AVC编码中的规格 ：High、Baseline、Main什么意思？还有High@L3.0、High@L4.0、High@L5.1等

咳咳，在这里首先要阐明所谓的AVC其实就是H.264标准，是由ITU-T和ISO/IEC组成的联合视频组（JVT，Joint Video Team）一起开发的，ITU-T给这个标准命名为H.264（以前叫做H.26L），而ISO/IEC称它为MPEG-4 高级视频编码（Advanced Video Coding，AVC），它定位于覆盖整个视频应用领域，包括：低码率的无线应用、标准清晰度和高清晰度的电视广播应用、Internet上的视频流应用，传输高清晰度的DVD视频以及应用于数码相机的高质量视频应用等等。
      AVC的规格分为三等，从低到高分别为：Baseline、Main、High。
             Baseline（最低Profile）级别支持I/P 帧，只支持无交错（Progressive，逐行扫描）和CAVLC（基于上下文自适应可变长编码），一般用于低阶或需要额外容错的应用，比如视频通话、手机视频等；
             Main（主要Profile）级别提供I/P/B 帧，支持无交错（Progressive）和交错（Interlaced，隔行扫描），同样提供对于CAVLC 和CABAC（熵编码） 的支持，用于主流消费类电子产品规格如低解码（相对而言）的mp4、便携的视频播放器、PSP和Ipod等；
             High（高端Profile，也叫FRExt）级别在Main的基础上增加了8x8 内部预测、自定义量化、无损视频编码和更多的YUV 格式（如4：4：4）用于广播及视频碟片存储（蓝光影片），高清电视的应用。

      AVC 的规格主要是针对兼容性的，不同的规格能在相同级别上的平台应用。
      至于Baseline@L x.x、Main@L x.x、High@L x.x形式则是在不同级别下的码流级别，数值越大码流就越大，更耗费资源。所以就码流而言High@L3.0<High@L4.0<High@L5.1。

Levels

As the term is used in the standard, a "level" is a specified set of constraints indicating a degree of required decoder performance for a profile. For example, a level of support within a profile will specify the maximum picture resolution, frame rate, and bit rate that a decoder may be capable of using. A decoder that conforms to a given level is required to be capable of decoding all bitstreams that are encoded for that level and for all lower levels.

Levels with maximum property valuesLevelMax decoding speedMax frame sizeMax video bit rate
for video coding layer (VCL)
kbit/sExamples for high resolution
@ highest frame rate
(max stored frames)Luma samples/sMacroblocks/sLuma samplesMacroblocksBaseline, Extended
and Main ProfilesHigh Profile1380,1601,48525,344996480128×96@30.9 (8)
176×144@15.0 (4)1b380,1601,48525,34499128160128×96@30.9 (8)
176×144@15.0 (4)1.1768,0003,000101,376396192240176×144@30.3 (9)
320×240@10.0 (3)
352×288@7.5 (2)1.21,536,0006,000101,376396384480320×240@20.0 (7)
352×288@15.2 (6)1.33,041,28011,880101,376396768960320×240@36.0 (7)
352×288@30.0 (6)23,041,28011,880101,3763962,0002,500320×240@36.0 (7)
352×288@30.0 (6)2.15,068,80019,800202,7527924,0005,000352×480@30.0 (7)
352×576@25.0 (6)2.25,184,00020,250404,7201,6204,0005,000352×480@30.7(10)
352×576@25.6 (7)
720×480@15.0 (6)
720×576@12.5 (5)310,368,00040,500404,7201,62010,00012,500352×480@61.4 (12)
352×576@51.1 (10)
720×480@30.0 (6)
720×576@25.0 (5)3.127,648,000108,000921,6003,60014,00017,500720×480@80.0 (13)
720×576@66.7 (11)
1280×720@30.0 (5)3.255,296,000216,0001,310,7205,12020,00025,0001,280×720@60.0 (5)
1,280×1,024@42.2 (4)462,914,560245,7602,097,1528,19220,00025,0001,280×720@68.3 (9)
1,920×1,080@30.1 (4)
2,048×1,024@30.0 (4)4.162,914,560245,7602,097,1528,19250,00062,5001,280×720@68.3 (9)
1,920×1,080@30.1 (4)
2,048×1,024@30.0 (4)4.2133,693,440522,2402,228,2248,70450,00062,5001,280×720@145.1 (9)
1,920×1,080@64.0 (4)
2,048×1,080@60.0 (4)5150,994,944589,8245,652,48022,080135,000168,7501,920×1,080@72.3 (13)
2,048×1,024@72.0 (13)
2,048×1,080@67.8 (12)
2,560×1,920@30.7 (5)
3,672×1,536@26.7 (5)5.1251,658,240983,0409,437,18436,864240,000300,0001,920×1,080@120.5 (16)
2,560×1,920@51.2 (9)
4,096×2,048@30.0 (5)
4,096×2,160@28.5 (5)
4,096×2,304@26.7 (5)5.2530,841,6002,073,6009,437,18436,864240,000300,0001,920×1,080@172.0 (16)
2,560×1,920@108.0 (9)
4,096×2,048@63.3 (5)
4,096×2,160@60.0 (5)
4,096×2,304@56.3 (5)

The maximum bit rate for High Profile is 1.25 times that of the Base/Extended/Main Profiles, 3 times for Hi10P, and 4 times for Hi422P/Hi444PP.

The number of luma samples is 16x16=256 times the number of macroblocks (and the number of luma samples per second is 256 times the number of macroblocks per second).