mpeg2_vld_intra_n.h

h263,jpeg,mpeg2编解码核心程序(TI DSP C64xx)

/* ======================================================================== */
/*  NAME                                                                    */
/*      mpeg2_vld_intra                                                     */
/*                                                                          */
/*  PLATFORM                                                                */
/*      C6400                                                               */
/*                                                                          */
/*  DESCRIPTION                                                             */
/*      This routine takes a bitstream of an MPEG-2 intra coded macroblock  */
/*      and returns the decoded IDCT coefficients. The routine is           */
/*      implemented as specified in the MPEG-2 standard text (ISO/IEC       */
/*      13818-2). The routine checks the coded block pattern (cbp),         */
/*      performs DC and AC decoding inlcuding, variable length decode,      */
/*      run-length expansion, inverse zigzag, dequantization, saturation    */
/*      and mismatch control.                                               */
/*                                                                          */
/*  USAGE                                                                   */
/*      This routine is C callable, and has the following C prototype:      */
/*                                                                          */
/*      void mpeg2_vld_intra                                                */
/*      (                                                                   */
/*          const short    *restrict Wptr,                                  */
/*          short          *restrict outi,                                  */
/*          IMG_mpeg2_vld  *restrict Mpeg2v,                                */
/*          int            dc_pred[3],                                      */
/*          int            mode_12Q4,                                       */
/*          int            num_blocks,                                      */
/*          int            bsbuf_words                                      */
/*      );                                                                  */
/*                                                                          */
/*        Wptr:   Pointer to array that contains quantization matrix. The   */
/*                elements of the quantization matrix in *Wptr must be      */
/*                ordered according to the scan pattern used (zigzag or     */
/*                alternate scan). Video format 4:2:0 requires one          */
/*                quantization matrix (64 array elements).  For formats     */
/*                4:2:2 and 4:4:4 two quantization matrices (one for luma   */
/*                and one for chroma) must specified in the array (128      */
/*                array elements).                                          */
/*                                                                          */
/*        outi:   Pointer to the IDCT coefficients output array             */
/*                (6*64 elements), elements must be set to zero prior to    */
/*                function call.                                            */
/*                                                                          */
/*        Mpeg2v: Pointer to the context object containing the coding       */
/*                parameters of the MB to be decoded and the current state  */
/*                of the bitstream buffer. The structure is described       */
/*                below.                                                    */
/*                                                                          */
/*       dc_pred: Intra DC prediction array, the first element of dc_pred   */
/*                is the DC prediction for Y, the second for Cr and the     */
/*                third for Cb.                                             */
/*                                                                          */
/*     mode_12Q4: 0: Coefficients are returned in normal 16-bit integer     */
/*                format.                                                   */
/*                Otherwise: Coefficients are returned in 12Q4 format       */
/*                (normal 16-bit integer format left shifted by 4). This    */
/*                mode is useful for directly passing the coefficients      */
/*                into the IMG_idct_8x8 routine.                            */
/*                                                                          */
/*    num_blocks: Number of blocks that the MB contains. Valid values are   */
/*                6 for 4:2:0, 8 for 4:2:2 and 12 for 4:4:4 format.         */
/*                                                                          */
/*   bsbuf_words: Size of bitstream buffer in words. Must be a power of 2.  */
/*                Bitstream buffer must be aligned at an address boundary   */
/*                equal to its size in bytes (bitstream buffer is           */
/*                addressed circularly by this routine.)                    */
/*                                                                          */
/*      The structure Mpeg2v is defined as follows:                         */
/*                                                                          */
/*        #ifndef IMG_MPEG2_VLD_STRUCT_                                     */
/*        #define IMG_MPEG2_VLD_STRUCT_ 1                                   */
/*                                                                          */
/*        typedef struct {                                                  */
/*            unsigned int  *bsbuf;      // pointer to bitstream buffer     */
/*            unsigned int  next_wptr;   // next word to read from buffer   */
/*            unsigned int  bptr;        // bit position within word        */
/*            unsigned int  word1;       // word aligned buffer             */
/*            unsigned int  word2;       // word aligned buffer             */
/*            unsigned int  top0;        // top 32 bits of bitstream        */
/*            unsigned int  top1;        // next 32 bits of bitstream       */
/*            const unsigned char *scan; // inverse zigzag scan matrix      */
/*            unsigned int  intravlc;    // intra_vlc_format                */
/*            unsigned int  quant_scale; // quant_scale                     */
/*            unsigned int  dc_prec;     // intra_dc_precision              */
/*            unsigned int  cbp;         // coded_block_pattern             */
/*            unsigned int  fault;       // fault condition (returned)      */
/*            unsigned int  reserved;    // reserved                        */
/*        } IMG_mpeg2_vld;                                                  */
/*                                                                          */
/*        #endif                                                            */
/*                                                                          */
/*      The Mpeg2v variables should have a fixed layout since they are      */
/*      accessed by this routine.  If the layout is changed, the            */
/*      corresponding changes have to be made in the assembly code too.     */
/*                                                                          */
/*      The routine sets the fault flag Mpeg2v.fault to 1 if an invalid     */
/*      VLC code was encountered or the total run went beyond 63. In        */
/*      theses cases the decoder has to resynchronize.                      */
/*S                                                                        S*/
/*S     The following files contain the required VLD look-up tables:       S*/
/*S                                                                        S*/
/*S         b14s_tbl.c    : run-level VLD table (1152 bytes, Table B-14)   S*/
/*S         b15s_tbl.c    : run-level VLD table (1152 bytes, Table B-15)   S*/
/*S         b14_len_tbl.c : code word length table (640 bytes, Table B-14) S*/
/*S         b15_len_tbl.c : code word length table (640 bytes, Table B-15) S*/
/*                                                                          */
/*      Before calling the routine the bitstream variables in Mpeg2v        */
/*      have to be initialized. If bsbuf is a circular buffer and bsptr     */
/*      contains the number of bits in the buffer that already have         */
/*      been consumed, then next_wptr, bptr, word1, word2, top0 and         */
/*      top1 are initialized as follows:                                    */
/*                                                                          */
/*      1. nextwptr: bsptr may not be a multiple of 32, therefore obtain    */
/*      the next lower multiple of 32.                                      */
/*                                                                          */
/*          next_wptr = (bsptr >> 5);                                       */
/*                                                                          */