Editing VHS (section)

==== Hi-Fi audio system ====
Around 1984, JVC added ''Hi-Fi'' audio to VHS (model HR-D725U, in response to Betamax's introduction of Beta Hi-Fi.) Both VHS Hi-Fi and Betamax Hi-Fi delivered flat full-range frequency response (20&nbsp;Hz to 20&nbsp;kHz), excellent 70&nbsp;dB [[signal-to-noise ratio]] (in consumer space, second only to the [[compact disc]]), [[dynamic range]] of 90&nbsp;dB, and [[professional audio]]-grade channel separation (more than 70&nbsp;dB). VHS Hi-Fi audio is achieved by using audio frequency modulation (AFM), modulating the two stereo channels (L, R) on two different frequency-modulated carriers and embedding the combined modulated audio signal pair into the video signal. To avoid crosstalk and interference from the primary video carrier, VHS's implementation of AFM relied on a form of magnetic recording called ''depth [[multiplexing]]''. The modulated [[Sound recording and reproduction|audio]] carrier pair was placed in the hitherto-unused frequency range between the luminance and the color carrier (below 1.6&nbsp;MHz), and recorded first. Subsequently, the video head erases and re-records the video signal (combined luminance and color signal) over the same tape surface, but the video signal's higher center frequency results in a shallower magnetization of the tape, allowing both the video and residual AFM audio signal to coexist on tape. (PAL versions of Beta Hi-Fi use this same technique). During playback, VHS Hi-Fi recovers the depth-recorded AFM signal by subtracting the audio head's signal (which contains the AFM signal contaminated by a weak image of the video signal) from the video head's signal (which contains only the video signal), then demodulates the left and right audio channels from their respective frequency carriers. The result of the complex process was audio of high fidelity, which was uniformly solid across all tape-speeds (EP, LP or SP.) Since JVC had gone through the complexity of ensuring Hi-Fi's backward compatibility with non-Hi-Fi VCRs, virtually all studio home video releases produced after this time contained Hi-Fi audio tracks, in addition to the linear audio track. Under normal circumstances, all Hi-Fi VHS VCRs will record Hi-Fi and linear audio simultaneously to ensure compatibility with VCRs without Hi-Fi playback, though only early high-end Hi-Fi machines provided linear stereo compatibility.

The sound quality of Hi-Fi VHS stereo is comparable to some extent to the quality of [[Compact disc|CD]] audio, particularly when recordings were made on high-end or professional VHS machines that have a manual audio recording level control. This high quality compared to other consumer audio recording formats such as [[compact cassette]] attracted the attention of amateur and hobbyist recording artists. [[Home recording]] enthusiasts occasionally recorded high quality stereo [[Audio mixing (recorded music)|mixdown]]s and [[master recordings]] from [[multitrack recording|multitrack]] audio tape onto consumer-level Hi-Fi VCRs. However, because the VHS Hi-Fi recording process is intertwined with the VCR's video-recording function, advanced editing functions such as audio-only or video-only dubbing are impossible. A short-lived alternative to the HiFi feature for recording mixdowns of hobbyist audio-only projects was a [[PCM adaptor]] so that high-bandwidth digital video could use a grid of black-and-white dots on an analog video carrier to give pro-grade digital sounds though [[Digital Audio Tape|DAT]] tapes made this obsolete.

Some VHS decks also had a "simulcast" switch, allowing users to record an external audio input along with off-air pictures. Some televised concerts offered a stereo simulcast soundtrack on FM radio and as such, events like ''[[Live Aid]]'' were recorded by thousands of people with a full stereo soundtrack despite the fact that stereo TV broadcasts were some years off (especially in regions that adopted [[NICAM]]). Other examples of this included network television shows such as ''[[Friday Night Videos]]'' and [[MTV]] for its first few years in existence. Likewise, some countries, most notably [[South Africa]], provided alternate language audio tracks for TV programming through an FM radio simulcast.

The considerable complexity and additional hardware limited VHS Hi-Fi to high-end decks for many years. While linear stereo all but disappeared from home VHS decks, it was not until the 1990s that Hi-Fi became a more common feature on VHS decks. Even then, most customers were unaware of its significance and merely enjoyed the better audio performance of the newer decks. VHS Hi-Fi audio has been standardized in IEC 60774-2.<ref>{{Cite web |title=Helical-scan video tape cassette system using 12,65 mm (0,5 in) magnetic tape on type VHS – Part 2: FM audio recording |url=https://webstore.iec.ch/preview/info_iec60774-2%7Bed1.0%7Db.pdf |website=webstore.iec.ch}}</ref>

===== Issues with Hi-Fi audio =====
Due to the path followed by the video and Hi-Fi audio heads being striped and discontinuous—unlike that of the linear audio track—head-switching is required to provide a continuous audio signal. While the video signal can easily hide the head-switching point in the invisible vertical retrace section of the signal, so that the exact switching point is not very important, the same is obviously not possible with a continuous audio signal that has no inaudible sections. Hi-Fi audio is thus dependent on a much more exact alignment of the head switching point than is required for non-HiFi VHS machines. Misalignments may lead to imperfect joining of the signal, resulting in low-pitched buzzing.<ref name="stason">{{cite web|url=http://stason.org/TULARC/entertainment/audio/general/14-18-Is-VHS-Hi-Fi-sound-perfect-Is-Beta-Hi-Fi-sound-perfec.html14.18|title=14.18 Is VHS Hi-Fi sound perfect? Is Beta Hi-Fi sound perfect?|work=stason.org | access-date=August 6, 2019}}</ref> The problem is known as "head chatter", and tends to increase as the audio heads wear down.

Another issue that made VHS Hi-Fi imperfect for music is the inaccurate reproduction of levels (softer and louder) which are not re-created as the original source.<ref name="stason"/>