FFmpeg
mss1.c
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1 /*
2  * Microsoft Screen 1 (aka Windows Media Video V7 Screen) decoder
3  * Copyright (c) 2012 Konstantin Shishkov
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  * Microsoft Screen 1 (aka Windows Media Video V7 Screen) decoder
25  */
26 
27 #include "avcodec.h"
28 #include "internal.h"
29 #include "mss12.h"
30 
31 typedef struct MSS1Context {
35 } MSS1Context;
36 
38 {
39  for (;;) {
40  if (c->high >= 0x8000) {
41  if (c->low < 0x8000) {
42  if (c->low >= 0x4000 && c->high < 0xC000) {
43  c->value -= 0x4000;
44  c->low -= 0x4000;
45  c->high -= 0x4000;
46  } else {
47  return;
48  }
49  } else {
50  c->value -= 0x8000;
51  c->low -= 0x8000;
52  c->high -= 0x8000;
53  }
54  }
55  c->value <<= 1;
56  c->low <<= 1;
57  c->high <<= 1;
58  c->high |= 1;
59  c->value |= get_bits1(c->gbc.gb);
60  }
61 }
62 
63 ARITH_GET_BIT(arith)
64 
65 static int arith_get_bits(ArithCoder *c, int bits)
66 {
67  int range = c->high - c->low + 1;
68  int val = (((c->value - c->low + 1) << bits) - 1) / range;
69  int prob = range * val;
70 
71  c->high = ((prob + range) >> bits) + c->low - 1;
72  c->low += prob >> bits;
73 
75 
76  return val;
77 }
78 
79 static int arith_get_number(ArithCoder *c, int mod_val)
80 {
81  int range = c->high - c->low + 1;
82  int val = ((c->value - c->low + 1) * mod_val - 1) / range;
83  int prob = range * val;
84 
85  c->high = (prob + range) / mod_val + c->low - 1;
86  c->low += prob / mod_val;
87 
88  arith_normalise(c);
89 
90  return val;
91 }
92 
93 static int arith_get_prob(ArithCoder *c, int16_t *probs)
94 {
95  int range = c->high - c->low + 1;
96  int val = ((c->value - c->low + 1) * probs[0] - 1) / range;
97  int sym = 1;
98 
99  while (probs[sym] > val)
100  sym++;
101 
102  c->high = range * probs[sym - 1] / probs[0] + c->low - 1;
103  c->low += range * probs[sym] / probs[0];
104 
105  return sym;
106 }
107 
108 ARITH_GET_MODEL_SYM(arith)
109 
111 {
112  c->low = 0;
113  c->high = 0xFFFF;
114  c->value = get_bits(gb, 16);
115  c->gbc.gb = gb;
116  c->get_model_sym = arith_get_model_sym;
117  c->get_number = arith_get_number;
118 }
119 
120 static int decode_pal(MSS12Context *ctx, ArithCoder *acoder)
121 {
122  int i, ncol, r, g, b;
123  uint32_t *pal = ctx->pal + 256 - ctx->free_colours;
124 
125  if (!ctx->free_colours)
126  return 0;
127 
128  ncol = arith_get_number(acoder, ctx->free_colours + 1);
129  for (i = 0; i < ncol; i++) {
130  r = arith_get_bits(acoder, 8);
131  g = arith_get_bits(acoder, 8);
132  b = arith_get_bits(acoder, 8);
133  *pal++ = (0xFFU << 24) | (r << 16) | (g << 8) | b;
134  }
135 
136  return !!ncol;
137 }
138 
139 static int mss1_decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
140  AVPacket *avpkt)
141 {
142  MSS1Context *ctx = avctx->priv_data;
143  MSS12Context *c = &ctx->ctx;
144  GetBitContext gb;
145  ArithCoder acoder;
146  int pal_changed = 0;
147  int ret;
148 
149  if ((ret = init_get_bits8(&gb, avpkt->data, avpkt->size)) < 0)
150  return ret;
151 
152  arith_init(&acoder, &gb);
153 
154  if ((ret = ff_reget_buffer(avctx, ctx->pic)) < 0)
155  return ret;
156 
157  c->pal_pic = ctx->pic->data[0] + ctx->pic->linesize[0] * (avctx->height - 1);
158  c->pal_stride = -ctx->pic->linesize[0];
159  c->keyframe = !arith_get_bit(&acoder);
160  if (c->keyframe) {
161  c->corrupted = 0;
163  pal_changed = decode_pal(c, &acoder);
164  ctx->pic->key_frame = 1;
166  } else {
167  if (c->corrupted)
168  return AVERROR_INVALIDDATA;
169  ctx->pic->key_frame = 0;
171  }
172  c->corrupted = ff_mss12_decode_rect(&ctx->sc, &acoder, 0, 0,
173  avctx->width, avctx->height);
174  if (c->corrupted)
175  return AVERROR_INVALIDDATA;
176  memcpy(ctx->pic->data[1], c->pal, AVPALETTE_SIZE);
177  ctx->pic->palette_has_changed = pal_changed;
178 
179  if ((ret = av_frame_ref(data, ctx->pic)) < 0)
180  return ret;
181 
182  *got_frame = 1;
183 
184  /* always report that the buffer was completely consumed */
185  return avpkt->size;
186 }
187 
189 {
190  MSS1Context * const c = avctx->priv_data;
191  int ret;
192 
193  c->ctx.avctx = avctx;
194 
195  c->pic = av_frame_alloc();
196  if (!c->pic)
197  return AVERROR(ENOMEM);
198 
199  ret = ff_mss12_decode_init(&c->ctx, 0, &c->sc, NULL);
200  if (ret < 0)
201  av_frame_free(&c->pic);
202 
203  avctx->pix_fmt = AV_PIX_FMT_PAL8;
204 
205  return ret;
206 }
207 
209 {
210  MSS1Context * const ctx = avctx->priv_data;
211 
212  av_frame_free(&ctx->pic);
213  ff_mss12_decode_end(&ctx->ctx);
214 
215  return 0;
216 }
217 
219  .name = "mss1",
220  .long_name = NULL_IF_CONFIG_SMALL("MS Screen 1"),
221  .type = AVMEDIA_TYPE_VIDEO,
222  .id = AV_CODEC_ID_MSS1,
223  .priv_data_size = sizeof(MSS1Context),
225  .close = mss1_decode_end,
227  .capabilities = AV_CODEC_CAP_DR1,
228 };
static int decode_pal(MSS12Context *ctx, ArithCoder *acoder)
Definition: mss1.c:120
#define NULL
Definition: coverity.c:32
const char const char void * val
Definition: avisynth_c.h:863
#define AVERROR_INVALIDDATA
Invalid data found when processing input.
Definition: error.h:59
This structure describes decoded (raw) audio or video data.
Definition: frame.h:268
ptrdiff_t const GLvoid * data
Definition: opengl_enc.c:100
int high
Definition: mss12.h:49
av_cold int ff_mss12_decode_init(MSS12Context *c, int version, SliceContext *sc1, SliceContext *sc2)
Definition: mss12.c:565
static unsigned int get_bits(GetBitContext *s, int n)
Read 1-25 bits.
Definition: get_bits.h:379
const char * g
Definition: vf_curves.c:115
static av_cold int init(AVCodecContext *avctx)
Definition: avrndec.c:35
int value
Definition: mss12.h:49
int corrupted
Definition: mss12.h:89
int size
Definition: avcodec.h:1478
enum AVPixelFormat pix_fmt
Pixel format, see AV_PIX_FMT_xxx.
Definition: avcodec.h:1775
static av_cold int mss1_decode_end(AVCodecContext *avctx)
Definition: mss1.c:208
AVCodec.
Definition: avcodec.h:3477
static void decode(AVCodecContext *dec_ctx, AVPacket *pkt, AVFrame *frame, FILE *outfile)
Definition: decode_audio.c:42
int ff_mss12_decode_rect(SliceContext *sc, ArithCoder *acoder, int x, int y, int width, int height)
Definition: mss12.c:529
int ff_reget_buffer(AVCodecContext *avctx, AVFrame *frame)
Identical in function to av_frame_make_writable(), except it uses ff_get_buffer() to allocate the buf...
Definition: decode.c:2011
uint32_t pal[256]
Definition: mss12.h:77
#define av_cold
Definition: attributes.h:82
AVFrame * av_frame_alloc(void)
Allocate an AVFrame and set its fields to default values.
Definition: frame.c:189
8 bits with AV_PIX_FMT_RGB32 palette
Definition: pixfmt.h:77
int keyframe
Definition: mss12.h:87
#define AVPALETTE_SIZE
Definition: pixfmt.h:32
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
int av_frame_ref(AVFrame *dst, const AVFrame *src)
Set up a new reference to the data described by the source frame.
Definition: frame.c:443
static int arith_get_bits(ArithCoder *c, int bits)
Definition: mss1.c:65
uint8_t * data
Definition: avcodec.h:1477
static void arith_normalise(ArithCoder *c)
Definition: mss1.c:37
#define prob(name, subs,...)
Definition: cbs_vp9.c:374
#define U(x)
Definition: vp56_arith.h:37
#define i(width, name, range_min, range_max)
Definition: cbs_h2645.c:260
static int arith_get_prob(ArithCoder *c, int16_t *probs)
Definition: mss1.c:93
void av_frame_free(AVFrame **frame)
Free the frame and any dynamically allocated objects in it, e.g.
Definition: frame.c:202
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification. ...
Definition: internal.h:186
const char * r
Definition: vf_curves.c:114
#define ARITH_GET_MODEL_SYM(prefix)
Definition: mss12.h:118
const char * name
Name of the codec implementation.
Definition: avcodec.h:3484
uint8_t bits
Definition: vp3data.h:202
AVCodecContext * avctx
Definition: mss12.h:76
#define b
Definition: input.c:41
enum AVPictureType pict_type
Picture type of the frame.
Definition: frame.h:351
int width
picture width / height.
Definition: avcodec.h:1738
ptrdiff_t pal_stride
Definition: mss12.h:80
av_cold int ff_mss12_decode_end(MSS12Context *c)
Definition: mss12.c:677
Libavcodec external API header.
int linesize[AV_NUM_DATA_POINTERS]
For video, size in bytes of each picture line.
Definition: frame.h:299
static int init_get_bits8(GetBitContext *s, const uint8_t *buffer, int byte_size)
Initialize GetBitContext.
Definition: get_bits.h:677
main external API structure.
Definition: avcodec.h:1565
static int mss1_decode_frame(AVCodecContext *avctx, void *data, int *got_frame, AVPacket *avpkt)
Definition: mss1.c:139
AVFrame * pic
Definition: mss1.c:33
static unsigned int get_bits1(GetBitContext *s)
Definition: get_bits.h:498
int palette_has_changed
Tell user application that palette has changed from previous frame.
Definition: frame.h:425
SliceContext sc
Definition: mss1.c:34
uint8_t * data[AV_NUM_DATA_POINTERS]
pointer to the picture/channel planes.
Definition: frame.h:282
common internal api header.
void ff_mss12_slicecontext_reset(SliceContext *sc)
Definition: mss12.c:429
static int arith_get_number(ArithCoder *c, int mod_val)
Definition: mss1.c:79
MSS12Context ctx
Definition: mss1.c:32
int free_colours
Definition: mss12.h:86
void * priv_data
Definition: avcodec.h:1592
static av_cold int mss1_decode_init(AVCodecContext *avctx)
Definition: mss1.c:188
int low
Definition: mss12.h:49
int key_frame
1 -> keyframe, 0-> not
Definition: frame.h:346
#define ARITH_GET_BIT(prefix)
Definition: mss12.h:102
union ArithCoder::@118 gbc
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
GetBitContext * gb
Definition: mss12.h:51
AVCodec ff_mss1_decoder
Definition: mss1.c:218
This structure stores compressed data.
Definition: avcodec.h:1454
#define AV_CODEC_CAP_DR1
Codec uses get_buffer() for allocating buffers and supports custom allocators.
Definition: avcodec.h:981
uint8_t * pal_pic
Definition: mss12.h:78
Predicted.
Definition: avutil.h:275
Common header for Microsoft Screen 1 and 2.
static void arith_init(ArithCoder *c, GetBitContext *gb)
Definition: mss1.c:110