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 AVFrame *prev;

35 } KgvContext;

37 static void decode_flush(AVCodecContext *avctx)

38 {

39 KgvContext * const c = avctx->priv_data;

41 av_frame_free(&c->prev);

42 }

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;

56 if (avpkt->size < 2)

57 return AVERROR_INVALIDDATA;

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

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

61 buf += 2;

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

64 return res;

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

67 av_frame_unref(c->prev);

68 avcodec_set_dimensions(avctx, w, h);

69 }

71 maxcnt = w * h;

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 }

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

83 offsets[i] = -1;

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

86 int code = AV_RL16(buf);

87 buf += 2;

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

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

91 outcnt++;

92 } else {

93 int count;

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

96 // copy from previous frame

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

98 int start;

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 c->prev = av_frame_alloc();

161 if (!c->prev)

162 return AVERROR(ENOMEM);

163

164 avctx->pix_fmt = AV_PIX_FMT_RGB555;

165 avctx->flags |= CODEC_FLAG_EMU_EDGE;

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 };

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