This section documents various codes used in the file format; handler codes (that declare track types) and group types (as used in the AVC specification) in particular.

Code	Abstract	Type	Defined in/by
3gag	Text track3GPP PSS Annex G video buffer parameters	group	3GPP
alst	Alternative startup sequence	group	ISO
avcb	AVC HRD parameters	group	3GPP
avll	AVC layer description group	group	AVC
avss	AVC Sub-sequence group	group	AVC
dtrt	SVC decode re-timing	group	AVC
mvif	MVC Scalability Information	group	AVC
rash	Rate share	group	ISO
roll	Pre/Post roll group	group	AVC, ISO
scif	SVC Scalability Information	group	AVC
scnm	AVC/SVC/MVC map groups	group	AVC
vipr	View priority	group	AVC
3gsd	3GPP Scene Description	handler	3GPP
ID32	ID3 version 2 meta-data handler (meta box)	handler	inline
auxv	Auxiliary video	handler	ISO
cpad	CPCM Auxiliary Metadata	handler	DVB
crsm	ClockReferenceStream	handler	MPEG-4
dmbd	DVB Mandatory Metadata	handler	DVB
dtva	TV-Anytime Metadata, according to DVB specifications	handler	DVB
fdsm	Font data streams (defined in part MPEG-4 part 18)	handler	MPEG-4
gesm	General MPEG-4 systems streams (without specific handler)	handler	see (1) below
hint	Hint track	handler	ISO
hpix	Hipix Rich Picture Format	handler	HIPIX
ipdc	DVB IPDC ESG Metadata	handler	DVB
ipsm	IPMP Stream	handler	MPEG-4
m7sm	MPEG7Stream	handler	MPEG-4
meta	Metadata	handler	ISO
mjsm	MPEG-J Stream	handler	MPEG-4
mp21	MPEG-21 Digital item	handler	MPEG-21
ocsm	ObjectContentInfoStream	handler	MPEG-4
odsm	ObjectDescriptorStream	handler	MPEG-4
sdsm	SceneDescriptionStream	handler	MPEG-4
skmm	Key Management Messages	handler	DVB
smhr	Samsung Video Metadata Handler	handler	Samsung
soun	Audio track	handler	ISO
subt	Subtitle track handler	handler	DECE
text	Text track	handler	3GPP
tmcd	Timecode Track	handler	Apple
uri$20	URI identified metadata	handler	DVB
vide	Video track	handler	ISO
fdel	File delivery reference	item ref.	ISO
iloc	Item data location	item ref.	ISO
cenc	Common Encryption	protection scheme	ISO-CENC
cpcm	CPCM (DVB BlueBook A094) protected content	protection scheme	DVB
odkm	OMA DRM KMS protection scheme	protection scheme	OMA DRM 2.0
bitr	Track differs in bitrate	track sel.	ISO
cdec	Track differs by codec type in the Sample Entry	track sel.	ISO
cgsc	The track can be coarse-grain scaled.	track sel.	ISO
fgsc	The track can be fine-grain scaled.	track sel.	ISO
frar	Track differs in frame rate	track sel.	ISO
mela	Track differs in language	track sel.	ISO
mpsz	Track differs in the maximum RTP Packet size	track sel.	ISO
mtyp	Track differs in media type (handler type)	track sel.	ISO
resc	The track can be region-of-interest scaled.	track sel.	ISO
scsz	Track differs in width and/or height	track sel.	ISO
spsc	The track can be spatially scaled.	track sel.	ISO
tesc	The track can be temporally scaled.	track sel.	ISO

1. There only exists a defined set of handler code-points in MP4 file format allowing declaration of most known MPEG-4 Systems streams. However there is no provision for private MPEG-4 streams, which may be used by the file creator. This will likely push the file creator into using one of the defined handler types, which is wrong and may corrupt processing by some file readers. This is a generic handler type to indicate that the media is an MPEG-4 systems stream, without further details on the stream type itself. The associated sample descriptions must still remain the same, i.e. "mp4s" as used with all MPEG-4 systems streams.