SWORD1: Improve speech endianess detection in mac version

Because of the way the speech is compressed with duplicate samples
being stored with a negative size and a single value, when reading the
data with the wrong endianess we can end up with a lot of duplicate
samples which biased the result with the way the old heuristic was
coded. Hopefully this change to skip duplicate samples will make it
more robust.

1 files changed, 20 insertions, 13 deletions

diff --git a/engines/sword1/sound.cpp b/engines/sword1/sound.cpp
index ddde7f4235..fbe14aae27 100644
--- a/engines/sword1/sound.cpp
+++ b/engines/sword1/sound.cpp
@@ -126,27 +126,34 @@ void Sound::checkSpeechFileEndianness() {
 	if (sampleSize) {
 		uint32 size;
 		// Compute average of difference between two consecutive samples for both BE and LE
+		// The way uncompressSpeech works we may get un incorrect number of identical consecutive samples
+		// when using the wrong endianess. To avoid biasing the result we this we skip all duplicate values.
 		_bigEndianSpeech = false;
 		int16 *data = uncompressSpeech(index + _cowHeaderSize, sampleSize, &size);
 		if (data) {
-			if (size > 4000)
-				size = 2000;
-			else
-				size /= 2;
+			uint32 max_cpt = size > 2000 ? 2000 : size;
 			double le_diff_sum = 0.;
-			for (uint32 i = 1; i < size; ++i)
-				le_diff_sum += fabs((double)(data[i] - data[i - 1]));
+			int le_cpt = 0;
+			for (uint32 i = 1; i < size && le_cpt < max_cpt; ++i) {
+				if (data[i] != data[i-1]) {
+					le_diff_sum += fabs((double)(data[i] - data[i - 1]));
+					++le_cpt;
+				}
+			}
+			le_diff_sum /= le_cpt;
 			delete[] data;
 			_bigEndianSpeech = true;
 			data = uncompressSpeech(index + _cowHeaderSize, sampleSize, &size);
 			if (data) {
-				if (size > 4000)
-					size = 2000;
-				else
-					size /= 2;
 				double be_diff_sum = 0.;
-				for (uint32 i = 1; i < size; ++i)
-					be_diff_sum += fabs((double)(data[i] - data[i - 1]));
+				int be_cpt = 0;
+				for (uint32 i = 1; i < size && be_cpt < le_cpt; ++i) {
+					if (data[i] != data[i-1]) {
+						be_diff_sum += fabs((double)(data[i] - data[i - 1]));
+						++be_cpt;
+					}
+				}
+				be_diff_sum /= be_cpt;
 				delete [] data;
 				// Set the big endian flag
 				_bigEndianSpeech = (be_diff_sum < le_diff_sum);
@@ -154,7 +161,7 @@ void Sound::checkSpeechFileEndianness() {
 					debug(6, "Mac version: using big endian speech file");
 				else
 					debug(6, "Mac version: using little endian speech file");
-				debug(8, "Speech endianness heuristic: average = %f for BE and %f for LE, computed on %d samples)", be_diff_sum / (size - 1), le_diff_sum / (size - 1), size);
+				debug(8, "Speech endianness heuristic: average = %f for BE (%d samples) and %f for LE (%d samples)", be_diff_sum, be_cpt, le_diff_sum, le_cpt);
 			} else
 				_bigEndianSpeech = false;
 		}