2 * Microsoft Screen 3 (aka Microsoft ATC Screen) decoder
3 * Copyright (c) 2012 Konstantin Shishkov
5 * This file is part of FFmpeg.
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.
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.
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
24 * Microsoft Screen 3 (aka Microsoft ATC Screen) decoder
28 #include "bytestream.h"
33 #define HEADER_SIZE 27
35 #define MODEL2_SCALE 13
36 #define MODEL_SCALE 15
37 #define MODEL256_SEC_SCALE 9
39 typedef struct Model2 {
40 int upd_val, till_rescale;
41 unsigned zero_freq, zero_weight;
42 unsigned total_freq, total_weight;
45 typedef struct Model {
46 int weights[16], freqs[16];
49 int upd_val, max_upd_val, till_rescale;
52 typedef struct Model256 {
53 int weights[256], freqs[256];
57 int upd_val, max_upd_val, till_rescale;
60 #define RAC_BOTTOM 0x01000000
61 typedef struct RangeCoder {
62 const uint8_t *src, *src_end;
76 typedef struct BlockTypeContext {
81 typedef struct FillBlockCoder {
86 typedef struct ImageBlockCoder {
87 Model256 esc_model, vec_entry_model;
92 typedef struct DCTBlockCoder {
94 ptrdiff_t prev_dc_stride;
103 typedef struct HaarBlockCoder {
109 typedef struct MSS3Context {
110 AVCodecContext *avctx;
115 BlockTypeContext btype[3];
116 FillBlockCoder fill_coder[3];
117 ImageBlockCoder image_coder[3];
118 DCTBlockCoder dct_coder[3];
119 HaarBlockCoder haar_coder[3];
126 static void model2_reset(Model2 *m)
130 m->zero_freq = 0x1000;
131 m->total_freq = 0x2000;
136 static void model2_update(Model2 *m, int bit)
146 m->total_weight += m->upd_val;
147 if (m->total_weight > 0x2000) {
148 m->total_weight = (m->total_weight + 1) >> 1;
149 m->zero_weight = (m->zero_weight + 1) >> 1;
150 if (m->total_weight == m->zero_weight)
151 m->total_weight = m->zero_weight + 1;
153 m->upd_val = m->upd_val * 5 >> 2;
156 scale = 0x80000000u / m->total_weight;
157 m->zero_freq = m->zero_weight * scale >> 18;
158 m->total_freq = m->total_weight * scale >> 18;
159 m->till_rescale = m->upd_val;
162 static void model_update(Model *m, int val)
171 m->tot_weight += m->upd_val;
173 if (m->tot_weight > 0x8000) {
175 for (i = 0; i < m->num_syms; i++) {
176 m->weights[i] = (m->weights[i] + 1) >> 1;
177 m->tot_weight += m->weights[i];
180 scale = 0x80000000u / m->tot_weight;
181 for (i = 0; i < m->num_syms; i++) {
182 m->freqs[i] = sum * scale >> 16;
183 sum += m->weights[i];
186 m->upd_val = m->upd_val * 5 >> 2;
187 if (m->upd_val > m->max_upd_val)
188 m->upd_val = m->max_upd_val;
189 m->till_rescale = m->upd_val;
192 static void model_reset(Model *m)
197 for (i = 0; i < m->num_syms - 1; i++)
199 m->weights[m->num_syms - 1] = 0;
201 m->upd_val = m->num_syms;
203 model_update(m, m->num_syms - 1);
205 m->upd_val = (m->num_syms + 6) >> 1;
208 static av_cold void model_init(Model *m, int num_syms)
210 m->num_syms = num_syms;
211 m->max_upd_val = 8 * num_syms + 48;
216 static void model256_update(Model256 *m, int val)
226 m->tot_weight += m->upd_val;
228 if (m->tot_weight > 0x8000) {
230 for (i = 0; i < 256; i++) {
231 m->weights[i] = (m->weights[i] + 1) >> 1;
232 m->tot_weight += m->weights[i];
235 scale = 0x80000000u / m->tot_weight;
237 for (i = 0; i < 256; i++) {
238 m->freqs[i] = sum * scale >> 16;
239 sum += m->weights[i];
240 send = m->freqs[i] >> MODEL256_SEC_SCALE;
242 m->secondary[sidx++] = i - 1;
244 while (sidx < m->sec_size)
245 m->secondary[sidx++] = 255;
247 m->upd_val = m->upd_val * 5 >> 2;
248 if (m->upd_val > m->max_upd_val)
249 m->upd_val = m->max_upd_val;
250 m->till_rescale = m->upd_val;
253 static void model256_reset(Model256 *m)
257 for (i = 0; i < 255; i++)
264 model256_update(m, 255);
266 m->upd_val = (256 + 6) >> 1;
269 static av_cold void model256_init(Model256 *m)
271 m->max_upd_val = 8 * 256 + 48;
272 m->sec_size = (1 << 6) + 2;
277 static void rac_init(RangeCoder *c, const uint8_t *src, int size)
282 c->src_end = src + size;
284 for (i = 0; i < FFMIN(size, 4); i++)
285 c->low = (c->low << 8) | *c->src++;
286 c->range = 0xFFFFFFFF;
290 static void rac_normalise(RangeCoder *c)
295 if (c->src < c->src_end) {
297 } else if (!c->low) {
301 if (c->range >= RAC_BOTTOM)
306 static int rac_get_bit(RangeCoder *c)
312 bit = (c->range <= c->low);
316 if (c->range < RAC_BOTTOM)
322 static int rac_get_bits(RangeCoder *c, int nbits)
327 val = c->low / c->range;
328 c->low -= c->range * val;
330 if (c->range < RAC_BOTTOM)
336 static int rac_get_model2_sym(RangeCoder *c, Model2 *m)
340 helper = m->zero_freq * (c->range >> MODEL2_SCALE);
341 bit = (c->low >= helper);
349 if (c->range < RAC_BOTTOM)
352 model2_update(m, bit);
357 static int rac_get_model_sym(RangeCoder *c, Model *m)
361 unsigned prob, prob2, helper;
365 c->range >>= MODEL_SCALE;
367 end = m->num_syms >> 1;
370 helper = m->freqs[end] * c->range;
371 if (helper <= c->low) {
378 end = (end2 + val) >> 1;
379 } while (end != val);
381 c->range = prob2 - prob;
382 if (c->range < RAC_BOTTOM)
385 model_update(m, val);
390 static int rac_get_model256_sym(RangeCoder *c, Model256 *m)
392 int prob, prob2, helper, val;
397 c->range >>= MODEL_SCALE;
399 helper = c->low / c->range;
400 ssym = helper >> MODEL256_SEC_SCALE;
401 val = m->secondary[ssym];
403 end = start = m->secondary[ssym + 1] + 1;
404 while (end > val + 1) {
405 ssym = (end + val) >> 1;
406 if (m->freqs[ssym] <= helper) {
410 end = (end + val) >> 1;
414 prob = m->freqs[val] * c->range;
416 prob2 = m->freqs[val + 1] * c->range;
419 c->range = prob2 - prob;
420 if (c->range < RAC_BOTTOM)
423 model256_update(m, val);
428 static int decode_block_type(RangeCoder *c, BlockTypeContext *bt)
430 bt->last_type = rac_get_model_sym(c, &bt->bt_model[bt->last_type]);
432 return bt->last_type;
435 static int decode_coeff(RangeCoder *c, Model *m)
439 val = rac_get_model_sym(c, m);
441 sign = rac_get_bit(c);
444 val = (1 << val) + rac_get_bits(c, val);
453 static void decode_fill_block(RangeCoder *c, FillBlockCoder *fc,
454 uint8_t *dst, ptrdiff_t stride, int block_size)
458 fc->fill_val += decode_coeff(c, &fc->coef_model);
460 for (i = 0; i < block_size; i++, dst += stride)
461 memset(dst, fc->fill_val, block_size);
464 static void decode_image_block(RangeCoder *c, ImageBlockCoder *ic,
465 uint8_t *dst, ptrdiff_t stride, int block_size)
473 vec_size = rac_get_model_sym(c, &ic->vec_size_model) + 2;
474 for (i = 0; i < vec_size; i++)
475 vec[i] = rac_get_model256_sym(c, &ic->vec_entry_model);
478 memset(prev_line, 0, sizeof(prev_line));
480 for (j = 0; j < block_size; j++) {
483 for (i = 0; i < block_size; i++) {
486 A = rac_get_model_sym(c, &ic->vq_model[A + B * 5 + C * 25]);
492 dst[i] = rac_get_model256_sym(c, &ic->esc_model);
498 static int decode_dct(RangeCoder *c, DCTBlockCoder *bc, int *block,
501 int skip, val, sign, pos = 1, zz_pos, dc;
502 int blk_pos = bx + by * bc->prev_dc_stride;
504 memset(block, 0, sizeof(*block) * 64);
506 dc = decode_coeff(c, &bc->dc_model);
511 l = bc->prev_dc[blk_pos - 1];
512 tl = bc->prev_dc[blk_pos - 1 - bc->prev_dc_stride];
513 t = bc->prev_dc[blk_pos - bc->prev_dc_stride];
515 if (FFABS(t - tl) <= FFABS(l - tl))
520 dc += bc->prev_dc[blk_pos - bc->prev_dc_stride];
523 dc += bc->prev_dc[bx - 1];
525 bc->prev_dc[blk_pos] = dc;
526 block[0] = dc * bc->qmat[0];
529 val = rac_get_model256_sym(c, &bc->ac_model);
544 sign = rac_get_model2_sym(c, &bc->sign_model);
547 val = (1 << val) + rac_get_bits(c, val);
552 zz_pos = ff_zigzag_direct[pos];
553 block[zz_pos] = val * bc->qmat[zz_pos];
557 return pos == 64 ? 0 : -1;
560 static void decode_dct_block(RangeCoder *c, DCTBlockCoder *bc,
561 uint8_t *dst, ptrdiff_t stride, int block_size,
562 int *block, int mb_x, int mb_y)
566 int nblocks = block_size >> 3;
571 for (j = 0; j < nblocks; j++) {
572 for (i = 0; i < nblocks; i++) {
573 if (decode_dct(c, bc, block, bx + i, by + j)) {
577 ff_mss34_dct_put(dst + i * 8, stride, block);
583 static void decode_haar_block(RangeCoder *c, HaarBlockCoder *hc,
584 uint8_t *dst, ptrdiff_t stride,
585 int block_size, int *block)
587 const int hsize = block_size >> 1;
588 int A, B, C, D, t1, t2, t3, t4;
591 for (j = 0; j < block_size; j++) {
592 for (i = 0; i < block_size; i++) {
593 if (i < hsize && j < hsize)
594 block[i] = rac_get_model256_sym(c, &hc->coef_model);
596 block[i] = decode_coeff(c, &hc->coef_hi_model);
597 block[i] *= hc->scale;
601 block -= block_size * block_size;
603 for (j = 0; j < hsize; j++) {
604 for (i = 0; i < hsize; i++) {
606 B = block[i + hsize];
607 C = block[i + hsize * block_size];
608 D = block[i + hsize * block_size + hsize];
614 dst[i * 2] = av_clip_uint8(t1 - t2);
615 dst[i * 2 + stride] = av_clip_uint8(t1 + t2);
616 dst[i * 2 + 1] = av_clip_uint8(t3 - t4);
617 dst[i * 2 + 1 + stride] = av_clip_uint8(t3 + t4);
624 static void reset_coders(MSS3Context *ctx, int quality)
628 for (i = 0; i < 3; i++) {
629 ctx->btype[i].last_type = SKIP_BLOCK;
630 for (j = 0; j < 5; j++)
631 model_reset(&ctx->btype[i].bt_model[j]);
632 ctx->fill_coder[i].fill_val = 0;
633 model_reset(&ctx->fill_coder[i].coef_model);
634 model256_reset(&ctx->image_coder[i].esc_model);
635 model256_reset(&ctx->image_coder[i].vec_entry_model);
636 model_reset(&ctx->image_coder[i].vec_size_model);
637 for (j = 0; j < 125; j++)
638 model_reset(&ctx->image_coder[i].vq_model[j]);
639 if (ctx->dct_coder[i].quality != quality) {
640 ctx->dct_coder[i].quality = quality;
641 ff_mss34_gen_quant_mat(ctx->dct_coder[i].qmat, quality, !i);
643 memset(ctx->dct_coder[i].prev_dc, 0,
644 sizeof(*ctx->dct_coder[i].prev_dc) *
645 ctx->dct_coder[i].prev_dc_stride *
646 ctx->dct_coder[i].prev_dc_height);
647 model_reset(&ctx->dct_coder[i].dc_model);
648 model2_reset(&ctx->dct_coder[i].sign_model);
649 model256_reset(&ctx->dct_coder[i].ac_model);
650 if (ctx->haar_coder[i].quality != quality) {
651 ctx->haar_coder[i].quality = quality;
652 ctx->haar_coder[i].scale = 17 - 7 * quality / 50;
654 model_reset(&ctx->haar_coder[i].coef_hi_model);
655 model256_reset(&ctx->haar_coder[i].coef_model);
659 static av_cold void init_coders(MSS3Context *ctx)
663 for (i = 0; i < 3; i++) {
664 for (j = 0; j < 5; j++)
665 model_init(&ctx->btype[i].bt_model[j], 5);
666 model_init(&ctx->fill_coder[i].coef_model, 12);
667 model256_init(&ctx->image_coder[i].esc_model);
668 model256_init(&ctx->image_coder[i].vec_entry_model);
669 model_init(&ctx->image_coder[i].vec_size_model, 3);
670 for (j = 0; j < 125; j++)
671 model_init(&ctx->image_coder[i].vq_model[j], 5);
672 model_init(&ctx->dct_coder[i].dc_model, 12);
673 model256_init(&ctx->dct_coder[i].ac_model);
674 model_init(&ctx->haar_coder[i].coef_hi_model, 12);
675 model256_init(&ctx->haar_coder[i].coef_model);
679 static int mss3_decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
682 const uint8_t *buf = avpkt->data;
683 int buf_size = avpkt->size;
684 MSS3Context *c = avctx->priv_data;
685 RangeCoder *acoder = &c->coder;
688 int dec_width, dec_height, dec_x, dec_y, quality, keyframe;
689 int x, y, i, mb_width, mb_height, blk_size, btype;
692 if (buf_size < HEADER_SIZE) {
693 av_log(avctx, AV_LOG_ERROR,
694 "Frame should have at least %d bytes, got %d instead\n",
695 HEADER_SIZE, buf_size);
696 return AVERROR_INVALIDDATA;
699 bytestream2_init(&gb, buf, buf_size);
700 keyframe = bytestream2_get_be32(&gb);
701 if (keyframe & ~0x301) {
702 av_log(avctx, AV_LOG_ERROR, "Invalid frame type %X\n", keyframe);
703 return AVERROR_INVALIDDATA;
705 keyframe = !(keyframe & 1);
706 bytestream2_skip(&gb, 6);
707 dec_x = bytestream2_get_be16(&gb);
708 dec_y = bytestream2_get_be16(&gb);
709 dec_width = bytestream2_get_be16(&gb);
710 dec_height = bytestream2_get_be16(&gb);
712 if (dec_x + dec_width > avctx->width ||
713 dec_y + dec_height > avctx->height ||
714 (dec_width | dec_height) & 0xF) {
715 av_log(avctx, AV_LOG_ERROR, "Invalid frame dimensions %dx%d +%d,%d\n",
716 dec_width, dec_height, dec_x, dec_y);
717 return AVERROR_INVALIDDATA;
719 bytestream2_skip(&gb, 4);
720 quality = bytestream2_get_byte(&gb);
721 if (quality < 1 || quality > 100) {
722 av_log(avctx, AV_LOG_ERROR, "Invalid quality setting %d\n", quality);
723 return AVERROR_INVALIDDATA;
725 bytestream2_skip(&gb, 4);
727 if (keyframe && !bytestream2_get_bytes_left(&gb)) {
728 av_log(avctx, AV_LOG_ERROR, "Keyframe without data found\n");
729 return AVERROR_INVALIDDATA;
731 if (!keyframe && c->got_error)
735 if ((ret = ff_reget_buffer(avctx, c->pic)) < 0)
737 c->pic->key_frame = keyframe;
738 c->pic->pict_type = keyframe ? AV_PICTURE_TYPE_I : AV_PICTURE_TYPE_P;
739 if (!bytestream2_get_bytes_left(&gb)) {
740 if ((ret = av_frame_ref(data, c->pic)) < 0)
747 reset_coders(c, quality);
749 rac_init(acoder, buf + HEADER_SIZE, buf_size - HEADER_SIZE);
751 mb_width = dec_width >> 4;
752 mb_height = dec_height >> 4;
753 dst[0] = c->pic->data[0] + dec_x + dec_y * c->pic->linesize[0];
754 dst[1] = c->pic->data[1] + dec_x / 2 + (dec_y / 2) * c->pic->linesize[1];
755 dst[2] = c->pic->data[2] + dec_x / 2 + (dec_y / 2) * c->pic->linesize[2];
756 for (y = 0; y < mb_height; y++) {
757 for (x = 0; x < mb_width; x++) {
758 for (i = 0; i < 3; i++) {
761 btype = decode_block_type(acoder, c->btype + i);
764 decode_fill_block(acoder, c->fill_coder + i,
765 dst[i] + x * blk_size,
766 c->pic->linesize[i], blk_size);
769 decode_image_block(acoder, c->image_coder + i,
770 dst[i] + x * blk_size,
771 c->pic->linesize[i], blk_size);
774 decode_dct_block(acoder, c->dct_coder + i,
775 dst[i] + x * blk_size,
776 c->pic->linesize[i], blk_size,
780 decode_haar_block(acoder, c->haar_coder + i,
781 dst[i] + x * blk_size,
782 c->pic->linesize[i], blk_size,
786 if (c->got_error || acoder->got_error) {
787 av_log(avctx, AV_LOG_ERROR, "Error decoding block %d,%d\n",
790 return AVERROR_INVALIDDATA;
794 dst[0] += c->pic->linesize[0] * 16;
795 dst[1] += c->pic->linesize[1] * 8;
796 dst[2] += c->pic->linesize[2] * 8;
799 if ((ret = av_frame_ref(data, c->pic)) < 0)
807 static av_cold int mss3_decode_end(AVCodecContext *avctx)
809 MSS3Context * const c = avctx->priv_data;
812 av_frame_free(&c->pic);
813 for (i = 0; i < 3; i++)
814 av_freep(&c->dct_coder[i].prev_dc);
819 static av_cold int mss3_decode_init(AVCodecContext *avctx)
821 MSS3Context * const c = avctx->priv_data;
826 if ((avctx->width & 0xF) || (avctx->height & 0xF)) {
827 av_log(avctx, AV_LOG_ERROR,
828 "Image dimensions should be a multiple of 16.\n");
829 return AVERROR_INVALIDDATA;
833 for (i = 0; i < 3; i++) {
834 int b_width = avctx->width >> (2 + !!i);
835 int b_height = avctx->height >> (2 + !!i);
836 c->dct_coder[i].prev_dc_stride = b_width;
837 c->dct_coder[i].prev_dc_height = b_height;
838 c->dct_coder[i].prev_dc = av_malloc(sizeof(*c->dct_coder[i].prev_dc) *
840 if (!c->dct_coder[i].prev_dc) {
841 av_log(avctx, AV_LOG_ERROR, "Cannot allocate buffer\n");
842 av_frame_free(&c->pic);
844 av_freep(&c->dct_coder[i].prev_dc);
847 return AVERROR(ENOMEM);
851 c->pic = av_frame_alloc();
853 mss3_decode_end(avctx);
854 return AVERROR(ENOMEM);
857 avctx->pix_fmt = AV_PIX_FMT_YUV420P;
864 AVCodec ff_msa1_decoder = {
866 .long_name = NULL_IF_CONFIG_SMALL("MS ATC Screen"),
867 .type = AVMEDIA_TYPE_VIDEO,
868 .id = AV_CODEC_ID_MSA1,
869 .priv_data_size = sizeof(MSS3Context),
870 .init = mss3_decode_init,
871 .close = mss3_decode_end,
872 .decode = mss3_decode_frame,
873 .capabilities = AV_CODEC_CAP_DR1,