yading@10: /*
yading@10:  * RTJpeg decoding functions
yading@10:  * Copyright (c) 2006 Reimar Doeffinger
yading@10:  *
yading@10:  * This file is part of FFmpeg.
yading@10:  *
yading@10:  * FFmpeg is free software; you can redistribute it and/or
yading@10:  * modify it under the terms of the GNU Lesser General Public
yading@10:  * License as published by the Free Software Foundation; either
yading@10:  * version 2.1 of the License, or (at your option) any later version.
yading@10:  *
yading@10:  * FFmpeg is distributed in the hope that it will be useful,
yading@10:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
yading@10:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
yading@10:  * Lesser General Public License for more details.
yading@10:  *
yading@10:  * You should have received a copy of the GNU Lesser General Public
yading@10:  * License along with FFmpeg; if not, write to the Free Software
yading@10:  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
yading@10:  */
yading@10: #include "libavutil/common.h"
yading@10: #include "get_bits.h"
yading@10: #include "rtjpeg.h"
yading@10: 
yading@10: #define PUT_COEFF(c) \
yading@10:     i = scan[coeff--]; \
yading@10:     block[i] = (c) * quant[i];
yading@10: 
yading@10: /// aligns the bitstream to the given power of two
yading@10: #define ALIGN(a) \
yading@10:     n = (-get_bits_count(gb)) & (a - 1); \
yading@10:     if (n) {skip_bits(gb, n);}
yading@10: 
yading@10: /**
yading@10:  * @brief read one block from stream
yading@10:  * @param gb contains stream data
yading@10:  * @param block where data is written to
yading@10:  * @param scan array containing the mapping stream address -> block position
yading@10:  * @param quant quantization factors
yading@10:  * @return 0 means the block is not coded, < 0 means an error occurred.
yading@10:  *
yading@10:  * Note: GetBitContext is used to make the code simpler, since all data is
yading@10:  * aligned this could be done faster in a different way, e.g. as it is done
yading@10:  * in MPlayer libmpcodecs/native/rtjpegn.c.
yading@10:  */
yading@10: static inline int get_block(GetBitContext *gb, int16_t *block, const uint8_t *scan,
yading@10:                             const uint32_t *quant) {
yading@10:     int coeff, i, n;
yading@10:     int8_t ac;
yading@10:     uint8_t dc = get_bits(gb, 8);
yading@10: 
yading@10:     // block not coded
yading@10:     if (dc == 255)
yading@10:        return 0;
yading@10: 
yading@10:     // number of non-zero coefficients
yading@10:     coeff = get_bits(gb, 6);
yading@10:     if (get_bits_left(gb) < (coeff << 1))
yading@10:         return -1;
yading@10: 
yading@10:     // normally we would only need to clear the (63 - coeff) last values,
yading@10:     // but since we do not know where they are we just clear the whole block
yading@10:     memset(block, 0, 64 * sizeof(int16_t));
yading@10: 
yading@10:     // 2 bits per coefficient
yading@10:     while (coeff) {
yading@10:         ac = get_sbits(gb, 2);
yading@10:         if (ac == -2)
yading@10:             break; // continue with more bits
yading@10:         PUT_COEFF(ac);
yading@10:     }
yading@10: 
yading@10:     // 4 bits per coefficient
yading@10:     ALIGN(4);
yading@10:     if (get_bits_left(gb) < (coeff << 2))
yading@10:         return -1;
yading@10:     while (coeff) {
yading@10:         ac = get_sbits(gb, 4);
yading@10:         if (ac == -8)
yading@10:             break; // continue with more bits
yading@10:         PUT_COEFF(ac);
yading@10:     }
yading@10: 
yading@10:     // 8 bits per coefficient
yading@10:     ALIGN(8);
yading@10:     if (get_bits_left(gb) < (coeff << 3))
yading@10:         return -1;
yading@10:     while (coeff) {
yading@10:         ac = get_sbits(gb, 8);
yading@10:         PUT_COEFF(ac);
yading@10:     }
yading@10: 
yading@10:     PUT_COEFF(dc);
yading@10:     return 1;
yading@10: }
yading@10: 
yading@10: /**
yading@10:  * @brief decode one rtjpeg YUV420 frame
yading@10:  * @param c context, must be initialized via ff_rtjpeg_decode_init
yading@10:  * @param f AVFrame to place decoded frame into. If parts of the frame
yading@10:  *          are not coded they are left unchanged, so consider initializing it
yading@10:  * @param buf buffer containing input data
yading@10:  * @param buf_size length of input data in bytes
yading@10:  * @return number of bytes consumed from the input buffer
yading@10:  */
yading@10: int ff_rtjpeg_decode_frame_yuv420(RTJpegContext *c, AVFrame *f,
yading@10:                                   const uint8_t *buf, int buf_size) {
yading@10:     GetBitContext gb;
yading@10:     int w = c->w / 16, h = c->h / 16;
yading@10:     int x, y;
yading@10:     uint8_t *y1 = f->data[0], *y2 = f->data[0] + 8 * f->linesize[0];
yading@10:     uint8_t *u = f->data[1], *v = f->data[2];
yading@10:     init_get_bits(&gb, buf, buf_size * 8);
yading@10:     for (y = 0; y < h; y++) {
yading@10:         for (x = 0; x < w; x++) {
yading@10: #define BLOCK(quant, dst, stride) do { \
yading@10:     int res = get_block(&gb, block, c->scan, quant); \
yading@10:     if (res < 0) \
yading@10:         return res; \
yading@10:     if (res > 0) \
yading@10:         c->dsp->idct_put(dst, stride, block); \
yading@10: } while (0)
yading@10:             int16_t *block = c->block;
yading@10:             BLOCK(c->lquant, y1, f->linesize[0]);
yading@10:             y1 += 8;
yading@10:             BLOCK(c->lquant, y1, f->linesize[0]);
yading@10:             y1 += 8;
yading@10:             BLOCK(c->lquant, y2, f->linesize[0]);
yading@10:             y2 += 8;
yading@10:             BLOCK(c->lquant, y2, f->linesize[0]);
yading@10:             y2 += 8;
yading@10:             BLOCK(c->cquant, u,  f->linesize[1]);
yading@10:             u += 8;
yading@10:             BLOCK(c->cquant, v,  f->linesize[2]);
yading@10:             v += 8;
yading@10:         }
yading@10:         y1 += 2 * 8 * (f->linesize[0] - w);
yading@10:         y2 += 2 * 8 * (f->linesize[0] - w);
yading@10:         u += 8 * (f->linesize[1] - w);
yading@10:         v += 8 * (f->linesize[2] - w);
yading@10:     }
yading@10:     return get_bits_count(&gb) / 8;
yading@10: }
yading@10: 
yading@10: /**
yading@10:  * @brief initialize an RTJpegContext, may be called multiple times
yading@10:  * @param c context to initialize
yading@10:  * @param dsp specifies the idct to use for decoding
yading@10:  * @param width width of image, will be rounded down to the nearest multiple
yading@10:  *              of 16 for decoding
yading@10:  * @param height height of image, will be rounded down to the nearest multiple
yading@10:  *              of 16 for decoding
yading@10:  * @param lquant luma quantization table to use
yading@10:  * @param cquant chroma quantization table to use
yading@10:  */
yading@10: void ff_rtjpeg_decode_init(RTJpegContext *c, DSPContext *dsp,
yading@10:                            int width, int height,
yading@10:                            const uint32_t *lquant, const uint32_t *cquant) {
yading@10:     int i;
yading@10:     c->dsp = dsp;
yading@10:     for (i = 0; i < 64; i++) {
yading@10:         int z = ff_zigzag_direct[i];
yading@10:         int p = c->dsp->idct_permutation[i];
yading@10:         z = ((z << 3) | (z >> 3)) & 63; // rtjpeg uses a transposed variant
yading@10: 
yading@10:         // permute the scan and quantization tables for the chosen idct
yading@10:         c->scan[i] = c->dsp->idct_permutation[z];
yading@10:         c->lquant[p] = lquant[i];
yading@10:         c->cquant[p] = cquant[i];
yading@10:     }
yading@10:     c->w = width;
yading@10:     c->h = height;
yading@10: }