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/*
* 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 "avcodec.h"
#include "internal.h"
#include "mss12.h"
typedef struct MSS1Context {
MSS12Context ctx;
AVFrame *pic;
SliceContext sc;
} MSS1Context;
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->gbc.gb);
}
}
ARITH_GET_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, int16_t *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;
}
ARITH_GET_MODEL_SYM()
static void arith_init(ArithCoder *c, GetBitContext *gb)
{
c->low = 0;
c->high = 0xFFFF;
c->value = get_bits(gb, 16);
c->gbc.gb = gb;
c->get_model_sym = arith_get_model_sym;
c->get_number = arith_get_number;
}
static int decode_pal(MSS12Context *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++ = (0xFFU << 24) | (r << 16) | (g << 8) | b;
}
return !!ncol;
}
static int mss1_decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
AVPacket *avpkt)
{
MSS1Context *ctx = avctx->priv_data;
MSS12Context *c = &ctx->ctx;
GetBitContext gb;
ArithCoder acoder;
int pal_changed = 0;
int ret;
if ((ret = init_get_bits8(&gb, avpkt->data, avpkt->size)) < 0)
return ret;
arith_init(&acoder, &gb);
if ((ret = ff_reget_buffer(avctx, ctx->pic)) < 0)
return ret;
c->pal_pic = ctx->pic->data[0] + ctx->pic->linesize[0] * (avctx->height - 1);
c->pal_stride = -ctx->pic->linesize[0];
c->keyframe = !arith_get_bit(&acoder);
if (c->keyframe) {
c->corrupted = 0;
ff_mss12_slicecontext_reset(&ctx->sc);
pal_changed = decode_pal(c, &acoder);
ctx->pic->key_frame = 1;
ctx->pic->pict_type = AV_PICTURE_TYPE_I;
} else {
if (c->corrupted)
return AVERROR_INVALIDDATA;
ctx->pic->key_frame = 0;
ctx->pic->pict_type = AV_PICTURE_TYPE_P;
}
c->corrupted = ff_mss12_decode_rect(&ctx->sc, &acoder, 0, 0,
avctx->width, avctx->height);
if (c->corrupted)
return AVERROR_INVALIDDATA;
memcpy(ctx->pic->data[1], c->pal, AVPALETTE_SIZE);
ctx->pic->palette_has_changed = pal_changed;
if ((ret = av_frame_ref(data, ctx->pic)) < 0)
return ret;
*got_frame = 1;
/* always report that the buffer was completely consumed */
return avpkt->size;
}
static av_cold int mss1_decode_init(AVCodecContext *avctx)
{
MSS1Context * const c = avctx->priv_data;
int ret;
c->ctx.avctx = avctx;
c->pic = av_frame_alloc();
if (!c->pic)
return AVERROR(ENOMEM);
ret = ff_mss12_decode_init(&c->ctx, 0, &c->sc, NULL);
avctx->pix_fmt = AV_PIX_FMT_PAL8;
return ret;
}
static av_cold int mss1_decode_end(AVCodecContext *avctx)
{
MSS1Context * const ctx = avctx->priv_data;
av_frame_free(&ctx->pic);
ff_mss12_decode_end(&ctx->ctx);
return 0;
}
AVCodec ff_mss1_decoder = {
.name = "mss1",
.long_name = NULL_IF_CONFIG_SMALL("MS Screen 1"),
.type = AVMEDIA_TYPE_VIDEO,
.id = AV_CODEC_ID_MSS1,
.priv_data_size = sizeof(MSS1Context),
.init = mss1_decode_init,
.close = mss1_decode_end,
.decode = mss1_decode_frame,
.capabilities = CODEC_CAP_DR1,
};
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