yading@10: /*
yading@10:  * Microsoft Screen 1 (aka Windows Media Video V7 Screen) decoder
yading@10:  * Copyright (c) 2012 Konstantin Shishkov
yading@10:  *
yading@10:  * This file is part of FFmpeg.
yading@10:  *
yading@10:  * FFmpeg is free software; you can redistribute it and/or
yading@10:  * modify it under the terms of the GNU Lesser General Public
yading@10:  * License as published by the Free Software Foundation; either
yading@10:  * version 2.1 of the License, or (at your option) any later version.
yading@10:  *
yading@10:  * FFmpeg is distributed in the hope that it will be useful,
yading@10:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
yading@10:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
yading@10:  * Lesser General Public License for more details.
yading@10:  *
yading@10:  * You should have received a copy of the GNU Lesser General Public
yading@10:  * License along with FFmpeg; if not, write to the Free Software
yading@10:  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
yading@10:  */
yading@10: 
yading@10: /**
yading@10:  * @file
yading@10:  * Microsoft Screen 1 (aka Windows Media Video V7 Screen) decoder
yading@10:  */
yading@10: 
yading@10: #include "avcodec.h"
yading@10: #include "internal.h"
yading@10: #include "mss12.h"
yading@10: 
yading@10: typedef struct MSS1Context {
yading@10:     MSS12Context   ctx;
yading@10:     AVFrame        pic;
yading@10:     SliceContext   sc;
yading@10: } MSS1Context;
yading@10: 
yading@10: static void arith_normalise(ArithCoder *c)
yading@10: {
yading@10:     for (;;) {
yading@10:         if (c->high >= 0x8000) {
yading@10:             if (c->low < 0x8000) {
yading@10:                 if (c->low >= 0x4000 && c->high < 0xC000) {
yading@10:                     c->value -= 0x4000;
yading@10:                     c->low   -= 0x4000;
yading@10:                     c->high  -= 0x4000;
yading@10:                 } else {
yading@10:                     return;
yading@10:                 }
yading@10:             } else {
yading@10:                 c->value -= 0x8000;
yading@10:                 c->low   -= 0x8000;
yading@10:                 c->high  -= 0x8000;
yading@10:             }
yading@10:         }
yading@10:         c->value <<= 1;
yading@10:         c->low   <<= 1;
yading@10:         c->high  <<= 1;
yading@10:         c->high   |= 1;
yading@10:         c->value  |= get_bits1(c->gbc.gb);
yading@10:     }
yading@10: }
yading@10: 
yading@10: ARITH_GET_BIT()
yading@10: 
yading@10: static int arith_get_bits(ArithCoder *c, int bits)
yading@10: {
yading@10:     int range = c->high - c->low + 1;
yading@10:     int val   = (((c->value - c->low + 1) << bits) - 1) / range;
yading@10:     int prob  = range * val;
yading@10: 
yading@10:     c->high   = ((prob + range) >> bits) + c->low - 1;
yading@10:     c->low   += prob >> bits;
yading@10: 
yading@10:     arith_normalise(c);
yading@10: 
yading@10:     return val;
yading@10: }
yading@10: 
yading@10: static int arith_get_number(ArithCoder *c, int mod_val)
yading@10: {
yading@10:     int range = c->high - c->low + 1;
yading@10:     int val   = ((c->value - c->low + 1) * mod_val - 1) / range;
yading@10:     int prob  = range * val;
yading@10: 
yading@10:     c->high   = (prob + range) / mod_val + c->low - 1;
yading@10:     c->low   += prob / mod_val;
yading@10: 
yading@10:     arith_normalise(c);
yading@10: 
yading@10:     return val;
yading@10: }
yading@10: 
yading@10: static int arith_get_prob(ArithCoder *c, int16_t *probs)
yading@10: {
yading@10:     int range = c->high - c->low + 1;
yading@10:     int val   = ((c->value - c->low + 1) * probs[0] - 1) / range;
yading@10:     int sym   = 1;
yading@10: 
yading@10:     while (probs[sym] > val)
yading@10:         sym++;
yading@10: 
yading@10:     c->high = range * probs[sym - 1] / probs[0] + c->low - 1;
yading@10:     c->low += range * probs[sym]     / probs[0];
yading@10: 
yading@10:     return sym;
yading@10: }
yading@10: 
yading@10: ARITH_GET_MODEL_SYM()
yading@10: 
yading@10: static void arith_init(ArithCoder *c, GetBitContext *gb)
yading@10: {
yading@10:     c->low           = 0;
yading@10:     c->high          = 0xFFFF;
yading@10:     c->value         = get_bits(gb, 16);
yading@10:     c->gbc.gb        = gb;
yading@10:     c->get_model_sym = arith_get_model_sym;
yading@10:     c->get_number    = arith_get_number;
yading@10: }
yading@10: 
yading@10: static int decode_pal(MSS12Context *ctx, ArithCoder *acoder)
yading@10: {
yading@10:     int i, ncol, r, g, b;
yading@10:     uint32_t *pal = ctx->pal + 256 - ctx->free_colours;
yading@10: 
yading@10:     if (!ctx->free_colours)
yading@10:         return 0;
yading@10: 
yading@10:     ncol = arith_get_number(acoder, ctx->free_colours + 1);
yading@10:     for (i = 0; i < ncol; i++) {
yading@10:         r = arith_get_bits(acoder, 8);
yading@10:         g = arith_get_bits(acoder, 8);
yading@10:         b = arith_get_bits(acoder, 8);
yading@10:         *pal++ = (0xFFU << 24) | (r << 16) | (g << 8) | b;
yading@10:     }
yading@10: 
yading@10:     return !!ncol;
yading@10: }
yading@10: 
yading@10: static int mss1_decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
yading@10:                              AVPacket *avpkt)
yading@10: {
yading@10:     const uint8_t *buf = avpkt->data;
yading@10:     int buf_size = avpkt->size;
yading@10:     MSS1Context *ctx = avctx->priv_data;
yading@10:     MSS12Context *c = &ctx->ctx;
yading@10:     GetBitContext gb;
yading@10:     ArithCoder acoder;
yading@10:     int pal_changed = 0;
yading@10:     int ret;
yading@10: 
yading@10:     init_get_bits(&gb, buf, buf_size * 8);
yading@10:     arith_init(&acoder, &gb);
yading@10: 
yading@10:     if ((ret = ff_reget_buffer(avctx, &ctx->pic)) < 0)
yading@10:         return ret;
yading@10: 
yading@10:     c->pal_pic    =  ctx->pic.data[0] + ctx->pic.linesize[0] * (avctx->height - 1);
yading@10:     c->pal_stride = -ctx->pic.linesize[0];
yading@10:     c->keyframe   = !arith_get_bit(&acoder);
yading@10:     if (c->keyframe) {
yading@10:         c->corrupted = 0;
yading@10:         ff_mss12_slicecontext_reset(&ctx->sc);
yading@10:         pal_changed        = decode_pal(c, &acoder);
yading@10:         ctx->pic.key_frame = 1;
yading@10:         ctx->pic.pict_type = AV_PICTURE_TYPE_I;
yading@10:     } else {
yading@10:         if (c->corrupted)
yading@10:             return AVERROR_INVALIDDATA;
yading@10:         ctx->pic.key_frame = 0;
yading@10:         ctx->pic.pict_type = AV_PICTURE_TYPE_P;
yading@10:     }
yading@10:     c->corrupted = ff_mss12_decode_rect(&ctx->sc, &acoder, 0, 0,
yading@10:                                         avctx->width, avctx->height);
yading@10:     if (c->corrupted)
yading@10:         return AVERROR_INVALIDDATA;
yading@10:     memcpy(ctx->pic.data[1], c->pal, AVPALETTE_SIZE);
yading@10:     ctx->pic.palette_has_changed = pal_changed;
yading@10: 
yading@10:     if ((ret = av_frame_ref(data, &ctx->pic)) < 0)
yading@10:         return ret;
yading@10: 
yading@10:     *got_frame      = 1;
yading@10: 
yading@10:     /* always report that the buffer was completely consumed */
yading@10:     return buf_size;
yading@10: }
yading@10: 
yading@10: static av_cold int mss1_decode_init(AVCodecContext *avctx)
yading@10: {
yading@10:     MSS1Context * const c = avctx->priv_data;
yading@10:     int ret;
yading@10: 
yading@10:     c->ctx.avctx       = avctx;
yading@10: 
yading@10:     avcodec_get_frame_defaults(&c->pic);
yading@10: 
yading@10:     ret = ff_mss12_decode_init(&c->ctx, 0, &c->sc, NULL);
yading@10: 
yading@10:     avctx->pix_fmt = AV_PIX_FMT_PAL8;
yading@10: 
yading@10:     return ret;
yading@10: }
yading@10: 
yading@10: static av_cold int mss1_decode_end(AVCodecContext *avctx)
yading@10: {
yading@10:     MSS1Context * const ctx = avctx->priv_data;
yading@10: 
yading@10:     av_frame_unref(&ctx->pic);
yading@10:     ff_mss12_decode_end(&ctx->ctx);
yading@10: 
yading@10:     return 0;
yading@10: }
yading@10: 
yading@10: AVCodec ff_mss1_decoder = {
yading@10:     .name           = "mss1",
yading@10:     .type           = AVMEDIA_TYPE_VIDEO,
yading@10:     .id             = AV_CODEC_ID_MSS1,
yading@10:     .priv_data_size = sizeof(MSS1Context),
yading@10:     .init           = mss1_decode_init,
yading@10:     .close          = mss1_decode_end,
yading@10:     .decode         = mss1_decode_frame,
yading@10:     .capabilities   = CODEC_CAP_DR1,
yading@10:     .long_name      = NULL_IF_CONFIG_SMALL("MS Screen 1"),
yading@10: };