length,string

Video
4,"h263"	H.263
4,"mp4s"	MPEG-4 Part 2
4,"h264"	MPEG-4 Part 10/H.264


Audio
4,"vrbs"	Xiph.org Vorbis
4,"mp2 "	MP3
4,"mp3 "	MP2
4,"ac3 "	AC3
4,"aac "	AAC/MPEG-4 Part 3