flashsvenc.c
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1 /*
2  * Flash Screen Video encoder
3  * Copyright (C) 2004 Alex Beregszaszi
4  * Copyright (C) 2006 Benjamin Larsson
5  *
6  * This file is part of Libav.
7  *
8  * Libav is free software; you can redistribute it and/or
9  * modify it under the terms of the GNU Lesser General Public
10  * License as published by the Free Software Foundation; either
11  * version 2.1 of the License, or (at your option) any later version.
12  *
13  * Libav is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16  * Lesser General Public License for more details.
17  *
18  * You should have received a copy of the GNU Lesser General Public
19  * License along with Libav; if not, write to the Free Software
20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21  */
22 
23 /* Encoding development sponsored by http://fh-campuswien.ac.at */
24 
36 /*
37  * Encoding ideas: A basic encoder would just use a fixed block size.
38  * Block sizes can be multiples of 16, from 16 to 256. The blocks don't
39  * have to be quadratic. A brute force search with a set of different
40  * block sizes should give a better result than to just use a fixed size.
41  *
42  * TODO:
43  * Don't reencode the frame in brute force mode if the frame is a dupe.
44  * Speed up. Make the difference check faster.
45  */
46 
47 #include <stdio.h>
48 #include <stdlib.h>
49 #include <zlib.h>
50 
51 #include "avcodec.h"
52 #include "put_bits.h"
53 #include "bytestream.h"
54 
55 
56 typedef struct FlashSVContext {
58  uint8_t *previous_frame;
59  AVFrame frame;
62  uint8_t *tmpblock;
63  uint8_t *encbuffer;
64  int block_size;
65  z_stream zstream;
68 
69 static int copy_region_enc(uint8_t *sptr, uint8_t *dptr, int dx, int dy,
70  int h, int w, int stride, uint8_t *pfptr)
71 {
72  int i, j;
73  uint8_t *nsptr;
74  uint8_t *npfptr;
75  int diff = 0;
76 
77  for (i = dx + h; i > dx; i--) {
78  nsptr = sptr + i * stride + dy * 3;
79  npfptr = pfptr + i * stride + dy * 3;
80  for (j = 0; j < w * 3; j++) {
81  diff |= npfptr[j] ^ nsptr[j];
82  dptr[j] = nsptr[j];
83  }
84  dptr += w * 3;
85  }
86  if (diff)
87  return 1;
88  return 0;
89 }
90 
92 {
93  FlashSVContext *s = avctx->priv_data;
94 
95  s->avctx = avctx;
96 
97  if (avctx->width > 4095 || avctx->height > 4095) {
98  av_log(avctx, AV_LOG_ERROR,
99  "Input dimensions too large, input must be max 4096x4096 !\n");
100  return AVERROR_INVALIDDATA;
101  }
102 
103  // Needed if zlib unused or init aborted before deflateInit
104  memset(&s->zstream, 0, sizeof(z_stream));
105 
106  s->last_key_frame = 0;
107 
108  s->image_width = avctx->width;
109  s->image_height = avctx->height;
110 
111  s->tmpblock = av_mallocz(3 * 256 * 256);
112  s->encbuffer = av_mallocz(s->image_width * s->image_height * 3);
113 
114  if (!s->tmpblock || !s->encbuffer) {
115  av_log(avctx, AV_LOG_ERROR, "Memory allocation failed.\n");
116  return AVERROR(ENOMEM);
117  }
118 
119  return 0;
120 }
121 
122 
123 static int encode_bitstream(FlashSVContext *s, AVFrame *p, uint8_t *buf,
124  int buf_size, int block_width, int block_height,
125  uint8_t *previous_frame, int *I_frame)
126 {
127 
128  PutBitContext pb;
129  int h_blocks, v_blocks, h_part, v_part, i, j;
130  int buf_pos, res;
131  int pred_blocks = 0;
132 
133  init_put_bits(&pb, buf, buf_size * 8);
134 
135  put_bits(&pb, 4, block_width / 16 - 1);
136  put_bits(&pb, 12, s->image_width);
137  put_bits(&pb, 4, block_height / 16 - 1);
138  put_bits(&pb, 12, s->image_height);
139  flush_put_bits(&pb);
140  buf_pos = 4;
141 
142  h_blocks = s->image_width / block_width;
143  h_part = s->image_width % block_width;
144  v_blocks = s->image_height / block_height;
145  v_part = s->image_height % block_height;
146 
147  /* loop over all block columns */
148  for (j = 0; j < v_blocks + (v_part ? 1 : 0); j++) {
149 
150  int y_pos = j * block_height; // vertical position in frame
151  int cur_blk_height = (j < v_blocks) ? block_height : v_part;
152 
153  /* loop over all block rows */
154  for (i = 0; i < h_blocks + (h_part ? 1 : 0); i++) {
155  int x_pos = i * block_width; // horizontal position in frame
156  int cur_blk_width = (i < h_blocks) ? block_width : h_part;
157  int ret = Z_OK;
158  uint8_t *ptr = buf + buf_pos;
159 
160  /* copy the block to the temp buffer before compression
161  * (if it differs from the previous frame's block) */
162  res = copy_region_enc(p->data[0], s->tmpblock,
163  s->image_height - (y_pos + cur_blk_height + 1),
164  x_pos, cur_blk_height, cur_blk_width,
165  p->linesize[0], previous_frame);
166 
167  if (res || *I_frame) {
168  unsigned long zsize = 3 * block_width * block_height;
169  ret = compress2(ptr + 2, &zsize, s->tmpblock,
170  3 * cur_blk_width * cur_blk_height, 9);
171 
172  //ret = deflateReset(&s->zstream);
173  if (ret != Z_OK)
175  "error while compressing block %dx%d\n", i, j);
176 
177  bytestream_put_be16(&ptr, zsize);
178  buf_pos += zsize + 2;
179  av_dlog(s->avctx, "buf_pos = %d\n", buf_pos);
180  } else {
181  pred_blocks++;
182  bytestream_put_be16(&ptr, 0);
183  buf_pos += 2;
184  }
185  }
186  }
187 
188  if (pred_blocks)
189  *I_frame = 0;
190  else
191  *I_frame = 1;
192 
193  return buf_pos;
194 }
195 
196 
197 static int flashsv_encode_frame(AVCodecContext *avctx, uint8_t *buf,
198  int buf_size, void *data)
199 {
200  FlashSVContext * const s = avctx->priv_data;
201  AVFrame *pict = data;
202  AVFrame * const p = &s->frame;
203  uint8_t *pfptr;
204  int res;
205  int I_frame = 0;
206  int opt_w = 4, opt_h = 4;
207 
208  *p = *pict;
209 
210  /* First frame needs to be a keyframe */
211  if (avctx->frame_number == 0) {
213  if (!s->previous_frame) {
214  av_log(avctx, AV_LOG_ERROR, "Memory allocation failed.\n");
215  return AVERROR(ENOMEM);
216  }
217  I_frame = 1;
218  }
219 
220  if (p->linesize[0] < 0)
221  pfptr = s->previous_frame - (s->image_height - 1) * p->linesize[0];
222  else
223  pfptr = s->previous_frame;
224 
225  /* Check the placement of keyframes */
226  if (avctx->gop_size > 0 &&
227  avctx->frame_number >= s->last_key_frame + avctx->gop_size) {
228  I_frame = 1;
229  }
230 
231  if (buf_size < s->image_width * s->image_height * 3) {
232  //Conservative upper bound check for compressed data
233  av_log(avctx, AV_LOG_ERROR, "buf_size %d < %d\n",
234  buf_size, s->image_width * s->image_height * 3);
235  return -1;
236  }
237 
238  res = encode_bitstream(s, p, buf, buf_size, opt_w * 16, opt_h * 16,
239  pfptr, &I_frame);
240 
241  //save the current frame
242  if (p->linesize[0] > 0)
243  memcpy(s->previous_frame, p->data[0], s->image_height * p->linesize[0]);
244  else
245  memcpy(s->previous_frame,
246  p->data[0] + p->linesize[0] * (s->image_height - 1),
247  s->image_height * FFABS(p->linesize[0]));
248 
249  //mark the frame type so the muxer can mux it correctly
250  if (I_frame) {
252  p->key_frame = 1;
253  s->last_key_frame = avctx->frame_number;
254  av_dlog(avctx, "Inserting keyframe at frame %d\n", avctx->frame_number);
255  } else {
257  p->key_frame = 0;
258  }
259 
260  avctx->coded_frame = p;
261 
262  return res;
263 }
264 
266 {
267  FlashSVContext *s = avctx->priv_data;
268 
269  deflateEnd(&s->zstream);
270 
271  av_free(s->encbuffer);
273  av_free(s->tmpblock);
274 
275  return 0;
276 }
277 
279  .name = "flashsv",
280  .type = AVMEDIA_TYPE_VIDEO,
281  .id = CODEC_ID_FLASHSV,
282  .priv_data_size = sizeof(FlashSVContext),
284  .encode = flashsv_encode_frame,
286  .pix_fmts = (const enum PixelFormat[]){PIX_FMT_BGR24, PIX_FMT_NONE},
287  .long_name = NULL_IF_CONFIG_SMALL("Flash Screen Video"),
288 };
289