Pretty useful link, but the direct answer to the question is this

The R5 is a retail DVD from region 5. Region 5 consists of Russia, the Indian subcontinent, most of Africa, North Korea, and Mongolia. R5 releases differ from normal releases in that they are a direct Telecine transfer of the film without any of the image processing. If the DVD does not contain an English-language audio track, the R5 video is synced to a previously released English audio track. Then a LiNE tag is added.[11] This means that the sound often is not as good as DVD-Rips. To account for the lesser audio quality typically present in R5 releases, some release groups take the high quality Russian or Ukrainian 5.1 channel audio track included with the R5 DVD and modify it with audio editing software. They remove the non-English spoken portion of the audio and sync the remaining portion, which contains high quality sound effects and music with a previously recorded source of English vocals usually taken from a LiNE tagged release. The result of this process is an almost retail DVD quality surround sound audio track which is included in the movie release. Releases of this type are normally tagged AC3.5.1.HQ and details about what was done to the audio track as well as the video are present in the release notes accompanying the pirated movie.[12]

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