Merged revision(s) 20538 from trunk/OpenMPT:

[Mod] M15: The heuristics in r20524 were a bit too loose, also identifying some GMC files as SoundTracker modules. Tighten the song title check again to previous values, but ignore it if a sufficent amount of sample headers has "real-looking" sample names (starting with a disk name like st-01:...).
........


git-svn-id: https://source.openmpt.org/svn/openmpt/branches/OpenMPT-1.30@20540 56274372-70c3-4bfc-bfc3-4c3a0b034d27

soundlib/Load_mod.cpp

@@ -324,6 +324,11 @@ struct MODSampleHeader
  + ((loopStart > length * 2) ? 1 : 0);
  }
 
+ bool HasDiskName() const
+ {
+ return (!memcmp(name, "st-", 3) || !memcmp(name, "ST-", 3)) && name[5] == ':';
+ }
+
  // Suggested threshold for rejecting invalid files based on cumulated score returned by GetInvalidByteScore
  static constexpr uint32 INVALID_BYTE_THRESHOLD = 40;
 
@@ -1370,15 +1375,13 @@ static bool ValidateHeader(const M15FileHeaders &fileHeaders)
  // However, there are quite a few SoundTracker modules in the wild with random
  // characters. To still be able to distguish them from other formats, we just reject
  // files with *too* many bogus characters. Arbitrary threshold: 48 bogus characters in total
- // or more than 11 invalid characters just in the title alone (just enough to make scramble_2.mod load).
- uint32 invalidChars = CountInvalidChars(fileHeaders.songname);
- if(invalidChars > 11)
- {
- return false;
- }
+ // or more than 5 invalid characters just in the title alone
+ uint32 invalidCharsInTitle = CountInvalidChars(fileHeaders.songname);
+ uint32 invalidChars = invalidCharsInTitle;
 
  SmpLength totalSampleLen = 0;
  uint8 allVolumes = 0;
+ uint8 diskNameCount = 0;
 
  for(SAMPLEINDEX smp = 0; smp < 15; smp++)
  {
@@ -1389,6 +1392,8 @@ static bool ValidateHeader(const M15FileHeaders &fileHeaders)
  // schmokk.mod has a non-zero value here but it should not be treated as finetune
  if(sampleHeader.finetune != 0)
  invalidChars += 16;
+ if(sampleHeader.HasDiskName())
+ diskNameCount++;
 
  // Sanity checks - invalid character count adjusted for ata.mod (MD5 937b79b54026fa73a1a4d3597c26eace, SHA1 3322ca62258adb9e0ae8e9afe6e0c29d39add874)
  if(invalidChars > 48
@@ -1402,6 +1407,12 @@ static bool ValidateHeader(const M15FileHeaders &fileHeaders)
  allVolumes |= sampleHeader.volume;
  }
 
+ // scramble_2.mod has a lot of garbage in the song title, but it has lots of sample names starting with st-01, so we consider those to be more important than the garbage bytes.
+ if(invalidCharsInTitle > 5 && diskNameCount < 4)
+ {
+ return false;
+ }
+
  // Reject any files with no (or only silent) samples at all, as this might just be a random binary file (e.g. ID3 tags with tons of padding)
  if(totalSampleLen == 0 || allVolumes == 0)
  {
@@ -1507,7 +1518,7 @@ bool CSoundFile::ReadM15(FileReader &file, ModLoadingFlags loadFlags)
 
  totalSampleLen += mptSmp.nLength;
 
- if(m_szNames[smp][0] && ((memcmp(m_szNames[smp].buf, "st-", 3) && memcmp(m_szNames[smp].buf, "ST-", 3)) || m_szNames[smp][5] != ':'))
+ if(m_szNames[smp][0] && sampleHeader.HasDiskName())
  {
  // Ultimate Soundtracker 1.8 and D.O.C. SoundTracker IX always have sample names containing disk names.
  hasDiskNames = false;