By comparison, gonzo pornography puts the camera right into the action, often with one or more of the participants both filming and performing sexual acts, without the usual separation between camera and performers seen in conventional porn and cinema. Production of such films was profitable, and a number of producers specialised in their production. Pornographic films are produced and supplied on a variety of media, depending on demand and the technology available, including traditional film stock in various formats, video for home viewing, DVD, Internet download, cable TV and other media. A bisexual threesome may involve a man having sex with a man and a woman, the woman having sex with a man and a woman, or all three having sex with each other. Some are aroused from wetting their diapers, others like messing their diapers. Rubber pornography involves rubber, porn milf latex, and similar materials. Some people get sexual pleasure by inserting objects, such as urethral sounds, into the urethra , a practice known as urethral play or sounding. In contrast, a celebrity may take the route of openly releasing the tape and benefit directly from royalties as well as indirectly from the publicity. Female masturbation involves the stroking or rubbing of a woman vulva, especially her gay movies clitoris, with an index or hentai movies middle fingers, or both. Andrews cross or spreader bars. In some creampie films, both gay and straight, intercourse and internal ejaculation are followed by performers licking up the semen that has dripped from their bodies. A celebrity sex tape is typically an amateur pornographic video recording involving one or more celebrity famous person which has, intentionally or unintentionally, been made available publicly. Studies have found that masturbation is frequent in humans of both sexes and all ages, although there is variation. Sadism describes sexual pleasure derived by inflicting pain, degradation, humiliation on another person or causing another person to suffer. Low et al.