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FFmpeg/libavcodec/mss4.c

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  1. /*

  2.  * Microsoft Screen 4 (aka Microsoft Expression Encoder Screen) decoder

  3.  * Copyright (c) 2012 Konstantin Shishkov

  4.  *

  5.  * This file is part of FFmpeg.

  6.  *

  7.  * FFmpeg is free software; you can redistribute it and/or

  8.  * modify it under the terms of the GNU Lesser General Public

  9.  * License as published by the Free Software Foundation; either

  10.  * version 2.1 of the License, or (at your option) any later version.

  11.  *

  12.  * FFmpeg is distributed in the hope that it will be useful,

  13.  * but WITHOUT ANY WARRANTY; without even the implied warranty of

  14.  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

  15.  * Lesser General Public License for more details.

  16.  *

  17.  * You should have received a copy of the GNU Lesser General Public

  18.  * License along with FFmpeg; if not, write to the Free Software

  19.  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

  20.  */

  21. 

  22. /**

  23.  * @file

  24.  * Microsoft Screen 4 (aka Microsoft Titanium Screen 2,

  25.  * aka Microsoft Expression Encoder Screen) decoder

  26.  */

  27. 

  28. #include "avcodec.h"

  29. #include "bytestream.h"

  30. #include "dsputil.h"

  31. #include "get_bits.h"

  32. #include "mss34dsp.h"

  33. #include "unary.h"

  34. 

  35. #define HEADER_SIZE 8

  36. 

  37. enum FrameType {

  38.     INTRA_FRAME = 0,

  39.     INTER_FRAME,

  40.     SKIP_FRAME

  41. };

  42. 

  43. enum BlockType {

  44.     SKIP_BLOCK = 0,

  45.     DCT_BLOCK,

  46.     IMAGE_BLOCK,

  47. };

  48. 

  49. enum CachePos {

  50.     LEFT = 0,

  51.     TOP_LEFT,

  52.     TOP,

  53. };

  54. 

  55. static const uint8_t mss4_dc_vlc_lens[2][16] = {

  56.     { 0, 1, 5, 1, 1, 1, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0 },

  57.     { 0, 3, 1, 1, 1, 1, 1, 1, 1, 2, 0, 0, 0, 0, 0, 0 }

  58. };

  59. 

  60. static const uint8_t mss4_ac_vlc_lens[2][16] = {

  61.     { 0, 2, 1, 3, 3, 2, 4, 3, 5, 5, 4, 4, 0, 0, 1, 125 },

  62.     { 0, 2, 1, 2, 4, 4, 3, 4, 7, 5, 4, 4, 0, 1, 2, 119 }

  63. };

  64. 

  65. static const uint8_t mss4_ac_vlc_syms[2][162] = {

  66.   { 0x01, 0x02, 0x03, 0x00, 0x04, 0x11, 0x05, 0x12,

  67.     0x21, 0x31, 0x41, 0x06, 0x13, 0x51, 0x61, 0x07,

  68.     0x22, 0x71, 0x14, 0x32, 0x81, 0x91, 0xA1, 0x08,

  69.     0x23, 0x42, 0xB1, 0xC1, 0x15, 0x52, 0xD1, 0xF0,

  70.     0x24, 0x33, 0x62, 0x72, 0x82, 0x09, 0x0A, 0x16,

  71.     0x17, 0x18, 0x19, 0x1A, 0x25, 0x26, 0x27, 0x28,

  72.     0x29, 0x2A, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39,

  73.     0x3A, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49,

  74.     0x4A, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59,

  75.     0x5A, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69,

  76.     0x6A, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79,

  77.     0x7A, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89,

  78.     0x8A, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98,

  79.     0x99, 0x9A, 0xA2, 0xA3, 0xA4, 0xA5, 0xA6, 0xA7,

  80.     0xA8, 0xA9, 0xAA, 0xB2, 0xB3, 0xB4, 0xB5, 0xB6,

  81.     0xB7, 0xB8, 0xB9, 0xBA, 0xC2, 0xC3, 0xC4, 0xC5,

  82.     0xC6, 0xC7, 0xC8, 0xC9, 0xCA, 0xD2, 0xD3, 0xD4,

  83.     0xD5, 0xD6, 0xD7, 0xD8, 0xD9, 0xDA, 0xE1, 0xE2,

  84.     0xE3, 0xE4, 0xE5, 0xE6, 0xE7, 0xE8, 0xE9, 0xEA,

  85.     0xF1, 0xF2, 0xF3, 0xF4, 0xF5, 0xF6, 0xF7, 0xF8,

  86.     0xF9, 0xFA  },

  87.   { 0x00, 0x01, 0x02, 0x03, 0x11, 0x04, 0x05, 0x21,

  88.     0x31, 0x06, 0x12, 0x41, 0x51, 0x07, 0x61, 0x71,

  89.     0x13, 0x22, 0x32, 0x81, 0x08, 0x14, 0x42, 0x91,

  90.     0xA1, 0xB1, 0xC1, 0x09, 0x23, 0x33, 0x52, 0xF0,

  91.     0x15, 0x62, 0x72, 0xD1, 0x0A, 0x16, 0x24, 0x34,

  92.     0xE1, 0x25, 0xF1, 0x17, 0x18, 0x19, 0x1A, 0x26,

  93.     0x27, 0x28, 0x29, 0x2A, 0x35, 0x36, 0x37, 0x38,

  94.     0x39, 0x3A, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48,

  95.     0x49, 0x4A, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58,

  96.     0x59, 0x5A, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68,

  97.     0x69, 0x6A, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78,

  98.     0x79, 0x7A, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,

  99.     0x88, 0x89, 0x8A, 0x92, 0x93, 0x94, 0x95, 0x96,

  100.     0x97, 0x98, 0x99, 0x9A, 0xA2, 0xA3, 0xA4, 0xA5,

  101.     0xA6, 0xA7, 0xA8, 0xA9, 0xAA, 0xB2, 0xB3, 0xB4,

  102.     0xB5, 0xB6, 0xB7, 0xB8, 0xB9, 0xBA, 0xC2, 0xC3,

  103.     0xC4, 0xC5, 0xC6, 0xC7, 0xC8, 0xC9, 0xCA, 0xD2,

  104.     0xD3, 0xD4, 0xD5, 0xD6, 0xD7, 0xD8, 0xD9, 0xDA,

  105.     0xE2, 0xE3, 0xE4, 0xE5, 0xE6, 0xE7, 0xE8, 0xE9,

  106.     0xEA, 0xF2, 0xF3, 0xF4, 0xF5, 0xF6, 0xF7, 0xF8,

  107.     0xF9, 0xFA  }

  108. };

  109. 

  110. static const uint8_t vec_len_syms[2][4] = {

  111.     { 4, 2, 3, 1 },

  112.     { 4, 1, 2, 3 }

  113. };

  114. 

  115. static const uint8_t mss4_vec_entry_vlc_lens[2][16] = {

  116.     { 0, 2, 2, 3, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 },

  117.     { 0, 1, 5, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }

  118. };

  119. 

  120. static const uint8_t mss4_vec_entry_vlc_syms[2][9] = {

  121.     { 0, 7, 6, 5, 8, 4, 3, 1, 2 },

  122.     { 0, 2, 3, 4, 5, 6, 7, 1, 8 }

  123. };

  124. 

  125. #define MAX_ENTRIES  162

  126. 

  127. typedef struct MSS4Context {

  128.     AVFrame    pic;

  129.     DSPContext dsp;

  130. 

  131.     VLC        dc_vlc[2], ac_vlc[2];

  132.     VLC        vec_entry_vlc[2];

  133.     int        block[64];

  134.     uint8_t    imgbuf[3][16 * 16];

  135. 

  136.     int        quality;

  137.     uint16_t   quant_mat[2][64];

  138. 

  139.     int        *prev_dc[3];

  140.     int        dc_stride[3];

  141.     int        dc_cache[4][4];

  142. 

  143.     int        prev_vec[3][4];

  144. } MSS4Context;

  145. 

  146. static av_cold int mss4_init_vlc(VLC *vlc, const uint8_t *lens,

  147.                                  const uint8_t *syms, int num_syms)

  148. {

  149.     uint8_t  bits[MAX_ENTRIES];

  150.     uint16_t codes[MAX_ENTRIES];

  151.     int i, j;

  152.     int prefix = 0, max_bits = 0, idx = 0;

  153. 

  154.     for (i = 0; i < 16; i++) {

  155.         for (j = 0; j < lens[i]; j++) {

  156.             bits[idx]  = i + 1;

  157.             codes[idx] = prefix++;

  158.             max_bits   = i + 1;

  159.             idx++;

  160.         }

  161.         prefix <<= 1;

  162.     }

  163. 

  164.     return ff_init_vlc_sparse(vlc, FFMIN(max_bits, 9), num_syms, bits, 1, 1,

  165.                               codes, 2, 2, syms, 1, 1, 0);

  166. }

  167. 

  168. static av_cold int mss4_init_vlcs(MSS4Context *ctx)

  169. {

  170.     int ret, i;

  171. 

  172.     for (i = 0; i < 2; i++) {

  173.         ret = mss4_init_vlc(&ctx->dc_vlc[i], mss4_dc_vlc_lens[i], NULL, 12);

  174.         if (ret)

  175.             return ret;

  176.         ret = mss4_init_vlc(&ctx->ac_vlc[i], mss4_ac_vlc_lens[i],

  177.                             mss4_ac_vlc_syms[i], 162);

  178.         if (ret)

  179.             return ret;

  180.         ret = mss4_init_vlc(&ctx->vec_entry_vlc[i], mss4_vec_entry_vlc_lens[i],

  181.                             mss4_vec_entry_vlc_syms[i], 9);

  182.         if (ret)

  183.             return ret;

  184.     }

  185.     return 0;

  186. }

  187. 

  188. static av_cold void mss4_free_vlcs(MSS4Context *ctx)

  189. {

  190.     int i;

  191. 

  192.     for (i = 0; i < 2; i++) {

  193.         ff_free_vlc(&ctx->dc_vlc[i]);

  194.         ff_free_vlc(&ctx->ac_vlc[i]);

  195.         ff_free_vlc(&ctx->vec_entry_vlc[i]);

  196.     }

  197. }

  198. 

  199. /* This function returns values in the range

  200.  * (-range + 1; -range/2] U [range/2; range - 1)

  201.  * i.e.

  202.  * nbits = 0 -> 0

  203.  * nbits = 1 -> -1, 1

  204.  * nbits = 2 -> -3, -2, 2, 3

  205.  */

  206. static av_always_inline int get_coeff_bits(GetBitContext *gb, int nbits)

  207. {

  208.     int val;

  209. 

  210.     if (!nbits)

  211.         return 0;

  212. 

  213.     val = get_bits(gb, nbits);

  214.     if (val < (1 << (nbits - 1)))

  215.         val -= (1 << nbits) - 1;

  216. 

  217.     return val;

  218. }

  219. 

  220. static inline int get_coeff(GetBitContext *gb, VLC *vlc)

  221. {

  222.     int val = get_vlc2(gb, vlc->table, vlc->bits, 2);

  223. 

  224.     return get_coeff_bits(gb, val);

  225. }

  226. 

  227. static int mss4_decode_dct(GetBitContext *gb, VLC *dc_vlc, VLC *ac_vlc,

  228.                            int *block, int *dc_cache,

  229.                            int bx, int by, uint16_t *quant_mat)

  230. {

  231.     int skip, val, pos = 1, zz_pos, dc;

  232. 

  233.     memset(block, 0, sizeof(*block) * 64);

  234. 

  235.     dc = get_coeff(gb, dc_vlc);

  236.     // DC prediction is the same as in MSS3

  237.     if (by) {

  238.         if (bx) {

  239.             int l, tl, t;

  240. 

  241.             l  = dc_cache[LEFT];

  242.             tl = dc_cache[TOP_LEFT];

  243.             t  = dc_cache[TOP];

  244. 

  245.             if (FFABS(t - tl) <= FFABS(l - tl))

  246.                 dc += l;

  247.             else

  248.                 dc += t;

  249.         } else {

  250.             dc += dc_cache[TOP];

  251.         }

  252.     } else if (bx) {

  253.         dc += dc_cache[LEFT];

  254.     }

  255.     dc_cache[LEFT] = dc;

  256.     block[0]       = dc * quant_mat[0];

  257. 

  258.     while (pos < 64) {

  259.         val = get_vlc2(gb, ac_vlc->table, 9, 2);

  260.         if (!val)

  261.             return 0;

  262.         if (val == -1)

  263.             return -1;

  264.         if (val == 0xF0) {

  265.             pos += 16;

  266.             continue;

  267.         }

  268.         skip = val >> 4;

  269.         val  = get_coeff_bits(gb, val & 0xF);

  270.         pos += skip;

  271.         if (pos >= 64)

  272.             return -1;

  273. 

  274.         zz_pos = ff_zigzag_direct[pos];

  275.         block[zz_pos] = val * quant_mat[zz_pos];

  276.         pos++;

  277.     }

  278. 

  279.     return pos == 64 ? 0 : -1;

  280. }

  281. 

  282. static int mss4_decode_dct_block(MSS4Context *c, GetBitContext *gb,

  283.                                  uint8_t *dst[3], int mb_x, int mb_y)

  284. {

  285.     int i, j, k, ret;

  286.     uint8_t *out = dst[0];

  287. 

  288.     for (j = 0; j < 2; j++) {

  289.         for (i = 0; i < 2; i++) {

  290.             int xpos = mb_x * 2 + i;

  291.             c->dc_cache[j][TOP_LEFT] = c->dc_cache[j][TOP];

  292.             c->dc_cache[j][TOP]      = c->prev_dc[0][mb_x * 2 + i];

  293.             ret = mss4_decode_dct(gb, c->dc_vlc, c->ac_vlc, c->block,

  294.                                   c->dc_cache[j],

  295.                                   xpos, mb_y * 2 + j, c->quant_mat[0]);

  296.             if (ret)

  297.                 return ret;

  298.             c->prev_dc[0][mb_x * 2 + i] = c->dc_cache[j][LEFT];

  299. 

  300.             ff_mss34_dct_put(out + xpos * 8, c->pic.linesize[0],

  301.                              c->block);

  302.         }

  303.         out += 8 * c->pic.linesize[0];

  304.     }

  305. 

  306.     for (i = 1; i < 3; i++) {

  307.         c->dc_cache[i + 1][TOP_LEFT] = c->dc_cache[i + 1][TOP];

  308.         c->dc_cache[i + 1][TOP]      = c->prev_dc[i][mb_x];

  309.         ret = mss4_decode_dct(gb, c->dc_vlc + 1, c->ac_vlc + 1,

  310.                               c->block, c->dc_cache[i + 1], mb_x, mb_y,

  311.                               c->quant_mat[1]);

  312.         if (ret)

  313.             return ret;

  314.         c->prev_dc[i][mb_x] = c->dc_cache[i + 1][LEFT];

  315. 

  316.         ff_mss34_dct_put(c->imgbuf[i], 8, c->block);

  317.         out = dst[i] + mb_x * 16;

  318.         // Since the DCT block is coded as YUV420 and the whole frame as YUV444,

  319.         // we need to scale chroma.

  320.         for (j = 0; j < 16; j++) {

  321.             for (k = 0; k < 8; k++)

  322.                 AV_WN16A(out + k * 2, c->imgbuf[i][k + (j & ~1) * 4] * 0x101);

  323.             out += c->pic.linesize[i];

  324.         }

  325.     }

  326. 

  327.     return 0;

  328. }

  329. 

  330. static void read_vec_pos(GetBitContext *gb, int *vec_pos, int *sel_flag,

  331.                          int *sel_len, int *prev)

  332. {

  333.     int i, y_flag = 0;

  334. 

  335.     for (i = 2; i >= 0; i--) {

  336.         if (!sel_flag[i]) {

  337.             vec_pos[i] = 0;

  338.             continue;

  339.         }

  340.         if ((!i && !y_flag) || get_bits1(gb)) {

  341.             if (sel_len[i] > 0) {

  342.                 int pval = prev[i];

  343.                 vec_pos[i] = get_bits(gb, sel_len[i]);

  344.                 if (vec_pos[i] >= pval)

  345.                     vec_pos[i]++;

  346.             } else {

  347.                 vec_pos[i] = !prev[i];

  348.             }

  349.             y_flag = 1;

  350.         } else {

  351.             vec_pos[i] = prev[i];

  352.         }

  353.     }

  354. }

  355. 

  356. static int get_value_cached(GetBitContext *gb, int vec_pos, uint8_t *vec,

  357.                             int vec_size, int component, int shift, int *prev)

  358. {

  359.     if (vec_pos < vec_size)

  360.         return vec[vec_pos];

  361.     if (!get_bits1(gb))

  362.         return prev[component];

  363.     prev[component] = get_bits(gb, 8 - shift) << shift;

  364.     return prev[component];

  365. }

  366. 

  367. #define MKVAL(vals)  (vals[0] | (vals[1] << 3) | (vals[2] << 6))

  368. 

  369. /* Image mode - the hardest to comprehend MSS4 coding mode.

  370.  *

  371.  * In this mode all three 16x16 blocks are coded together with a method

  372.  * remotely similar to the methods employed in MSS1-MSS3.

  373.  * The idea is that every component has a vector of 1-4 most common symbols

  374.  * and an escape mode for reading new value from the bitstream. Decoding

  375.  * consists of retrieving pixel values from the vector or reading new ones

  376.  * from the bitstream; depending on flags read from the bitstream, these vector

  377.  * positions can be updated or reused from the state of the previous line

  378.  * or previous pixel.

  379.  */

  380. static int mss4_decode_image_block(MSS4Context *ctx, GetBitContext *gb,

  381.                                    uint8_t *picdst[3], int mb_x, int mb_y)

  382. {

  383.     uint8_t vec[3][4];

  384.     int     vec_len[3];

  385.     int     sel_len[3], sel_flag[3];

  386.     int     i, j, k, mode, split;

  387.     int     prev_vec1 = 0, prev_split = 0;

  388.     int     vals[3] = { 0 };

  389.     int     prev_pix[3] = { 0 };

  390.     int     prev_mode[16] = { 0 };

  391.     uint8_t *dst[3];

  392. 

  393.     const int val_shift = ctx->quality == 100 ? 0 : 2;

  394. 

  395.     for (i = 0; i < 3; i++)

  396.         dst[i] = ctx->imgbuf[i];

  397. 

  398.     for (i = 0; i < 3; i++) {

  399.         vec_len[i] = vec_len_syms[!!i][get_unary(gb, 0, 3)];

  400.         for (j = 0; j < vec_len[i]; j++) {

  401.             vec[i][j]  = get_coeff(gb, &ctx->vec_entry_vlc[!!i]);

  402.             vec[i][j] += ctx->prev_vec[i][j];

  403.             ctx->prev_vec[i][j] = vec[i][j];

  404.         }

  405.         sel_flag[i] = vec_len[i] > 1;

  406.         sel_len[i]  = vec_len[i] > 2 ? vec_len[i] - 2 : 0;

  407.     }

  408. 

  409.     for (j = 0; j < 16; j++) {

  410.         if (get_bits1(gb)) {

  411.             split = 0;

  412.             if (get_bits1(gb)) {

  413.                 prev_mode[0] = 0;

  414.                 vals[0] = vals[1] = vals[2] = 0;

  415.                 mode = 2;

  416.             } else {

  417.                 mode = get_bits1(gb);

  418.                 if (mode)

  419.                     split = get_bits(gb, 4);

  420.             }

  421.             for (i = 0; i < 16; i++) {

  422.                 if (mode <= 1) {

  423.                     vals[0] =  prev_mode[i]       & 7;

  424.                     vals[1] = (prev_mode[i] >> 3) & 7;

  425.                     vals[2] =  prev_mode[i] >> 6;

  426.                     if (mode == 1 && i == split) {

  427.                         read_vec_pos(gb, vals, sel_flag, sel_len, vals);

  428.                     }

  429.                 } else if (mode == 2) {

  430.                     if (get_bits1(gb))

  431.                         read_vec_pos(gb, vals, sel_flag, sel_len, vals);

  432.                 }

  433.                 for (k = 0; k < 3; k++)

  434.                     *dst[k]++ = get_value_cached(gb, vals[k], vec[k],

  435.                                                  vec_len[k], k,

  436.                                                  val_shift, prev_pix);

  437.                 prev_mode[i] = MKVAL(vals);

  438.             }

  439.         } else {

  440.             if (get_bits1(gb)) {

  441.                 split = get_bits(gb, 4);

  442.                 if (split >= prev_split)

  443.                     split++;

  444.                 prev_split = split;

  445.             } else {

  446.                 split = prev_split;

  447.             }

  448.             if (split) {

  449.                 vals[0] =  prev_mode[0]       & 7;

  450.                 vals[1] = (prev_mode[0] >> 3) & 7;

  451.                 vals[2] =  prev_mode[0] >> 6;

  452.                 for (i = 0; i < 3; i++) {

  453.                     for (k = 0; k < split; k++) {

  454.                         *dst[i]++ = get_value_cached(gb, vals[i], vec[i],

  455.                                                      vec_len[i], i, val_shift,

  456.                                                      prev_pix);

  457.                         prev_mode[k] = MKVAL(vals);

  458.                     }

  459.                 }

  460.             }

  461. 

  462.             if (split != 16) {

  463.                 vals[0] =  prev_vec1       & 7;

  464.                 vals[1] = (prev_vec1 >> 3) & 7;

  465.                 vals[2] =  prev_vec1 >> 6;

  466.                 if (get_bits1(gb)) {

  467.                     read_vec_pos(gb, vals, sel_flag, sel_len, vals);

  468.                     prev_vec1 = MKVAL(vals);

  469.                 }

  470.                 for (i = 0; i < 3; i++) {

  471.                     for (k = 0; k < 16 - split; k++) {

  472.                         *dst[i]++ = get_value_cached(gb, vals[i], vec[i],

  473.                                                      vec_len[i], i, val_shift,

  474.                                                      prev_pix);

  475.                         prev_mode[split + k] = MKVAL(vals);

  476.                     }

  477.                 }

  478.             }

  479.         }

  480.     }

  481. 

  482.     for (i = 0; i < 3; i++)

  483.         for (j = 0; j < 16; j++)

  484.             memcpy(picdst[i] + mb_x * 16 + j * ctx->pic.linesize[i],

  485.                    ctx->imgbuf[i] + j * 16, 16);

  486. 

  487.     return 0;

  488. }

  489. 

  490. static inline void mss4_update_dc_cache(MSS4Context *c, int mb_x)

  491. {

  492.     int i;

  493. 

  494.     c->dc_cache[0][TOP]  = c->prev_dc[0][mb_x * 2 + 1];

  495.     c->dc_cache[0][LEFT] = 0;

  496.     c->dc_cache[1][TOP]  = 0;

  497.     c->dc_cache[1][LEFT] = 0;

  498. 

  499.     for (i = 0; i < 2; i++)

  500.         c->prev_dc[0][mb_x * 2 + i] = 0;

  501. 

  502.     for (i = 1; i < 3; i++) {

  503.         c->dc_cache[i + 1][TOP]  = c->prev_dc[i][mb_x];

  504.         c->dc_cache[i + 1][LEFT] = 0;

  505.         c->prev_dc[i][mb_x]      = 0;

  506.     }

  507. }

  508. 

  509. static int mss4_decode_frame(AVCodecContext *avctx, void *data, int *data_size,

  510.                              AVPacket *avpkt)

  511. {

  512.     const uint8_t *buf = avpkt->data;

  513.     int buf_size = avpkt->size;

  514.     MSS4Context *c = avctx->priv_data;

  515.     GetBitContext gb;

  516.     GetByteContext bc;

  517.     uint8_t *dst[3];

  518.     int width, height, quality, frame_type;

  519.     int x, y, i, mb_width, mb_height, blk_type;

  520.     int ret;

  521. 

  522.     if (buf_size < HEADER_SIZE) {

  523.         av_log(avctx, AV_LOG_ERROR,

  524.                "Frame should have at least %d bytes, got %d instead\n",

  525.                HEADER_SIZE, buf_size);

  526.         return AVERROR_INVALIDDATA;

  527.     }

  528. 

  529.     bytestream2_init(&bc, buf, buf_size);

  530.     width      = bytestream2_get_be16(&bc);

  531.     height     = bytestream2_get_be16(&bc);

  532.     bytestream2_skip(&bc, 2);

  533.     quality    = bytestream2_get_byte(&bc);

  534.     frame_type = bytestream2_get_byte(&bc);

  535. 

  536.     if (width > avctx->width ||

  537.         height != avctx->height) {

  538.         av_log(avctx, AV_LOG_ERROR, "Invalid frame dimensions %dx%d\n",

  539.                width, height);

  540.         return AVERROR_INVALIDDATA;

  541.     }

  542.     if (quality < 1 || quality > 100) {

  543.         av_log(avctx, AV_LOG_ERROR, "Invalid quality setting %d\n", quality);

  544.         return AVERROR_INVALIDDATA;

  545.     }

  546.     if ((frame_type & ~3) || frame_type == 3) {

  547.         av_log(avctx, AV_LOG_ERROR, "Invalid frame type %d\n", frame_type);

  548.         return AVERROR_INVALIDDATA;

  549.     }

  550. 

  551.     if (frame_type != SKIP_FRAME && !bytestream2_get_bytes_left(&bc)) {

  552.         av_log(avctx, AV_LOG_ERROR,

  553.                "Empty frame found but it is not a skip frame.\n");

  554.         return AVERROR_INVALIDDATA;

  555.     }

  556. 

  557.     c->pic.reference    = 3;

  558.     c->pic.buffer_hints = FF_BUFFER_HINTS_VALID    |

  559.                           FF_BUFFER_HINTS_PRESERVE |

  560.                           FF_BUFFER_HINTS_REUSABLE;

  561.     if ((ret = avctx->reget_buffer(avctx, &c->pic)) < 0) {

  562.         av_log(avctx, AV_LOG_ERROR, "reget_buffer() failed\n");

  563.         return ret;

  564.     }

  565.     c->pic.key_frame = (frame_type == INTRA_FRAME);

  566.     c->pic.pict_type = (frame_type == INTRA_FRAME) ? AV_PICTURE_TYPE_I

  567.                                                    : AV_PICTURE_TYPE_P;

  568.     if (frame_type == SKIP_FRAME) {

  569.         *data_size = sizeof(AVFrame);

  570.         *(AVFrame*)data = c->pic;

  571. 

  572.         return buf_size;

  573.     }

  574. 

  575.     if (c->quality != quality) {

  576.         c->quality = quality;

  577.         for (i = 0; i < 2; i++)

  578.             ff_mss34_gen_quant_mat(c->quant_mat[i], quality, !i);

  579.     }

  580. 

  581.     init_get_bits(&gb, buf + HEADER_SIZE, (buf_size - HEADER_SIZE) * 8);

  582. 

  583.     mb_width  = FFALIGN(width,  16) >> 4;

  584.     mb_height = FFALIGN(height, 16) >> 4;

  585.     dst[0] = c->pic.data[0];

  586.     dst[1] = c->pic.data[1];

  587.     dst[2] = c->pic.data[2];

  588. 

  589.     memset(c->prev_vec, 0, sizeof(c->prev_vec));

  590.     for (y = 0; y < mb_height; y++) {

  591.         memset(c->dc_cache, 0, sizeof(c->dc_cache));

  592.         for (x = 0; x < mb_width; x++) {

  593.             blk_type = decode012(&gb);

  594.             switch (blk_type) {

  595.             case DCT_BLOCK:

  596.                 if (mss4_decode_dct_block(c, &gb, dst, x, y) < 0) {

  597.                     av_log(avctx, AV_LOG_ERROR,

  598.                            "Error decoding DCT block %d,%d\n",

  599.                            x, y);

  600.                     return AVERROR_INVALIDDATA;

  601.                 }

  602.                 break;

  603.             case IMAGE_BLOCK:

  604.                 if (mss4_decode_image_block(c, &gb, dst, x, y) < 0) {

  605.                     av_log(avctx, AV_LOG_ERROR,

  606.                            "Error decoding VQ block %d,%d\n",

  607.                            x, y);

  608.                     return AVERROR_INVALIDDATA;

  609.                 }

  610.                 break;

  611.             case SKIP_BLOCK:

  612.                 if (frame_type == INTRA_FRAME) {

  613.                     av_log(avctx, AV_LOG_ERROR, "Skip block in intra frame\n");

  614.                     return AVERROR_INVALIDDATA;

  615.                 }

  616.                 break;

  617.             }

  618.             if (blk_type != DCT_BLOCK)

  619.                 mss4_update_dc_cache(c, x);

  620.         }

  621.         dst[0] += c->pic.linesize[0] * 16;

  622.         dst[1] += c->pic.linesize[1] * 16;

  623.         dst[2] += c->pic.linesize[2] * 16;

  624.     }

  625. 

  626.     *data_size = sizeof(AVFrame);

  627.     *(AVFrame*)data = c->pic;

  628. 

  629.     return buf_size;

  630. }

  631. 

  632. static av_cold int mss4_decode_init(AVCodecContext *avctx)

  633. {

  634.     MSS4Context * const c = avctx->priv_data;

  635.     int i;

  636. 

  637.     if (mss4_init_vlcs(c)) {

  638.         av_log(avctx, AV_LOG_ERROR, "Cannot initialise VLCs\n");

  639.         mss4_free_vlcs(c);

  640.         return AVERROR(ENOMEM);

  641.     }

  642.     for (i = 0; i < 3; i++) {

  643.         c->dc_stride[i] = FFALIGN(avctx->width, 16) >> (2 + !!i);

  644.         c->prev_dc[i]   = av_malloc(sizeof(**c->prev_dc) * c->dc_stride[i]);

  645.         if (!c->prev_dc[i]) {

  646.             av_log(avctx, AV_LOG_ERROR, "Cannot allocate buffer\n");

  647.             mss4_free_vlcs(c);

  648.             return AVERROR(ENOMEM);

  649.         }

  650.     }

  651. 

  652.     avctx->pix_fmt     = PIX_FMT_YUV444P;

  653.     avctx->coded_frame = &c->pic;

  654. 

  655.     return 0;

  656. }

  657. 

  658. static av_cold int mss4_decode_end(AVCodecContext *avctx)

  659. {

  660.     MSS4Context * const c = avctx->priv_data;

  661.     int i;

  662. 

  663.     if (c->pic.data[0])

  664.         avctx->release_buffer(avctx, &c->pic);

  665.     for (i = 0; i < 3; i++)

  666.         av_freep(&c->prev_dc[i]);

  667.     mss4_free_vlcs(c);

  668. 

  669.     return 0;

  670. }

  671. 

  672. AVCodec ff_mts2_decoder = {

  673.     .name           = "mts2",

  674.     .type           = AVMEDIA_TYPE_VIDEO,

  675.     .id             = AV_CODEC_ID_MTS2,

  676.     .priv_data_size = sizeof(MSS4Context),

  677.     .init           = mss4_decode_init,

  678.     .close          = mss4_decode_end,

  679.     .decode         = mss4_decode_frame,

  680.     .capabilities   = CODEC_CAP_DR1,

  681.     .long_name      = NULL_IF_CONFIG_SMALL("MS Expression Encoder Screen"),

  682. };