| 翻訳と辞書 |
| control track ： ウィキペディア英語版 |
control track
A control track is a track that runs along an outside edge of a standard analog videotape (including VHS). The control track encodes a series of pulses, each pulse corresponding to the beginning of each frame. This allows the video tape player to synchronize its scan speed and tape speed to the speed of the recording. Thus, the recorded control track defines the speed of playback (e.g. SP, LP, EP, etc.), and it is also what drives the relative counter clock that most VCRs have.
== Significance and use ==
The control track is used to fine-tune the tape speed during playback, so that the high speed rotating heads remained exactly on their helical tracks rather than somewhere between two adjacent tracks (known as "tracking"). Since good tracking depends on precise distances between the rotating drum and the fixed control/audio head reading the linear tracks, which usually varies by a couple of micrometers between machines due to manufacturing tolerances, most VCRs offer tracking adjustment, either manual or automatic, to correct such mismatches.
The control track is also used to hold ''index marks'', which were normally written at the beginning of each recording session, and can be found using the VCR's ''index search'' function: this will fast-wind forward or backward to the ''n''th specified index mark, and resume playback from there. At times, higher-end VCRs provided functions for the user to manually add and remove these marks〔http://www.crutchfield.com/S-PFiOFC1Dt8s/learn/learningcenter/home/vcr_glossary.html〕〔(JVC HR-S7300 manual ): features list: ''"..., Index Search, Manual Index Mark/Erase ..."''〕 — so that, for example, they coincide with the actual start of the television program — but this feature later became hard to find.
By the late 1990s, some high-end VCRs offered more sophisticated indexing. For example, Panasonic's Tape Library system assigned an ID number to each cassette, and logged recording information (channel, date, time and optional program title entered by the user) both on the cassette and in the VCR's memory for up to 900 recordings (600 with titles).〔(Panasonic Video Cassette Recorder NV-HS960 Series Operating Instructions ), VQT8880, Matsushita Electric Industrial Co., Ltd.〕
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
■ウィキペディアで「control track」の詳細全文を読む
スポンサード リンク
| 翻訳と辞書 : 翻訳のためのインターネットリソース |
Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.
|
|