FFmpeg: libavcodec/kgv1dec.c Source File

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libavcodec

kgv1dec.c

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1 /*

2 * Kega Game Video (KGV1) decoder

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 */

22 /**

23 * @file

24 * Kega Game Video decoder

25 */

27 #include "libavutil/common.h"

28 #include "libavutil/intreadwrite.h"

29 #include "libavutil/imgutils.h"

30 #include "avcodec.h"

31 #include "internal.h"

33 typedef struct {

34 AVCodecContext *avctx;

35 AVFrame prev;

36 } KgvContext;

38 static void decode_flush(AVCodecContext *avctx)

39 {

40 KgvContext * const c = avctx->priv_data;

42 av_frame_unref(&c->prev);

43 }

45 static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame,

46 AVPacket *avpkt)

47 {

48 AVFrame *frame = data;

49 const uint8_t *buf = avpkt->data;

50 const uint8_t *buf_end = buf + avpkt->size;

51 KgvContext * const c = avctx->priv_data;

52 int offsets[8];

53 uint8_t *out, *prev;

54 int outcnt = 0, maxcnt;

55 int w, h, i, res;

57 if (avpkt->size < 2)

58 return AVERROR_INVALIDDATA;

60 w = (buf[0] + 1) * 8;

61 h = (buf[1] + 1) * 8;

62 buf += 2;

64 if ((res = av_image_check_size(w, h, 0, avctx)) < 0)

65 return res;

67 if (w != avctx->width || h != avctx->height) {

68 av_frame_unref(&c->prev);

69 avcodec_set_dimensions(avctx, w, h);

70 }

72 maxcnt = w * h;

74 if ((res = ff_get_buffer(avctx, frame, AV_GET_BUFFER_FLAG_REF)) < 0)

75 return res;

76 out = frame->data[0];

77 if (c->prev.data[0]) {

78 prev = c->prev.data[0];

79 } else {

80 prev = NULL;

81 }

83 for (i = 0; i < 8; i++)

84 offsets[i] = -1;

86 while (outcnt < maxcnt && buf_end - 2 >= buf) {

87 int code = AV_RL16(buf);

88 buf += 2;

90 if (!(code & 0x8000)) {

91 AV_WN16A(&out[2 * outcnt], code); // rgb555 pixel coded directly

92 outcnt++;

93 } else {

94 int count;

96 if ((code & 0x6000) == 0x6000) {

97 // copy from previous frame

98 int oidx = (code >> 10) & 7;

99 int start;

100

101 count = (code & 0x3FF) + 3;

102

103 if (offsets[oidx] < 0) {

104 if (buf_end - 3 < buf)

105 break;

106 offsets[oidx] = AV_RL24(buf);

107 buf += 3;

108 }

109

110 start = (outcnt + offsets[oidx]) % maxcnt;

111

112 if (maxcnt - start < count || maxcnt - outcnt < count)

113 break;

114

115 if (!prev) {

116 av_log(avctx, AV_LOG_ERROR,

117 "Frame reference does not exist\n");

118 break;

119 }

120

121 memcpy(out + 2 * outcnt, prev + 2 * start, 2 * count);

122 } else {

123 // copy from earlier in this frame

124 int offset = (code & 0x1FFF) + 1;

125

126 if (!(code & 0x6000)) {

127 count = 2;

128 } else if ((code & 0x6000) == 0x2000) {

129 count = 3;

130 } else {

131 if (buf_end - 1 < buf)

132 break;

133 count = 4 + *buf++;

134 }

135

136 if (outcnt < offset || maxcnt - outcnt < count)

137 break;

138

139 av_memcpy_backptr(out + 2 * outcnt, 2 * offset, 2 * count);

140 }

141 outcnt += count;

142 }

143 }

144

145 if (outcnt - maxcnt)

146 av_log(avctx, AV_LOG_DEBUG, "frame finished with %d diff\n", outcnt - maxcnt);

147

148 av_frame_unref(&c->prev);

149 if ((res = av_frame_ref(&c->prev, frame)) < 0)

150 return res;

151

152 *got_frame = 1;

153

154 return avpkt->size;

155 }

156

157 static av_cold int decode_init(AVCodecContext *avctx)

158 {

159 KgvContext * const c = avctx->priv_data;

160

161 c->avctx = avctx;

162 avctx->pix_fmt = AV_PIX_FMT_RGB555;

163 avctx->flags |= CODEC_FLAG_EMU_EDGE;

164

165 return 0;

166 }

167

168 static av_cold int decode_end(AVCodecContext *avctx)

169 {

170 decode_flush(avctx);

171 return 0;

172 }

173

174 AVCodec ff_kgv1_decoder = {

175 .name = "kgv1",

176 .type = AVMEDIA_TYPE_VIDEO,

177 .id = AV_CODEC_ID_KGV1,

178 .priv_data_size = sizeof(KgvContext),

179 .init = decode_init,

180 .close = decode_end,

181 .decode = decode_frame,

182 .flush = decode_flush,

183 .long_name = NULL_IF_CONFIG_SMALL("Kega Game Video"),

184 .capabilities = CODEC_CAP_DR1,

185 };

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