【多媒体封装格式详解】---MP4【1】

MP4(MPEG-4 Part 14)是一种常见的多媒体容器格式，它是在“ISO/IEC 14496-14”标准文件中定义的。

1.最小组成单元 BOX

像FLV的tag、MKV的EBML、ASF文件中的 ASF object.mp4 是由一系列的box组成，他的最小组成单元就是box.

size;指明了整个box所占用的大小，包括header部分.

type;表示这个box的类型。(附表1)

largesize;如果box很大超过了uint32的最大数值，size就被设置为1，并用接下来的 largesize来存放大小。

2.mp4文件整体结构

mp4文件说白了就是一系列box组成，大box里面有小box。

接下来会深入到具体的box里面，来具体分析mp4格式

未完待续.....

附表1

Code	Abstract	Defined in/by
ainf	Asset information to identify, license and play
albm	Album title and track number (user-data)
auth	Media author name (user-data)
avcn	AVC NAL Unit Storage Box
bloc	Base location and purchase location for license acquisition
bpcc	Bits per component
buff	Buffering information
bxml	binary XML container
ccid	OMA DRM Content ID
cdef	type and ordering of the components within the codestream
clsf	Media classification (user-data)
cmap	mapping between a palette and codestream components
co64	64-bit chunk offset
colr	specifies the colourspace of the image
cprt	copyright etc. (user-data)
crhd	reserved for ClockReferenceStream header
cslg	composition to decode timeline mapping
ctts	(composition) time to sample
cvru	OMA DRM Cover URI
dcfD	Marlin DCF Duration, user-data atom type
dinf	data information box, container
dref	data reference box, declares source(s) of media data in track
dscp	Media description (user-data)
dsgd	DVB Sample Group Description Box
dstg	DVB Sample to Group Box
edts	edit list container
elst	an edit list
feci	FEC Informatiom
fecr	FEC Reservoir
fiin	FD Item Information
fire	File Reservoir
fpar	File Partition
free	free space
frma	original format box
ftyp	file type and compatibility	,
gitn	Group ID to name
gnre	Media genre (user-data)
grpi	OMA DRM Group ID
hdlr	handler, declares the media (handler) type
hmhd	hint media header, overall information (hint track only)
hpix	Hipix Rich Picture (user-data or meta-data)
icnu	OMA DRM Icon URI
ID32	ID3 version 2 container
idat	Item data
ihdr	Image Header
iinf	item information
iloc	item location
imif	IPMP Information box
infu	OMA DRM Info URL
iods	Object Descriptor container box
iphd	reserved for IPMP Stream header
ipmc	IPMP Control Box
ipro	item protection
iref	Item reference
jP$20$20	JPEG 2000 Signature
jp2c	JPEG 2000 contiguous codestream
jp2h	Header
jp2i	intellectual property information
kywd	Media keywords (user-data)
loci	Media location information (user-data)
lrcu	OMA DRM Lyrics URI
m7hd	reserved for MPEG7Stream header
mdat	media data container
mdhd	media header, overall information about the media
mdia	container for the media information in a track
mdri	Mutable DRM information
meco	additional metadata container
mehd	movie extends header box
mere	metabox relation
meta	Metadata container
mfhd	movie fragment header
mfra	Movie fragment random access
mfro	Movie fragment random access offset
minf	media information container
mjhd	reserved for MPEG-J Stream header
moof	movie fragment
moov	container for all the meta-data
mvcg	Multiview group
mvci	Multiview Information
mvex	movie extends box
mvhd	movie header, overall declarations
mvra	Multiview Relation Attribute
nmhd	Null media header, overall information (some tracks only)
ochd	reserved for ObjectContentInfoStream header
odaf	OMA DRM Access Unit Format
odda	OMA DRM Content Object
odhd	reserved for ObjectDescriptorStream header
odhe	OMA DRM Discrete Media Headers
odrb	OMA DRM Rights Object
odrm	OMA DRM Container
odtt	OMA DRM Transaction Tracking
ohdr	OMA DRM Common headers
padb	sample padding bits
paen	Partition Entry
pclr	palette which maps a single component in index space to a multiple- component image
pdin	Progressive download information
perf	Media performer name (user-data)
pitm	primary item reference
res$20	grid resolution
resc	grid resolution at which the image was captured
resd	default grid resolution at which the image should be displayed
rtng	Media rating (user-data)
sbgp	Sample to Group box
schi	scheme information box
schm	scheme type box
sdep	Sample dependency
sdhd	reserved for SceneDescriptionStream header
sdtp	Independent and Disposable Samples Box
sdvp	SD Profile Box
segr	file delivery session group
senc	Sample specific encryption data
sgpd	Sample group definition box
sidx	Segment Index Box
sinf	protection scheme information box
skip	free space
smhd	sound media header, overall information (sound track only)
srmb	System Renewability Message
srmc	System Renewability Message container
srpp	STRP Process
stbl	sample table box, container for the time/space map
stco	chunk offset, partial data-offset information
stdp	sample degradation priority
sthd	Subtitle Media Header Box
stsc	sample-to-chunk, partial data-offset information
stsd	sample descriptions (codec types, initialization etc.)
stsh	shadow sync sample table
stss	sync sample table (random access points)
stsz	sample sizes (framing)
stts	(decoding) time-to-sample
styp	Segment Type Box
stz2	compact sample sizes (framing)
subs	Sub-sample information
swtc	Multiview Group Relation
tfad	Track fragment adjustment box
tfhd	Track fragment header
tfma	Track fragment media adjustment box
tfra	Track fragment radom access
tibr	Tier Bit rate
tiri	Tier Information
titl	Media title (user-data)
tkhd	Track header, overall information about the track
traf	Track fragment
trak	container for an individual track or stream
tref	track reference container
trex	track extends defaults
trgr	Track grouping information
trik	Facilitates random access and trick play modes
trun	track fragment run
tsel	Track selection (user-data)
udta	user-data
uinf	a tool by which a vendor may provide access to additional information associated with a UUID
UITS	Unique Identifier Technology Solution
ulst	a list of UUID’s
url$20	a URL
uuid	user-extension box
vmhd	video media header, overall information (video track only)
vwdi	Multiview Scene Information
xml$20	a tool by which vendors can add XML formatted information
xml$20	XML container
yrrc	Year when media was recorded (user-data)

QuickTime Codes

Code	Abstract	Defined in/by
clip	Visual clipping region container
crgn	Visual clipping region definition
ctab	Track color-table
elng	Extended Language Tag
imap	Track input map definition
kmat	Compressed visual track matte
load	Track pre-load definitions
matt	Visual track matte for compositing
pnot	Preview container
wide	Expansion space reservation