Strip one frame from the file length to compensate the legacy off-by-…

…one issue
mixxxdj · Dec 30, 2022 · 30fe711 · 30fe711
1 parent 96a0156
commit 30fe711
Showing 1 changed file with 11 additions and 4 deletions.
diff --git a/src/sources/soundsourcemp3.cpp b/src/sources/soundsourcemp3.cpp
@@ -234,6 +234,7 @@ SoundSource::OpenResult SoundSourceMp3::tryOpen(
     // 7000 days of audio duration.
     quint64 sumBitrateFrames = 0; // nominator
     quint64 cntBitrateFrames = 0; // denominator
+    long madFrameLength = 0;
 
     mad_header madHeader;
     mad_header_init(&madHeader);
@@ -264,7 +265,7 @@ SoundSource::OpenResult SoundSourceMp3::tryOpen(
         static_assert(MAD_UNITS_8000_HZ == 8000);
         const mad_units madUnits = static_cast<mad_units>(madSampleRate);
 
-        const long madFrameLength = mad_timer_count(madHeader.duration, madUnits);
+        madFrameLength = mad_timer_count(madHeader.duration, madUnits);
         if (0 >= madFrameLength) {
             kLogger.warning() << "Skipping MP3 frame with invalid length"
                               << madFrameLength
@@ -386,7 +387,11 @@ SoundSource::OpenResult SoundSourceMp3::tryOpen(
         return OpenResult::Failed;
     }
     initSampleRateOnce(getSampleRateByIndex(mostCommonSampleRateIndex));
-    initFrameIndexRangeOnce(IndexRange::forward(0, m_curFrameIndex));
+
+    // Because of an off-by-one issue we need to short the file by one frame.
+    // See comments in restartDecoding()
+    DEBUG_ASSERT(m_curFrameIndex - madFrameLength == m_seekFrameList.back().frameIndex);
+    initFrameIndexRangeOnce(IndexRange::forward(0, m_seekFrameList.back().frameIndex));
 
     // Calculate average bitrate values
     DEBUG_ASSERT(m_seekFrameList.size() > 0); // see above
@@ -398,8 +403,10 @@ SoundSource::OpenResult SoundSourceMp3::tryOpen(
         kLogger.warning() << "Bitrate cannot be calculated from headers";
     }
 
-    // Terminate m_seekFrameList
-    addSeekFrame(m_curFrameIndex, nullptr);
+    // Terminate m_seekFrameList by removing the last frame.
+    // This is not needed because it would decode data past the last frame
+    // due to the legacy off-by-one issue
+    m_seekFrameList.back().pInputData = nullptr;
     DEBUG_ASSERT(m_seekFrameList.back().frameIndex == frameIndexMax());
 
     // Restart decoding at the beginning of the audio stream