Fix CD audio issue with Monkey Island

CHANGELOG

@@ -1,5 +1,7 @@
 0.83.8
-  - 
+  - Fixed Monkey Island CD audio issue with the game
+    The Secret of Monkey Island when talking to pirate
+    in the Scumm Bar. Fix logic per kcgen. (Wengier)
 0.83.7
   - The primary DOSBox-X Wiki is now located at the
     URL: https://dosbox-x.com/wiki (Wengier)

src/dos/cdrom.h

@@ -227,7 +227,9 @@ class CDROM_Interface_Image : public CDROM_Interface
 		virtual uint32_t   getRate() = 0;
 		virtual uint8_t    getChannels() = 0;
 		virtual int      getLength() = 0;
+		virtual void setAudioPosition(uint32_t pos) = 0;
 		const uint16_t chunkSize = 0;
+		uint32_t audio_pos = UINT32_MAX; // last position when playing audio
 	};
 
     //! \brief Binary file reader for the image
@@ -247,6 +249,7 @@ class CDROM_Interface_Image : public CDROM_Interface
 		uint32_t          getRate() { return 44100; }
 		uint8_t           getChannels() { return 2; }
 		int             getLength();
+		void setAudioPosition(uint32_t pos) { audio_pos = pos; }
 	private:
 		std::ifstream   *file;
 	};
@@ -267,10 +270,9 @@ class CDROM_Interface_Image : public CDROM_Interface
 		uint32_t          getRate();
 		uint8_t           getChannels();
 		int             getLength();
+        void setAudioPosition(uint32_t pos) {}
 	private:
 		Sound_Sample    *sample = nullptr;
-		// ensure the first seek isn't cached by starting with an impossibly-large position
-		uint32_t        track_pos = (std::numeric_limits<uint32_t>::max)();
 	};
 
 public:

src/dos/cdrom_image.cpp

@@ -102,9 +102,10 @@ CDROM_Interface_Image::BinaryFile::~BinaryFile()
 	file = nullptr;
 }
 
-bool CDROM_Interface_Image::BinaryFile::read(uint8_t *buffer, int seek, int count)
+bool CDROM_Interface_Image::BinaryFile::read(uint8_t *buffer, int offset, int count)
 {
-	file->seekg(seek, ios::beg);
+    if (!seek(offset)) return false;
+	file->seekg(offset, ios::beg);
 	file->read((char*)buffer, count);
 	return !(file->fail());
 }
@@ -129,14 +130,21 @@ uint16_t CDROM_Interface_Image::BinaryFile::getEndian()
 
 bool CDROM_Interface_Image::BinaryFile::seek(uint32_t offset)
 {
+	if (static_cast<uint32_t>(file->tellg()) == offset)
+		return true;
 	file->seekg(offset, ios::beg);
 	return !file->fail();
 }
 
 uint16_t CDROM_Interface_Image::BinaryFile::decode(uint8_t *buffer)
 {
+    if (static_cast<uint32_t>(file->tellg()) != audio_pos)
+		if (!seek(audio_pos)) return 0;
+
 	file->read((char*)buffer, chunkSize);
-	return (uint16_t)file->gcount();
+    const uint16_t bytes_read = (uint16_t)file->gcount();
+    audio_pos += bytes_read;
+	return bytes_read;
 }
 
 CDROM_Interface_Image::AudioFile::AudioFile(const char *filename, bool &error)
@@ -182,8 +190,16 @@ bool CDROM_Interface_Image::AudioFile::seek(uint32_t offset)
 	const auto begin = std::chrono::steady_clock::now();
 	#endif
 
+	if (audio_pos == offset) {
+#ifdef DEBUG
+		LOG_MSG("CDROM: seek to %u avoided with position-tracking", offset);
+#endif
+		return true;
+    }
+
 	// Convert the byte-offset to a time offset (milliseconds)
 	const bool result = Sound_Seek(sample, lround(offset/176.4f));
+	audio_pos = result ? offset : UINT32_MAX;
 
 	#ifdef DEBUG
 	const auto end = std::chrono::steady_clock::now();
@@ -196,6 +212,7 @@ bool CDROM_Interface_Image::AudioFile::seek(uint32_t offset)
 uint16_t CDROM_Interface_Image::AudioFile::decode(uint8_t *buffer)
 {
 	const uint16_t bytes = Sound_Decode(sample);
+    audio_pos += bytes;
 	memcpy(buffer, sample->buffer, bytes);
 	return bytes;
 }
@@ -423,6 +440,7 @@ bool CDROM_Interface_Image::PlayAudioSector(unsigned long start, unsigned long l
 
 		// only initialize the player elements if our track is playable
 		if (is_playable) {
+            trackFile->setAudioPosition(offset);
 			const uint8_t channels = trackFile->getChannels();
 			const uint32_t rate = trackFile->getRate();