Automated dialogue replacement is a technique employed to enhance or alter an actor's dialogue after a scene has been shot. It involves an actor watching the original video and re-performing each line in time with their lip movements. This could be needed because of a lacklustre vocal performance or to bring about a subtle change in the actor's lines, such as a slight change in inflection, or simply that some dialogue is needed for an animation or video game. One of the most common uses for ADR is unwanted background noise, such as police sirens in the background of a medieval set. This can be negated by shotgun microphones – a highly directional microphone that rejects sound off-axis – but even some background noise can bleed through. “Apocalypse Now” supposedly had 90% of the audio as ADR, due to very noisy sets.
Whilst some smaller, independent movies avoid ADR due to budgetary constraints, it can be indispensable since they may not be able to lock down and control the sound in certain sets in the same manner that a big budget blockbuster can. The origin's of ADR can be seen in the black-and-white days, where the pretty faces would perform in front of the camera and their less attractive counterparts would be hidden behind a microphone.
Considered by many as a necessary evil of the movie industry, it is a widely held view that the dialogue produced in ADR will rarely come close to the performance in the original shot. The actor's voice is often lower pitched and quieter (since they tend not to be as hyped up as they are on set). This can be countered by digitally shifting the pitch of the voice, recording in a more authentic environment or bringing the director into the studio to encourage the actor. There is also the challenge for the actor to get his lines perfectly in sync with his lips. The typical method involved a line running across the screen, with three beeps (followed by a fourth silent beep) counting down to the cue point.
The whole ADR process is nowhere near as mind-numbing as it was in the pre-digital era, where each individual segment of film (which required ADR) was put on a projector and cycled again and again until the dialogue was suitable. Thanks to digital editing, the recorded dialogue can be manipulated to better synchronise with the video, and some software is able to match the peaks of the newly recorded dialogue with the original, messy dialogue, such that it perfectly fits in with the video.
Since a large proportion of many films soundscape is built in post-production, is it even worth recording sound on set anymore? Absolutely, much of the original audio can easily be salvaged and spliced into the final mix, especially the background noise and general ambience to help everything sound more natural. It will also save a huge amount of time and money; most actors would rather keep their original performance than go into an ADR studio and re-record dialogue. All things considered, it is an invaluable tool that allows film makers to help mitigate several audio issues which can ruin a movie.
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