For storage of Y:U:V image data (MacroSystem) yuvn.doc: --------------------------------------------------------------------------- FORM YUVN developed by: MS MacroSystem Computer GmbH (Germany) Henning Friedl (18.4.92) --------------------------------------------------------------------------- FORM YUVN The IFF-format YUVN is designed to store YUV-pictures which mainly are used in broadcast television. YUVN supports CCIR-601-2 which is a worldwide standard for PAL- and NTSC-television. --------------------------------------------------------------------------- Chunk 'YCHD' The required property 'YCHD' holds a header which describes the dimensions of the image and some other information which are necessary to understand the data in the following data-chunks. The chunk 'YCHD' must appear before the first data-chunk ('DATY'). You will find all definitions of this chunk in the file 'yuvn.i'. --------------------------------------------------------------------------- Explanations on the components of the chunk 'YCHD': ychd_Width ychd_Width indicates the width of the stored image. Using YUV_MODE_411, the width must be a multiple of four, usind YUV_MODE_422 or YUV_MODE_211 it must be a multiple of two! Using YUV_MODE_444, YUV_MODE_400, YUV_MODE_222 or YUV_MODE_200 width may be any value. The number of U- and V-pixels per line depends on the used YUV_MODE. See the table below for details. Mode | Y-pixels | U-pixels | V-pixels -----------------------------+----------------+----------------+--------------- YCHD_MODE_400, YCHD_MODE_200 | ychd_Width | - | - YCHD_MODE_411 | ychd_Width (4) | ychd_Width / 4 | ychd_Width / 4 YCHD_MODE_422, YCHD_MODE_211 | ychd_Width (2) | ychd_Width / 2 | ychd_Width / 2 YCHD_MODE_444, YCHD_MODE_222 | ychd_Width | ychd_Width | ychd_Width (2) means, in this mode ychd_Width MUST be a multiple of two! (4) means, in this mode ychd_Width MUST be a multiple of four! ychd_Height ychd_Height indicates the height (number of rows) of the image. If a full-frame picture is stored, ychd_Height must be a multiple of two! ychd_PageWidth, ychd_PageHeight These fields describe the dimensions of the source page. The image itself can be smaller or larger. If not used, set this to ychd_Width and ychd_Height. ychd_LeftEdge, ychd_TopEdge These fields indicate the desired position of this image within the destination picture. If not used, set to 0,0. ychd_xAspect, ychd_yAspect The aspect ratio of a single pixel in the stored image. If you do not know the correct values (you should know them) use the following: PAL-nonlace: 22/44 NTSC-nonlace: 22/52 PAL-lace: 22/22 NTSC-lace: 22/26 See also: 'Finding the Aspect Ratio' by Carolyn Scheppner (AmigaMail 9/10-91) ychd_Compress Type of compression. 0, if none. ychd_Flags Different Flags. Currently only bit-0 (YCHDB_LACE) is defined. It should be set if the stored image has been a full-frame image within an interlace video-source (TV, VTR, ...). ychd_Mode The type of YUV-format. If you only want to save the luminance information (black-and-white) set ychd_Mode to YCHD_MODE_400. If you save the additional color-difference-signals U and V set ychd_Mode to YCHD_MODE_411, YCHD_MODE_422 or YCHD_MODE_444 depending what format you want to save. With lores-pictures use YCHD_MODE_200, YCHD_MODE_211 or YCHD_MODE_222. ychd_Norm Information on the TV-system you got this picture from. If you really do not know set ychd_Norm to YCHD_NORM_UNKNOWN. The better way is to set it to the correct value YCHD_NORM_PAL or YCHD_NORM_NTSC! --------------------------------------------------------------------------- The data-chunks DATY, DATU and DATV In the IFF-file the chunks DATY, DATU and DATV must appear in this order. The optional chunks DATU and DATV are both needed in color-pictures. The data-chunk DATY The chunk DATY contains the luminance-data (Y) of the YUV-picture. Each pixel is stored in one byte (8 bits), the values follow the CCIR-standard. Y ranges from 16 (black) to 235 (white). Isolated pixels may go lightly beyond the limits but 0 and 255 must not appear! The number of pixels in one line is given in ychd_Width. One line directly follows the other, there are no pad-bytes between two lines even if ychd_Width is odd. Only at the end of the chunk a pad-byte ($00) might be inserted according the IFF guidelines. Within a full-frame- (interlaced-) picture the lines are ordered as if it was a non-lace picture (first line, first frame then first line, second frame then second line first frame, ...). This is the same in IFF-ILBM or the order of the bitmaps in Amiga-memory. The data-chunks DATU and DATV The chunks DATU and DATV are optional, they have to appear in color-pictures because they contain the color-difference-signals. Each pixel is stored in one byte (8 bits), the values follow the CCIR-standard. The values range from 16 to 240 (128 means 0). For calculations you have to subtract 128 so U or V are in a range from -112 to 112 where 0 means no color. Isolated pixels may go lightly beyond the limits but 0 and 255 must not appear! --------------------------------------------------------------------------- yuvn.i: --------------------------------------------------------------------------- IFND YUVN_I YUVN_I SET 1 ;--------------------------------------------------------------------------- IFND EXEC_TYPES_I INCLUDE "exec/types.i" ENDC ;--------------------------------------------------------------------------- ;---- ID's used in FORM YUVN ID_YUVN: equ 'YUVN' ;the FORM-ID ID_YCHD: equ 'YCHD' ;the header-chunk-ID ID_DATY: equ 'DATY' ;the Y-data-chunk-ID ID_DATU: equ 'DATU' ;the U-data-chunk-ID ID_DATV: equ 'DATV' ;the V-data-chunk-ID ;---- values for ychd_Compress COMPRESS_NONE equ 0 ;no comression ;---- values for ychd_Flags YCHDB_LACE equ 0 ;if set the data-chunks contain YCHDF_LACE equ 1 ;a full-frame (interlaced) picture ;---- values for ychd_Mode YCHD_MODE_400 equ 0 ;a black-and-white picture (no DATU and DATV) YCHD_MODE_411 equ 1 ;a YUV-411 picture YCHD_MODE_422 equ 2 ;a YUV-422 picture YCHD_MODE_444 equ 3 ;a YUV-444 picture YCHD_MODE_200 equ 8 ;a lores black-and-white picture YCHD_MODE_211 equ 9 ;a lores color picture (422, but lores) YCHD_MODE_222 equ 10 ;a lores color picture (444, but lores) YCHD_MODEB_LORES equ 3 ;test this bit to check for lores/hires YCHD_MODEF_LORES equ 8 ;---- values for ychd_Norm YCHD_NORM_UNKNOWN equ 0 ;unknown, try to avoid this YCHD_NORM_PAL equ 1 ;PAL 4.433 MHz YCHD_NORM_NTSC equ 2 ;NTSC 3.579 MHz ;---- the FORM-YUVN DataHeader: 'YCHD' STRUCTURE __YCHD_Header,0 UWORD ychd_Width ;picture width in Y-pixels UWORD ychd_Height ;picture height (rows) UWORD ychd_PageWidth ;source page width & height, UWORD ychd_PageHeight ; normally same as Width and Height UWORD ychd_LeftEdge ;position within the source page, UWORD ychd_TopEdge ; normally 0,0 UBYTE ychd_AspectX ;pixel aspect (width : height) UBYTE ychd_AspectY ; UBYTE ychd_Compress ;(see above) UBYTE ychd_Flags ;(see above) UBYTE ychd_Mode ;(see above) UBYTE ychd_Norm ;(see above) WORD ychd_reserved2 ;must be 0 LONG ychd_reserved3 ;must be 0 LABEL ychd_SIZEOF ;--------------------------------------------------------------------------- ; Warning, the UBYTE fields are byte-packed, C-compilers should not add pad ; bytes! ;--------------------------------------------------------------------------- ENDC ; YUVN_I