progressive scanning. YouTube's statistics shows that interlaced videos are still being uploaded to YouTube, and there is no sign of that dwindling. YouTube attributes this to uploading of made-for-TV content. Quality and formats YouTube originally offered videos at only one quality level, displayed at a resolution of 320×240 pixels using the Sorenson Spark codec (a variant of H.263), with mono MP3 audio. In June 2007, YouTube added an option to watch videos in 3GP format on mobile phones. In March 2008, a high-quality mode was added, which increased the resolution to 480×360 pixels. In December 2008, 720p HD support was added. At the time of the 720p launch, the YouTube player was changed from a 4:3 aspect ratio to a widescreen 16:9. With this new feature, YouTube began a switchover t