gxf.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

/*
 * GXF demuxer.
 * Copyright (c) 2006 Reimar Doeffinger.
 *
 * 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
 */
#include "avformat.h"
#include "common.h"
#include "gxf.h"

typedef struct {
    int64_t first_field;
    int64_t last_field;
    AVRational frames_per_second;
    int32_t fields_per_frame;
} st_info_t;

/**
 * \brief parses a packet header, extracting type and length
 * \param pb ByteIOContext to read header from
 * \param type detected packet type is stored here
 * \param length detected packet length, excluding header is stored here
 * \return 0 if header not found or contains invalid data, 1 otherwise
 */
static int parse_packet_header(ByteIOContext *pb, pkt_type_t *type, int *length) {
    if (get_be32(pb))
        return 0;
    if (get_byte(pb) != 1)
        return 0;
    *type = get_byte(pb);
    *length = get_be32(pb);
    if ((*length >> 24) || *length < 16)
        return 0;
    *length -= 16;
    if (get_be32(pb))
        return 0;
    if (get_byte(pb) != 0xe1)
        return 0;
    if (get_byte(pb) != 0xe2)
        return 0;
    return 1;
}

/**
 * \brief check if file starts with a PKT_MAP header
 */
static int gxf_probe(AVProbeData *p) {
    static const uint8_t startcode[] = {0, 0, 0, 0, 1, 0xbc}; // start with map packet
    static const uint8_t endcode[] = {0, 0, 0, 0, 0xe1, 0xe2};
    if (!memcmp(p->buf, startcode, sizeof(startcode)) &&
        !memcmp(&p->buf[16 - sizeof(endcode)], endcode, sizeof(endcode)))
        return AVPROBE_SCORE_MAX;
    return 0;
}

/**
 * \brief gets the stream index for the track with the specified id, creates new
 *        stream if not found
 * \param stream id of stream to find / add
 * \param format stream format identifier
 */
static int get_sindex(AVFormatContext *s, int id, int format) {
    int i;
    AVStream *st = NULL;
    for (i = 0; i < s->nb_streams; i++) {
        if (s->streams[i]->id == id)
            return i;
    }
    st = av_new_stream(s, id);
    switch (format) {
        case 3:
        case 4:
            st->codec->codec_type = CODEC_TYPE_VIDEO;
            st->codec->codec_id = CODEC_ID_MJPEG;
            break;
        case 13:
        case 15:
            st->codec->codec_type = CODEC_TYPE_VIDEO;
            st->codec->codec_id = CODEC_ID_DVVIDEO;
            break;
        case 14:
        case 16:
            st->codec->codec_type = CODEC_TYPE_VIDEO;
            st->codec->codec_id = CODEC_ID_DVVIDEO;
            break;
        case 11:
        case 12:
        case 20:
            st->codec->codec_type = CODEC_TYPE_VIDEO;
            st->codec->codec_id = CODEC_ID_MPEG2VIDEO;
            st->need_parsing = AVSTREAM_PARSE_HEADERS; //get keyframe flag etc.
            break;
        case 22:
        case 23:
            st->codec->codec_type = CODEC_TYPE_VIDEO;
            st->codec->codec_id = CODEC_ID_MPEG1VIDEO;
            st->need_parsing = AVSTREAM_PARSE_HEADERS; //get keyframe flag etc.
            break;
        case 9:
            st->codec->codec_type = CODEC_TYPE_AUDIO;
            st->codec->codec_id = CODEC_ID_PCM_S24LE;
            st->codec->channels = 1;
            st->codec->sample_rate = 48000;
            st->codec->bit_rate = 3 * 1 * 48000 * 8;
            st->codec->block_align = 3 * 1;
            st->codec->bits_per_sample = 24;
            break;
        case 10:
            st->codec->codec_type = CODEC_TYPE_AUDIO;
            st->codec->codec_id = CODEC_ID_PCM_S16LE;
            st->codec->channels = 1;
            st->codec->sample_rate = 48000;
            st->codec->bit_rate = 2 * 1 * 48000 * 8;
            st->codec->block_align = 2 * 1;
            st->codec->bits_per_sample = 16;
            break;
        case 17:
            st->codec->codec_type = CODEC_TYPE_AUDIO;
            st->codec->codec_id = CODEC_ID_AC3;
            st->codec->channels = 2;
            st->codec->sample_rate = 48000;
            break;
        // timecode tracks:
        case 7:
        case 8:
        case 24:
            st->codec->codec_type = CODEC_TYPE_DATA;
            st->codec->codec_id = CODEC_ID_NONE;
            break;
        default:
            st->codec->codec_type = CODEC_TYPE_UNKNOWN;
            st->codec->codec_id = CODEC_ID_NONE;
            break;
    }
    return s->nb_streams - 1;
}

/**
 * \brief filters out interesting tags from material information.
 * \param len length of tag section, will be adjusted to contain remaining bytes
 * \param si struct to store collected information into
 */
static void gxf_material_tags(ByteIOContext *pb, int *len, st_info_t *si) {
    si->first_field = AV_NOPTS_VALUE;
    si->last_field = AV_NOPTS_VALUE;
    while (*len >= 2) {
        mat_tag_t tag = get_byte(pb);
        int tlen = get_byte(pb);
        *len -= 2;
        if (tlen > *len)
            return;
        *len -= tlen;
        if (tlen == 4) {
            uint32_t value = get_be32(pb);
            if (tag == MAT_FIRST_FIELD)
                si->first_field = value;
            else if (tag == MAT_LAST_FIELD)
                si->last_field = value;
        } else
            url_fskip(pb, tlen);
    }
}

/**
 * \brief convert fps tag value to AVRational fps
 * \param fps fps value from tag
 * \return fps as AVRational, or 0 / 0 if unknown
 */
static AVRational fps_tag2avr(int32_t fps) {
    extern const AVRational ff_frame_rate_tab[];
    if (fps < 1 || fps > 9) fps = 9;
    return ff_frame_rate_tab[9 - fps]; // values have opposite order
}

/**
 * \brief convert UMF attributes flags to AVRational fps
 * \param fps fps value from flags
 * \return fps as AVRational, or 0 / 0 if unknown
 */
static AVRational fps_umf2avr(uint32_t flags) {
    static const AVRational map[] = {{50, 1}, {60000, 1001}, {24, 1},
        {25, 1}, {30000, 1001}};
    int idx =  av_log2((flags & 0x7c0) >> 6);
    return map[idx];
}

/**
 * \brief filters out interesting tags from track information.
 * \param len length of tag section, will be adjusted to contain remaining bytes
 * \param si struct to store collected information into
 */
static void gxf_track_tags(ByteIOContext *pb, int *len, st_info_t *si) {
    si->frames_per_second = (AVRational){0, 0};
    si->fields_per_frame = 0;
    while (*len >= 2) {
        track_tag_t tag = get_byte(pb);
        int tlen = get_byte(pb);
        *len -= 2;
        if (tlen > *len)
            return;
        *len -= tlen;
        if (tlen == 4) {
            uint32_t value = get_be32(pb);
            if (tag == TRACK_FPS)
                si->frames_per_second = fps_tag2avr(value);
            else if (tag == TRACK_FPF && (value == 1 || value == 2))
                si->fields_per_frame = value;
        } else
            url_fskip(pb, tlen);
    }
}

/**
 * \brief read index from FLT packet into stream 0 av_index
 */
static void gxf_read_index(AVFormatContext *s, int pkt_len) {
    ByteIOContext *pb = &s->pb;
    AVStream *st = s->streams[0];
    uint32_t fields_per_map = get_le32(pb);
    uint32_t map_cnt = get_le32(pb);
    int i;
    pkt_len -= 8;
    if (map_cnt > 1000) {
        av_log(s, AV_LOG_ERROR, "GXF: too many index entries %u (%x)\n", map_cnt, map_cnt);
        map_cnt = 1000;
    }
    if (pkt_len < 4 * map_cnt) {
        av_log(s, AV_LOG_ERROR, "GXF: invalid index length\n");
        url_fskip(pb, pkt_len);
        return;
    }
    pkt_len -= 4 * map_cnt;
    av_add_index_entry(st, 0, 0, 0, 0, 0);
    for (i = 0; i < map_cnt; i++)
        av_add_index_entry(st, (uint64_t)get_le32(pb) * 1024,