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感谢老狼朋友提供的资料
我发现你只考虑了动态扩展录音的HDCD,而不是普通HDCD的情况。
只有对于动态扩展(Peak Extended)录音的HDCD(占HDCD的小比例部分)来说,才会在技术上出现6dB电平问题(非动态扩展HDCD和普通CD的电平是相同的),而这个动态扩展还原是通过解码过程(不是数字滤波)实现的,在此过程中产生的6dB的电平差异也会在这个过程中得到弥补,而且这个动态扩展功能是可以根据识别信号来关闭的,请参阅我从 www.hdcd.com 中摘录的如下内容:
Amplitude Encoding/Gain Structure
Two optional HDCD features are available to the recording engineer to reduce the 44.1-kHz, 24-bit signal to 16 bits while retaining many 24-bit sonic benefits. Both of these features can be turned on or off depending on the sonic requirements of the source material.
Peak Extend is a reversible soft limiter that allows the engineer to increase the peak signal level by up to 6 dB without "overs." These peaks are precisely reconstructed when decoded, increasing dynamic range by 6 dB. For undecoded playback, Peak Extend provides all the advantages of an excellent limiter.
Low Level Range Extend gradually increases the gain on low-level signals (starting at -45 dBfs) by 4 dB over a 20-dB range. Decoded playback reverses the added gain, providing low-level resolution beyond 16 bits. For undecoded playback, the increased gain compensates for the lack of low-level resolution in inexpensive CD playback systems, producing a sound more like the original high-resolution master.
即使这个动态扩展功能不能随非动态扩展信号而关闭的话,其对普通HDCD和普通CD的影响还是相同的。
需要声明的一点是:我从开始到现在的态度,并不是强调HDCD的必要性,而是强调其是否有意义。 |
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