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 "codec_internal.h"
29 #include "internal.h"
30 #include "mss12.h"
31 
32 typedef struct MSS1Context {
36 } MSS1Context;
37 
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 }
65 
66 ARITH_GET_BIT(arith)
67 
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;
73 
74  c->high = ((prob + range) >> bits) + c->low - 1;
75  c->low += prob >> bits;
76 
78 
79  return val;
80 }
81 
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;
87 
88  c->high = (prob + range) / mod_val + c->low - 1;
89  c->low += prob / mod_val;
90 
92 
93  return val;
94 }
95 
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 
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;
167  pal_changed = decode_pal(c, &acoder);
168  ctx->pic->key_frame = 1;
169  ctx->pic->pict_type = AV_PICTURE_TYPE_I;
170  } else {
171  if (c->corrupted)
172  return AVERROR_INVALIDDATA;
173  ctx->pic->key_frame = 0;
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  ctx->pic->palette_has_changed = pal_changed;
182 
183  if ((ret = av_frame_ref(rframe, ctx->pic)) < 0)
184  return ret;
185 
186  *got_frame = 1;
187 
188  /* always report that the buffer was completely consumed */
189  return avpkt->size;
190 }
191 
193 {
194  MSS1Context * const c = avctx->priv_data;
195  int ret;
196 
197  c->ctx.avctx = avctx;
198 
199  c->pic = av_frame_alloc();
200  if (!c->pic)
201  return AVERROR(ENOMEM);
202 
203  ret = ff_mss12_decode_init(&c->ctx, 0, &c->sc, NULL);
204  if (ret < 0)
205  av_frame_free(&c->pic);
206 
207  avctx->pix_fmt = AV_PIX_FMT_PAL8;
208 
209  return ret;
210 }
211 
213 {
214  MSS1Context * const ctx = avctx->priv_data;
215 
216  av_frame_free(&ctx->pic);
217  ff_mss12_decode_end(&ctx->ctx);
218 
219  return 0;
220 }
221 
223  .p.name = "mss1",
224  .p.long_name = NULL_IF_CONFIG_SMALL("MS Screen 1"),
225  .p.type = AVMEDIA_TYPE_VIDEO,
226  .p.id = AV_CODEC_ID_MSS1,
227  .priv_data_size = sizeof(MSS1Context),
229  .close = mss1_decode_end,
231  .p.capabilities = AV_CODEC_CAP_DR1,
232  .caps_internal = FF_CODEC_CAP_INIT_THREADSAFE,
233 };
MSS1Context
Definition: mss1.c:32
get_bits_left
static int get_bits_left(GetBitContext *gb)
Definition: get_bits.h:850
r
const char * r
Definition: vf_curves.c:116
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:111
AVFrame
This structure describes decoded (raw) audio or video data.
Definition: frame.h:325
internal.h
AVPacket::data
uint8_t * data
Definition: packet.h:374
arith_get_prob
static int arith_get_prob(ArithCoder *c, int16_t *probs)
Definition: mss1.c:96
b
#define b
Definition: input.c:34
mss12.h
FFCodec
Definition: codec_internal.h:112
mss1_decode_init
static av_cold int mss1_decode_init(AVCodecContext *avctx)
Definition: mss1.c:192
mss1_decode_frame
static int mss1_decode_frame(AVCodecContext *avctx, AVFrame *rframe, int *got_frame, AVPacket *avpkt)
Definition: mss1.c:143
init
static int init
Definition: av_tx.c:47
get_bits
static unsigned int get_bits(GetBitContext *s, int n)
Read 1-25 bits.
Definition: get_bits.h:380
FFCodec::p
AVCodec p
The public AVCodec.
Definition: codec_internal.h:116
U
#define U(x)
Definition: vp56_arith.h:37
GetBitContext
Definition: get_bits.h:62
val
static double val(void *priv, double ch)
Definition: aeval.c:77
av_frame_alloc
AVFrame * av_frame_alloc(void)
Allocate an AVFrame and set its fields to default values.
Definition: frame.c:99
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:678
FF_CODEC_DECODE_CB
#define FF_CODEC_DECODE_CB(func)
Definition: codec_internal.h:254
g
const char * g
Definition: vf_curves.c:117
bits
uint8_t bits
Definition: vp3data.h:141
ctx
AVFormatContext * ctx
Definition: movenc.c:48
ArithCoder
Definition: dstdec.c:58
MSS1Context::ctx
MSS12Context ctx
Definition: mss1.c:33
ff_mss1_decoder
const FFCodec ff_mss1_decoder
Definition: mss1.c:222
NULL
#define NULL
Definition: coverity.c:32
AV_CODEC_ID_MSS1
@ AV_CODEC_ID_MSS1
Definition: codec_id.h:212
AVPALETTE_SIZE
#define AVPALETTE_SIZE
Definition: pixfmt.h:32
AV_PICTURE_TYPE_I
@ AV_PICTURE_TYPE_I
Intra.
Definition: avutil.h:274
get_bits1
static unsigned int get_bits1(GetBitContext *s)
Definition: get_bits.h:499
c
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:212
SliceContext
Definition: mss12.h:70
ARITH_GET_BIT
#define ARITH_GET_BIT(prefix)
Definition: mss12.h:104
AV_CODEC_CAP_DR1
#define AV_CODEC_CAP_DR1
Codec uses get_buffer() or get_encode_buffer() for allocating buffers and supports custom allocators.
Definition: codec.h:52
AVPacket::size
int size
Definition: packet.h:375
NULL_IF_CONFIG_SMALL
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification.
Definition: internal.h:117
av_frame_ref
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:343
codec_internal.h
MSS12Context
Definition: mss12.h:77
arith_get_bits
static int arith_get_bits(ArithCoder *c, int bits)
Definition: mss1.c:68
i
#define i(width, name, range_min, range_max)
Definition: cbs_h2645.c:271
arith_init
static void arith_init(ArithCoder *c, GetBitContext *gb)
Definition: mss1.c:113
ff_mss12_decode_end
av_cold int ff_mss12_decode_end(MSS12Context *c)
Definition: mss12.c:692
FF_CODEC_CAP_INIT_THREADSAFE
#define FF_CODEC_CAP_INIT_THREADSAFE
The codec does not modify any global variables in the init function, allowing to call the init functi...
Definition: codec_internal.h:31
AVCodec::name
const char * name
Name of the codec implementation.
Definition: codec.h:203
arith_normalise
static void arith_normalise(ArithCoder *c)
Definition: mss1.c:38
AVCodecContext::height
int height
Definition: avcodec.h:562
AVCodecContext::pix_fmt
enum AVPixelFormat pix_fmt
Pixel format, see AV_PIX_FMT_xxx.
Definition: avcodec.h:599
avcodec.h
AV_PIX_FMT_PAL8
@ AV_PIX_FMT_PAL8
8 bits with AV_PIX_FMT_RGB32 palette
Definition: pixfmt.h:77
ff_reget_buffer
int ff_reget_buffer(AVCodecContext *avctx, AVFrame *frame, int flags)
Identical in function to ff_get_buffer(), except it reuses the existing buffer if available.
Definition: decode.c:1521
ret
ret
Definition: filter_design.txt:187
prob
#define prob(name, subs,...)
Definition: cbs_vp9.c:372
AVCodecContext
main external API structure.
Definition: avcodec.h:389
decode_pal
static int decode_pal(MSS12Context *ctx, ArithCoder *acoder)
Definition: mss1.c:124
MSS1Context::sc
SliceContext sc
Definition: mss1.c:35
ff_mss12_decode_rect
int ff_mss12_decode_rect(SliceContext *sc, ArithCoder *acoder, int x, int y, int width, int height)
Definition: mss12.c:542
AV_PICTURE_TYPE_P
@ AV_PICTURE_TYPE_P
Predicted.
Definition: avutil.h:275
AVMEDIA_TYPE_VIDEO
@ AVMEDIA_TYPE_VIDEO
Definition: avutil.h:201
MSS1Context::pic
AVFrame * pic
Definition: mss1.c:34
AVCodecContext::priv_data
void * priv_data
Definition: avcodec.h:416
AVPacket
This structure stores compressed data.
Definition: packet.h:351
ff_mss12_slicecontext_reset
void ff_mss12_slicecontext_reset(SliceContext *sc)
Definition: mss12.c:436
AVCodecContext::width
int width
picture width / height.
Definition: avcodec.h:562
AVERROR_INVALIDDATA
#define AVERROR_INVALIDDATA
Invalid data found when processing input.
Definition: error.h:61
ff_mss12_decode_init
av_cold int ff_mss12_decode_init(MSS12Context *c, int version, SliceContext *sc1, SliceContext *sc2)
Definition: mss12.c:580