提到High Profile H.264解碼許多人并不了解，那么到底什么是High Profile H.264解碼？其應用效果又是如何呢？
作為行業(yè)標準，H.264編碼體系定義了4種不同的Profile(類)：
- Baseline(基線類) 提供I/P幀，僅支持progressive(逐行掃描)和CAVLC；
- Main(主要類) 提供I/P/B/SP/SI幀，僅支持progressive(逐行掃描)和CAVLC；
- Extended(擴展類) 提供I/P/B幀，支持progressive(逐行掃描)和interlaced(隔行掃描)，提供CAVLC或CABAC；
- High Profile(高端類)（它們各自下分成許多個層）： （也就是FRExt）在Main Profile基礎上新增：8x8 intra prediction(8x8 幀內預測), custom quant(自定義量化), lossless video coding(無損視頻編碼), 更多的yuv格式（4:4:4...）；
H.264 在高清中具有最小體積。在同等圖像質量下，采用H.264技術壓縮后的數(shù)據(jù)量只有MPEG2的1/8，MPEG4的1/3，相對Xvid、 Divx等屬于MPEG4編碼而言，其體積優(yōu)勢明顯，在互聯(lián)網(wǎng)上，H.264資源處在爆發(fā)趨勢。而High Profile是H.264解碼中的高端類型，擁有最完善的支持程度、最優(yōu)秀的特性，可以說是高清視頻編碼中的勞斯萊斯，只有征服了這個優(yōu)秀的編碼，MP4才能將H.264完全掌控，也才能充分享受到高清視頻帶來的視覺震撼，意義非凡。
針對當前高清是視頻會議行業(yè)的主流發(fā)展趨勢，而目前高清普及的主要阻力之一就是帶寬的限制。而High Profile H.264技術在同等視頻質量的情況下可節(jié)省50%的帶寬，為客戶節(jié)省大量的網(wǎng)絡帶寬成本。據(jù)業(yè)內專家介紹，此次H.264 High Profile的推出是視頻技術的一個巨大進步，其意義不亞于2003年從H.263向H.264過渡的價值。它將為目前正在推廣的高清視頻通信應用掃清了令人頭疼的網(wǎng)絡帶寬障礙，不僅如此，這些變化對于包括CIF、標清等品質的視頻通信應用也同樣適用。
Profiles（English）
The standard includes the following seven sets of capabilities, which are referred to as profiles, targeting specific classes of applications:
- Baseline Profile (BP): Primarily for lower-cost applications with limited computing resources, this profile is used widely in videoconferencing and mobile applications.
- Main Profile (MP): Originally intended as the mainstream consumer profile for broadcast and storage applications, the importance of this profile faded when the High profile was developed for those applications.
- Extended Profile (XP): Intended as the streaming video profile, this profile has relatively high compression capability and some extra tricks for robustness to data losses and server stream switching.
- High Profile (HiP): The primary profile for broadcast and disc storage applications, particularly for high-definition television applications (this is the profile adopted into HD DVD and Blu-ray Disc, for example).
- High 10 Profile (Hi10P): Going beyond today's mainstream consumer product capabilities, this profile builds on top of the High Profile—adding support for up to 10 bits per sample of decoded picture precision.
- High 4:2:2 Profile (Hi422P): Primarily targeting professional applications that use interlaced video, this profile builds on top of the High 10 Profile—adding support for the 4:2:2 chroma subsampling format while using up to 10 bits per sample of decoded picture precision.
- High 4:4:4 Predictive Profile (Hi444PP): This profile builds on top of the High 4:2:2 Profile—supporting up to 4:4:4 chroma sampling, up to 14 bits per sample, and additionally supporting efficient lossless region coding and the coding of each picture as three separate color planes.
In addition, the standard contains four additional all-Intra profiles, which are defined as simple subsets of other corresponding profiles. These are mostly for professional (e.g., camera and editing system) applications:
- High 10 Intra Profile: The High 10 Profile constrained to all-Intra use.
- High 4:2:2 Intra Profile: The High 4:2:2 Profile constrained to all-Intra use.
- High 4:4:4 Intra Profile: The High 4:4:4 Profile constrained to all-Intra use.
- CAVLC 4:4:4 Intra Profile: The High 4:4:4 Profile constrained to all-Intra use and to CAVLC entropy coding (i.e., not supporting CABAC).
As a result of the Scalable Video Coding extension, the standard contains three additional scalable profiles, which are defined as a combination of the H.264/AVC profile for the base layer (2nd word in scalable profile name) and tools that achieve the scalable extension:
- Scalable Baseline Profile: Primarily targeting video conferencing, mobile, and surveillance applications, this profile builds on top of a constrained version of the H.264/AVC Baseline profile to which the base layer (a subset of the bitstream) must conform. For the scalability tools, a subset of the available tools is enabled.
- Scalable High Profile: Primarily targeting broadcast and streaming applications, this profile builds on top of the H.264/AVC High Profile to which the base layer must conform.
- Scalable High Intra Profile: Primarily targeting production applications, this profile is the Scalable High Profile constrained to all-Intra use.
| |
Baseline |
Extended |
Main |
High |
High 10 |
High 4:2:2 |
High 4:4:4
Predictive |
| I and P Slices |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
| B Slices |
No |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
| SI and SP Slices |
No |
Yes |
No |
No |
No |
No |
No |
| Multiple Reference Frames |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
| In-Loop Deblocking Filter |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
| CAVLC Entropy Coding |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
| CABAC Entropy Coding |
No |
No |
Yes |
Yes |
Yes |
Yes |
Yes |
| Flexible Macroblock Ordering (FMO) |
Yes |
Yes |
No |
No |
No |
No |
No |
| Arbitrary Slice Ordering (ASO) |
Yes |
Yes |
No |
No |
No |
No |
No |
| Redundant Slices (RS) |
Yes |
Yes |
No |
No |
No |
No |
No |
| Data Partitioning |
No |
Yes |
No |
No |
No |
No |
No |
| Interlaced Coding (PicAFF, MBAFF) |
No |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
| 4:2:0 Chroma Format |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
| Monochrome Video Format (4:0:0) |
No |
No |
No |
Yes |
Yes |
Yes |
Yes |
| 4:2:2 Chroma Format |
No |
No |
No |
No |
No |
Yes |
Yes |
| 4:4:4 Chroma Format |
No |
No |
No |
No |
No |
No |
Yes |
| 8 Bit Sample Depth |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
| 9 and 10 Bit Sample Depth |
No |
No |
No |
No |
Yes |
Yes |
Yes |
| 11 to 14 Bit Sample Depth |
No |
No |
No |
No |
No |
No |
Yes |
| 8x8 vs. 4x4 Transform Adaptivity |
No |
No |
No |
Yes |
Yes |
Yes |
Yes |
| Quantization Scaling Matrices |
No |
No |
No |
Yes |
Yes |
Yes |
Yes |
| Separate Cb and Cr QP control |
No |
No |
No |
Yes |
Yes |
Yes |
Yes |
| Separate Color Plane Coding |
No |
No |
No |
No |
No |
No |
Yes |
| Predictive Lossless Coding |
No |
No |
No |
No |
No |
No |
Yes |
| |
Baseline |
Extended |
Main |
High |
High 10 |
High 4:2:2 |
High 4:4:4
Predictive | | | |
