2 * Flash Screen Video decoder
3 * Copyright (C) 2004 Alex Beregszaszi
4 * Copyright (C) 2006 Benjamin Larsson
6 * This file is part of Libav.
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.
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.
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
25 * Flash Screen Video decoder
26 * @author Alex Beregszaszi
27 * @author Benjamin Larsson
30 /* Bitstream description
31 * The picture is divided into blocks that are zlib compressed.
33 * The decoder is fed complete frames, the frameheader contains:
34 * 4bits of block width
35 * 12bits of frame width
36 * 4bits of block height
37 * 12bits of frame height
39 * Directly after the header are the compressed blocks. The blocks
40 * have their compressed size represented with 16bits in the beginnig.
41 * If the size = 0 then the block is unchanged from the previous frame.
42 * All blocks are decompressed until the buffer is consumed.
44 * Encoding ideas, a basic encoder would just use a fixed block size.
45 * Block sizes can be multipels of 16, from 16 to 256. The blocks don't
46 * have to be quadratic. A brute force search with a set of diffrent
47 * block sizes should give a better result then to just use a fixed size.
57 typedef struct FlashSVContext {
58 AVCodecContext *avctx;
60 int image_width, image_height;
61 int block_width, block_height;
68 static void copy_region(uint8_t *sptr, uint8_t *dptr,
69 int dx, int dy, int h, int w, int stride)
73 for (i = dx + h; i > dx; i--) {
74 memcpy(dptr + (i * stride) + dy * 3, sptr, w * 3);
80 static av_cold int flashsv_decode_init(AVCodecContext *avctx)
82 FlashSVContext *s = avctx->priv_data;
83 int zret; // Zlib return code
86 s->zstream.zalloc = Z_NULL;
87 s->zstream.zfree = Z_NULL;
88 s->zstream.opaque = Z_NULL;
89 zret = inflateInit(&(s->zstream));
91 av_log(avctx, AV_LOG_ERROR, "Inflate init error: %d\n", zret);
94 avctx->pix_fmt = PIX_FMT_BGR24;
95 s->frame.data[0] = NULL;
101 static int flashsv_decode_frame(AVCodecContext *avctx, void *data,
102 int *data_size, AVPacket *avpkt)
104 const uint8_t *buf = avpkt->data;
105 int buf_size = avpkt->size;
106 FlashSVContext *s = avctx->priv_data;
107 int h_blocks, v_blocks, h_part, v_part, i, j;
110 /* no supplementary picture */
116 init_get_bits(&gb, buf, buf_size * 8);
118 /* start to parse the bitstream */
119 s->block_width = 16 * (get_bits(&gb, 4) + 1);
120 s->image_width = get_bits(&gb, 12);
121 s->block_height = 16 * (get_bits(&gb, 4) + 1);
122 s->image_height = get_bits(&gb, 12);
124 /* calculate amount of blocks and the size of the border blocks */
125 h_blocks = s->image_width / s->block_width;
126 h_part = s->image_width % s->block_width;
127 v_blocks = s->image_height / s->block_height;
128 v_part = s->image_height % s->block_height;
130 /* the block size could change between frames, make sure the buffer
131 * is large enough, if not, get a larger one */
132 if (s->block_size < s->block_width * s->block_height) {
133 av_free(s->tmpblock);
134 if ((s->tmpblock = av_malloc(3 * s->block_width * s->block_height)) == NULL) {
135 av_log(avctx, AV_LOG_ERROR, "Can't allocate decompression buffer.\n");
136 return AVERROR(ENOMEM);
139 s->block_size = s->block_width * s->block_height;
141 /* init the image size once */
142 if ((avctx->width == 0) && (avctx->height == 0)) {
143 avctx->width = s->image_width;
144 avctx->height = s->image_height;
147 /* check for changes of image width and image height */
148 if ((avctx->width != s->image_width) || (avctx->height != s->image_height)) {
149 av_log(avctx, AV_LOG_ERROR, "Frame width or height differs from first frames!\n");
150 av_log(avctx, AV_LOG_ERROR, "fh = %d, fv %d vs ch = %d, cv = %d\n", avctx->height,
151 avctx->width,s->image_height, s->image_width);
155 av_log(avctx, AV_LOG_DEBUG, "image: %dx%d block: %dx%d num: %dx%d part: %dx%d\n",
156 s->image_width, s->image_height, s->block_width, s->block_height,
157 h_blocks, v_blocks, h_part, v_part);
159 s->frame.reference = 1;
160 s->frame.buffer_hints = FF_BUFFER_HINTS_VALID | FF_BUFFER_HINTS_PRESERVE | FF_BUFFER_HINTS_REUSABLE;
161 if (avctx->reget_buffer(avctx, &s->frame) < 0) {
162 av_log(avctx, AV_LOG_ERROR, "reget_buffer() failed\n");
166 /* loop over all block columns */
167 for (j = 0; j < v_blocks + (v_part ? 1 : 0); j++) {
169 int hp = j * s->block_height; // horiz position in frame
170 int hs = (j < v_blocks) ? s->block_height : v_part; // size of block
173 /* loop over all block rows */
174 for (i = 0; i < h_blocks + (h_part ? 1 : 0); i++) {
175 int wp = i * s->block_width; // vert position in frame
176 int ws = (i < h_blocks) ? s->block_width : h_part; // size of block
178 /* get the size of the compressed zlib chunk */
179 int size = get_bits(&gb, 16);
180 if (8 * size > get_bits_left(&gb)) {
181 avctx->release_buffer(avctx, &s->frame);
182 s->frame.data[0] = NULL;
187 /* no change, don't do anything */
189 /* decompress block */
190 int ret = inflateReset(&(s->zstream));
192 av_log(avctx, AV_LOG_ERROR, "error in decompression (reset) of block %dx%d\n", i, j);
195 s->zstream.next_in = buf + (get_bits_count(&gb) / 8);
196 s->zstream.avail_in = size;
197 s->zstream.next_out = s->tmpblock;
198 s->zstream.avail_out = s->block_size*3;
199 ret = inflate(&(s->zstream), Z_FINISH);
200 if (ret == Z_DATA_ERROR) {
201 av_log(avctx, AV_LOG_ERROR, "Zlib resync occurred\n");
202 inflateSync(&(s->zstream));
203 ret = inflate(&(s->zstream), Z_FINISH);
206 if ((ret != Z_OK) && (ret != Z_STREAM_END)) {
207 av_log(avctx, AV_LOG_ERROR, "error in decompression of block %dx%d: %d\n", i, j, ret);
210 copy_region(s->tmpblock, s->frame.data[0], s->image_height - (hp + hs + 1),
211 wp, hs, ws, s->frame.linesize[0]);
212 skip_bits_long(&gb, 8 * size); /* skip the consumed bits */
217 *data_size = sizeof(AVFrame);
218 *(AVFrame*)data = s->frame;
220 if ((get_bits_count(&gb) / 8) != buf_size)
221 av_log(avctx, AV_LOG_ERROR, "buffer not fully consumed (%d != %d)\n",
222 buf_size, (get_bits_count(&gb) / 8));
224 /* report that the buffer was completely consumed */
229 static av_cold int flashsv_decode_end(AVCodecContext *avctx)
231 FlashSVContext *s = avctx->priv_data;
232 inflateEnd(&(s->zstream));
233 /* release the frame if needed */
234 if (s->frame.data[0])
235 avctx->release_buffer(avctx, &s->frame);
237 /* free the tmpblock */
238 av_free(s->tmpblock);
244 AVCodec ff_flashsv_decoder = {
246 .type = AVMEDIA_TYPE_VIDEO,
247 .id = CODEC_ID_FLASHSV,
248 .priv_data_size = sizeof(FlashSVContext),
249 .init = flashsv_decode_init,
250 .close = flashsv_decode_end,
251 .decode = flashsv_decode_frame,
252 .capabilities = CODEC_CAP_DR1,
253 .pix_fmts = (const enum PixelFormat[]){PIX_FMT_BGR24, PIX_FMT_NONE},
254 .long_name = NULL_IF_CONFIG_SMALL("Flash Screen Video v1"),