Audio source decoding improvements.

- Streaming sources now also stream the file contents instead of loading it into memory, by default. Added a new stream type enum parameter to newSource ("file" or "memory").
- Audio file decoding now chooses the most appropriate decoder based on the file contents instead of the file extension.
- Videos now stream audio from the file instead of loading all of the video file into memory for use with audio decoding.

src/modules/sound/Decoder.cpp

@@ -29,13 +29,16 @@ namespace sound
 
 love::Type Decoder::type("Decoder", &Object::type);
 
-Decoder::Decoder(Data *data, int bufferSize)
-	: data(data)
+Decoder::Decoder(Stream *stream, int bufferSize)
+	: stream(stream)
 	, bufferSize(bufferSize)
 	, sampleRate(DEFAULT_SAMPLE_RATE)
 	, buffer(0)
 	, eof(false)
 {
+	if (!stream->isReadable() || !stream->isSeekable())
+		throw love::Exception("Decoder input stream must be readable and seekable.");
+
 	buffer = new char[bufferSize];
 }
 
@@ -65,5 +68,12 @@ bool Decoder::isFinished()
 	return eof;
 }
 
+STRINGMAP_CLASS_BEGIN(Decoder, Decoder::StreamSource, Decoder::STREAM_MAX_ENUM, streamSource)
+{
+	{ "memory", Decoder::STREAM_MEMORY },
+	{ "file",   Decoder::STREAM_FILE   },
+}
+STRINGMAP_CLASS_END(Decoder, Decoder::StreamSource, Decoder::STREAM_MAX_ENUM, streamSource)
+
 } // sound
 } // love