There is no doubt that we are in the midst of a rapid evolution of codec design. Traditional codecs, some might call them legacy codecs, are gaining evolutionary improvements. These codecs include HDCAM, AVC-Intra 50 and 100 as well as AVCHD 1.0. This article will, after a brief overview of AVC-Intra and ProRes 422 as well as the new sensors that drive codec evolution, focus on AVC-Ultra. There are five flavors of ProRes 422 in comparison to uncompressed video. (See Table 1.)
Although ProRes 422 codecs are 10-bit codecs, they may carry 12-bit data values. However, they vary in terms of color space and compression ratios. ProRes 4444, however, has additional functionality. The first three 4’s indicate that the codec is capable of carrying either RGB values or luminance plus two chroma components, with all three values present for each pixel. The fourth 4 indicates that an alpha value can be carried along with each pixel. When cameras record ProRes 4444, the fourth value is not present, making the data stream simply 4:4:4.
The advantage of the ProRes proxy codec is best experienced in Final Cut X. When you import any type of data, you have the option of automatically, in the background, creating a ProRes 422 or proxy version of the original file. You then edit the 4:2:2 10-/12-bit proxy video, which allows real-time editing of most any format on almost any Mac. During export, the original file is used as a source of all image data.
AVCHD has evolved to version 2, which has two new features: the ability to record at frame rates of 50fps or 60fps, and to record at 28Mb/s at these higher frame rates. To date, the AVCHD specification has not been enhanced to support Quad HD or 4K2K images. For this reason, cameras, such as the JVC HMQ10, record Quad HD in generic AVC/H.264. Using Level 5.1 or Level 5.2, 24fps or 60fps respectively can be recorded.
Panasonic’s AVC-Intra is available in two formats: a 50Mb/s codec and a 100Mb/s codec. AVC-Intra records a complete range of frame rates. At 1920 x 1080: 23.98p, 25p, 29.97p, 50i and 59.94i. At 1280 x 720: 23.98p, 25p, 29.97p, 50p and 59.94p. The characteristics of each of these two flavors differ. (See Table 2.)