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/*
* RTJpeg decoding functions
* Copyright (c) 2006 Reimar Doeffinger
* |
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* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either |
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* version 2.1 of the License, or (at your option) any later version. |
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* |
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* FFmpeg is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public |
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* License along with FFmpeg; if not, write to the Free Software |
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/ |
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#include "libavutil/common.h" |
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#include "get_bits.h" |
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#include "rtjpeg.h"
#define PUT_COEFF(c) \
i = scan[coeff--]; \
block[i] = (c) * quant[i];
|
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/// aligns the bitstream to the given power of two |
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#define ALIGN(a) \
n = (-get_bits_count(gb)) & (a - 1); \
if (n) {skip_bits(gb, n);}
/** |
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* @brief read one block from stream
* @param gb contains stream data
* @param block where data is written to
* @param scan array containing the mapping stream address -> block position
* @param quant quantization factors
* @return 0 means the block is not coded, < 0 means an error occurred. |
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*
* Note: GetBitContext is used to make the code simpler, since all data is
* aligned this could be done faster in a different way, e.g. as it is done |
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* in MPlayer libmpcodecs/native/rtjpegn.c. |
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*/ |
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static inline int get_block(GetBitContext *gb, int16_t *block, const uint8_t *scan, |
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const uint32_t *quant) { |
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int coeff, i, n;
int8_t ac;
uint8_t dc = get_bits(gb, 8);
// block not coded
if (dc == 255)
return 0;
// number of non-zero coefficients
coeff = get_bits(gb, 6); |
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if (get_bits_left(gb) < (coeff << 1)) |
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return AVERROR_INVALIDDATA; |
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|
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// normally we would only need to clear the (63 - coeff) last values,
// but since we do not know where they are we just clear the whole block |
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memset(block, 0, 64 * sizeof(int16_t)); |
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// 2 bits per coefficient
while (coeff) {
ac = get_sbits(gb, 2);
if (ac == -2)
break; // continue with more bits
PUT_COEFF(ac);
}
// 4 bits per coefficient
ALIGN(4); |
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if (get_bits_left(gb) < (coeff << 2)) |
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return AVERROR_INVALIDDATA; |
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while (coeff) {
ac = get_sbits(gb, 4);
if (ac == -8)
break; // continue with more bits
PUT_COEFF(ac);
}
// 8 bits per coefficient
ALIGN(8); |
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if (get_bits_left(gb) < (coeff << 3)) |
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return AVERROR_INVALIDDATA; |
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while (coeff) {
ac = get_sbits(gb, 8);
PUT_COEFF(ac);
}
PUT_COEFF(dc);
return 1;
}
/** |
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* @brief decode one rtjpeg YUV420 frame |
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* @param c context, must be initialized via ff_rtjpeg_decode_init |
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* @param f AVFrame to place decoded frame into. If parts of the frame |
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* are not coded they are left unchanged, so consider initializing it |
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* @param buf buffer containing input data
* @param buf_size length of input data in bytes
* @return number of bytes consumed from the input buffer |
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*/ |
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int ff_rtjpeg_decode_frame_yuv420(RTJpegContext *c, AVFrame *f,
const uint8_t *buf, int buf_size) { |
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GetBitContext gb;
int w = c->w / 16, h = c->h / 16; |
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int x, y, ret; |
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uint8_t *y1 = f->data[0], *y2 = f->data[0] + 8 * f->linesize[0];
uint8_t *u = f->data[1], *v = f->data[2]; |
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if ((ret = init_get_bits8(&gb, buf, buf_size)) < 0)
return ret;
|
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for (y = 0; y < h; y++) {
for (x = 0; x < w; x++) { |
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#define BLOCK(quant, dst, stride) do { \
int res = get_block(&gb, block, c->scan, quant); \
if (res < 0) \
return res; \
if (res > 0) \ |
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c->idsp.idct_put(dst, stride, block); \ |
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} while (0) |
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int16_t *block = c->block; |
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BLOCK(c->lquant, y1, f->linesize[0]); |
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y1 += 8; |
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BLOCK(c->lquant, y1, f->linesize[0]); |
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y1 += 8; |
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BLOCK(c->lquant, y2, f->linesize[0]); |
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y2 += 8; |
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BLOCK(c->lquant, y2, f->linesize[0]); |
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y2 += 8; |
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BLOCK(c->cquant, u, f->linesize[1]); |
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u += 8; |
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BLOCK(c->cquant, v, f->linesize[2]); |
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v += 8;
}
y1 += 2 * 8 * (f->linesize[0] - w);
y2 += 2 * 8 * (f->linesize[0] - w);
u += 8 * (f->linesize[1] - w);
v += 8 * (f->linesize[2] - w);
}
return get_bits_count(&gb) / 8;
}
/** |
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* @brief initialize an RTJpegContext, may be called multiple times
* @param c context to initialize
* @param width width of image, will be rounded down to the nearest multiple |
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* of 16 for decoding |
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* @param height height of image, will be rounded down to the nearest multiple |
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* of 16 for decoding |
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* @param lquant luma quantization table to use
* @param cquant chroma quantization table to use |
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*/ |
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void ff_rtjpeg_decode_init(RTJpegContext *c, int width, int height, |
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const uint32_t *lquant, const uint32_t *cquant) { |
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int i;
for (i = 0; i < 64; i++) { |
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int p = c->idsp.idct_permutation[i]; |
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c->lquant[p] = lquant[i];
c->cquant[p] = cquant[i];
}
c->w = width;
c->h = height;
} |
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void ff_rtjpeg_init(RTJpegContext *c, AVCodecContext *avctx)
{
int i;
|
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ff_idctdsp_init(&c->idsp, avctx); |
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for (i = 0; i < 64; i++) {
int z = ff_zigzag_direct[i];
z = ((z << 3) | (z >> 3)) & 63; // rtjpeg uses a transposed variant
// permute the scan and quantization tables for the chosen idct |
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c->scan[i] = c->idsp.idct_permutation[z]; |
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}
} |