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228 lines
6.0 KiB
228 lines
6.0 KiB
/* |
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* Microsoft Screen 1 (aka Windows Media Video V7 Screen) decoder |
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* Copyright (c) 2012 Konstantin Shishkov |
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* |
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* This file is part of Libav. |
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* |
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* Libav is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU Lesser General Public |
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* License as published by the Free Software Foundation; either |
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* version 2.1 of the License, or (at your option) any later version. |
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* |
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* Libav is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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* Lesser General Public License for more details. |
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* |
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* You should have received a copy of the GNU Lesser General Public |
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* License along with Libav; if not, write to the Free Software |
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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*/ |
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/** |
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* @file |
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* Microsoft Screen 1 (aka Windows Media Video V7 Screen) decoder |
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*/ |
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#include "avcodec.h" |
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#include "internal.h" |
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#include "mss12.h" |
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typedef struct MSS1Context { |
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MSS12Context ctx; |
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AVFrame *pic; |
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SliceContext sc; |
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} MSS1Context; |
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static void arith1_normalise(ArithCoder *c) |
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{ |
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for (;;) { |
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if (c->high >= 0x8000) { |
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if (c->low < 0x8000) { |
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if (c->low >= 0x4000 && c->high < 0xC000) { |
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c->value -= 0x4000; |
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c->low -= 0x4000; |
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c->high -= 0x4000; |
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} else { |
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return; |
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} |
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} else { |
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c->value -= 0x8000; |
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c->low -= 0x8000; |
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c->high -= 0x8000; |
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} |
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} |
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c->value <<= 1; |
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c->low <<= 1; |
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c->high <<= 1; |
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c->high |= 1; |
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c->value |= get_bits1(c->gbc.gb); |
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} |
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} |
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ARITH_GET_BIT(1) |
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static int arith_get_bits(ArithCoder *c, int bits) |
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{ |
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int range = c->high - c->low + 1; |
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int val = (((c->value - c->low + 1) << bits) - 1) / range; |
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int prob = range * val; |
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c->high = ((prob + range) >> bits) + c->low - 1; |
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c->low += prob >> bits; |
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arith1_normalise(c); |
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return val; |
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} |
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static int arith_get_number(ArithCoder *c, int mod_val) |
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{ |
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int range = c->high - c->low + 1; |
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int val = ((c->value - c->low + 1) * mod_val - 1) / range; |
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int prob = range * val; |
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c->high = (prob + range) / mod_val + c->low - 1; |
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c->low += prob / mod_val; |
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arith1_normalise(c); |
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return val; |
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} |
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static int arith1_get_prob(ArithCoder *c, int16_t *probs) |
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{ |
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int range = c->high - c->low + 1; |
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int val = ((c->value - c->low + 1) * probs[0] - 1) / range; |
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int sym = 1; |
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while (probs[sym] > val) |
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sym++; |
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c->high = range * probs[sym - 1] / probs[0] + c->low - 1; |
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c->low += range * probs[sym] / probs[0]; |
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return sym; |
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} |
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ARITH_GET_MODEL_SYM(1) |
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static void arith_init(ArithCoder *c, GetBitContext *gb) |
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{ |
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c->low = 0; |
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c->high = 0xFFFF; |
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c->value = get_bits(gb, 16); |
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c->gbc.gb = gb; |
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c->get_model_sym = arith1_get_model_sym; |
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c->get_number = arith_get_number; |
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} |
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static int decode_pal(MSS12Context *ctx, ArithCoder *acoder) |
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{ |
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int i, ncol, r, g, b; |
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uint32_t *pal = ctx->pal + 256 - ctx->free_colours; |
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if (!ctx->free_colours) |
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return 0; |
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ncol = arith_get_number(acoder, ctx->free_colours + 1); |
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for (i = 0; i < ncol; i++) { |
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r = arith_get_bits(acoder, 8); |
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g = arith_get_bits(acoder, 8); |
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b = arith_get_bits(acoder, 8); |
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*pal++ = (r << 16) | (g << 8) | b; |
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} |
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return !!ncol; |
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} |
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static int mss1_decode_frame(AVCodecContext *avctx, void *data, int *got_frame, |
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AVPacket *avpkt) |
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{ |
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const uint8_t *buf = avpkt->data; |
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int buf_size = avpkt->size; |
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MSS1Context *ctx = avctx->priv_data; |
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MSS12Context *c = &ctx->ctx; |
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GetBitContext gb; |
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ArithCoder acoder; |
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int pal_changed = 0; |
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int ret; |
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init_get_bits(&gb, buf, buf_size * 8); |
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arith_init(&acoder, &gb); |
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if ((ret = ff_reget_buffer(avctx, ctx->pic)) < 0) { |
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av_log(avctx, AV_LOG_ERROR, "reget_buffer() failed\n"); |
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return ret; |
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} |
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c->pal_pic = ctx->pic->data[0] + ctx->pic->linesize[0] * (avctx->height - 1); |
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c->pal_stride = -ctx->pic->linesize[0]; |
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c->keyframe = !arith1_get_bit(&acoder); |
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if (c->keyframe) { |
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c->corrupted = 0; |
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ff_mss12_slicecontext_reset(&ctx->sc); |
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pal_changed = decode_pal(c, &acoder); |
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ctx->pic->key_frame = 1; |
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ctx->pic->pict_type = AV_PICTURE_TYPE_I; |
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} else { |
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if (c->corrupted) |
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return AVERROR_INVALIDDATA; |
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ctx->pic->key_frame = 0; |
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ctx->pic->pict_type = AV_PICTURE_TYPE_P; |
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} |
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c->corrupted = ff_mss12_decode_rect(&ctx->sc, &acoder, 0, 0, |
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avctx->width, avctx->height); |
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if (c->corrupted) |
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return AVERROR_INVALIDDATA; |
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memcpy(ctx->pic->data[1], c->pal, AVPALETTE_SIZE); |
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ctx->pic->palette_has_changed = pal_changed; |
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if ((ret = av_frame_ref(data, ctx->pic)) < 0) |
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return ret; |
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*got_frame = 1; |
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/* always report that the buffer was completely consumed */ |
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return buf_size; |
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} |
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static av_cold int mss1_decode_init(AVCodecContext *avctx) |
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{ |
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MSS1Context * const c = avctx->priv_data; |
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int ret; |
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c->ctx.avctx = avctx; |
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c->pic = av_frame_alloc(); |
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if (!c->pic) |
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return AVERROR(ENOMEM); |
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ret = ff_mss12_decode_init(&c->ctx, 0, &c->sc, NULL); |
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avctx->pix_fmt = AV_PIX_FMT_PAL8; |
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return ret; |
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} |
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static av_cold int mss1_decode_end(AVCodecContext *avctx) |
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{ |
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MSS1Context * const ctx = avctx->priv_data; |
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av_frame_free(&ctx->pic); |
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ff_mss12_decode_end(&ctx->ctx); |
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return 0; |
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} |
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AVCodec ff_mss1_decoder = { |
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.name = "mss1", |
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.long_name = NULL_IF_CONFIG_SMALL("MS Screen 1"), |
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.type = AVMEDIA_TYPE_VIDEO, |
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.id = AV_CODEC_ID_MSS1, |
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.priv_data_size = sizeof(MSS1Context), |
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.init = mss1_decode_init, |
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.close = mss1_decode_end, |
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.decode = mss1_decode_frame, |
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.capabilities = AV_CODEC_CAP_DR1, |
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};
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