mjpegdec.c

ffmpeg的完整源代码和作者自己写的文档。不但有在Linux的工程哦

/*
 * MJPEG decoder
 * Copyright (c) 2000, 2001 Fabrice Bellard.
 * Copyright (c) 2003 Alex Beregszaszi
 * Copyright (c) 2003-2004 Michael Niedermayer
 *
 * Support for external huffman table, various fixes (AVID workaround),
 * aspecting, new decode_frame mechanism and apple mjpeg-b support
 *                                  by Alex Beregszaszi
 *
 * 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 mjpegdec.c
 * MJPEG decoder.
 */

//#define DEBUG
#include <assert.h>

#include "avcodec.h"
#include "dsputil.h"
#include "mjpeg.h"
#include "mjpegdec.h"
#include "jpeglsdec.h"


static int build_vlc(VLC *vlc, const uint8_t *bits_table, const uint8_t *val_table,
                      int nb_codes, int use_static, int is_ac)
{
    uint8_t huff_size[256+16];
    uint16_t huff_code[256+16];

    assert(nb_codes <= 256);

    memset(huff_size, 0, sizeof(huff_size));
    ff_mjpeg_build_huffman_codes(huff_size, huff_code, bits_table, val_table);

    if(is_ac){
        memmove(huff_size+16, huff_size, sizeof(uint8_t)*nb_codes);
        memmove(huff_code+16, huff_code, sizeof(uint16_t)*nb_codes);
        memset(huff_size, 0, sizeof(uint8_t)*16);
        memset(huff_code, 0, sizeof(uint16_t)*16);
        nb_codes += 16;
    }

    return init_vlc(vlc, 9, nb_codes, huff_size, 1, 1, huff_code, 2, 2, use_static);
}

static void build_basic_mjpeg_vlc(MJpegDecodeContext * s) {
    build_vlc(&s->vlcs[0][0], ff_mjpeg_bits_dc_luminance,
              ff_mjpeg_val_dc_luminance, 12, 0, 0);
    build_vlc(&s->vlcs[0][1], ff_mjpeg_bits_dc_chrominance,
              ff_mjpeg_val_dc_chrominance, 12, 0, 0);
    build_vlc(&s->vlcs[1][0], ff_mjpeg_bits_ac_luminance,
              ff_mjpeg_val_ac_luminance, 251, 0, 1);
    build_vlc(&s->vlcs[1][1], ff_mjpeg_bits_ac_chrominance,
              ff_mjpeg_val_ac_chrominance, 251, 0, 1);
}

int ff_mjpeg_decode_init(AVCodecContext *avctx)
{
    MJpegDecodeContext *s = avctx->priv_data;

    s->avctx = avctx;
    dsputil_init(&s->dsp, avctx);
    ff_init_scantable(s->dsp.idct_permutation, &s->scantable, ff_zigzag_direct);
    s->buffer_size = 0;
    s->buffer = NULL;
    s->start_code = -1;
    s->first_picture = 1;
    s->org_height = avctx->coded_height;

    build_basic_mjpeg_vlc(s);

    if (avctx->flags & CODEC_FLAG_EXTERN_HUFF)
    {
        av_log(avctx, AV_LOG_INFO, "mjpeg: using external huffman table\n");
        init_get_bits(&s->gb, avctx->extradata, avctx->extradata_size*8);
        if (ff_mjpeg_decode_dht(s)) {
            av_log(avctx, AV_LOG_ERROR, "mjpeg: error using external huffman table, switching back to internal\n");
            build_basic_mjpeg_vlc(s);
        }
    }
    if (avctx->extradata_size > 9 &&
        AV_RL32(avctx->extradata + 4) == MKTAG('f','i','e','l')) {
        if (avctx->extradata[9] == 6) { /* quicktime icefloe 019 */
            s->interlace_polarity = 1; /* bottom field first */
            av_log(avctx, AV_LOG_DEBUG, "mjpeg bottom field first\n");
        }
    }

    return 0;
}


/* quantize tables */
int ff_mjpeg_decode_dqt(MJpegDecodeContext *s)
{
    int len, index, i, j;

    len = get_bits(&s->gb, 16) - 2;

    while (len >= 65) {
        /* only 8 bit precision handled */
        if (get_bits(&s->gb, 4) != 0)
        {
            av_log(s->avctx, AV_LOG_ERROR, "dqt: 16bit precision\n");
            return -1;
        }
        index = get_bits(&s->gb, 4);
        if (index >= 4)
            return -1;
        av_log(s->avctx, AV_LOG_DEBUG, "index=%d\n", index);
        /* read quant table */
        for(i=0;i<64;i++) {
            j = s->scantable.permutated[i];
            s->quant_matrixes[index][j] = get_bits(&s->gb, 8);
        }

        //XXX FIXME finetune, and perhaps add dc too
        s->qscale[index]= FFMAX(
            s->quant_matrixes[index][s->scantable.permutated[1]],
            s->quant_matrixes[index][s->scantable.permutated[8]]) >> 1;
        av_log(s->avctx, AV_LOG_DEBUG, "qscale[%d]: %d\n", index, s->qscale[index]);
        len -= 65;
    }

    return 0;
}

/* decode huffman tables and build VLC decoders */
int ff_mjpeg_decode_dht(MJpegDecodeContext *s)
{
    int len, index, i, class, n, v, code_max;
    uint8_t bits_table[17];
    uint8_t val_table[256];

    len = get_bits(&s->gb, 16) - 2;

    while (len > 0) {
        if (len < 17)
            return -1;
        class = get_bits(&s->gb, 4);
        if (class >= 2)
            return -1;
        index = get_bits(&s->gb, 4);
        if (index >= 4)
            return -1;
        n = 0;
        for(i=1;i<=16;i++) {
            bits_table[i] = get_bits(&s->gb, 8);
            n += bits_table[i];
        }
        len -= 17;
        if (len < n || n > 256)
            return -1;

        code_max = 0;
        for(i=0;i<n;i++) {
            v = get_bits(&s->gb, 8);
            if (v > code_max)
                code_max = v;
            val_table[i] = v;
        }
        len -= n;

        /* build VLC and flush previous vlc if present */
        free_vlc(&s->vlcs[class][index]);
        av_log(s->avctx, AV_LOG_DEBUG, "class=%d index=%d nb_codes=%d\n",
               class, index, code_max + 1);
        if(build_vlc(&s->vlcs[class][index], bits_table, val_table, code_max + 1, 0, class > 0) < 0){
            return -1;
        }
    }
    return 0;
}

int ff_mjpeg_decode_sof(MJpegDecodeContext *s)
{
    int len, nb_components, i, width, height, pix_fmt_id;

    /* XXX: verify len field validity */
    len = get_bits(&s->gb, 16);
    s->bits= get_bits(&s->gb, 8);

    if(s->pegasus_rct) s->bits=9;
    if(s->bits==9 && !s->pegasus_rct) s->rct=1;    //FIXME ugly

    if (s->bits != 8 && !s->lossless){
        av_log(s->avctx, AV_LOG_ERROR, "only 8 bits/component accepted\n");
        return -1;
    }

    height = get_bits(&s->gb, 16);
    width = get_bits(&s->gb, 16);

    //HACK for odd_height.mov
    if(s->interlaced && s->width == width && s->height == height + 1)
        height= s->height;

    av_log(s->avctx, AV_LOG_DEBUG, "sof0: picture: %dx%d\n", width, height);
    if(avcodec_check_dimensions(s->avctx, width, height))
        return -1;

    nb_components = get_bits(&s->gb, 8);
    if (nb_components <= 0 ||
        nb_components > MAX_COMPONENTS)
        return -1;
    if (s->ls && !(s->bits <= 8 || nb_components == 1)){
        av_log(s->avctx, AV_LOG_ERROR, "only <= 8 bits/component or 16-bit gray accepted for JPEG-LS\n");
        return -1;
    }
    s->nb_components = nb_components;
    s->h_max = 1;
    s->v_max = 1;
    for(i=0;i<nb_components;i++) {
        /* component id */
        s->component_id[i] = get_bits(&s->gb, 8) - 1;
        s->h_count[i] = get_bits(&s->gb, 4);
        s->v_count[i] = get_bits(&s->gb, 4);
        /* compute hmax and vmax (only used in interleaved case) */
        if (s->h_count[i] > s->h_max)
            s->h_max = s->h_count[i];
        if (s->v_count[i] > s->v_max)
            s->v_max = s->v_count[i];
        s->quant_index[i] = get_bits(&s->gb, 8);
        if (s->quant_index[i] >= 4)
            return -1;
        av_log(s->avctx, AV_LOG_DEBUG, "component %d %d:%d id: %d quant:%d\n", i, s->h_count[i],
               s->v_count[i], s->component_id[i], s->quant_index[i]);
    }

    if(s->ls && (s->h_max > 1 || s->v_max > 1)) {
        av_log(s->avctx, AV_LOG_ERROR, "Subsampling in JPEG-LS is not supported.\n");
        return -1;
    }

    if(s->v_max==1 && s->h_max==1 && s->lossless==1) s->rgb=1;

    /* if different size, realloc/alloc picture */
    /* XXX: also check h_count and v_count */
    if (width != s->width || height != s->height) {
        av_freep(&s->qscale_table);

        s->width = width;
        s->height = height;
        s->interlaced = 0;

        /* test interlaced mode */
        if (s->first_picture &&
            s->org_height != 0 &&
            s->height < ((s->org_height * 3) / 4)) {
            s->interlaced = 1;
            s->bottom_field = s->interlace_polarity;
            s->picture.interlaced_frame = 1;
            s->picture.top_field_first = !s->interlace_polarity;
            height *= 2;
        }

        avcodec_set_dimensions(s->avctx, width, height);

        s->qscale_table= av_mallocz((s->width+15)/16);

        s->first_picture = 0;
    }

    if(s->interlaced && (s->bottom_field == !s->interlace_polarity))
        return 0;

    /* XXX: not complete test ! */
    pix_fmt_id = (s->h_count[0] << 20) | (s->v_count[0] << 16) |
                 (s->h_count[1] << 12) | (s->v_count[1] <<  8) |
                 (s->h_count[2] <<  4) |  s->v_count[2];
    av_log(s->avctx, AV_LOG_DEBUG, "pix fmt id %x\n", pix_fmt_id);
    switch(pix_fmt_id){
    case 0x222222:
    case 0x111111:
        if(s->rgb){
            s->avctx->pix_fmt = PIX_FMT_RGB32;
        }else if(s->nb_components==3)
            s->avctx->pix_fmt = s->cs_itu601 ? PIX_FMT_YUV444P : PIX_FMT_YUVJ444P;
        else
            s->avctx->pix_fmt = PIX_FMT_GRAY8;
        break;
    case 0x110000:
        s->avctx->pix_fmt = PIX_FMT_GRAY8;
        break;
    case 0x121111:
        s->avctx->pix_fmt = s->cs_itu601 ? PIX_FMT_YUV440P : PIX_FMT_YUVJ440P;
        break;
    case 0x211111:
    case 0x221212:
        s->avctx->pix_fmt = s->cs_itu601 ? PIX_FMT_YUV422P : PIX_FMT_YUVJ422P;
        break;
    case 0x221111:
        s->avctx->pix_fmt = s->cs_itu601 ? PIX_FMT_YUV420P : PIX_FMT_YUVJ420P;
        break;
    default:
        av_log(s->avctx, AV_LOG_ERROR, "Unhandled pixel format 0x%x\n", pix_fmt_id);
        return -1;
    }
    if(s->ls){
        if(s->nb_components > 1)
            s->avctx->pix_fmt = PIX_FMT_RGB24;
        else if(s->bits <= 8)
            s->avctx->pix_fmt = PIX_FMT_GRAY8;
        else
            s->avctx->pix_fmt = PIX_FMT_GRAY16;
    }

    if(s->picture.data[0])
        s->avctx->release_buffer(s->avctx, &s->picture);

    s->picture.reference= 0;
    if(s->avctx->get_buffer(s->avctx, &s->picture) < 0){
        av_log(s->avctx, AV_LOG_ERROR, "get_buffer() failed\n");
        return -1;
    }
    s->picture.pict_type= I_TYPE;
    s->picture.key_frame= 1;

    for(i=0; i<3; i++){
        s->linesize[i]= s->picture.linesize[i] << s->interlaced;
    }

//    printf("%d %d %d %d %d %d\n", s->width, s->height, s->linesize[0], s->linesize[1], s->interlaced, s->avctx->height);

    if (len != (8+(3*nb_components)))
    {