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* Apple MJPEG-B decoder
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* Copyright (c) 2002 Alex Beregszaszi
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* This file is part of FFmpeg.
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* FFmpeg 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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* FFmpeg 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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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; 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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* Apple MJPEG-B decoder.
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static int mjpegb_decode_frame(AVCodecContext *avctx,
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void *data, int *data_size,
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uint8_t *buf, int buf_size)
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MJpegDecodeContext *s = avctx->priv_data;
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uint8_t *buf_end, *buf_ptr;
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AVFrame *picture = data;
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GetBitContext hgb; /* for the header */
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uint32_t dqt_offs, dht_offs, sof_offs, sos_offs, second_field_offs;
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uint32_t field_size, sod_offs;
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buf_end = buf + buf_size;
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/* reset on every SOI */
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s->restart_interval = 0;
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s->mjpb_skiptosod = 0;
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init_get_bits(&hgb, buf_ptr, /*buf_size*/(buf_end - buf_ptr)*8);
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skip_bits(&hgb, 32); /* reserved zeros */
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if (get_bits_long(&hgb, 32) != MKBETAG('m','j','p','g'))
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av_log(avctx, AV_LOG_WARNING, "not mjpeg-b (bad fourcc)\n");
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field_size = get_bits_long(&hgb, 32); /* field size */
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av_log(avctx, AV_LOG_DEBUG, "field size: 0x%x\n", field_size);
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skip_bits(&hgb, 32); /* padded field size */
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second_field_offs = get_bits_long(&hgb, 32);
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av_log(avctx, AV_LOG_DEBUG, "second field offs: 0x%x\n", second_field_offs);
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dqt_offs = get_bits_long(&hgb, 32);
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av_log(avctx, AV_LOG_DEBUG, "dqt offs: 0x%x\n", dqt_offs);
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init_get_bits(&s->gb, buf+dqt_offs, (buf_end - (buf+dqt_offs))*8);
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ff_mjpeg_decode_dqt(s);
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dht_offs = get_bits_long(&hgb, 32);
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av_log(avctx, AV_LOG_DEBUG, "dht offs: 0x%x\n", dht_offs);
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init_get_bits(&s->gb, buf+dht_offs, (buf_end - (buf+dht_offs))*8);
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ff_mjpeg_decode_dht(s);
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sof_offs = get_bits_long(&hgb, 32);
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av_log(avctx, AV_LOG_DEBUG, "sof offs: 0x%x\n", sof_offs);
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init_get_bits(&s->gb, buf+sof_offs, (buf_end - (buf+sof_offs))*8);
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if (ff_mjpeg_decode_sof(s) < 0)
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sos_offs = get_bits_long(&hgb, 32);
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av_log(avctx, AV_LOG_DEBUG, "sos offs: 0x%x\n", sos_offs);
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sod_offs = get_bits_long(&hgb, 32);
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av_log(avctx, AV_LOG_DEBUG, "sod offs: 0x%x\n", sod_offs);
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// init_get_bits(&s->gb, buf+sos_offs, (buf_end - (buf+sos_offs))*8);
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init_get_bits(&s->gb, buf+sos_offs, field_size*8);
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s->mjpb_skiptosod = (sod_offs - sos_offs - show_bits(&s->gb, 16));
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ff_mjpeg_decode_sos(s);
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s->bottom_field ^= 1;
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/* if not bottom field, do not output image yet */
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if (s->bottom_field && second_field_offs)
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buf_ptr = buf + second_field_offs;
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second_field_offs = 0;
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//XXX FIXME factorize, this looks very similar to the EOI code
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*picture= s->picture;
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*data_size = sizeof(AVFrame);
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picture->quality= FFMAX(FFMAX(s->qscale[0], s->qscale[1]), s->qscale[2]);
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picture->qscale_table= s->qscale_table;
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memset(picture->qscale_table, picture->quality, (s->width+15)/16);
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if(avctx->debug & FF_DEBUG_QP)
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av_log(avctx, AV_LOG_DEBUG, "QP: %d\n", picture->quality);
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picture->quality*= FF_QP2LAMBDA;
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return buf_ptr - buf;
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AVCodec mjpegb_decoder = {
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sizeof(MJpegDecodeContext),
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ff_mjpeg_decode_init,