MPEG-4第2部分具有一些很棒的面部和身体动作概念，但在MPEG-4第10部分(H.264)中消失了.为什么? [英] MPEG-4 Part 2 had some awesome face- and body- motion concepts, but they disappeared in MPEG-4 Part 10 (H.264). Why?

问题描述

在过去的几周中，我有机会阅读了两个文档:

During the last few weeks, I had the opportunity to read two documents:

• 人们仅称其为"mpeg-4"的MPEG-4 Part 2规范(ISO/IEC 14496-2)
• MPEG-4第10部分规范(ISO/IEC 14496-10)，也称为"h.264"或"AVC"

在阅读了"mpeg-4"中的所有很棒的主意之后，例如识别面部表情，人的肢体运动和精灵，我感到非常兴奋.对于1999年以来的一个想法，这些想法听起来很有趣，甚至很棒.

After having read all the cool ideas in "mpeg-4" like identifying facial expression, motion of limbs of people, and sprites, I got really excited. The ideas sound very fun, maybe even fantastic, for an idea from 1999.

但是随后我阅读了"h.264"标准，但这些想法都没有.关于如何对像素进行编码的讨论很多，但没有一个真正酷的想法.

But then I read the "h.264" standard, and none of those ideas were there. There was a lot of discussion on how to encode pixels, but none of the really cool ideas.

发生了什么事?为什么这些想法被删除了?

What happened? Why were these ideas removed?

这不是代码问题，但是作为一名程序员，我觉得我应该尝试理解规范背后的许多意图.如果我编写的代码坚持使用规范的精神，那么更有可能利用整个规范.

This is not a code question, but as a programmer I feel I should attempt to understand as much of the intent behind a specification. If the code I write adheres to the spirit in which the specification was meant to be used, it's more likely to be positioned to take advantage of the entire specification.

推荐答案

您似乎在假设MPEG-4 Part 10规范在MPEG-4 Part 2上有所改进，而事实是这两个规范无关，没有什么共同点，甚至是由不同的人开发的(MPEG制定了第2部分规范，而ITU-T，ISO，IEC和MPEG共同制定了第10部分规范).

You seem to be making the assumption that the MPEG-4 Part 10 specification improves on MPEG-4 Part 2, while the fact is that these two specifications are unrelated, have nothing in common and were even developed by different people (MPEG developed the Part 2 specification, while ITU-T, ISO, IEC and MPEG together developed the Part 10 specification).

请记住，ISO/IEC 14496标准是适用于视听编码不同方面的一系列规范.第2部分规范的目标是对不同种类的视觉对象(视频，3D对象等)进行编码.第10部分的目标是为视频提供非常有效和高质量的编码.该标准的其他部分涉及其他方面，例如，第3部分规范涉及音频编码，第12部分和第15部分定义了最常用于包装第10部分视频(即H.264)和第3部分的容器文件格式音频(即AAC)转换为单个文件，即所谓的.mp4格式.

Keep in mind that ISO/IEC 14496 standard is a collection of specifications that apply to different aspects of audiovisual encoding. The goal of the Part 2 specification is to encode different kinds of visual objects (video, 3D objects, etc.). The goal of Part 10 is to provide a very efficient and high quality encoding for video. Other parts of the standard deal with other aspects, for example the Part 3 specification deals with audio encoding, and Parts 12 and 15 define a container file format that is most typically used to wrap Part 10 video (i.e. H.264) and Part 3 audio (i.e. AAC) into a single file, the so called .mp4 format.

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