FFmpeg: libavcodec/mss1.c Source File

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libavcodec

mss1.c

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1 /*

2 * Microsoft Screen 1 (aka Windows Media Video V7 Screen) 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 * Microsoft Screen 1 (aka Windows Media Video V7 Screen) decoder

25 */

27 #include "avcodec.h"

28 #include "codec_internal.h"

29 #include "decode.h"

30 #include "mss12.h"

32 typedef struct MSS1Context {

33 MSS12Context ctx;

34 AVFrame *pic;

35 SliceContext sc;

36 } MSS1Context;

38 static void arith_normalise(ArithCoder *c)

39 {

40 for (;;) {

41 if (c->high >= 0x8000) {

42 if (c->low < 0x8000) {

43 if (c->low >= 0x4000 && c->high < 0xC000) {

44 c->value -= 0x4000;

45 c->low -= 0x4000;

46 c->high -= 0x4000;

47 } else {

48 return;

49 }

50 } else {

51 c->value -= 0x8000;

52 c->low -= 0x8000;

53 c->high -= 0x8000;

54 }

55 }

56 c->value <<= 1;

57 c->low <<= 1;

58 c->high <<= 1;

59 c->high |= 1;

60 if (get_bits_left(c->gbc.gb) < 1)

61 c->overread++;

62 c->value |= get_bits1(c->gbc.gb);

63 }

64 }

66 ARITH_GET_BIT(arith)

68 static int arith_get_bits(ArithCoder *c, int bits)

69 {

70 int range = c->high - c->low + 1;

71 int val = (((c->value - c->low + 1) << bits) - 1) / range;

72 int prob = range * val;

74 c->high = ((prob + range) >> bits) + c->low - 1;

75 c->low += prob >> bits;

77 arith_normalise(c);

79 return val;

80 }

82 static int arith_get_number(ArithCoder *c, int mod_val)

83 {

84 int range = c->high - c->low + 1;

85 int val = ((c->value - c->low + 1) * mod_val - 1) / range;

86 int prob = range * val;

88 c->high = (prob + range) / mod_val + c->low - 1;

89 c->low += prob / mod_val;

91 arith_normalise(c);

93 return val;

94 }

96 static int arith_get_prob(ArithCoder *c, int16_t *probs)

97 {

98 int range = c->high - c->low + 1;

99 int val = ((c->value - c->low + 1) * probs[0] - 1) / range;

100 int sym = 1;

101

102 while (probs[sym] > val)

103 sym++;

104

105 c->high = range * probs[sym - 1] / probs[0] + c->low - 1;

106 c->low += range * probs[sym] / probs[0];

107

108 return sym;

109 }

110

111 ARITH_GET_MODEL_SYM(arith)

112

113 static void arith_init(ArithCoder *c, GetBitContext *gb)

114 {

115 c->low = 0;

116 c->high = 0xFFFF;

117 c->value = get_bits(gb, 16);

118 c->overread = 0;

119 c->gbc.gb = gb;

120 c->get_model_sym = arith_get_model_sym;

121 c->get_number = arith_get_number;

122 }

123

124 static int decode_pal(MSS12Context *ctx, ArithCoder *acoder)

125 {

126 int i, ncol, r, g, b;

127 uint32_t *pal = ctx->pal + 256 - ctx->free_colours;

128

129 if (!ctx->free_colours)

130 return 0;

131

132 ncol = arith_get_number(acoder, ctx->free_colours + 1);

133 for (i = 0; i < ncol; i++) {

134 r = arith_get_bits(acoder, 8);

135 g = arith_get_bits(acoder, 8);

136 b = arith_get_bits(acoder, 8);

137 *pal++ = (0xFFU << 24) | (r << 16) | (g << 8) | b;

138 }

139

140 return !!ncol;

141 }

142

143 static int mss1_decode_frame(AVCodecContext *avctx, AVFrame *rframe,

144 int *got_frame, AVPacket *avpkt)

145 {

146 MSS1Context *ctx = avctx->priv_data;

147 MSS12Context *c = &ctx->ctx;

148 GetBitContext gb;

149 ArithCoder acoder;

150 int pal_changed = 0;

151 int ret;

152

153 if ((ret = init_get_bits8(&gb, avpkt->data, avpkt->size)) < 0)

154 return ret;

155

156 arith_init(&acoder, &gb);

157

158 if ((ret = ff_reget_buffer(avctx, ctx->pic, 0)) < 0)

159 return ret;

160

161 c->pal_pic = ctx->pic->data[0] + ctx->pic->linesize[0] * (avctx->height - 1);

162 c->pal_stride = -ctx->pic->linesize[0];

163 c->keyframe = !arith_get_bit(&acoder);

164 if (c->keyframe) {

165 c->corrupted = 0;

166 ff_mss12_slicecontext_reset(&ctx->sc);

167 pal_changed = decode_pal(c, &acoder);

168 ctx->pic->flags |= AV_FRAME_FLAG_KEY;

169 ctx->pic->pict_type = AV_PICTURE_TYPE_I;

170 } else {

171 if (c->corrupted)

172 return AVERROR_INVALIDDATA;

173 ctx->pic->flags &= ~AV_FRAME_FLAG_KEY;

174 ctx->pic->pict_type = AV_PICTURE_TYPE_P;

175 }

176 c->corrupted = ff_mss12_decode_rect(&ctx->sc, &acoder, 0, 0,

177 avctx->width, avctx->height);

178 if (c->corrupted)

179 return AVERROR_INVALIDDATA;

180 memcpy(ctx->pic->data[1], c->pal, AVPALETTE_SIZE);

181 #if FF_API_PALETTE_HAS_CHANGED

182 FF_DISABLE_DEPRECATION_WARNINGS

183 ctx->pic->palette_has_changed = pal_changed;

184 FF_ENABLE_DEPRECATION_WARNINGS

185 #endif

186

187 if ((ret = av_frame_ref(rframe, ctx->pic)) < 0)

188 return ret;

189

190 *got_frame = 1;

191

192 /* always report that the buffer was completely consumed */

193 return avpkt->size;

194 }

195

196 static av_cold int mss1_decode_init(AVCodecContext *avctx)

197 {

198 MSS1Context * const c = avctx->priv_data;

199 int ret;

200

201 c->ctx.avctx = avctx;

202

203 c->pic = av_frame_alloc();

204 if (!c->pic)

205 return AVERROR(ENOMEM);

206

207 ret = ff_mss12_decode_init(&c->ctx, 0, &c->sc, NULL);

208 if (ret < 0)

209 return ret;

210

211 avctx->pix_fmt = AV_PIX_FMT_PAL8;

212

213 return ret;

214 }

215

216 static av_cold int mss1_decode_end(AVCodecContext *avctx)

217 {

218 MSS1Context * const ctx = avctx->priv_data;

219

220 av_frame_free(&ctx->pic);

221 ff_mss12_decode_end(&ctx->ctx);

222

223 return 0;

224 }

225

226 const FFCodec ff_mss1_decoder = {

227 .p.name = "mss1",

228 CODEC_LONG_NAME("MS Screen 1"),

229 .p.type = AVMEDIA_TYPE_VIDEO,

230 .p.id = AV_CODEC_ID_MSS1,

231 .priv_data_size = sizeof(MSS1Context),

232 .init = mss1_decode_init,

233 .close = mss1_decode_end,

234 FF_CODEC_DECODE_CB(mss1_decode_frame),

235 .p.capabilities = AV_CODEC_CAP_DR1,

236 .caps_internal = FF_CODEC_CAP_INIT_CLEANUP,

237 };

FF_ENABLE_DEPRECATION_WARNINGS

#define FF_ENABLE_DEPRECATION_WARNINGS

Definition: internal.h:73

MSS1Context

Definition: mss1.c:32

FF_CODEC_CAP_INIT_CLEANUP

#define FF_CODEC_CAP_INIT_CLEANUP

The codec allows calling the close function for deallocation even if the init function returned a fai...

Definition: codec_internal.h:42

get_bits_left

static int get_bits_left(GetBitContext *gb)

Definition: get_bits.h:695

const char * r

Definition: vf_curves.c:126

AVERROR

Filter the word "frame" indicates either a video frame or a group of audio as stored in an AVFrame structure Format for each input and each output the list of supported formats For video that means pixel format For audio that means channel sample they are references to shared objects When the negotiation mechanism computes the intersection of the formats supported at each end of a all references to both lists are replaced with a reference to the intersection And when a single format is eventually chosen for a link amongst the remaining all references to the list are updated That means that if a filter requires that its input and output have the same format amongst a supported all it has to do is use a reference to the same list of formats query_formats can leave some formats unset and return AVERROR(EAGAIN) to cause the negotiation mechanism toagain later. That can be used by filters with complex requirements to use the format negotiated on one link to set the formats supported on another. Frame references ownership and permissions

arith_get_number

static int arith_get_number(ArithCoder *c, int mod_val)

Definition: mss1.c:82

ARITH_GET_MODEL_SYM

#define ARITH_GET_MODEL_SYM(prefix)

Definition: mss12.h:120

av_frame_free

void av_frame_free(AVFrame **frame)

Free the frame and any dynamically allocated objects in it, e.g.

Definition: frame.c:130

AVFrame

This structure describes decoded (raw) audio or video data.

Definition: frame.h:344

AVPacket::data

uint8_t * data

Definition: packet.h:522

arith_get_prob

static int arith_get_prob(ArithCoder *c, int16_t *probs)

Definition: mss1.c:96

#define b

Definition: input.c:41

mss12.h

FFCodec

Definition: codec_internal.h:127

mss1_decode_init

static av_cold int mss1_decode_init(AVCodecContext *avctx)

Definition: mss1.c:196

mss1_decode_frame

static int mss1_decode_frame(AVCodecContext *avctx, AVFrame *rframe, int *got_frame, AVPacket *avpkt)

Definition: mss1.c:143

get_bits

static unsigned int get_bits(GetBitContext *s, int n)

Read 1-25 bits.

Definition: get_bits.h:335

FFCodec::p

AVCodec p

The public AVCodec.

Definition: codec_internal.h:131

GetBitContext

Definition: get_bits.h:108

val

static double val(void *priv, double ch)

Definition: aeval.c:78

av_frame_alloc

AVFrame * av_frame_alloc(void)

Allocate an AVFrame and set its fields to default values.

Definition: frame.c:118

av_cold

#define av_cold

Definition: attributes.h:90

init_get_bits8

static int init_get_bits8(GetBitContext *s, const uint8_t *buffer, int byte_size)

Initialize GetBitContext.

Definition: get_bits.h:545

AV_FRAME_FLAG_KEY

#define AV_FRAME_FLAG_KEY

A flag to mark frames that are keyframes.

Definition: frame.h:595

FF_CODEC_DECODE_CB

#define FF_CODEC_DECODE_CB(func)

Definition: codec_internal.h:287

AVFormatContext::flags

int flags

Flags modifying the (de)muxer behaviour.

Definition: avformat.h:1406

const char * g

Definition: vf_curves.c:127

bits

uint8_t bits

Definition: vp3data.h:128

ctx

AVFormatContext * ctx

Definition: movenc.c:48

decode.h

ArithCoder

Definition: dstdec.c:57

CODEC_LONG_NAME

#define CODEC_LONG_NAME(str)

Definition: codec_internal.h:272

MSS1Context::ctx

MSS12Context ctx

Definition: mss1.c:33

ff_mss1_decoder

const FFCodec ff_mss1_decoder

Definition: mss1.c:226

NULL

#define NULL

Definition: coverity.c:32

AV_CODEC_ID_MSS1

@ AV_CODEC_ID_MSS1

Definition: codec_id.h:214

AVPALETTE_SIZE

#define AVPALETTE_SIZE

Definition: pixfmt.h:32

AV_PICTURE_TYPE_I

@ AV_PICTURE_TYPE_I

Intra.

Definition: avutil.h:279

get_bits1

static unsigned int get_bits1(GetBitContext *s)

Definition: get_bits.h:388

Undefined Behavior In the C some operations are like signed integer dereferencing freed accessing outside allocated Undefined Behavior must not occur in a C it is not safe even if the output of undefined operations is unused The unsafety may seem nit picking but Optimizing compilers have in fact optimized code on the assumption that no undefined Behavior occurs Optimizing code based on wrong assumptions can and has in some cases lead to effects beyond the output of computations The signed integer overflow problem in speed critical code Code which is highly optimized and works with signed integers sometimes has the problem that often the output of the computation does not c

Definition: undefined.txt:32

mss1_decode_end

static av_cold int mss1_decode_end(AVCodecContext *avctx)

Definition: mss1.c:216

SliceContext

Definition: mss12.h:70

ARITH_GET_BIT

#define ARITH_GET_BIT(prefix)

Definition: mss12.h:104

init

int(* init)(AVBSFContext *ctx)

Definition: dts2pts.c:365