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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" |
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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); |
} |
} |
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ARITH_GET_BIT(arith) |
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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; |
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c->high = ((prob + range) >> bits) + c->low - 1; |
c->low += prob >> bits; |
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arith_normalise(c); |
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return val; |
} |
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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; |
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c->high = (prob + range) / mod_val + c->low - 1; |
c->low += prob / mod_val; |
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arith_normalise(c); |
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return val; |
} |
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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; |
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while (probs[sym] > val) |
sym++; |
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c->high = range * probs[sym - 1] / probs[0] + c->low - 1; |
c->low += range * probs[sym] / probs[0]; |
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return sym; |
} |
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ARITH_GET_MODEL_SYM(arith) |
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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; |
} |
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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; |
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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; |
} |
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return !!ncol; |
} |
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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; |
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if ((ret = init_get_bits8(&gb, avpkt->data, avpkt->size)) < 0) |
return ret; |
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arith_init(&acoder, &gb); |
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if ((ret = ff_reget_buffer(avctx, ctx->pic)) < 0) |
return ret; |
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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; |
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if ((ret = av_frame_ref(data, ctx->pic)) < 0) |
return ret; |
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*got_frame = 1; |
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/* always report that the buffer was completely consumed */ |
return avpkt->size; |
} |
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static av_cold int mss1_decode_init(AVCodecContext *avctx) |
{ |
MSS1Context * const c = avctx->priv_data; |
int ret; |
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c->ctx.avctx = avctx; |
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c->pic = av_frame_alloc(); |
if (!c->pic) |
return AVERROR(ENOMEM); |
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ret = ff_mss12_decode_init(&c->ctx, 0, &c->sc, NULL); |
if (ret < 0) |
av_frame_free(&c->pic); |
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avctx->pix_fmt = AV_PIX_FMT_PAL8; |
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return ret; |
} |
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static av_cold int mss1_decode_end(AVCodecContext *avctx) |
{ |
MSS1Context * const ctx = avctx->priv_data; |
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av_frame_free(&ctx->pic); |
ff_mss12_decode_end(&ctx->ctx); |
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return 0; |
} |
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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 = AV_CODEC_CAP_DR1, |
}; |