+double
+AudioRegion::rms (Progress* p) const
+{
+ framepos_t fpos = _start;
+ framepos_t const fend = _start + _length;
+ uint32_t const n_chan = n_channels ();
+ double rms = 0;
+
+ framecnt_t const blocksize = 64 * 1024;
+ Sample buf[blocksize];
+
+ framecnt_t total = 0;
+
+ if (n_chan == 0) {
+ return 0;
+ }
+
+ while (fpos < fend) {
+ framecnt_t const to_read = min (fend - fpos, blocksize);
+ total += to_read;
+ for (uint32_t c = 0; c < n_chan; ++c) {
+ if (read_raw_internal (buf, fpos, to_read, c) != to_read) {
+ return 0;
+ }
+ for (framepos_t i = 0; i < to_read; ++i) {
+ rms += buf[i] * buf[i];
+ }
+ fpos += to_read;
+ if (p) {
+ p->set_progress (float (fpos - _start) / _length);
+ if (p->cancelled ()) {
+ return -1;
+ }
+ }
+ }
+ }
+ return sqrt (rms / (double)(total * n_chan));
+}
+