The open/close/pause sequence of mouth movements corresponding to an animated character's dialogue. One of the reasons that dubbed dialogue for foreign animation does not always correspond to the literal translation of the original dialogue is that it must be adapted to match the mouth flaps. If it isn't, the illusion of animated speech is dispelled, resulting in a "bad Hercules movie" effect.
Through analysis by speech scientists and animators, the Disney studios developed a set of facial motion combinations that can represent all sounds a human makes in English. These are called phonemes. They are grouped by sounds that look almost the same when spoken, but sound different.
Good information about the "Preston Blair" phoneme series can be found here
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Some software programs are now available that can generate animation data for lip-sync based on input audio and scripts. Examples of this are the professional animation software "Magpie Pro", as well as lip-sync systems built into the video games Half-Life 2 and The Movies.
Small sets of mouth flaps are useful in animation because they give flexibility in recording dialogue (depending on which method you prefer). Incidentally, it also makes it much easier to dub into other languages. The higher budget of movies, however, forces ADR to sometimes add words that obviously shouldn't be coming out of a certain mouth movement. (Indeed, some TV dubs do this as well.) See Lip Lock.
Definitely an issue for translators — when the character's been handed dinner and the most logical thing to say is "thanks", but the original is "Ndiyabulela" or "Shnorhakalutyun", the challenge is on. At best, it can lead to Woolseyism, at worst to a bunch of syllables that sound incredibly awkward.
Contrast Motionless Chin (when the mouth moves but the jaw doesn't follow).
Examples:
Anime & Manga
- Nadia: The Secret of Blue Water: In an interview, Gargoyle's English voice actor, David Jones, mentions being incredibly lucky to voice a character who always wears a mask; that way, matching the flaps isn't a concern.
Asian Animation
- Pleasant Goat and Big Big Wolf has a specific form of Mouth Flaps that extends to the works of Creative Power Entertaining before and after it in general. The company animates their characters with very simplistic lip movements, their mouths simply flapping up and down without syncing to the dialogue, both within and outside of the original Chinese versions. There are certain instances where their lip movements are more complexly animated.
Films — Animation
- Channel Chasers: The characters in the Speed Racer-esque universe have their mouths repeatedly open and close with little to no lip spectrum when speaking, to mimic the actual show's anime nature.
- Rejected: The characters' mouth flaps are intentionally mismatched with the dialogue.
- Reynard the Fox: The dialogue of animals with long snouts and/or beaks is animated by having them open and close their jaws or bills at different paces and some variation but little to no vocalization.
- The Saga of Windwagon Smith: Curiously, the only character whose mouth is animated very repeatedly is Captain Windwagon Smith himself, with his Lantern Jaw of Justice always moving the same. This is alleviated by how smooth and varied the sequence is despite the low framerate.
- Titanic: The Legend Goes On: The characters are so awkwardly animated that, every time they talk, it's only one or two mouth flaps on loop that might get stretched when they scream, but that's it.
Video Games
- Dune (1992): Mouth movements are superbly synced, in a game that came out as early as 1992, thanks to the Hemouth lips synchronization system developed by Danièle and Rémi Herbulot (the former being the director and one of the main programmers of the game).
- Endless Ocean: In Blue World, despite there not being any actual voice work in the game. Even your character Mouth Flaps without even having textual dialogue.
- Final Fantasy XII: The characters' mouths will sometimes move much faster than their lines would suggest, most notably in the scene where Vaan delivers the sword to Vossler.
- Half-Life: Due to engine limitations, the characters in the first game begin moving their mouths or continue doing so despite their voice actors not having started/already finished their dialogue.
- Demon Slayer: Kimetsu no Yaiba - The Hinokami Chronicles: When the Kasugai Crows relay their messages, they are animated as exaggeratedly opening and closing their beaks over and over, even after their voice actors have stopped talking.
- Mother 3: Unlike previous installments, here, the characters' sprites visibly move their lips whenever they talk.
Web Animation
- Invoked and often exaggerated in Girl-chan in Paradise, as a parody of the standard-issue anime-style mouth flaps and the occasional difficulties found in dubbing them. It varies by character; Kotomaru's lips always flap around rhythmically with no attempt to look like natural speech, while by contrast Yusuke's lips are meticulously animated to match his words exactly.
- Totally averted in My Pride as a combination of a cost-cutting measure and a stylistic choice. The lions open their mouths to speak, but their lips don't move at all while they're doing so, making the series look more like a Motion Comic than animation during conversations. The voice actors have mused that the characters might just be roaring and that they're dubbing those roars into English.
- Natural Habitat Shorts: In a short about nest parasitic cuckoos, Robert (the cuckoo imposter "twin" brother) is made to appear alien, imposing, and just wrong through three things—his deep voice that obviously doesn't belong to a child, his towering height, and the fact his beak flaps don't match his speak.
Western Animation
- This a very common practice among TV animation, especially among companies known for more limited animation shows such as DiC Entertainment or Filmation.
- The Animals of Farthing Wood: Prior to the Animation Bump, the first series relies heavily on cyclic animated sequences, including those for the dialogues, which mostly comprise the animals' jaws or beaks opening and closing when needed.
- Big City Greens:
- Initially, Tilly's dialogue lines were uttered with generic up and down mouth movements, much like a puppet. Since Art Evolution kicked in since "Big Deal", she's been given more elaborate animation.
- "People Watching": The characters in Cricket's "Falcon Tuxedo" story use this type of mouth movement, in keeping with the Animesque style of the sequence.
- Freakazoid!: This animation technique gets parodied with the lip-sinking scene in "Sewer or Later".
- Hi Hi Puffy AmiYumi: The characters are animated with this type of mouth movement, given the fact that the protagonists are a Japanese band, making the rest of the art style accordingly Anime-esque.
- Kappa Mikey: Zigzagged. Only the Japanese characters have this type of mouth movement when speaking, befitting it resembling an anime itself, but Mikey's mouth covers the full spectrum of lip movements.
- Super Robot Monkey Team Hyperforce Go!: The speaking animations consist of the same five or six mouth movements repeated on loop. There's some variety, such as when the characters interject, but that's about it.
- The Tales Of Waterville: For whatever reason, the mouths of the characters appear to be hand-drawn animated, and their mouth movements are just off the charts because of it. Jake, Missy, & The Behavior Bees avert this, on the other hand, by having actual computer-generated mouths that match their models.
- Wunschpunsch: Each character has their own small subset of repetitive mouth flaps used for all of their dialogues. This is especially noticeable for characters like the raven Jacobo, who has a beak instead of a mouth.