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ffmpeg / libavcodec / mjpegbdec.c @ 2912e87a

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/*
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 * Apple MJPEG-B decoder
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 * Copyright (c) 2002 Alex Beregszaszi
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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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 * Apple MJPEG-B decoder.
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 */
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#include "avcodec.h"
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#include "mjpeg.h"
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#include "mjpegdec.h"
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static uint32_t read_offs(AVCodecContext *avctx, GetBitContext *gb, uint32_t size, const char *err_msg){
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    uint32_t offs= get_bits_long(gb, 32);
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    if(offs >= size){
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        av_log(avctx, AV_LOG_WARNING, err_msg, offs, size);
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        return 0;
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    }
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    return offs;
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}
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static int mjpegb_decode_frame(AVCodecContext *avctx,
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                              void *data, int *data_size,
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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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    MJpegDecodeContext *s = avctx->priv_data;
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    const 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_ptr = buf;
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    buf_end = buf + buf_size;
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read_header:
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    /* reset on every SOI */
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    s->restart_interval = 0;
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    s->restart_count = 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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    {
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        av_log(avctx, AV_LOG_WARNING, "not mjpeg-b (bad fourcc)\n");
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        return 0;
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    }
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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 = read_offs(avctx, &hgb, buf_end - buf_ptr, "second_field_offs is %d and size is %d\n");
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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 = read_offs(avctx, &hgb, buf_end - buf_ptr, "dqt is %d and size is %d\n");
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    av_log(avctx, AV_LOG_DEBUG, "dqt offs: 0x%x\n", dqt_offs);
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    if (dqt_offs)
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    {
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        init_get_bits(&s->gb, buf_ptr+dqt_offs, (buf_end - (buf_ptr+dqt_offs))*8);
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        s->start_code = DQT;
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        ff_mjpeg_decode_dqt(s);
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    }
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    dht_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "dht is %d and size is %d\n");
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    av_log(avctx, AV_LOG_DEBUG, "dht offs: 0x%x\n", dht_offs);
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    if (dht_offs)
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    {
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        init_get_bits(&s->gb, buf_ptr+dht_offs, (buf_end - (buf_ptr+dht_offs))*8);
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        s->start_code = DHT;
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        ff_mjpeg_decode_dht(s);
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    }
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    sof_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "sof is %d and size is %d\n");
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    av_log(avctx, AV_LOG_DEBUG, "sof offs: 0x%x\n", sof_offs);
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    if (sof_offs)
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    {
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        init_get_bits(&s->gb, buf_ptr+sof_offs, (buf_end - (buf_ptr+sof_offs))*8);
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        s->start_code = SOF0;
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        if (ff_mjpeg_decode_sof(s) < 0)
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            return -1;
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    }
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    sos_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "sos is %d and size is %d\n");
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    av_log(avctx, AV_LOG_DEBUG, "sos offs: 0x%x\n", sos_offs);
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    sod_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "sof is %d and size is %d\n");
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    av_log(avctx, AV_LOG_DEBUG, "sod offs: 0x%x\n", sod_offs);
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    if (sos_offs)
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    {
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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_ptr+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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        s->start_code = SOS;
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        ff_mjpeg_decode_sos(s);
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    }
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    if (s->interlaced) {
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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 != s->interlace_polarity && second_field_offs)
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        {
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            buf_ptr = buf + second_field_offs;
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            second_field_offs = 0;
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            goto read_header;
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            }
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    }
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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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    if(!s->lossless){
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        picture->quality= FFMAX3(s->qscale[0], s->qscale[1], s->qscale[2]);
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        picture->qstride= 0;
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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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    }
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    return buf_ptr - buf;
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}
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AVCodec ff_mjpegb_decoder = {
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    "mjpegb",
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    AVMEDIA_TYPE_VIDEO,
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    CODEC_ID_MJPEGB,
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    sizeof(MJpegDecodeContext),
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    ff_mjpeg_decode_init,
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    NULL,
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    ff_mjpeg_decode_end,
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    mjpegb_decode_frame,
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    CODEC_CAP_DR1,
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    NULL,
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    .max_lowres = 3,
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    .long_name = NULL_IF_CONFIG_SMALL("Apple MJPEG-B"),
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};