Television became available in crude experimental forms in the late 1920s. After World War II, an improved form became popular in the United States and Britain, and television sets became commonplace in homes, businesses, and institutions. During the 1950s, television was the primary medium for influencing public opinion. In the mid-1960s, color broadcasting was introduced in the US and most other developed countries. The availability of storage media such as VHS tape (1976), DVDs (1997), and high-definition Blu-ray Discs (2006) enabled viewers to watch recorded material such as movies. At the end of the first decade of the 2000s, digital television transmissions greatly increased in popularity. Another development was the move from standard-definition television (SDTV) (576i, with 576 interlaced lines of resolution and 480i) to high-definition television (HDTV), which provides a resolution that is substantially higher. HDTV may be transmitted in various formats: 1080p, 1080i and 720p. Since 2010, with the invention of smart television, Internet television has increased the availability of television programs and movies via the Internet through services such as Netflix, iPlayer, Hulu, Roku and Chromecast.