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PT	Encoding Name	Audio/Video (A/V)	Clock Rate (Hz)	Channels	Reference
0	PCMU	A	8000	1	[RFC3551]
1	Reserved
2	Reserved
3	GSM	A	8000	1	[RFC3551]
4	G723	A	8000	1	[Vineet_Kumar][RFC3551]
5	DVI4	A	8000	1	[RFC3551]
6	DVI4	A	16000	1	[RFC3551]
7	LPC	A	8000	1	[RFC3551]
8	PCMA	A	8000	1	[RFC3551]
9	G722	A	8000	1	[RFC3551]
10	L16	A	44100	2	[RFC3551]
11	L16	A	44100	1	[RFC3551]
12	QCELP	A	8000	1	[RFC3551]
13	CN	A	8000	1	[RFC3389]
14	MPA	A	90000		[RFC3551][RFC2250]
15	G728	A	8000	1	[RFC3551]
16	DVI4	A	11025	1	[Joseph_Di_Pol]
17	DVI4	A	22050	1	[Joseph_Di_Pol]
18	G729	A	8000	1	[RFC3551]
19	Reserved	A
20	Unassigned	A
21	Unassigned	A
22	Unassigned	A
23	Unassigned	A
24	Unassigned	V
25	CelB	V	90000		[RFC2029]
26	JPEG	V	90000		[RFC2435]
27	Unassigned	V
28	nv	V	90000		[RFC3551]
29	Unassigned	V
30	Unassigned	V
31	H261	V	90000		[RFC4587]
32	MPV	V	90000		[RFC2250]
33	MP2T	AV	90000		[RFC2250]
34	H263	V	90000		[Chunrong_Zhu]
35-71	Unassigned	?
72-76	Reserved for RTCP conflict avoidance				[RFC3551]
77-95	Unassigned	?
96-127	dynamic	?			[RFC3551]

除了上表中明确指定PT值的负载类型，还有些负载类型由于诞生的较晚，没有具体的PT值，只能使用动态（dynamic）PT值，即96到127，这就是为什么大家普遍指定H264的PT值为96。下表中列出了没有具体PT值的负载类型。

Media Type	Subtype	Clock Rate (Hz)	Channels (audio)	Reference
application	1d-interleaved-parityfec			[RFC6015]
application	h224	4800		[RFC4573]
application	parityfec			[RFC3009]
application	raptorfec			[RFC6682]
application	rtx			[RFC4588]
application	smpte336m			[RFC6597]
application	ulpfec			[RFC5109]
audio	1d-interleaved-parityfec			[RFC6015]
audio	32kadpcm	8000		[RFC3802][RFC2421]
audio	ac3			[RFC4184]
audio	AMR	8000		[RFC4867][RFC3267]
audio	AMR-WB	16000		[RFC4867][RFC3267]
audio	amr-wb+	72000		[RFC4352]
audio	atrac3	44100		[RFC5584]
audio	ATRAC-ADVANCED-LOSSLESS			[RFC5584]
audio	atrac-x			[RFC5584]
audio	BV16	8000		[RFC4298]
audio	BV32	16000		[RFC4298]
audio	clearmode	8000	1	[RFC4040]
audio	CN			[RFC3389]
audio	DAT12			[RFC3190]
audio	dsr-es201108			[RFC3557]
audio	dsr-es202050	8000		[RFC4060]
audio	dsr-es202211	8000		[RFC4060]
audio	dsr-es202212	8000		[RFC4060]
audio	DV			[RFC6469]
audio	eac3			[RFC4598]
audio	EVRC	8000	1	[RFC4788]
audio	EVRC0	8000	1	[RFC4788]
audio	EVRC1	8000	1	[RFC4788]
audio	EVRCB	8000	1	[RFC4788]
audio	EVRCB0	8000	1	[RFC4788]
audio	EVRCB1	8000	1	[RFC4788]
audio	EVRCWB			[RFC5188]
audio	EVRCWB0			[RFC5188]
audio	EVRCWB1			[RFC5188]
audio	fwdred			[RFC6354]
audio	g719	48000		[RFC5404]
audio	G7221	16000	1	[RFC5577]
audio	G726-16	8000	1	[RFC3551][RFC4856]
audio	G726-24	8000	1	[RFC3551][RFC4856]
audio	G726-32	8000	1	[RFC3551][RFC4856]
audio	G726-40	8000	1	[RFC3551][RFC4856]
audio	G729D	8000	1	[RFC3551][RFC4856]
audio	G729E	8000	1	[RFC3551][RFC4856]
audio	GSM-EFR	8000	1	[RFC3551][RFC4856]
audio	L8			[RFC3551][RFC4856]
audio	raptorfec			[RFC6682]
audio	RED			[RFC2198][RFC3555]
audio	rtx			[RFC4588]
audio	VDVI		1	[RFC3551][RFC4856]
audio	L20			[RFC3190]
audio	L24			[RFC3190]
audio	MP4A-LATM			[RFC3016]
audio	mpa-robust	90000		[RFC5219]
audio	parityfec			[RFC5109]
audio	SMV	8000	1	[RFC3558]
audio	SMV0	8000	1	[RFC3558]
audio	t140c			[RFC4351]
audio	t38			[RFC4612]
audio	telephone-event			[RFC4733]
audio	tone			[RFC4733]
audio	DVI4			[RFC4856]
audio	G722			[RFC4856]
audio	G723			[RFC4856]
audio	G728			[RFC4856]
audio	G729			[RFC4856]
audio	GSM			[RFC4856]
audio	L16			[RFC4856]
audio	LPC			[RFC4856]
audio	PCMA			[RFC4856]
audio	PCMU			[RFC4856]
audio	G7291	16000		[RFC4749][RFC5459]
audio	GSM-HR-08	8000		[RFC5993]
audio	iLBC	8000		[RFC3952]
audio	ip-mr_v2.5	16000		[RFC6262]
audio	MPA	90000		[RFC3555]
audio	mpeg4-generic			[RFC3640][RFC5691][RFC6295]
audio	PCMA-WB	16000		[RFC5391]
audio	PCMU-WB	16000		[RFC5391]
audio	QCELP			[RFC3555]
audio	rtp-midi			[RFC6295]
audio	speex			[RFC5574]
audio	uemclip			[RFC5686]
audio	ulpfec			[RFC5109]
audio	VMR-WB	16000		[RFC4348][RFC4424]
audio	vorbis			[RFC5215]
audio	vorbis-config			[RFC5215]
text	1d-interleaved-parityfec			[RFC6015]
text	fwdred			[RFC6354]
text	parityfec			[RFC3009]
text	raptorfec			[RFC6682]
text	red	1000		[RFC4102]
text	rtx			[RFC4588]
text	t140	1000		[RFC4103]
text	ulpfec			[RFC5109]
video	BMPEG	90000		[RFC2343][RFC3555]
video	1d-interleaved-parityfec			[RFC6015]
video	3gpp-tt			[RFC4396]
video	BT656	90000		[RFC2431][RFC3555]
video	celB			[RFC3555]
video	DV	90000		[RFC6469]
video	H261			[RFC4587]
video	H263	90000		[RFC4628]
video	H263-1998	90000		[RFC4629]
video	H263-2000	90000		[RFC4629]
video	H264			[RFC6184]
video	H264-RCDO	90000		[RFC6185]
video	H264-SVC			[RFC6190]
video	JPEG			[RFC3555]
video	JPEG2000			[RFC5371]
video	MP1S	90000		[RFC2250][RFC3555]
video	MP2P	90000		[RFC2250][RFC3555]
video	MP2T			[RFC3555]
video	MP4V-ES	90000		[RFC3016]
video	mpeg4-generic			[RFC3640]
video	MPV			[RFC3555]
video	nv			[RFC4856]
video	parityfec			[RFC5109]
video	pointer	90000		[RFC2862]
video	raptorfec			[RFC6682]
video	raw	90000		[RFC4175]
video	rtx			[RFC4588]
video	SMPTE292M			[RFC3497]
video	ulpfec			[RFC5109]
video	vc1	90000		[RFC4425]

参考链接：https://www.ietf.org/assignments/rtp-parameters/rtp-parameters.xml