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Bug 327

Summary: SDL_BuildAudioCVT add useless endianness conversion in some cases
Product: SDL Reporter: Patrice Mandin <patmandin>
Component: audioAssignee: Ryan C. Gordon <icculus>
Status: RESOLVED FIXED QA Contact: Sam Lantinga <slouken>
Severity: normal    
Priority: P2    
Version: 1.2.9   
Hardware: All   
OS: All   

Description Patrice Mandin 2006-09-14 17:50:45 UTC 
Marked for 1.2.9, but still present in 1.2.x-svn, maybe fixed in 1.3 due to heavy changes.

When I build an audio conversion from 16 bits big endian (AUDIO_S16MSB) to 8 bits (AUDIO_S8), SDL adds a useless (and thus buggy for the end result) endianness conversion (the first filter added).

It happens because AUDIO_S16MSB = 0x1010 and AUDIO_S8 = 0x0008, and the masked values with 0x1000 fails in this case, whereas it is not a problem for AUDIO_S16LSB = 0x0010.

Shouldn't the endianness filter be present only when both formats (src and dest) are 16bits? Or are there other cases where this conversion should happen?
Comment 1 Ryan C. Gordon 2006-09-14 19:34:10 UTC 
This is definitely fixed in 1.3, since the datatype conversion code is completely rewritten, but I'll look at this for 1.2.

--ryan.
Comment 2 Patrice Mandin 2006-09-15 16:43:42 UTC 
This small check fixed the problem for me. It just checks both src and dst are 16bits to convert endianness. I will commit it if there are no problems.

@@ -1374,12 +1375,14 @@

        /* First filter:  Endian conversion from src to dst */
        if ( (src_format & 0x1000) != (dst_format & 0x1000)
-            && ((src_format & 0xff) != 8) ) {
+            && ((src_format & 0xff) == 16) && ((dst_format & 0xff) == 16)) {
                cvt->filters[cvt->filter_index++] = SDL_ConvertEndian;
        }
Comment 3 Ryan C. Gordon 2006-09-15 17:55:17 UTC 
Go ahead.

--ryan.