some code cleanup

README.md

@@ -100,7 +100,7 @@ to print out usage information. As an example, the following command
 `exhale.exe 5 C:\Music\Input.wav C:\Music\Output.m4a`
 
 converts file Input.wav to file Output.m4a at roughly 128 kbit/s (if
-the input signal is two-channel stereo) and in xHE-AAC audio format.
+the input signal is 2-channel stereo) and in Extended HE-AAC format.
 Note that, when calling the exhale application with a path (such as,
 e.g., `bin/exhale` or `bin\exhale.exe`), but specifying the input or
 output file without a file path (e.g., `Input.wav`), those files are
@@ -124,7 +124,7 @@ the window content changed, on `Add New`. Then select `Custom` under
                       SBR is disabled, or a...g when SBR is enabled)
 - *Format is:* lossy
 - *Highest BPS mode supported:* 24 (or 32, doesn't matter much)
-- *Encoder name:* xHE-AAC (exhale)
+- *Encoder name:* Extended HE-AAC (exhale)
 - *Bitrate (kbps):* (depends on bit-rate mode, see Usage above)
 - *Settings:* CVBR mode # (where # equals that in *Parameters*)
 

include/version.h

@@ -15,5 +15,5 @@
 # define EXHALELIB_VERSION_MINOR "1"
 #endif
 #ifndef EXHALELIB_VERSION_BUGFIX
-# define EXHALELIB_VERSION_BUGFIX ".1" // "RC" or ".0", ".1", ...
+# define EXHALELIB_VERSION_BUGFIX ".2" // "RC" or ".0", ".1", ...
 #endif

src/lib/bitStreamWriter.cpp

@@ -657,7 +657,7 @@ unsigned BitStreamWriter::writeStereoCoreToolInfo (const CoreCoderData& elData,
 #if !RESTRICT_TO_AAC
   if (timeWarping)
   {
-    m_auBitStream.write (0, 1); // common_tw not needed in xHE-AAC
+    m_auBitStream.write (0, 1); // common_tw not needed in BL USAC
     bitCount++;
   } // tw_mdct
 #endif
@@ -852,9 +852,9 @@ unsigned BitStreamWriter::createAudioFrame (CoreCoderData** const elementData,
     return 0; // invalid arguments error
   }
 #ifndef NO_PREROLL_DATA
-  if (ipf) // save last AU for ext. data
+  if ((ipf == 2) || (ipf == 1 && (numElements > 1 || !noiseFilling[0]))) // previous AU
   {
-    bitCount = __min (65532, (uint32_t) m_auBitStream.stream.size ());
+    bitCount = __min (nSamplesInFrame << 2, (uint32_t) m_auBitStream.stream.size ());
     memcpy (tempBuffer, &m_auBitStream.stream.front (), bitCount);
   }
 #endif
@@ -868,9 +868,9 @@ unsigned BitStreamWriter::createAudioFrame (CoreCoderData** const elementData,
   m_auBitStream.write (ipf ? 1 : 0, 1); // UsacExtElement, usacExtElementPresent
   if (ipf)
   {
-    const uint16_t idxPreRollExt = (uint16_t) elementData[0]->elementType;
-    const bool lowRatePreRollExt = (ipf == 1 && numElements == 1 && idxPreRollExt < ID_USAC_LFE);
-    const unsigned payloadLength = (lowRatePreRollExt ? 8 + idxPreRollExt * 6 : bitCount) + 3; // in bytes!
+    const uint16_t idxPreRollExt = elementData[0]->elementType & 1;
+    const bool lowRatePreRollExt = (ipf == 1 && numElements == 1 && noiseFilling[0]);
+    const unsigned payloadLength = (lowRatePreRollExt ? (8 + idxPreRollExt * 6) >> (sbrRatioShiftValue > 0 ? 0 : 1) : bitCount) + 3; // in bytes!
 
     m_auBitStream.write (0, 1); // usacExtElementUseDefaultLength = 0 (variable)
     m_auBitStream.write (CLIP_UCHAR (payloadLength), 8);
@@ -882,12 +882,17 @@ unsigned BitStreamWriter::createAudioFrame (CoreCoderData** const elementData,
 
     if (lowRatePreRollExt)
     {
-      while (ci < payloadLength - 3) m_auBitStream.write (zeroAu[idxPreRollExt][ci++], 8);
-    }
-    else
-    {
-      while (ci < bitCount) m_auBitStream.write (tempBuffer[ci++], 8); // write last AU
+      bitCount = payloadLength - 3;
+      memcpy (tempBuffer, zeroAu[idxPreRollExt], bitCount);
+      if (elementData[0]->elementType < ID_USAC_LFE)  // correct window_sequence
+      {
+        const USAC_WSEQ wsPrev0 = elementData[0]->icsInfoPrev[0].windowSequence;
+        const uint8_t wsPreRoll = uint8_t (wsPrev0 == EIGHT_SHORT || wsPrev0 == STOP_START ? LONG_START : wsPrev0);
+        // SCE/CPE: window_sequence at byte index 2/0, left-shifted by value 2/0
+        tempBuffer[2 - 2 * idxPreRollExt] |= wsPreRoll << (2 - 2 * idxPreRollExt);
+      }
     }
+    while (ci < bitCount) m_auBitStream.write (tempBuffer[ci++], 8); // write AU
     ci = 0;
     bitCount = (payloadLength > 254 ? 26 : 10) + (payloadLength << 3); // for ext. bits
   }

src/lib/exhaleEnc.h

@@ -1,5 +1,5 @@
 /* exhaleEnc.h - header file for class providing Extended HE-AAC encoding capability
- * written by C. R. Helmrich, last modified in 2020 - see License.htm for legal notices
+ * written by C. R. Helmrich, last modified in 2021 - see License.htm for legal notices
  *
  * The copyright in this software is being made available under the exhale Copyright License
  * and comes with ABSOLUTELY NO WARRANTY. This software may be subject to other third-
@@ -56,7 +56,7 @@ typedef enum USAC_CCFL : short
   CCFL_1024  = 1024 // LC
 } USAC_CCFL;
 
-// overall xHE-AAC encoding class
+// overall BL USAC encoding class
 class ExhaleEncoder : public ExhaleEncAPI
 {
 private:

src/lib/quantization.h

@@ -27,7 +27,7 @@
 #define SFB_QUANT_OFFSET 0.405396 // 1 - 0.5^(3/4)
 #endif
 
-// class for xHE-AAC quantization
+// class for BL USAC quantization
 class SfbQuantizer
 {
 private: