MP3 detection: Detect AAC files by some known magic bytes, otherwise the audio backend might crash if it tried to play the format.

Author: florianessl

src/audio_decoder.cpp

@@ -50,6 +50,12 @@ class WMAUnsupportedFormatDecoder : public AudioDecoder {
 	int FillBuffer(uint8_t*, int) override { return -1; };
 };
 const char wma_magic[] = { (char)0x30, (char)0x26, (char)0xB2, (char)0x75 };
+const std::array<char[2], 4> aac_magics = { {
+	{ (char)0xFF, (char)0xF1 },
+	{ (char)0xFF, (char)0xF0 },
+	{ (char)0xFF, (char)0xF8 },
+	{ (char)0xFF, (char)0xF9 }
+}};
 
 std::unique_ptr<AudioDecoderBase> AudioDecoder::Create(Filesystem_Stream::InputStream& stream, bool resample) {
 	char magic[4] = { 0 };
@@ -141,6 +147,13 @@ std::unique_ptr<AudioDecoderBase> AudioDecoder::Create(Filesystem_Stream::InputS
 				return mp3dec;
 			}
 
+			bool is_aac = std::any_of(aac_magics.begin(), aac_magics.end(), [&](auto& mpeg4_magic) {
+				return memcmp(magic, mpeg4_magic, 2);
+			});
+			if (is_aac) {
+				return nullptr;
+			}
+
 			// Parsing MP3s seems to be the only reliable way to detect them
 			if (Mpg123Decoder::IsMp3(stream)) {
 				stream.clear();