Beats: add helper to get fractional beats in frame range

mixxxdj · Jan 5, 2024 · 1a7af25 · 1a7af25
1 parent 0437d5e
commit 1a7af25
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diff --git a/src/track/beats.cpp b/src/track/beats.cpp
@@ -787,6 +787,29 @@ int Beats::numBeatsInRange(audio::FramePos startPosition, audio::FramePos endPos
     return i - 2;
 };
 
+double Beats::numFractionalBeatsInRange(audio::FramePos startPos, audio::FramePos endPos) const {
+    double pBeatPercentage;
+    // get the ratio of first beat / position:
+    // 1 - ((startPos - beat before range) / first beat length)
+    if (!getContext(startPos, nullptr, nullptr, nullptr, &pBeatPercentage)) {
+        return -1;
+    }
+    double numBeats = 1 - pBeatPercentage;
+
+    // get the last beat ratio:
+    // (endPos - last beat in range) / last beat length
+    if (!getContext(endPos, nullptr, nullptr, nullptr, &pBeatPercentage)) {
+        return -1;
+    }
+    numBeats += pBeatPercentage;
+
+    // get the beats inside the range
+    // subtract 1 because we already counted the first beat
+    numBeats += numBeatsInRange(findNextBeat(startPos), endPos) - 1;
+
+    return numBeats;
+}
+
 audio::FramePos Beats::findNextBeat(audio::FramePos position) const {
     return findNthBeat(position, 1);
 }

diff --git a/src/track/beats.h b/src/track/beats.h
@@ -350,6 +350,8 @@ class Beats : private std::enable_shared_from_this<Beats> {
     audio::FramePos snapPosToNearBeat(audio::FramePos position) const;
 
     int numBeatsInRange(audio::FramePos startPosition, audio::FramePos endPosition) const;
+    double numFractionalBeatsInRange(audio::FramePos startPosition,
+            audio::FramePos endPosition) const;
 
     /// Find the frame position N beats away from `position`. The number of beats may be
     /// negative and does not need to be an integer. In this case the returned position will