修复sdl音频重采样内存越界的bug以及修复重采样爆音bug

player/AudioSRC.cpp

@@ -51,29 +51,37 @@ int AudioSRC::getPCMData(char *buf, int size) {
         return _delegate->getPCMData(buf, size);
     }
 
-    if ((int)(size / _audio_cvt.len_ratio) != _origin_size) {
-        _origin_size = size / _audio_cvt.len_ratio;
-        _origin_buf.reset(new char[(std::max)(_origin_size, size)], [](char *ptr) {
+    //对应的未转换前pcm的长度
+    auto original_size = (int) (size / _audio_cvt.len_ratio);
+    if (original_size % 4 != 0) {
+        //必须为4byte的整数(双通道16bit一个采样就4个字节)
+        original_size = 4 * (original_size / 4) + 4;
+    }
+
+    //需要准备这么长的buf用于重采样
+    if ((int) (original_size * _audio_cvt.len_mult) != _buf_size) {
+        _buf_size = original_size * _audio_cvt.len_mult;
+        _buf.reset(new char[_buf_size], [](char *ptr) {
             delete[] ptr;
         });
-        InfoL << "origin pcm buffer size is:" << _origin_size << ", target pcm buffer size is:" << size;
+        InfoL << "origin pcm buffer size is:" << original_size << ", target pcm buffer size is:" << size;
     }
 
-    auto origin_size = _delegate->getPCMData(_origin_buf.get(), _origin_size);
+    auto origin_size = _delegate->getPCMData(_buf.get(), original_size );
     if (!origin_size) {
         //获取数据失败
         TraceL << "get empty pcm data";
         return 0;
     }
 
-    _audio_cvt.buf = (Uint8 *) _origin_buf.get();
+    _audio_cvt.buf = (Uint8 *) _buf.get();
     _audio_cvt.len = origin_size;
     if (0 != SDL_ConvertAudio(&_audio_cvt)) {
         WarnL << "SDL_ConvertAudio failed!";
         _audio_cvt.len_cvt = 0;
     }
     if (_audio_cvt.len_cvt) {
-        _target_buf.append(_origin_buf.get(), _audio_cvt.len_cvt);
+        _target_buf.append(_buf.get(), _audio_cvt.len_cvt);
     }
     if (_target_buf.size() < size) {
         return 0;

player/AudioSRC.h

@@ -55,8 +55,8 @@ public:
 
 private:
     bool _enabled = true;
-    int _origin_size = 0;
-    std::shared_ptr<char> _origin_buf;
+    int _buf_size = 0;
+    std::shared_ptr<char> _buf;
     AudioSRCDelegate *_delegate = nullptr;
     BufferLikeString _target_buf;
     SDL_AudioCVT _audio_cvt;