从sdp中的profile-level-id识别h264配置文件和级别? [英] Identify h264 profile and level from profile-level-id in sdp?
问题描述
在SIP视频通话中，视频流的接收者以其解码器的功能进行响应.
In a SIP video call, the receiver of the video stream respond with the capabilities of its decoder.
定义为profile-level-id的参数.这是profile-level-id参数的示例值:428014
The parameter which defines that is the profile-level-id. Here is an example value of the profile-level-id parameter: 428014
RFC 6184将其定义为
RFC 6184 defined that as
以下内容的base16 [7](十六进制)表示形式 在序列参数集NAL单元中指定了三个字节 在 1 中:1)profile_idc，2)在此引用的字节作为 profile-iop，由constraint_set0_flag的值组成， constraint_set1_flag，constraint_set2_flag， constraint_set3_flag，constraint_set4_flag， Constraint_set5_flag和reserved_zero_2位(以bit- 从最高有效位开始的有效顺序，以及 3)level_idc.
A base16 [7] (hexadecimal) representation of the following three bytes in the sequence parameter set NAL unit is specified in 1: 1) profile_idc, 2) a byte herein referred to as profile-iop, composed of the values of constraint_set0_flag, constraint_set1_flag, constraint_set2_flag, constraint_set3_flag, constraint_set4_flag, constraint_set5_flag, and reserved_zero_2bits in bit- significance order, starting from the most-significant bit, and 3) level_idc.
因此，可以从示例值中识别出以下参数:
According to that, the following parameters from the example value can be identified:
- profile_idc 42
- profile-iop 82
- level-idc 14
如何将这些数字与配置文件和<为h264定义的href ="http://en.wikipedia.org/wiki/H.264/MPEG-4_AVC#Levels" rel ="noreferrer">级别?
How to relate those numbers to the profiles and levels defined for h264?
推荐答案
For such things you should read actual H.264 spec not Wikipedia. Using it you can parse your example as
- profile_idc 0x42 == 66，所以它是基准配置文件
- profile-iop 0x80均值constraint_set0_flag = 1(因此它是受约束的基线"配置文件)，其他为0
- level-idc 0x14 == 20，所以它是2.0级
因此结果是受约束的基线"配置文件为2.0级
So result is Constrained Baseline profile Level 2.0
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