【mpeg2】mpeg2解码器开源实现：libmpeg2

Date:2018.10.11

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1、libmpeg2介绍及其源码下载

project homepage: http://libmpeg2.sourceforge.net/
sourcecode download: https://sourceforge.net/projects/libmpeg2/
github sourcecode download: https://github.com/aholtzma/mpeg2dec/tree/master
开源协议： GNU General Public License version 2.0（GPLv2）

摘抄自：http://libmpeg2.sourceforge.net/
About libmpeg2
   libmpeg2 is a free library for decoding mpeg-2 and mpeg-1 video streams. It is released under the terms of the GPL license.

The main goals in libmpeg2 development are:

1. Conformance - libmpeg2 is able to decode all mpeg streams that conform to certain restrictions: “constrained parameters” for mpeg-1, and “main profile” for mpeg-2. In practice, this is what most people are using. For streams that follow these restrictions, we believe libmpeg2 is 100% conformant to the mpeg standards - and we have a pretty extensive test suite to check this.
2. Speed - there has been huge efforts there, and we believe libmpeg2 is the fastest library around for what it does. Please tell us if you find a faster one! With typical video streams as found on DVD’s, and doing only decoding with no display, you should be able to get about 110 fps on a PIII/666, or 150 fps on an Athlon/950. This is less than 20 cycles per output pixel. In a real player program, the display routines will probably take as much time as the actual decoding!Speed - there has been huge efforts there, and we believe libmpeg2 is the fastest library around for what it does. Please tell us if you find a faster one! With typical video streams as found on DVD’s, and doing only decoding with no display, you should be able to get about 110 fps on a PIII/666, or 150 fps on an Athlon/950. This is less than 20 cycles per output pixel. In a real player program, the display routines will probably take as much time as the actual decoding!
3. Portability - most of the code is written in C, and when we use platform-specific optimizations (typically assembly routines, currently used for the motion compensation and the inverse cosine transform stages) we always have a generic C routine to fall back on. This should be portable to all architectures - at least we have heard reports from people running this code on x86, ppc, sparc, arm and sh4. Assembly-optimized implementations are available on x86 (MMX) and ppc (AltiVec) architectures. Ultrasparc (VIS) is probably the next on the list - we’ll see.
4. Reuseability - we do not want libmpeg2 to include any project-specific code, but it should still include enough features to be used by very diverse projects. We are only starting to get there - the best way to help here is to give us some feedback!
   The project homepage is at http://libmpeg2.sourceforge.net/

优化说明：
   开源mpeg2解码器libmpeg2进行了x86、arm、ppc、alpha和sparc架构的优化，没有进行aarch64的优化。

2、多平台编译测试

当前最新版本是libmpeg2-0.5.1。
libmpeg2解码库主要在Windows、Linux和ARM平台进行编译和性能测试。

2.1 Linux平台

编译很简单：

./configure
make 

编译生成的mpeg2解码器路径为： ./src/.libs/mpeg2dec

./mpeg2dec  -h
libmpeg2-0.5.1 - by Michel Lespinasse <walken@zoy.org> and Aaron Holtzman
usage: /home/soaringlee/Desktop/codecs/libmpeg2-0.5.1/src/.libs/lt-mpeg2dec [-h] [-o <mode>] [-s [<track>]] [-t <pid>] [-p] [-c] 
		[-v] [-b <bufsize>] <file>
	-h	display help and available video output modes
	-s	use program stream demultiplexer, track 0-15 or 0xe0-0xef
	-t	use transport stream demultiplexer, pid 0x10-0x1ffe
	-p	use pva demultiplexer
	-c	use c implementation, disables all accelerations
	-v	verbose information about the MPEG stream
	-b	set input buffer size, default 4096 bytes
	-o	video output mode
			null
			nullslice
			nullskip
			nullrgb16
			nullrgb32
			pgm
			pgmpipe
			md5

2.2 Windows平台

源码中没有windows平台的vs工程，首先需要建立库和demo的vs工程。
代码提取可以参考我的博客：
libmpeg2开源解码器的Windows工程搭建和编译

2.3 ARM平台

ARM32位：

./configure --host=arm-hisiv500-linux
make

ARM64位：

./configure --host=aarch64-unknown-linux
make

3、性能测试

3.1 Windows平台

测试配置：Intel® Core™ i5-6500 CPU @3.20GHZ
win32

分辨率	目标码率	平均解码帧率（汇编优化）/fps
720P	512k	532
720P	1024k	490
720P	1536k	473
720P	2048k	440

3.2 Linux平台

测试配置：Intel® Xeon® CPU E5-2667 v3 @3.2GHZ 32核

Linux32位平均性能：

分辨率	目标码率	平均解码帧率（纯C）fps	平均解码帧率（汇编优化）fps
720P	512k	874	2483
720P	1024k	730	2086
720P	1536k	669	1456
720P	2048k	640	1518

Linux64位平均性能：

分辨率	目标码率	平均解码帧率（纯C）fps	平均解码帧率（汇编优化）fps
720P	512k	1049	3267
720P	1024k	934	2400
720P	1536k	839	1975
720P	2048k	821	2086

3.3 ARM平台

测试配置：Hisi3519 ARMv7 32位架构
双核： A7@800MHZ, 32KB I-Cache
A17@1.25GHZ,32KB I-Cache
内存： 1GB
测试配置：Hisi3559 ARMv8 64位架构

ARM32位平均性能：

分辨率	目标码率	平均解码帧率（纯C）fps	平均解码帧率（汇编优化）fps
720P	512k	105	189
720P	1024k	94	150
720P	1536k	90	141
720P	2048k	90	140

ARM64位平均性能：

分辨率	目标码率	平均解码帧率（纯C）fps
720P	512k	248
720P	1024k	213
720P	1536k	201
720P	2048k	198

4、主要耗时模块分析

   通过gprof工具对Linux平台和Arm平台进行分析可知，libmpeg2解码器的主要耗时模块包括：插值模块、IDCT模块和Iquant模块。

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THE END!