M4A restore original decoder

Author: pschatzmann

src/AudioTools/AudioCodecs/ContainerM4A.h

@@ -768,12 +768,16 @@ class ContainerM4A : public ContainerDecoder {
   // write the result to the decoder or to the final output
   size_t writeResult(uint8_t* data, size_t len) {
     // if we have a decoder we only decode the supported type
+    const char* original_mime = p_decoder->selectedMime();
     if (p_decoder != nullptr) {
       if (!p_decoder->selectDecoder(mime())) {
         LOGE("Unsupported mime type %s", mime());
         return 0;
       }
-      return p_decoder->write(data, len);
+      size_t result = p_decoder->write(data, len);
+      // restore original decoder
+      p_decoder->selectDecoder(original_mime);
+      return result;
     }
     // No decoder, just return any result
     return p_print->write(data, len);

src/AudioTools/AudioCodecs/MultiDecoder.h

@@ -72,6 +72,7 @@ class MultiDecoder : public AudioDecoder {
   /// automatically from the determined mime type
   bool selectDecoder(const char* mime) {
     bool result = false;
+    if (mime = nullptr) return false;
     // do nothing if no change
     if (StrView(mime).equals(actual_decoder.mime)) {
       is_first = false;
@@ -81,6 +82,7 @@ class MultiDecoder : public AudioDecoder {
     end();
 
     // find the corresponding decoder
+    selected_mime = nullptr;
     for (int j = 0; j < decoders.size(); j++) {
       DecoderInfo info = decoders[j];
       if (StrView(info.mime).equals(mime)) {
@@ -93,12 +95,17 @@ class MultiDecoder : public AudioDecoder {
         }
         actual_decoder.decoder->begin();
         result = true;
+        selected_mime = mime;
       }
     }
     is_first = false;
     return result;
   }
 
+  const char* selectedMime() {
+    return selected_mime;
+  }
+
   size_t write(const uint8_t* data, size_t len) override {
     if (is_first) {
       const char* mime = nullptr;
@@ -150,6 +157,7 @@ class MultiDecoder : public AudioDecoder {
   CodecNOP nop;
   AbstractURLStream* p_url_stream = nullptr;
   bool is_first = true;
+  const char* selected_mime = nullptr;
 };
 
 }  // namespace audio_tools

src/AudioTools/CoreAudio/AudioMetaData/MimeDetector.h

@@ -28,8 +28,8 @@ class MimeDetector {
     setCheck("video/MP2T", checkMP2T);
     setCheck("audio/prs.sid", checkSID);
     setCheck("audio/mpeg", checkMP3Ext);
-    setCheck("audio/aac", checkAACExt);
     setCheck("audio/m4a", checkM4A);
+    setCheck("audio/aac", checkAACExt);
   }
 
   bool begin() {