down to its natural length if necessary */
 
-       off_t end = lseek (peakfile, 0, SEEK_END);
+       off_t end = lseek (_peakfile_fd, 0, SEEK_END);
 
        if (end > _peak_byte_max) {
-               ftruncate (peakfile, _peak_byte_max);
+               if (ftruncate (_peakfile_fd, _peak_byte_max)) {
+                       error << string_compose (_("could not truncate peakfile %1 to %2 (error: %3)"),
+                                                peakpath, _peak_byte_max, errno) << endmsg;
+               }
        }
 }
 
@@ -920,3 +945,58 @@ AudioSource::available_peaks (double zoom_factor) const
        return (end/sizeof(PeakData)) * _FPP;
 }
 
+void
+AudioSource::mark_streaming_write_completed ()
+{
+       Glib::Threads::Mutex::Lock lm (_peaks_ready_lock);
+
+       if (_peaks_built) {
+               PeaksReady (); /* EMIT SIGNAL */
+       }
+}
+
+void
+AudioSource::allocate_working_buffers (framecnt_t framerate)
+{
+       Glib::Threads::Mutex::Lock lm (_level_buffer_lock);
+
+
+       /* Note: we don't need any buffers allocated until
+          a level 1 audiosource is created, at which
+          time we'll call ::ensure_buffers_for_level()
+          with the right value and do the right thing.
+       */
+
+       if (!_mixdown_buffers.empty()) {
+               ensure_buffers_for_level_locked ( _mixdown_buffers.size(), framerate);
+       }
+}
+
+void
+AudioSource::ensure_buffers_for_level (uint32_t level, framecnt_t frame_rate)
+{
+       Glib::Threads::Mutex::Lock lm (_level_buffer_lock);
+       ensure_buffers_for_level_locked (level, frame_rate);
+}
+
+void
+AudioSource::ensure_buffers_for_level_locked (uint32_t level, framecnt_t frame_rate)
+{
+       framecnt_t nframes = (framecnt_t) floor (Config->get_audio_playback_buffer_seconds() * frame_rate);
+
+       /* this may be called because either "level" or "frame_rate" have
+        * changed. and it may be called with "level" smaller than the current
+        * number of buffers, because a new compound region has been created at
+        * a more shallow level than the deepest one we currently have.
+        */
+
+       uint32_t limit = max ((size_t) level, _mixdown_buffers.size());
+
+       _mixdown_buffers.clear ();
+       _gain_buffers.clear ();
+
+       for (uint32_t n = 0; n < limit; ++n) {
+               _mixdown_buffers.push_back (boost::shared_array<Sample> (new Sample[nframes]));
+               _gain_buffers.push_back (boost::shared_array<gain_t> (new gain_t[nframes]));
+       }
+}