Correcting errors and minor modifications

With this parameters "-vcodec", "copy", "-acodec", "copy" the output video was wrong(starting time was wrong and the video freezed after a few seconds)
But when i remove those the output video was exaclty like I want to

moviepy/video/io/ffmpeg_tools.py

@@ -30,13 +30,13 @@ def ffmpeg_extract_subclip(filename, t1, t2, targetname=None):
     name,ext = os.path.splitext(filename)
     if not targetname:
         T1, T2 = [int(1000*t) for t in [t1, t2]]
-        targetname = name+ "%sSUB%d_%d.%s"(name, T1, T2, ext)
+        targetname = "%sSUB%d_%d.%s"%(name, T1, T2, ext)
 
     cmd = [get_setting("FFMPEG_BINARY"),"-y",
       "-i", filename,
       "-ss", "%0.2f"%t1,
       "-t", "%0.2f"%(t2-t1),
-      "-vcodec", "copy", "-acodec", "copy", targetname]
+      targetname]
 
     subprocess_call(cmd)