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标题: CD版本分析（原创） [打印本页]

作者: himan19 时间: 2006-12-18 14:32
标题: CD版本分析（原创）
先引用一段话

It's not a secret that the Internet and file-exchanging networks are literally overloaded with music. The plenty of various formats which compress music files just favours this situation. Files in formats with lossy encoding and the highest degree of compression, like MP3, have got the greatest prevalence. While playing such files using cheap acoustic systems one can hardly distinguish their dissimilarity from the original ones, but all the distortions become evident when listening such disks on a Hi-Fi systems or using stereo headphones, especially if one has an opportunity to compare a record with its original. That is why when purchasing traditional audio CDs with music a question naturally arises whether this or that record is an authentic one or just a fake made by somebody who has just downloaded lossy encoded records from the Internet and recorded them to the blank CDs under the guise of a solid firm.

Here is an example collection of audio CDs, bought during 2000-2004 years in Russian stores. As everyone can see, approximately 25% of them are so called fake audio CD, produced from lossy audio source, usially from low quality MPEGs. Tau Analyzer can help you to detect such CDs.

To detect these CDs we should found the MPEG-algorithm artefacts in audio data it contains.. The most useful and simple artefact is frequency cut-off - signal is missed or hardly deformed at frequencies about 18 kHz. The frequency cut-off (produced by ear-model of the sound, used by the MPEG algorithm) usially is pretty sharp at one or more high frequencies (16-20kHz). Music, produced from such MP3 has less distinct sound (for example, drums sounds, and other sharp sounds).

Other artefacts of MPEG-coding add specific type of noise, corresponding to the MPEG-coding errors (numerical noise), Fourier transformations artefacts, and decreased correlation between channels (so called sound center fluctuations).

Some studio companies, for example when making live records from concertos removes live noise very inaccurately, by simple cutting-off all the frequencies above 16-18 kHz using digital filtration. So the music produced have some same sound artefacts, as a popular MPEG algorithms.

Usually, MPEG-coding errors could be decreased using so-called dithering technique (it is a kind of smart smoothing the music). One could make sound more distinct by adding additional noise and smoothing the signal spectrum, the technique is known as noise-shaping. All these techniques does not allows you to listen original music, all you listen is music of less quality with some processing and artefacts old (MPEG) and new (different sound quality improving techniques, described above). All these problems could be detected without special tools if you have original and such a copy of the same record.

Please note: Tau Analyzer does not provide an absolutely warranty in results of detection. Sometimes the program can show a wrong result for the track (please see Testing Results). Thus, to make sure you should check all of the CD contents. In this case, the program can produce more trustable CD conclusion, except some special cases.

作者: himan19 时间: 2006-12-18 14:34
原版CD

看图2，20KZ处无滚降

原版1.JPG (50 KB, 下载次数: 39)

原版2.JPG (59 KB, 下载次数: 50)

作者: himan19 时间: 2006-12-18 14:37
引进版，
图2
20KHZ处有滚降

引进版2.JPG (51 KB, 下载次数: 42)

引进版1.JPG (58 KB, 下载次数: 43)

作者: himan19 时间: 2006-12-18 14:40
盗版
用原盘做母盘的

似乎好于引进版 [s:25]

盗版1.JPG (50 KB, 下载次数: 63)

盗版2.JPG (57 KB, 下载次数: 45)

作者: himan19 时间: 2006-12-18 14:44
相当糟糕的引进版

第一首歌竟是MPEG格式
[s:25] [s:25] [s:25]

引进1.JPG (31 KB, 下载次数: 42)

引进2.JPG (45 KB, 下载次数: 37)

作者: himan19 时间: 2006-12-18 14:46
盗版
MP3刻的

垃圾音质！！！！！！！！！！！！！！！！

在14KHZ处被截断了

盗版MP3盘1.JPG (48 KB, 下载次数: 46)

盗版MP3盘2.JPG (56 KB, 下载次数: 44)

作者: himan19 时间: 2006-12-18 14:49
比较好的引进版

用较好的母带

素质接近原版

好引进1.JPG (52 KB, 下载次数: 42)

好引进2.JPG (58 KB, 下载次数: 41)

作者: himan19 时间: 2006-12-18 14:56
刻录盘，网上APE，深蓝碟，2X倍速，民用刻录机

不比一般引进版好多少

kellu1.JPG (49 KB, 下载次数: 49)

kelu2.JPG (59 KB, 下载次数: 56)

作者: huangshun 时间: 2006-12-18 15:00
好的盗版)>=差的引进版
这一点我有体会

作者: himan19 时间: 2006-12-18 15:00
总结：原版>=好的引进版>好的盗版(原盘母带,年代较早期的盒装版)约=刻录盘(较好的)>=常见的引进版>垃圾引进版>普通盗版(翻录和碟太差,一些现在的简装版)>垃圾盗版(MP3刻的)

作者: 伍小然 时间: 2006-12-18 15:02
好东西。顶～～
长知识了～～

作者: 神州行我看行 时间: 2006-12-18 15:11
这是神魔软件吖？

作者: liuji 时间: 2006-12-18 15:15
偶是文科的看不懂

作者: elaing 时间: 2006-12-18 15:22
这个.....CE光谱图颜色怎么改????

作者: leo19841123 时间: 2006-12-18 15:35
只买原版碟，其他一律５４

作者: wishesme 时间: 2006-12-18 16:50
学到东西了,我一直以为刻录的会很好,现在看来不是了~~

作者: babyfacelmj 时间: 2006-12-18 16:54
又来一个全英文的

作者: skyzhouhao 时间: 2006-12-18 16:55
刻录不是音质很好,而是省钱很好.

作者: monloy 时间: 2006-12-18 21:26
其实我觉得这些数据上的区别耳朵未必能听出来~

如果听不出来那干脆买便宜的好了~很多时候贵的东西的音质是靠YY出来的。。

作者: punkding 时间: 2006-12-18 21:38
强啊！

作者: 吴振 时间: 2006-12-19 08:52
看不懂

作者: mrydsw 时间: 2006-12-19 09:42
我是穷人,,,,,我要省钱

作者: depeche 时间: 2006-12-19 16:58
学习了。。。

作者: ytq921 时间: 2006-12-19 17:49
深了深了

作者: mallet 时间: 2006-12-20 12:12
用的是什么软件呀？/

作者: junkers 时间: 2006-12-20 12:47
楼主的这两种图是用Tau Analyzer跑的?

作者: afield 时间: 2006-12-20 12:51
学习。
原版+刻录

作者: junkers 时间: 2006-12-20 13:04
我用Cooledit2跑了"Independence Day"原声中第十轨"International Code"是这个样子.不过是我在家用碟子抓的mdf/mds镜像.

CEX.JPG (127 KB, 下载次数: 36)

作者: bink182 时间: 2006-12-20 16:46
学习

作者: apds 时间: 2006-12-20 17:05

下面是引用wishesme于2006-12-18 16:50发表的:
学到东西了,我一直以为刻录的会很好,现在看来不是了~~

有个疑问,网上的APE是用原版盘做的吗?
理论上抓轨转APE,刻录这些环节应该都是无损的说...数字音乐载体应该不是关键吧...
希望有原版盘的朋友做下试验,用原盘抓APE然后刻录再比较,这才有说服力吧 [s:24]

偶一直认为原版APE无敌的说...CD没准还有读盘的问题...

作者: yangmetal 时间: 2006-12-20 18:49
Tau Analyzer
文章里有写，软件名字
呵呵，贴图有价值~~

作者: yangmetal 时间: 2006-12-20 18:53
呵呵，数字无损什么这话题没底了。
实践说明问题，lz的图挺说明问题了，限于盘基，抓轨，刻录这些物理条件，应该是不能和工业级压盘的精度比

作者: madcock 时间: 2006-12-20 20:03
强贴，仔细学习下

作者: k7788 时间: 2006-12-20 20:55
好贴～～

学习了～～～

作者: kalandaka 时间: 2006-12-26 16:03
技术贴,好好学习

作者: 仙梦情真 时间: 2006-12-26 19:22
强贴!留名!

作者: 爱秋风 时间: 2006-12-27 02:20
太专业了

作者: musicwall 时间: 2006-12-27 08:53
刻录盘的影响因素太多了，原则上说在听音系统还不算坏的情况下，原版和刻录之间的区别是很明显能听出来的。
好贴，加精，不过再多些解释让不太了解这些参数的兄弟能更明了就好了。

作者: zcczhangye 时间: 2006-12-27 13:02
好帖留名

作者: ls1228 时间: 2006-12-27 14:17
学习学习。。。顶！！

作者: 我是刚来的 时间: 2007-1-3 23:44
楼主能不能告诉我,上面那些测试的软件是哪一些软件,在哪里下载的,谢谢啊

作者: 龙城岁月 时间: 2007-1-4 10:12
若是原创，辛苦了

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