smokephil/ardour
1
0
Fork 0
mirror of https://github.com/Ardour/ardour.git synced 2025-12-07 07:14:56 +01:00
Code Issues Projects Releases Wiki Activity

audio_diskstream.cc: new interpolation classes which replace the old interpolation code for varispeed work

Browse source 
git-svn-id: svn://localhost/ardour2/branches/3.0@5387 d708f5d6-7413-0410-9779-e7cbd77b26cf
This commit is contained in:
Hans Baier 2009-07-19 20:54:52 +00:00
parent fcd29cc12b
commit 1efee9951a
1 changed files with 3 additions and 64 deletions
Download patch file Download diff file Expand all files Collapse all files

61
libs/ardour/audio_diskstream.cc
View file

@ -818,7 +818,6 @@ AudioDiskstream::process_varispeed_playback(nframes_t nframes, boost::shared_ptr
{ {
ChannelList::iterator chan; ChannelList::iterator chan;
/*
interpolation.set_speed (_target_speed); interpolation.set_speed (_target_speed);
int channel = 0; int channel = 0;
@ -827,69 +826,9 @@ AudioDiskstream::process_varispeed_playback(nframes_t nframes, boost::shared_ptr
playback_distance = interpolation.interpolate ( playback_distance = interpolation.interpolate (
channel, nframes, chaninfo->current_playback_buffer, chaninfo->speed_buffer); channel, nframes, chaninfo->current_playback_buffer, chaninfo->speed_buffer);
}
*/
// the idea behind phase is that when the speed is not 1.0, we have to
// interpolate between samples and then we have to store where we thought we were.
// rather than being at sample N or N+1, we were at N+0.8792922
// so the "phase" element, if you want to think about this way,
// varies from 0 to 1, representing the "offset" between samples
uint64_t phase = interpolation.get_last_phase();
interpolation.set_speed (_target_speed);
// acceleration
uint64_t phi = interpolation.get_phi();
uint64_t target_phi = interpolation.get_target_phi();
int64_t phi_delta;
// index in the input buffers
nframes_t i = 0;
// Linearly interpolate into the speed buffer
// using 40.24 fixed point math
//
// Fixed point is just an integer with an implied scaling factor.
// In 40.24 the scaling factor is 2^24 = 16777216,
// so a value of 10*2^24 (in integer space) is equivalent to 10.0.
//
// The advantage is that addition and modulus [like x = (x + y) % 2^40]
// have no rounding errors and no drift, and just require a single integer add.
// (swh)
const int64_t fractional_part_mask = 0xFFFFFF;
const Sample binary_scaling_factor = 16777216.0f;
// phi = fixed point speed
if (phi != target_phi) {
phi_delta = ((int64_t)(target_phi - phi)) / nframes;
} else {
phi_delta = 0;
}
for (chan = c->begin(); chan != c->end(); ++chan) {
Sample fractional_phase_part;
ChannelInfo* chaninfo (*chan);
i = 0;
phase = interpolation.get_last_phase();
for (nframes_t outsample = 0; outsample < nframes; ++outsample) {
i = phase >> 24;
fractional_phase_part = (phase & fractional_part_mask) / binary_scaling_factor;
chaninfo->speed_buffer[outsample] =
chaninfo->current_playback_buffer[i] * (1.0f - fractional_phase_part) +
chaninfo->current_playback_buffer[i+1] * fractional_phase_part;
phase += phi + phi_delta;
}
chaninfo->current_playback_buffer = chaninfo->speed_buffer; chaninfo->current_playback_buffer = chaninfo->speed_buffer;
} }
playback_distance = i; // + 1;
interpolation.set_last_phase (phase & fractional_part_mask);
} }
bool bool