/* * Microsoft Screen 1 (aka Windows Media Video V7 Screen) decoder * Copyright (c) 2012 Konstantin Shishkov * * This file is part of FFmpeg. * * FFmpeg is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * FFmpeg is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with FFmpeg; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ /** * @file * Microsoft Screen 1 (aka Windows Media Video V7 Screen) decoder */ #include "libavutil/intfloat.h" #include "libavutil/intreadwrite.h" #include "avcodec.h" #include "get_bits.h" enum SplitMode { SPLIT_VERT = 0, SPLIT_HOR, SPLIT_NONE }; typedef struct ArithCoder { int low, high, value; GetBitContext *gb; } ArithCoder; #define MODEL_MIN_SYMS 2 #define MODEL_MAX_SYMS 256 #define THRESH_ADAPTIVE -1 #define THRESH_LOW 15 #define THRESH_HIGH 50 typedef struct Model { int cum_prob[MODEL_MAX_SYMS + 1]; int weights[MODEL_MAX_SYMS + 1]; int idx2sym[MODEL_MAX_SYMS + 1]; int sym2idx[MODEL_MAX_SYMS + 1]; int num_syms; int thr_weight, threshold; } Model; static const int sec_order_sizes[4] = { 1, 7, 6, 1 }; enum ContextDirection { TOP_LEFT = 0, TOP, TOP_RIGHT, LEFT }; typedef struct PixContext { int cache_size, num_syms; uint8_t cache[12]; Model cache_model, full_model; Model sec_models[4][8][4]; } PixContext; typedef struct MSS1Context { AVCodecContext *avctx; AVFrame pic; uint8_t *pic_start; int pic_stride; uint8_t *mask; int mask_linesize; uint32_t pal[256]; int free_colours; Model intra_region, inter_region; Model pivot, edge_mode, split_mode; PixContext intra_pix_ctx, inter_pix_ctx; int corrupted; } MSS1Context; static void arith_init(ArithCoder *c, GetBitContext *gb) { c->low = 0; c->high = 0xFFFF; c->value = get_bits(gb, 16); c->gb = gb; } static void arith_normalise(ArithCoder *c) { for (;;) { if (c->high >= 0x8000) { if (c->low < 0x8000) { if (c->low >= 0x4000 && c->high < 0xC000) { c->value -= 0x4000; c->low -= 0x4000; c->high -= 0x4000; } else { return; } } else { c->value -= 0x8000; c->low -= 0x8000; c->high -= 0x8000; } } c->value <<= 1; c->low <<= 1; c->high <<= 1; c->high |= 1; c->value |= get_bits1(c->gb); } } static int arith_get_bit(ArithCoder *c) { int range = c->high - c->low + 1; int bit = (((c->value - c->low) << 1) + 1) / range; if (bit) c->low += range >> 1; else c->high = c->low + (range >> 1) - 1; arith_normalise(c); return bit; } static int arith_get_bits(ArithCoder *c, int bits) { int range = c->high - c->low + 1; int val = (((c->value - c->low + 1) << bits) - 1) / range; int prob = range * val; c->high = ((prob + range) >> bits) + c->low - 1; c->low += prob >> bits; arith_normalise(c); return val; } static int arith_get_number(ArithCoder *c, int mod_val) { int range = c->high - c->low + 1; int val = ((c->value - c->low + 1) * mod_val - 1) / range; int prob = range * val; c->high = (prob + range) / mod_val + c->low - 1; c->low += prob / mod_val; arith_normalise(c); return val; } static int arith_get_prob(ArithCoder *c, int *probs) { int range = c->high - c->low + 1; int val = ((c->value - c->low + 1) * probs[0] - 1) / range; int sym = 1; while (probs[sym] > val) sym++; c->high = range * probs[sym - 1] / probs[0] + c->low - 1; c->low += range * probs[sym] / probs[0]; return sym; } static int model_calc_threshold(Model *m) { int thr; if (m->thr_weight == -1) { thr = 2 * m->weights[m->num_syms] - 1; thr = ((thr >> 1) + 4 * m->cum_prob[0]) / thr; } else { thr = m->num_syms * m->thr_weight; } return FFMIN(thr, 0x3FFF); } static void model_reset(Model *m) { int i; for (i = 0; i <= m->num_syms; i++) { m->weights[i] = 1; m->cum_prob[i] = m->num_syms - i; } m->weights[0] = -1; m->idx2sym[0] = -1; m->sym2idx[m->num_syms] = -1; for (i = 0; i < m->num_syms; i++) { m->sym2idx[i] = i + 1; m->idx2sym[i + 1] = i; } } static av_cold void model_init(Model *m, int num_syms, int thr_weight) { m->num_syms = num_syms; m->thr_weight = thr_weight; m->threshold = model_calc_threshold(m); model_reset(m); } static void model_rescale_weights(Model *m) { int i; int cum_prob; if (m->thr_weight == -1) m->threshold = model_calc_threshold(m); while (m->cum_prob[0] > m->threshold) { cum_prob = 0; for (i = m->num_syms; i >= 0; i--) { m->cum_prob[i] = cum_prob; m->weights[i] = (m->weights[i] + 1) >> 1; cum_prob += m->weights[i]; } } } static void model_update(Model *m, int val) { int i; if (m->weights[val] == m->weights[val - 1]) { for (i = val; m->weights[i - 1] == m->weights[val]; i--); if (i != val) { int sym1, sym2; sym1 = m->idx2sym[val]; sym2 = m->idx2sym[i]; m->idx2sym[val] = sym2; m->idx2sym[i] = sym1; m->sym2idx[sym1] = i; m->sym2idx[sym2] = val; val = i; } } m->weights[val]++; for (i = val - 1; i >= 0; i--) m->cum_prob[i]++; model_rescale_weights(m); } static int arith_get_model_sym(ArithCoder *c, Model *m) { int idx, val; idx = arith_get_prob(c, m->cum_prob); val = m->idx2sym[idx]; model_update(m, idx); arith_normalise(c); return val; } static void pixctx_reset(PixContext *ctx) { int i, j, k; for (i = 0; i < ctx->cache_size; i++) ctx->cache[i] = i; model_reset(&ctx->cache_model); model_reset(&ctx->full_model); for (i = 0; i < 4; i++) for (j = 0; j < sec_order_sizes[i]; j++) for (k = 0; k < 4; k++) model_reset(&ctx->sec_models[i][j][k]); } static av_cold void pixctx_init(PixContext *ctx, int cache_size) { int i, j, k; ctx->cache_size = cache_size + 4; ctx->num_syms = cache_size; for (i = 0; i < ctx->cache_size; i++) ctx->cache[i] = i; model_init(&ctx->cache_model, ctx->num_syms + 1, THRESH_LOW); model_init(&ctx->full_model, 256, THRESH_HIGH); for (i = 0; i < 4; i++) { for (j = 0; j < sec_order_sizes[i]; j++) { for (k = 0; k < 4; k++) { model_init(&ctx->sec_models[i][j][k], 2 + i, i ? THRESH_LOW : THRESH_ADAPTIVE); } } } } static int decode_top_left_pixel(ArithCoder *acoder, PixContext *pctx) { int i, val, pix; val = arith_get_model_sym(acoder, &pctx->cache_model); if (val < pctx->num_syms) { pix = pctx->cache[val]; } else { pix = arith_get_model_sym(acoder, &pctx->full_model); for (i = 0; i < pctx->cache_size - 1; i++) if (pctx->cache[i] == pix) break; val = i; } if (val) { for (i = val; i > 0; i--) pctx->cache[i] = pctx->cache[i - 1]; pctx->cache[0] = pix; } return pix; } static int decode_pixel(ArithCoder *acoder, PixContext *pctx, uint8_t *ngb, int num_ngb) { int i, val, pix; val = arith_get_model_sym(acoder, &pctx->cache_model); if (val < pctx->num_syms) { int idx, j; idx = 0; for (i = 0; i < pctx->cache_size; i++) { for (j = 0; j < num_ngb; j++) if (pctx->cache[i] == ngb[j]) break; if (j == num_ngb) { if (idx == val) break; idx++; } } val = FFMIN(i, pctx->cache_size - 1); pix = pctx->cache[val]; } else { pix = arith_get_model_sym(acoder, &pctx->full_model); for (i = 0; i < pctx->cache_size - 1; i++) if (pctx->cache[i] == pix) break; val = i; } if (val) { for (i = val; i > 0; i--) pctx->cache[i] = pctx->cache[i - 1]; pctx->cache[0] = pix; } return pix; } static int decode_pixel_in_context(ArithCoder *acoder, PixContext *pctx, uint8_t *src, int stride, int x, int y, int has_right) { uint8_t neighbours[4]; uint8_t ref_pix[4]; int nlen; int layer = 0, sub; int pix; int i, j; if (!y) { memset(neighbours, src[-1], 4); } else { neighbours[TOP] = src[-stride]; if (!x) { neighbours[TOP_LEFT] = neighbours[LEFT] = neighbours[TOP]; } else { neighbours[TOP_LEFT] = src[-stride - 1]; neighbours[ LEFT] = src[-1]; } if (has_right) neighbours[TOP_RIGHT] = src[-stride + 1]; else neighbours[TOP_RIGHT] = neighbours[TOP]; } sub = 0; if (x >= 2 && src[-2] == neighbours[LEFT]) sub = 1; if (y >= 2 && src[-2 * stride] == neighbours[TOP]) sub |= 2; nlen = 1; ref_pix[0] = neighbours[0]; for (i = 1; i < 4; i++) { for (j = 0; j < nlen; j++) if (ref_pix[j] == neighbours[i]) break; if (j == nlen) ref_pix[nlen++] = neighbours[i]; } switch (nlen) { case 1: case 4: layer = 0; break; case 2: if (neighbours[TOP] == neighbours[TOP_LEFT]) { if (neighbours[TOP_RIGHT] == neighbours[TOP_LEFT]) layer = 3; else if (neighbours[LEFT] == neighbours[TOP_LEFT]) layer = 2; else layer = 4; } else if (neighbours[TOP_RIGHT] == neighbours[TOP_LEFT]) { if (neighbours[LEFT] == neighbours[TOP_LEFT]) layer = 1; else layer = 5; } else if (neighbours[LEFT] == neighbours[TOP_LEFT]) { layer = 6; } else { layer = 0; } break; case 3: if (neighbours[TOP] == neighbours[TOP_LEFT]) layer = 0; else if (neighbours[TOP_RIGHT] == neighbours[TOP_LEFT]) layer = 1; else if (neighbours[LEFT] == neighbours[TOP_LEFT]) layer = 2; else if (neighbours[TOP_RIGHT] == neighbours[TOP]) layer = 3; else if (neighbours[TOP] == neighbours[LEFT]) layer = 4; else layer = 5; break; } pix = arith_get_model_sym(acoder, &pctx->sec_models[nlen - 1][layer][sub]); if (pix < nlen) return ref_pix[pix]; else return decode_pixel(acoder, pctx, ref_pix, nlen); } static int decode_region(MSS1Context *ctx, ArithCoder *acoder, uint8_t *dst, int x, int y, int width, int height, int stride, PixContext *pctx) { int i, j; dst += x + y * stride; dst[0] = decode_top_left_pixel(acoder, pctx); for (j = 0; j < height; j++) { for (i = 0; i < width; i++) { if (!i && !j) continue; dst[i] = decode_pixel_in_context(acoder, pctx, dst + i, stride, i, j, width - i - 1); } dst += stride; } return 0; } static int decode_region_masked(MSS1Context *ctx, ArithCoder *acoder, uint8_t *dst, int stride, uint8_t *mask, int mask_stride, int x, int y, int width, int height, PixContext *pctx) { int i, j; dst += x + y * stride; mask += x + y * mask_stride; if (mask[0] != 0xFF) dst[0] = decode_top_left_pixel(acoder, pctx); for (j = 0; j < height; j++) { for (i = 0; i < width; i++) { if (!i && !j || mask[i] != 0xFF) continue; dst[i] = decode_pixel_in_context(acoder, pctx, dst + i, stride, i, j, width - i - 1); } dst += stride; mask += mask_stride; } return 0; } static av_cold void codec_init(MSS1Context *ctx) { model_init(&ctx->intra_region, 2, THRESH_ADAPTIVE); model_init(&ctx->inter_region, 2, THRESH_ADAPTIVE); model_init(&ctx->split_mode, 3, THRESH_HIGH); model_init(&ctx->edge_mode, 2, THRESH_HIGH); model_init(&ctx->pivot, 3, THRESH_LOW); pixctx_init(&ctx->intra_pix_ctx, 8); pixctx_init(&ctx->inter_pix_ctx, 2); ctx->corrupted = 1; } static void codec_reset(MSS1Context *ctx) { model_reset(&ctx->intra_region); model_reset(&ctx->inter_region); model_reset(&ctx->split_mode); model_reset(&ctx->edge_mode); model_reset(&ctx->pivot); pixctx_reset(&ctx->intra_pix_ctx); pixctx_reset(&ctx->inter_pix_ctx); ctx->corrupted = 0; } static int decode_pal(MSS1Context *ctx, ArithCoder *acoder) { int i, ncol, r, g, b; uint32_t *pal = ctx->pal + 256 - ctx->free_colours; if (!ctx->free_colours) return 0; ncol = arith_get_number(acoder, ctx->free_colours + 1); for (i = 0; i < ncol; i++) { r = arith_get_bits(acoder, 8); g = arith_get_bits(acoder, 8); b = arith_get_bits(acoder, 8); *pal++ = (r << 16) | (g << 8) | b; } return 0; } static int decode_pivot(MSS1Context *ctx, ArithCoder *acoder, int base) { int val, inv; inv = arith_get_model_sym(acoder, &ctx->edge_mode); val = arith_get_model_sym(acoder, &ctx->pivot) + 1; if (val > 2) { if ((base + 1) / 2 - 2 <= 0) { ctx->corrupted = 1; return 0; } val = arith_get_number(acoder, (base + 1) / 2 - 2) + 3; } if (val == base) { ctx->corrupted = 1; return 0; } return inv ? base - val : val; } static int decode_region_intra(MSS1Context *ctx, ArithCoder *acoder, int x, int y, int width, int height) { int mode; mode = arith_get_model_sym(acoder, &ctx->intra_region); if (!mode) { int i, pix; int stride = ctx->pic_stride; uint8_t *dst = ctx->pic_start + x + y * stride; pix = decode_top_left_pixel(acoder, &ctx->intra_pix_ctx); for (i = 0; i < height; i++, dst += stride) memset(dst, pix, width); } else { return decode_region(ctx, acoder, ctx->pic_start, x, y, width, height, ctx->pic_stride, &ctx->intra_pix_ctx); } return 0; } static int decode_intra(MSS1Context *ctx, ArithCoder *acoder, int x, int y, int width, int height) { int mode, pivot; if (ctx->corrupted) return -1; mode = arith_get_model_sym(acoder, &ctx->split_mode); switch (mode) { case SPLIT_VERT: pivot = decode_pivot(ctx, acoder, height); if (ctx->corrupted) return -1; if (decode_intra(ctx, acoder, x, y, width, pivot)) return -1; if (decode_intra(ctx, acoder, x, y + pivot, width, height - pivot)) return -1; break; case SPLIT_HOR: pivot = decode_pivot(ctx, acoder, width); if (ctx->corrupted) return -1; if (decode_intra(ctx, acoder, x, y, pivot, height)) return -1; if (decode_intra(ctx, acoder, x + pivot, y, width - pivot, height)) return -1; break; case SPLIT_NONE: return decode_region_intra(ctx, acoder, x, y, width, height); default: return -1; } return 0; } static int decode_region_inter(MSS1Context *ctx, ArithCoder *acoder, int x, int y, int width, int height) { int mode; mode = arith_get_model_sym(acoder, &ctx->inter_region); if (!mode) { mode = decode_top_left_pixel(acoder, &ctx->inter_pix_ctx); if (mode != 0xFF) { return 0; } else { return decode_region_intra(ctx, acoder, x, y, width, height); } } else { if (decode_region(ctx, acoder, ctx->mask, x, y, width, height, ctx->mask_linesize, &ctx->inter_pix_ctx) < 0) return -1; return decode_region_masked(ctx, acoder, ctx->pic_start, -ctx->pic.linesize[0], ctx->mask, ctx->mask_linesize, x, y, width, height, &ctx->intra_pix_ctx); } return 0; } static int decode_inter(MSS1Context *ctx, ArithCoder *acoder, int x, int y, int width, int height) { int mode, pivot; if (ctx->corrupted) return -1; mode = arith_get_model_sym(acoder, &ctx->split_mode); switch (mode) { case SPLIT_VERT: pivot = decode_pivot(ctx, acoder, height); if (decode_inter(ctx, acoder, x, y, width, pivot)) return -1; if (decode_inter(ctx, acoder, x, y + pivot, width, height - pivot)) return -1; break; case SPLIT_HOR: pivot = decode_pivot(ctx, acoder, width); if (decode_inter(ctx, acoder, x, y, pivot, height)) return -1; if (decode_inter(ctx, acoder, x + pivot, y, width - pivot, height)) return -1; break; case SPLIT_NONE: return decode_region_inter(ctx, acoder, x, y, width, height); default: return -1; } return 0; } static int mss1_decode_frame(AVCodecContext *avctx, void *data, int *data_size, AVPacket *avpkt) { const uint8_t *buf = avpkt->data; int buf_size = avpkt->size; MSS1Context *c = avctx->priv_data; GetBitContext gb; ArithCoder acoder; int pal_changed = 0; int ret; init_get_bits(&gb, buf, buf_size * 8); arith_init(&acoder, &gb); c->pic.reference = 3; c->pic.buffer_hints = FF_BUFFER_HINTS_VALID | FF_BUFFER_HINTS_PRESERVE | FF_BUFFER_HINTS_REUSABLE; if ((ret = avctx->reget_buffer(avctx, &c->pic)) < 0) { av_log(avctx, AV_LOG_ERROR, "reget_buffer() failed\n"); return ret; } c->pic_start = c->pic.data[0] + c->pic.linesize[0] * (avctx->height - 1); c->pic_stride = -c->pic.linesize[0]; if (!arith_get_bit(&acoder)) { codec_reset(c); pal_changed = decode_pal(c, &acoder); c->corrupted = decode_intra(c, &acoder, 0, 0, avctx->width, avctx->height); c->pic.key_frame = 1; c->pic.pict_type = AV_PICTURE_TYPE_I; } else { if (c->corrupted) return AVERROR_INVALIDDATA; c->corrupted = decode_inter(c, &acoder, 0, 0, avctx->width, avctx->height); c->pic.key_frame = 0; c->pic.pict_type = AV_PICTURE_TYPE_P; } if (c->corrupted) return AVERROR_INVALIDDATA; memcpy(c->pic.data[1], c->pal, AVPALETTE_SIZE); c->pic.palette_has_changed = pal_changed; *data_size = sizeof(AVFrame); *(AVFrame*)data = c->pic; /* always report that the buffer was completely consumed */ return buf_size; } static av_cold int mss1_decode_init(AVCodecContext *avctx) { MSS1Context * const c = avctx->priv_data; int i; c->avctx = avctx; if (avctx->extradata_size < 52 + 256 * 3) { av_log(avctx, AV_LOG_ERROR, "Insufficient extradata size %d\n", avctx->extradata_size); return AVERROR_INVALIDDATA; } if (AV_RB32(avctx->extradata) < avctx->extradata_size) { av_log(avctx, AV_LOG_ERROR, "Insufficient extradata size: expected %d got %d\n", AV_RB32(avctx->extradata), avctx->extradata_size); return AVERROR_INVALIDDATA; } av_log(avctx, AV_LOG_DEBUG, "Encoder version %d.%d\n", AV_RB32(avctx->extradata + 4), AV_RB32(avctx->extradata + 8)); c->free_colours = AV_RB32(avctx->extradata + 48); av_log(avctx, AV_LOG_DEBUG, "%d free colour(s)\n", c->free_colours); avctx->coded_width = AV_RB32(avctx->extradata + 20); avctx->coded_height = AV_RB32(avctx->extradata + 24); av_log(avctx, AV_LOG_DEBUG, "Display dimensions %dx%d\n", AV_RB32(avctx->extradata + 12), AV_RB32(avctx->extradata + 16)); av_log(avctx, AV_LOG_DEBUG, "Coded dimensions %dx%d\n", avctx->coded_width, avctx->coded_height); av_log(avctx, AV_LOG_DEBUG, "%g frames per second\n", av_int2float(AV_RB32(avctx->extradata + 28))); av_log(avctx, AV_LOG_DEBUG, "Bitrate %d bps\n", AV_RB32(avctx->extradata + 32)); av_log(avctx, AV_LOG_DEBUG, "Max. lead time %g ms\n", av_int2float(AV_RB32(avctx->extradata + 36))); av_log(avctx, AV_LOG_DEBUG, "Max. lag time %g ms\n", av_int2float(AV_RB32(avctx->extradata + 40))); av_log(avctx, AV_LOG_DEBUG, "Max. seek time %g ms\n", av_int2float(AV_RB32(avctx->extradata + 44))); for (i = 0; i < 256; i++) c->pal[i] = AV_RB24(avctx->extradata + 52 + i * 3); avctx->pix_fmt = PIX_FMT_PAL8; c->mask_linesize = FFALIGN(avctx->width, 16); c->mask = av_malloc(c->mask_linesize * avctx->height); if (!c->mask) { av_log(avctx, AV_LOG_ERROR, "Cannot allocate mask plane\n"); return AVERROR(ENOMEM); } avctx->coded_frame = &c->pic; codec_init(c); return 0; } static av_cold int mss1_decode_end(AVCodecContext *avctx) { MSS1Context * const c = avctx->priv_data; if (c->pic.data[0]) avctx->release_buffer(avctx, &c->pic); av_freep(&c->mask); return 0; } AVCodec ff_mss1_decoder = { .name = "mss1", .type = AVMEDIA_TYPE_VIDEO, .id = CODEC_ID_MSS1, .priv_data_size = sizeof(MSS1Context), .init = mss1_decode_init, .close = mss1_decode_end, .decode = mss1_decode_frame, .capabilities = CODEC_CAP_DR1, .long_name = NULL_IF_CONFIG_SMALL("MS Screen 1"), };