EFM - 光碟數位音響系統的調製方法

EFM - The Modulation Method for the Compact Disc Digital Audio System


作者：

HIROSHI OGAWA

Sony Corporation, Audio Technology Center, Tokyo, Japan

AND

KEES A. SCHOUHAMER IMMINK

Philips Research Laboratories, Eindhoven, The Netherlands

摘要：

光碟 (CD) 數位音響系統中的調製方法是由 Philips N.V. (Eindhoven, The Netherlands) 和 Sony Corporation (Tokyo, Japan) 所共同開發的。
這種方法稱為 8 至 14 (EFM)，是由一個 8 個資料位元轉換成 14 個通道位元後，再加上 3 個通道位元 (被用來連接每個轉換後的 14 個通道位元) 的區塊編碼。
這 3 個通道位元，稱為合併位元，是可選的，能夠抑制頻譜的低頻成份。

首先，列出此調製方法用於記錄或重現光碟上的數位音響信號，所需要的一些主要條件。
第二部分是針對以 EFM 當作調製方法的各種參數進行說明，來證明 EFM 對光碟而言是合適的。
第三部分是詳細說明一個實際的例子;
第四部分是以頻譜來更加了解。
最後，說明 EFM 在 CD 中是符合 CIRC 糾錯方法的。

這兩種方法 (EFM + CIRC) 的結合，對一個直徑為 12 公分的單面光碟能穩定的重現 2 通道 16 位元的音響信號，並有更長的播放時間而言是很重要的。

The modulation method employed in the Compact Disc (CD) digital audio system codeveloped by Philips N.V. (Eindhoven, The Netherlands) and Sony Corporation (Tokyo, Japan) is described.
This method, called eight-to-fourteen (EFM), is an 8 (data bit) ---> 14 (channel bit) conversion block code with a space of 3 channel bits for every converted 14 channel bits which is used to connect the blocks.
These 3 channel bits, called merging bits, are selectable, enabling the suppression of the low-frequency contents of the frequency spectrum.

First some of the major conditions are listed which are required of the modulation method used for recording/reproducing digital audio signals on an optical disk.
The various parameters of EFM as a modulation method are explained in the second part, proving the suitability of EFM for optical disks.
An actual example explains the method in detail; a frequency spectrum is also given to enhance understanding.
EFM is well matched with the error-correction method CIRC employed in the CD.

The combination of these two methods plays an important role in stably reproducing a 2-channel 16-bit audio signal on a 12-cm-diameter optical disk for more than playing time, single sided.


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來源：
1. H. Ogawa and K.A.S. Immink, 'EFM - The Modulation for the Compact Disc Digital Audio System', Collected Papers from the AES Premiere Conference, Rye, New York, pp. 178-188, 1982.

2. EFM - The Modulation Method for the Compact Disc Digital Audio System - Google 搜尋
http://www.google.com.tw/webhp?hl=z...al+Audio+System