标签：orm fixed crc packet ons from ber 一个 dex
ADTS全称是(Audio Data Transport Stream)，是AAC的一种十分常见的传输格式。转载请注明来自：http://www.binkery.com/
ADTS内容及结构
一般情况下ADTS的头信息都是7个字节，分为2部分：
adts_fixed_header();
adts_variable_header();
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转载请注明来自：http://www.binkery.com/
syntax
adts_fixed_header(){
syncword; 12 bslbf
ID; 1 bslbf
layer;2 uimsbf
protection_absent;1 bslbf
profile;2 uimsbf
sampling_frequency_index;4 uimsbf
private_bit;1 bslbf
channel_configuration;3 uimsbf
original_copy;1 bslbf
home;1 bslbf
}
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syncword ：同步头 总是0xFFF, all bits must be 1，代表着一个ADTS帧的开始转载请注明来自：http://www.binkery.com/
ID：MPEG Version: 0 for MPEG-4, 1 for MPEG-2转载请注明来自：http://www.binkery.com/
Layer：always: ‘00‘转载请注明来自：http://www.binkery.com/
profile：表示使用哪个级别的AAC，有些芯片只支持AAC LC 。在MPEG-2 AAC中定义了3种：
0:Main profile
1:Low Complexity profile(LC)
2:Scalable sampling Rate Profile(SSR)
3:Reserved
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sampling_frequency_index：表示使用的采样率下标，通过这个下标在 Sampling Frequencies[ ]数组中查找得知采样率的值。
There are 13 supported frequencies:
0: 96000 Hz
1: 88200 Hz
2: 64000 Hz
3: 48000 Hz
4: 44100 Hz
5: 32000 Hz
6: 24000 Hz
7: 22050 Hz
8: 16000 Hz
9: 12000 Hz
10: 11025 Hz
11: 8000 Hz
12: 7350 Hz
13: Reserved
14: Reserved
15: frequency is written explictly
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channel_configuration: 表示声道数
0: Defined in AOT Specifc Config
1: 1 channel: front-center
2: 2 channels: front-left, front-right
3: 3 channels: front-center, front-left, front-right
4: 4 channels: front-center, front-left, front-right, back-center
5: 5 channels: front-center, front-left, front-right, back-left, back-right
6: 6 channels: front-center, front-left, front-right, back-left, back-right, LFE-channel
7: 8 channels: front-center, front-left, front-right, side-left, side-right, back-left, back-right, LFE-channel
8-15: Reserved转载请注明来自：http://www.binkery.com/
syntax
adts_variable_header(){
copyright_identiflaction_bit;1 bslbf
copyright_identification_start;1 bslbf
acc_frame_length;13 bslbf;
adts_buffer_fullness; 11 bslbf
number_of_raw_data_blocks_in_frame;2 uimsfb
}转载请注明来自：http://www.binkery.com/
frame_length : 一个ADTS帧的长度包括ADTS头和AAC原始流.转载请注明来自：http://www.binkery.com/
adts_buffer_fullness：0x7FF 说明是码率可变的码流转载请注明来自：http://www.binkery.com/
下面是来自一个国外网站的介绍。http://wiki.multimedia.cx/index.php?title=ADTS 个人觉得这个网站的这个表结构的说明更加的形象一些。很好理解。1byte = 8 bits ， 每个字段占用多少bits，各个字段的意义。转载请注明来自：http://www.binkery.com/
Audio Data Transport Stream (ADTS) is a format, used by MPEG TS or Shoutcast to stream audio, usually AAC.转载请注明来自：http://www.binkery.com/
Structure
AAAAAAAA AAAABCCD EEFFFFGH HHIJKLMM MMMMMMMM MMMOOOOO OOOOOOPP (QQQQQQQQ QQQQQQQQ)
Header consists of 7 or 9 bytes (without or with CRC).
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Letter Length (bits) Description
A 12 syncword 0xFFF, all bits must be 1
B 1 MPEG Version: 0 for MPEG-4, 1 for MPEG-2
C 2 Layer: always 0
D 1 protection absent, Warning, set to 1 if there is no CRC and 0 if there is CRC
E 2 profile, the MPEG-4 Audio Object Type minus 1
F 4 MPEG-4 Sampling Frequency Index (15 is forbidden)
G 1 private stream, set to 0 when encoding, ignore when decoding
H 3 MPEG-4 Channel Configuration (in the case of 0, the channel configuration is sent via an inband
PCE)
I 1 originality, set to 0 when encoding, ignore when decoding
J 1 home, set to 0 when encoding, ignore when decoding
K 1 copyrighted stream, set to 0 when encoding, ignore when decoding
L 1 copyright start, set to 0 when encoding, ignore when decoding
M 13 frame length, this value must include 7 or 9 bytes of header length: FrameLength =
(ProtectionAbsent == 1 ? 7 : 9) + size(AACFrame)
O 11 Buffer fullness
P 2 Number of AAC frames (RDBs) in ADTS frame minus 1, for maximum compatibility always use 1 AAC frame
per ADTS frame
Q 16 CRC if protection absent is 0
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Usage in MPEG-TS
ADTS packet must be a content of PES packet. Pack AAC data inside ADTS frame, than pack inside PES packet, then mux
by TS packetizer.转载请注明来自：http://www.binkery.com/
Usage in Shoutcast
ADTS frames goes one by one in TCP stream. Look for syncword, parse header and look for next syncword after.
from：http://www.binkery.com/
标签：orm fixed crc packet ons from ber 一个 dex
原文地址：http://www.cnblogs.com/lidabo/p/7267042.html
