AVC编码中的规格 ：High、Baseline、Main什么意思？还有[email protected]、[email protected]、[email protected]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）和CAVLC，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），同样提供对于CAVLC 和CABAC 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[email protected]<[email protected]<[email protected]。

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 values

Level	Max decoding speed		Max frame size		Max video bit rate for video coding layer (VCL) kbit/s		Examples for high resolution @ highest frame rate (max stored frames)
	Luma samples/s	Macroblocks/s	Luma samples	Macroblocks	Baseline, Extended and Main Profiles	High Profile
1	380,160	1,485	25,344	99	64	80	128×[email protected] (8) 176×[email protected] (4)
1b	380,160	1,485	25,344	99	128	160	128×[email protected] (8) 176×[email protected] (4)
1.1	768,000	3,000	101,376	396	192	240	176×[email protected] (9) 320×[email protected] (3) 352×[email protected] (2)
1.2	1,536,000	6,000	101,376	396	384	480	320×[email protected] (7) 352×[email protected] (6)
1.3	3,041,280	11,880	101,376	396	768	960	320×[email protected] (7) 352×[email protected] (6)
2	3,041,280	11,880	101,376	396	2,000	2,500	320×[email protected] (7) 352×[email protected] (6)
2.1	5,068,800	19,800	202,752	792	4,000	5,000	352×[email protected] (7) 352×[email protected] (6)
2.2	5,184,000	20,250	404,720	1,620	4,000	5,000	352×[email protected](10) 352×[email protected] (7) 720×[email protected] (6) 720×[email protected] (5)
3	10,368,000	40,500	404,720	1,620	10,000	12,500	352×[email protected] (12) 352×[email protected] (10) 720×[email protected] (6) 720×[email protected] (5)
3.1	27,648,000	108,000	921,600	3,600	14,000	17,500	720×[email protected] (13) 720×[email protected] (11) 1280×[email protected] (5)
3.2	55,296,000	216,000	1,310,720	5,120	20,000	25,000	1,280×[email protected] (5) 1,280×1,[email protected] (4)
4	62,914,560	245,760	2,097,152	8,192	20,000	25,000	1,280×[email protected] (9) 1,920×1,[email protected] (4) 2,048×1,[email protected] (4)
4.1	62,914,560	245,760	2,097,152	8,192	50,000	62,500	1,280×[email protected] (9) 1,920×1,[email protected] (4) 2,048×1,[email protected] (4)
4.2	133,693,440	522,240	2,228,224	8,704	50,000	62,500	1,280×[email protected] (9) 1,920×1,[email protected] (4) 2,048×1,[email protected] (4)
5	150,994,944	589,824	5,652,480	22,080	135,000	168,750	1,920×1,[email protected] (13) 2,048×1,[email protected] (13) 2,048×1,[email protected] (12) 2,560×1,[email protected] (5) 3,672×1,[email protected] (5)
5.1	251,658,240	983,040	9,437,184	36,864	240,000	300,000	1,920×1,[email protected] (16) 2,560×1,[email protected] (9) 4,096×2,[email protected] (5) 4,096×2,[email protected] (5) 4,096×2,[email protected] (5)
5.2	530,841,600	2,073,600	9,437,184	36,864	240,000	300,000	1,920×1,[email protected] (16) 2,560×1,[email protected] (9) 4,096×2,[email protected] (5) 4,096×2,[email protected] (5) 4,096×2,[email protected] (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).

详情请参考wiki： http://en.wikipedia.org/wiki/H264