UID737966
威望11
金钱17904
交易诚信度0
主题21
帖子3171
注册时间2010-10-16
最后登录2026-3-19
高级会员
   
交易诚信度0
注册时间2010-10-16
|
原帖由 Dracula81 于 2011-4-14 14:47 发表 
另外你给别人资料的时候,你自己从来不看的吗?
楼主你真了不起,说你错了你第一反应是狡辩!你又把你的图发了一遍,自自己还没看出错来,在你贴那张图之前大家都在讨论音频回放系统,你那张图用来说明时也没说明是改为讨论ADC了!你自己仔细看看?是不是ADC的图?
ADC采样时采的是某个点的电平,但回放时,DAC出来的电平是一个点还是一个区间?如果是NOS多比特DAC,比如TDA1543,直接用示波器测输出的纯正弦波不是一条条线组成,是一个个阶梯组成,这个阶梯中水平部分叫“采样保持",要经过滤波后才平滑。如果是过取样多比特,斜边上的锯齿更多更细,以上波形我用低档数字示波器看过。但像CS4398这类PDM的DAC我用普源DS1025没看出锯齿来。
楼主说:“另外你给别人资料的时候,你自己从来不看的吗?”
楼主,我说了我的算法出处就这这篇文章,我不是每次都给你提供弹药吗? 昨天我提供的”中国期刊网的文章你下不来吗?为什么不用来反击我?
我提供的这篇文章来自国际最著名气杂志的一个网站,这篇文章原来是在杂志上出版的比较正规的科技论文,论文Jitter对音频的影响作了深入的分析。现在楼主举了文章中间部分分析的样本为例来反击我。我告诉楼主,你的红屁股又露出来了。
我告诉你答案:科技论文的结论都在最后面,你把文章看完了吗?我不喜欢直接贴别人的内容,但这次我也贴一下,免得不明真相的群众误解。
Conclusions
Is the digital audio interface flawed? We have examined the possibilities of both amplitude and timing errors corrupting audio data transmitted across an interface. The probability of received amplitude errors is not high, and indeed they are most likely to occur in the preamble of each interface subframe. This means that if a receiver can lock onto an incoming interface signal, then the audio word values are safe. However, jitter remains a concern; several jitter mechanisms exist for the biphase-mark-encoded signal, the biggest problem being that of bandwidth limitation at any stage of the interface. We have shown that band-limited interface jitter has a strong relationship to the bit structure of the serial interface code, and hence can be highly correlated with the transmitted audio data. Measurements have confirmed jitter levels of higher than 1ns in an above-average interface circuit.
The effects of jitter can be predicted by forming error models for different DAC architectures. It can be shown that, compared to low-oversampling multibit designs, pulse-density modulation converters are much more sensitive to jitter when producing low-frequency audio signals. This may explain certain subjective characteristics of PDM DACs that otherwise cannot be rationalized. A simple model of jitter-error audibility has shown that a DAC can tolerate white jitter noise of up to 180ps, but that even lower levels of sinusoidal jitter may be audible. These limits place tough constraints upon digital interface design, and it is recommended that interface receiver PLLs have closed-loop cutoff frequencies as low as possible. For the ultimate immunity to the effects of jitter, a second digital audio interface employed at the receiver can be used to slave the transmitter.
他文章中间部分对Jitter进行分析时,为方便计算(提高计算精度,一般分析都会尽量少碰底限)使用了较大的数字。
楼主你经过基本的科研训练吗?是重点大学本科毕业吗? |
|