From e8afb10f483a34f3679da1bbd015a9220364a6c7 Mon Sep 17 00:00:00 2001
From: David Madl <git@abanbytes.eu>
Date: Sun, 22 Mar 2026 15:16:54 +0100
Subject: [PATCH] bug: tweak loop delay to fit music rate

---
 app/src/main/cpp/PlaybackEngine.cpp | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/app/src/main/cpp/PlaybackEngine.cpp b/app/src/main/cpp/PlaybackEngine.cpp
index f22a607..3be2455 100644
--- a/app/src/main/cpp/PlaybackEngine.cpp
+++ b/app/src/main/cpp/PlaybackEngine.cpp
@@ -209,7 +209,8 @@ void PlaybackEngine::musicFeedThread() {
 
     int* channel_map = (int*) malloc(num_ch_out * sizeof(int));
 
-    int loop_delay_ms = 1000 * buf_size_samples / playbackRate.load();
+    // initial guess, as long as we do not have a music file (otherwise we should divide by mp3->rate)
+    size_t loop_delay_us = 1000000 * buf_size_samples / playbackRate.load();
 
     int idebug = 0;
 
@@ -241,8 +242,8 @@ void PlaybackEngine::musicFeedThread() {
         // (is it like double-buffering implemented in 'stretcher'?)
 
         if (num_samples == 0) {
-            //LOGD("waiting for getSamplesRequired()");
-            std::this_thread::sleep_for(std::chrono::milliseconds(loop_delay_ms));
+            LOGD("waiting %d us for getSamplesRequired()", loop_delay_us);
+            std::this_thread::sleep_for(std::chrono::microseconds(loop_delay_us));
             continue;
         }
 
@@ -252,6 +253,7 @@ void PlaybackEngine::musicFeedThread() {
         }
 
         if (!haveMusicFile.load()) {
+            loop_delay_us = 1000000 * num_samples / playbackRate.load();
             if(idebug++ < 10) {
                 LOGI("feed %d silence samples", num_samples);
                 // 1024, 512, 512
@@ -263,6 +265,7 @@ void PlaybackEngine::musicFeedThread() {
         }
 
         if(idebug++ < 10) {
+            loop_delay_us = 1000000 * num_samples / musicFile->rate;
             LOGI("feed %d music samples", num_samples);
             // feed 1024 music samples
             // => stretcher is asking for 1024 = getSamplesRequired()
@@ -275,14 +278,17 @@ void PlaybackEngine::musicFeedThread() {
         musicFile->offset = 0; // unused here
         if (err != MPG123_OK && err != MPG123_DONE) {
             // error!
-            LOGE("mpg123_read() err=%d done=%d", err, done);
+            LOGE("error reading mp3 file: mpg123_read() err=%d done=%d", err, done);
             // next iteration will play silence
             closeMusicFile();
+            stretcher.setTimeRatio(1.0); // buffer size for playing silence is computed from 'playbackRate', so reset timeRatio
             continue;
         }
         if(err == MPG123_DONE) {
             // next iteration will play silence
+            LOGI("finished reading mp3 file (MPG123_DONE)");
             closeMusicFile();
+            stretcher.setTimeRatio(1.0); // buffer size for playing silence is computed from 'playbackRate', so reset timeRatio
             continue;
         }