mvhd的协议描述如下：
8.2.2.1 Definition
Box Type: ‘mvhd’
Container: Movie Box (‘moov’)
Mandatory: Yes
Quantity: Exactly one
This box defines overall information which is media‐independent, and relevant to the entire
presentation considered as a whole.
8.2.2.2 Syntax
aligned(8) class FullBox(unsigned int(32) boxtype, unsigned int(8) v, bit(24) f)
extends Box(boxtype) {
unsigned int(8) version = v;
bit(24) flags = f;
}
aligned(8) class MovieHeaderBox extends FullBox(‘mvhd’, version, 0) {
if (version==1) {
unsigned int(64) creation_time;
unsigned int(64) modification_time;
unsigned int(32) timescale;
unsigned int(64) duration;
} else { // version==0
unsigned int(32) creation_time;
unsigned int(32) modification_time;
unsigned int(32) timescale;
unsigned int(32) duration;
}
template int(32) rate = 0x00010000; // typically 1.0
template int(16) volume = 0x0100; // typically, full volume
const bit(16) reserved = 0;
const unsigned int(32)[2] reserved = 0;
template int(32)[9] matrix =
{ 0x00010000,0,0,0,0x00010000,0,0,0,0x40000000 };
// Unity matrix
bit(32)[6] pre_defined = 0;
unsigned int(32) next_track_ID;
}
我们主要从mvhd中获取文件的创建时间、时长等信息。
具体分析一个mvhd 如下：
依然采用上述文件：
00000540: 6a03 8000 0006 d46d 6f6f 7600 0000 6c6d j……moov…lm
00000550: 7668 6400 0000 0000 0000 0000 0000 0000 vhd………….
00000560: 0003 e800 0000 2800 0100 0001 0000 0000 ……(………
00000570: 0000 0000 0000 0000 0100 0000 0000 0000 …………….
00000580: 0000 0000 0000 0000 0100 0000 0000 0000 …………….
00000590: 0000 0000 0000 0040 0000 0000 0000 0000 …….@……..
000005a0: 0000 0000 0000 0000 0000 0000 0000 0000 …………….
000005b0: 0000 0000 0000 0400 0002 2874 7261 6b00 ……….(trak.
000005c0: 0000 5c74 6b68 6400 0000 0300 0000 0000 ..\tkhd………
000005d0: 0000 0000 0000 0100 0000 0000 0000 2800 …………..(.
00 0000 6c atom size 6c == 108
6d 76 68 64 mvhd
version 8 bit 00
flags 00 00 00
creation_time 00 00 00 00
modification_time 00 00 00 00
timescale 00 00 03 e8 == 1000 timescale 是1000
duration 00 0000 28 == 40ms 时长为40ms
rate == 00 01 00 00
volume 01 00
reserved 00 00
reserved 32*2 00 00 00 00 00 00 00 00
matrix 32*9
pre_defined 32*6
next_track_id 00 0000 04
MP4 FFmpeg movenc mvhd box 写入 解析