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FFmpeg/libavcodec/escape130.c

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  1. /*

  2.  * Escape 130 Video Decoder

  3.  * Copyright (C) 2008 Eli Friedman (eli.friedman <at> gmail.com)

  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. #include "avcodec.h"

  23. 

  24. #define ALT_BITSTREAM_READER_LE

  25. #include "get_bits.h"

  26. 

  27. typedef struct Escape130Context {

  28.     AVFrame frame;

  29. } Escape130Context;

  30. 

  31. static int can_safely_read(GetBitContext* gb, int bits) {

  32.     return get_bits_count(gb) + bits <= gb->size_in_bits;

  33. }

  34. 

  35. /**

  36.  * Initialize the decoder

  37.  * @param avctx decoder context

  38.  * @return 0 success, negative on error

  39.  */

  40. static av_cold int escape130_decode_init(AVCodecContext *avctx)

  41. {

  42.     avctx->pix_fmt = PIX_FMT_YUV420P;

  43. 

  44.     return 0;

  45. }

  46. 

  47. static av_cold int escape130_decode_close(AVCodecContext *avctx)

  48. {

  49.     Escape130Context *s = avctx->priv_data;

  50. 

  51.     if (s->frame.data[0])

  52.         avctx->release_buffer(avctx, &s->frame);

  53. 

  54.     return 0;

  55. }

  56. 

  57. static unsigned decode_skip_count(GetBitContext* gb) {

  58.     unsigned value;

  59.     // This function reads a maximum of 27 bits,

  60.     // which is within the padding space

  61.     if (!can_safely_read(gb, 1))

  62.         return -1;

  63. 

  64.     value = get_bits1(gb);

  65.     if (value)

  66.         return 0;

  67. 

  68.     value = get_bits(gb, 3);

  69.     if (value)

  70.         return value;

  71. 

  72.     value = get_bits(gb, 8);

  73.     if (value)

  74.         return value + 7;

  75. 

  76.     value = get_bits(gb, 15);

  77.     if (value)

  78.         return value + 262;

  79. 

  80.     return -1;

  81. }

  82. 

  83. /**

  84.  * Decode a single frame

  85.  * @param avctx decoder context

  86.  * @param data decoded frame

  87.  * @param data_size size of the decoded frame

  88.  * @param buf input buffer

  89.  * @param buf_size input buffer size

  90.  * @return 0 success, -1 on error

  91.  */

  92. static int escape130_decode_frame(AVCodecContext *avctx,

  93.                                   void *data, int *data_size,

  94.                                   AVPacket *avpkt)

  95. {

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

  97.     int buf_size = avpkt->size;

  98.     Escape130Context *s = avctx->priv_data;

  99. 

  100.     GetBitContext gb;

  101.     unsigned i;

  102. 

  103.     uint8_t *old_y, *old_cb, *old_cr,

  104.             *new_y, *new_cb, *new_cr;

  105.     unsigned old_y_stride, old_cb_stride, old_cr_stride,

  106.              new_y_stride, new_cb_stride, new_cr_stride;

  107.     unsigned total_blocks = avctx->width * avctx->height / 4,

  108.              block_index, row_index = 0;

  109.     unsigned y[4] = {0}, cb = 16, cr = 16;

  110.     unsigned skip = -1;

  111. 

  112.     AVFrame new_frame = { { 0 } };

  113. 

  114.     init_get_bits(&gb, buf, buf_size * 8);

  115. 

  116.     if (!can_safely_read(&gb, 128))

  117.         return -1;

  118. 

  119.     // Header; no useful information in here

  120.     skip_bits_long(&gb, 128);

  121. 

  122.     new_frame.reference = 3;

  123.     if (avctx->get_buffer(avctx, &new_frame)) {

  124.         av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");

  125.         return -1;

  126.     }

  127. 

  128.     new_y = new_frame.data[0];

  129.     new_cb = new_frame.data[1];

  130.     new_cr = new_frame.data[2];

  131.     new_y_stride = new_frame.linesize[0];

  132.     new_cb_stride = new_frame.linesize[1];

  133.     new_cr_stride = new_frame.linesize[2];

  134.     old_y = s->frame.data[0];

  135.     old_cb = s->frame.data[1];

  136.     old_cr = s->frame.data[2];

  137.     old_y_stride = s->frame.linesize[0];

  138.     old_cb_stride = s->frame.linesize[1];

  139.     old_cr_stride = s->frame.linesize[2];

  140. 

  141.     av_log(NULL, AV_LOG_DEBUG,

  142.            "Strides: %i, %i\n",

  143.            new_y_stride, new_cb_stride);

  144. 

  145.     for (block_index = 0; block_index < total_blocks; block_index++) {

  146.         // Note that this call will make us skip the rest of the blocks

  147.         // if the frame prematurely ends

  148.         if (skip == -1)

  149.             skip = decode_skip_count(&gb);

  150. 

  151.         if (skip) {

  152.             if (old_y) {

  153.                 y[0] = old_y[0] / 4;

  154.                 y[1] = old_y[1] / 4;

  155.                 y[2] = old_y[old_y_stride] / 4;

  156.                 y[3] = old_y[old_y_stride+1] / 4;

  157.                 cb = old_cb[0] / 8;

  158.                 cr = old_cr[0] / 8;

  159.             } else {

  160.                 y[0] = y[1] = y[2] = y[3] = 0;

  161.                 cb = cr = 16;

  162.             }

  163.         } else {

  164.             if (get_bits1(&gb)) {

  165.                 unsigned sign_selector = get_bits(&gb, 6);

  166.                 unsigned difference_selector = get_bits(&gb, 2);

  167.                 unsigned y_base = 2 * get_bits(&gb, 5);

  168.                 static const uint8_t offset_table[] = {2, 4, 10, 20};

  169.                 static const int8_t sign_table[64][4] =

  170.                     { {0, 0, 0, 0},

  171.                       {-1, 1, 0, 0},

  172.                       {1, -1, 0, 0},

  173.                       {-1, 0, 1, 0},

  174.                       {-1, 1, 1, 0},

  175.                       {0, -1, 1, 0},

  176.                       {1, -1, 1, 0},

  177.                       {-1, -1, 1, 0},

  178.                       {1, 0, -1, 0},

  179.                       {0, 1, -1, 0},

  180.                       {1, 1, -1, 0},

  181.                       {-1, 1, -1, 0},

  182.                       {1, -1, -1, 0},

  183.                       {-1, 0, 0, 1},

  184.                       {-1, 1, 0, 1},

  185.                       {0, -1, 0, 1},

  186. 

  187.                       {0, 0, 0, 0},

  188.                       {1, -1, 0, 1},

  189.                       {-1, -1, 0, 1},

  190.                       {-1, 0, 1, 1},

  191.                       {-1, 1, 1, 1},

  192.                       {0, -1, 1, 1},

  193.                       {1, -1, 1, 1},

  194.                       {-1, -1, 1, 1},

  195.                       {0, 0, -1, 1},

  196.                       {1, 0, -1, 1},

  197.                       {-1, 0, -1, 1},

  198.                       {0, 1, -1, 1},

  199.                       {1, 1, -1, 1},

  200.                       {-1, 1, -1, 1},

  201.                       {0, -1, -1, 1},

  202.                       {1, -1, -1, 1},

  203. 

  204.                       {0, 0, 0, 0},

  205.                       {-1, -1, -1, 1},

  206.                       {1, 0, 0, -1},

  207.                       {0, 1, 0, -1},

  208.                       {1, 1, 0, -1},

  209.                       {-1, 1, 0, -1},

  210.                       {1, -1, 0, -1},

  211.                       {0, 0, 1, -1},

  212.                       {1, 0, 1, -1},

  213.                       {-1, 0, 1, -1},

  214.                       {0, 1, 1, -1},

  215.                       {1, 1, 1, -1},

  216.                       {-1, 1, 1, -1},

  217.                       {0, -1, 1, -1},

  218.                       {1, -1, 1, -1},

  219.                       {-1, -1, 1, -1},

  220. 

  221.                       {0, 0, 0, 0},

  222.                       {1, 0, -1, -1},

  223.                       {0, 1, -1, -1},

  224.                       {1, 1, -1, -1},

  225.                       {-1, 1, -1, -1},

  226.                       {1, -1, -1, -1} };

  227.                 for (i = 0; i < 4; i++) {

  228.                     y[i] = av_clip(y_base + offset_table[difference_selector] *

  229.                                             sign_table[sign_selector][i], 0, 63);

  230.                 }

  231.             } else if (get_bits1(&gb)) {

  232.                 if (get_bits1(&gb)) {

  233.                     unsigned y_base = get_bits(&gb, 6);

  234.                     for (i = 0; i < 4; i++)

  235.                         y[i] = y_base;

  236.                 } else {

  237.                     unsigned adjust_index = get_bits(&gb, 3);

  238.                     static const int8_t adjust[] = {-4, -3, -2, -1, 1, 2, 3, 4};

  239.                     for (i = 0; i < 4; i++)

  240.                         y[i] = av_clip(y[i] + adjust[adjust_index], 0, 63);

  241.                 }

  242.             }

  243. 

  244.             if (get_bits1(&gb)) {

  245.                 if (get_bits1(&gb)) {

  246.                     cb = get_bits(&gb, 5);

  247.                     cr = get_bits(&gb, 5);

  248.                 } else {

  249.                     unsigned adjust_index = get_bits(&gb, 3);

  250.                     static const int8_t adjust[2][8] =

  251.                         {  { 1, 1, 0, -1, -1, -1,  0,  1 },

  252.                            { 0, 1, 1,  1,  0, -1, -1, -1 } };

  253.                     cb = (cb + adjust[0][adjust_index]) & 31;

  254.                     cr = (cr + adjust[1][adjust_index]) & 31;

  255.                 }

  256.             }

  257.         }

  258. 

  259.         new_y[0] = y[0] * 4;

  260.         new_y[1] = y[1] * 4;

  261.         new_y[new_y_stride] = y[2] * 4;

  262.         new_y[new_y_stride + 1] = y[3] * 4;

  263.         *new_cb = cb * 8;

  264.         *new_cr = cr * 8;

  265. 

  266.         if (old_y)

  267.             old_y += 2, old_cb++, old_cr++;

  268.         new_y += 2, new_cb++, new_cr++;

  269.         row_index++;

  270.         if (avctx->width / 2 == row_index) {

  271.             row_index = 0;

  272.             if (old_y) {

  273.                 old_y  += old_y_stride * 2  - avctx->width;

  274.                 old_cb += old_cb_stride - avctx->width / 2;

  275.                 old_cr += old_cr_stride - avctx->width / 2;

  276.             }

  277.             new_y  += new_y_stride * 2  - avctx->width;

  278.             new_cb += new_cb_stride - avctx->width / 2;

  279.             new_cr += new_cr_stride - avctx->width / 2;

  280.         }

  281. 

  282.         skip--;

  283.     }

  284. 

  285.     av_log(NULL, AV_LOG_DEBUG,

  286.            "Escape sizes: %i, %i\n",

  287.            buf_size, get_bits_count(&gb) / 8);

  288. 

  289.     if (s->frame.data[0])

  290.         avctx->release_buffer(avctx, &s->frame);

  291. 

  292.     *(AVFrame*)data = s->frame = new_frame;

  293.     *data_size = sizeof(AVFrame);

  294. 

  295.     return buf_size;

  296. }

  297. 

  298. 

  299. AVCodec ff_escape130_decoder = {

  300.     .name           = "escape130",

  301.     .type           = AVMEDIA_TYPE_VIDEO,

  302.     .id             = CODEC_ID_ESCAPE130,

  303.     .priv_data_size = sizeof(Escape130Context),

  304.     .init           = escape130_decode_init,

  305.     .close          = escape130_decode_close,

  306.     .decode         = escape130_decode_frame,

  307.     .capabilities   = CODEC_CAP_DR1,

  308.     .long_name = NULL_IF_CONFIG_SMALL("Escape 130"),

  309. };