1、 1 Introduction and scope 1.1 Introduction The 16:9 aspect ratio employed by digital television standards affords a possibility of avoiding the use of pan and scan techniques when adapting works produced in aspect ratios other than 16:9. The ability to use letterbox and sidebar techniques allows for
2、 portrayal of the work in the form originally intended by the artists who created the original work. 1.2 Scope This practice describes a method of mapping images originating in aspect ratios different from 16:9 into a 16:9 scanning structure in a manner that retains the original aspect ratio of the
3、work. 2 Definitions For the purposes of this practice, the following definitions of terms apply: 2.1 letterbox: An image mapped into the total 16:9 display area such that the full width is utilized, but the full height is not (see figure 1). 2.2 sidebar: An image mapped into the total 16:9 display a
4、rea such that the full height of the display area is utilized, but the full width is not (see figure 2). Figure 1 Letterbox Figure 2 Sidebar image mapping Page 1 of 3 pages RP 199-2004Revision of RP 199-1999Copyright 2004 by THE SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS 595 W. Hartsdale Ave
5、., White Plains, NY 10607 (914) 761-1100 ApprovedNovember 8, 2004SMPTE RECOMMENDED PRACTICE Mapping of Pictures in Wide-Screen (16:9) Scanning Structure to Retain Original Aspect Ratio of the Work RP 199-2004 Page 2 of 3 pages 3 Mapping images into the scanning structure 3.1 Works shall be mapped in
6、to the 16:9 aspect ratio scanning structure as shown in algorithm 1. 3.2 Works shall be mapped into the 16:9 aspect ratio so that the center of the original image corresponds with the center of the 16:9 image. Algorithm 1 Calculation of the pixel mapping: Let: A = the aspect ratio of the film (ratio
7、 of width to height, expressed as a decimal) Ph= number of horizontal pixels in scanned film image Pv= number of vertical pixels in scanned film image TVh= number of horizontal pixels in television display system TVv= number of vertical pixels in television display system If: A 16/9 (1.78) Then: Ph=
8、 TVh Pv= TVh/ A Example: Transfer a 1.85:1 image using SMPTE 274M (1920 1080) Given: A = 1.85 (greater than 1.78) TVh= 1920 (number of horizontal pixels in television display system) TVv= 1080 (number of vertical pixels in television display system) Therefore: 1.85 1.78 (true) so Ph= TVh= 1920 horiz
9、ontal pixels in target image and Pv= TVh/ A = 1038 vertical pixels in target image NOTES 1 This leaves the determination of the original aspect ratio to the user of the film. Fractional results should be rounded up to the next highest pixel value. 2 Examples of common film formats are given in table
10、 1. RP 199-2004 Page 3 of 3 pages Table 1 Common film formats Film aspect ratio SMPTE 274M (1920 1080) SMPTE 296M (1280 720) PhPvPhPv1.33 1440 1080 960 720 1.66 1793 1080 1195 720 1.78 1920 1080 1280 720 1.85 1920 1038 1280 692 2.39 1920 803 1280 536 Annex A (informative) Bibliography SMPTE 274M, Te
11、levision 1920 x 1080 Scanning and Interface SMPTE 293M-2003, Television 720 x 483 Active Line at 59.94-Hz Progressive Scan Production Digital Representation SMPTE 296M-2001, Television 1280 x 720 Progressive Image Sample Structure Analog and Digital Representation and Analog Interface EG 25-2003, Telecine Scanning for Film Transfer to Television
