Dubbing is a form of post-synchronized revoicing that involves recording voices that do not belong to the on-screen actors, speaking in a language different from that of the source text and ideally in synch with the film image. But dubbing can also refer more generally to adding or replacing sound effects or spoken lines by the source actors themselves in the language of the film's production, often because of poor sound quality in the original recording or for the deletion of expletives from the theatrical version for release on television. While this latter form of post-synchronized revoicing is present in virtually all modern films, it is often called "looping" to distinguish it from dubbing as language translation. Another form of revoicing is the "voice-over," in which a nonsynchronous voice that does not replace the source text and language is added to the sound track but does not replace the source text and language. Popular in Russia and Poland and used more in television than in filmtranslation, voice-over is a relatively minor mode compared to dubbing and subtitling.
Subtitling, like voice-over, presents the translated and source languages simultaneously, but it transforms speech into writing without altering the source sound track. Subtitling may be either intralingual or interlingual. In the former, the written text that appears over the image is that of the source language. This kind of subtitling, for viewers who are deaf and hard-of-hearing, is often called "captioning," and it is in prevalent use in television broadcasting. Interlingual subtitling translates the source language into the target language (or languages) in the form of one or more lines of synchronized written text. These verbal messages may include not only speech, such as dialogue, commentary, and song lyrics, but also displays, such as written signs and newspaper headlines. Subtitles usually appear at the bottom of the screen, though their placement may vary among language groups. In bilingual subtitling countries such as Belgium, Finland, and Israel, film subtitles are often present in both languages.
The national preferences for subtitled or dubbed films stem from several factors, including historical and political circumstances, traditions and industries, costs, the form to which audiences are accustomed, and the generic and artistic standing of the films themselves. Before these can be considered, it is necessary to address the historical circumstances that gave rise to dubbing and subtitling and to their emergence as the preferred forms of verbal translation in film.