This format extension is one of the Speex Audio formats. It is an open-source codec developed by Xiph.Org. Used for creating voice messages and transmitting voice over packet-based networks with a low level of security. It is an audio file with recorded voice messages that are packaged in an OGG file. Only certain media players can open it.

Convert from SPX
1	SPX To AAC
2	SPX To AC3
3	SPX To AIFF
4	SPX To AMR
5	SPX To AU
6	SPX To CAF
7	SPX To CDDA
8	SPX To DSS
9	SPX To DTS
10	SPX To FLAC
11	SPX To GSM
12	SPX To M4A
13	SPX To M4R
14	SPX To MP2
15	SPX To MP3
16	SPX To MP4
17	SPX To OGA
18	SPX To OGG
19	SPX To OPUS
20	SPX To SLN
21	SPX To TTA
22	SPX To VOC
23	SPX To W64
24	SPX To WAV
25	SPX To WMA
26	SPX To WV
27	SPX To AVI
28	SPX To MPEG
29	SPX To MOV
30	SPX To FLV

Convert to SPX
1	AAC To SPX
2	AC3 To SPX
3	AIFF To SPX
4	AMR To SPX
5	AU To SPX
6	CAF To SPX
7	CDDA To SPX
8	DSS To SPX
9	DTS To SPX
10	FLAC To SPX
11	GSM To SPX
12	M4A To SPX
13	M4R To SPX
14	MP2 To SPX
15	MP3 To SPX
16	MP4 To SPX
17	OGA To SPX
18	OGG To SPX
19	OPUS To SPX
20	SLN To SPX
21	TTA To SPX
22	VOC To SPX
23	W64 To SPX
24	WAV To SPX
25	WMA To SPX
26	WV To SPX
27	AVI To SPX
28	MPEG To SPX
29	MOV To SPX
30	FLV To SPX