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  1. /*
  2.  * Kega Game Video (KGV1) decoder
  3.  * Copyright (c) 2010 Daniel Verkamp
  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.  * Kega Game Video decoder
  25.  */
  26.  
  27. #include "libavutil/common.h"
  28. #include "libavutil/intreadwrite.h"
  29. #include "libavutil/imgutils.h"
  30. #include "avcodec.h"
  31. #include "internal.h"
  32.  
  33. typedef struct {
  34.     AVFrame *prev;
  35. } KgvContext;
  36.  
  37. static void decode_flush(AVCodecContext *avctx)
  38. {
  39.     KgvContext * const c = avctx->priv_data;
  40.  
  41.     av_frame_unref(c->prev);
  42. }
  43.  
  44. static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
  45.                         AVPacket *avpkt)
  46. {
  47.     AVFrame *frame = data;
  48.     const uint8_t *buf = avpkt->data;
  49.     const uint8_t *buf_end = buf + avpkt->size;
  50.     KgvContext * const c = avctx->priv_data;
  51.     int offsets[8];
  52.     uint8_t *out, *prev;
  53.     int outcnt = 0, maxcnt;
  54.     int w, h, i, res;
  55.  
  56.     if (avpkt->size < 2)
  57.         return AVERROR_INVALIDDATA;
  58.  
  59.     w = (buf[0] + 1) * 8;
  60.     h = (buf[1] + 1) * 8;
  61.     buf += 2;
  62.  
  63.     if ((res = av_image_check_size(w, h, 0, avctx)) < 0)
  64.         return res;
  65.  
  66.     if (w != avctx->width || h != avctx->height) {
  67.         av_frame_unref(c->prev);
  68.         avcodec_set_dimensions(avctx, w, h);
  69.     }
  70.  
  71.     maxcnt = w * h;
  72.  
  73.     if ((res = ff_get_buffer(avctx, frame, AV_GET_BUFFER_FLAG_REF)) < 0)
  74.         return res;
  75.     out  = frame->data[0];
  76.     if (c->prev->data[0]) {
  77.         prev = c->prev->data[0];
  78.     } else {
  79.         prev = NULL;
  80.     }
  81.  
  82.     for (i = 0; i < 8; i++)
  83.         offsets[i] = -1;
  84.  
  85.     while (outcnt < maxcnt && buf_end - 2 >= buf) {
  86.         int code = AV_RL16(buf);
  87.         buf += 2;
  88.  
  89.         if (!(code & 0x8000)) {
  90.             AV_WN16A(&out[2 * outcnt], code); // rgb555 pixel coded directly
  91.             outcnt++;
  92.         } else {
  93.             int count;
  94.  
  95.             if ((code & 0x6000) == 0x6000) {
  96.                 // copy from previous frame
  97.                 int oidx = (code >> 10) & 7;
  98.                 int start;
  99.  
  100.                 count = (code & 0x3FF) + 3;
  101.  
  102.                 if (offsets[oidx] < 0) {
  103.                     if (buf_end - 3 < buf)
  104.                         break;
  105.                     offsets[oidx] = AV_RL24(buf);
  106.                     buf += 3;
  107.                 }
  108.  
  109.                 start = (outcnt + offsets[oidx]) % maxcnt;
  110.  
  111.                 if (maxcnt - start < count || maxcnt - outcnt < count)
  112.                     break;
  113.  
  114.                 if (!prev) {
  115.                     av_log(avctx, AV_LOG_ERROR,
  116.                            "Frame reference does not exist\n");
  117.                     break;
  118.                 }
  119.  
  120.                 memcpy(out + 2 * outcnt, prev + 2 * start, 2 * count);
  121.             } else {
  122.                 // copy from earlier in this frame
  123.                 int offset = (code & 0x1FFF) + 1;
  124.  
  125.                 if (!(code & 0x6000)) {
  126.                     count = 2;
  127.                 } else if ((code & 0x6000) == 0x2000) {
  128.                     count = 3;
  129.                 } else {
  130.                     if (buf_end - 1 < buf)
  131.                         break;
  132.                     count = 4 + *buf++;
  133.                 }
  134.  
  135.                 if (outcnt < offset || maxcnt - outcnt < count)
  136.                     break;
  137.  
  138.                 av_memcpy_backptr(out + 2 * outcnt, 2 * offset, 2 * count);
  139.             }
  140.             outcnt += count;
  141.         }
  142.     }
  143.  
  144.     if (outcnt - maxcnt)
  145.         av_log(avctx, AV_LOG_DEBUG, "frame finished with %d diff\n", outcnt - maxcnt);
  146.  
  147.     av_frame_unref(c->prev);
  148.     if ((res = av_frame_ref(c->prev, frame)) < 0)
  149.         return res;
  150.  
  151.     *got_frame = 1;
  152.  
  153.     return avpkt->size;
  154. }
  155.  
  156. static av_cold int decode_init(AVCodecContext *avctx)
  157. {
  158.     KgvContext * const c = avctx->priv_data;
  159.  
  160.     avctx->pix_fmt = AV_PIX_FMT_RGB555;
  161.     avctx->flags  |= CODEC_FLAG_EMU_EDGE;
  162.  
  163.     c->prev = av_frame_alloc();
  164.     if (!c->prev)
  165.         return AVERROR(ENOMEM);
  166.  
  167.     return 0;
  168. }
  169.  
  170. static av_cold int decode_end(AVCodecContext *avctx)
  171. {
  172.     KgvContext * const c = avctx->priv_data;
  173.     av_frame_free(&c->prev);
  174.     return 0;
  175. }
  176.  
  177. AVCodec ff_kgv1_decoder = {
  178.     .name           = "kgv1",
  179.     .long_name      = NULL_IF_CONFIG_SMALL("Kega Game Video"),
  180.     .type           = AVMEDIA_TYPE_VIDEO,
  181.     .id             = AV_CODEC_ID_KGV1,
  182.     .priv_data_size = sizeof(KgvContext),
  183.     .init           = decode_init,
  184.     .close          = decode_end,
  185.     .decode         = decode_frame,
  186.     .flush          = decode_flush,
  187.     .capabilities   = CODEC_CAP_DR1,
  188. };
  189.