Use threaded decoding in ffmpeg streaming.

Telegram/SourceFiles/core/utils.cpp

@@ -32,10 +32,6 @@ extern "C" {
 
 #include <QtNetwork/QSslSocket>
 
-#ifdef small
-#undef small
-#endif // small
-
 uint64 _SharedMemoryLocation[4] = { 0x00, 0x01, 0x02, 0x03 };
 
 // Base types compile-time check

Telegram/SourceFiles/ffmpeg/ffmpeg_utility.cpp

@@ -175,6 +175,7 @@ CodecPointer MakeCodecPointer(not_null<AVStream*> stream) {
 		return {};
 	}
 	av_codec_set_pkt_timebase(context, stream->time_base);
+	av_opt_set(context, "threads", "auto", 0);
 	av_opt_set_int(context, "refcounted_frames", 1, 0);
 
 	const auto codec = avcodec_find_decoder(context->codec_id);

Telegram/SourceFiles/stdafx.h

@@ -83,6 +83,14 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 #define __STDC_FORMAT_MACROS
 #endif // Q_OS_UNIX
 
+// Remove 'small' macro definition.
+#ifdef Q_OS_WIN
+#include <rpc.h>
+#ifdef small
+#undef small
+#endif // small
+#endif // Q_OS_WIN
+
 #include <array>
 #include <vector>
 #include <set>