mp3.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

/*
 * MP3 muxer and demuxer
 * Copyright (c) 2003 Fabrice Bellard.
 *
 * 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 "mpegaudio.h"
#include "avstring.h"

#define ID3v2_HEADER_SIZE 10
#define ID3v1_TAG_SIZE 128

#define ID3v1_GENRE_MAX 125

static const char *id3v1_genre_str[ID3v1_GENRE_MAX + 1] = {
    [0] = "Blues",
    [1] = "Classic Rock",
    [2] = "Country",
    [3] = "Dance",
    [4] = "Disco",
    [5] = "Funk",
    [6] = "Grunge",
    [7] = "Hip-Hop",
    [8] = "Jazz",
    [9] = "Metal",
    [10] = "New Age",
    [11] = "Oldies",
    [12] = "Other",
    [13] = "Pop",
    [14] = "R&B",
    [15] = "Rap",
    [16] = "Reggae",
    [17] = "Rock",
    [18] = "Techno",
    [19] = "Industrial",
    [20] = "Alternative",
    [21] = "Ska",
    [22] = "Death Metal",
    [23] = "Pranks",
    [24] = "Soundtrack",
    [25] = "Euro-Techno",
    [26] = "Ambient",
    [27] = "Trip-Hop",
    [28] = "Vocal",
    [29] = "Jazz+Funk",
    [30] = "Fusion",
    [31] = "Trance",
    [32] = "Classical",
    [33] = "Instrumental",
    [34] = "Acid",
    [35] = "House",
    [36] = "Game",
    [37] = "Sound Clip",
    [38] = "Gospel",
    [39] = "Noise",
    [40] = "AlternRock",
    [41] = "Bass",
    [42] = "Soul",
    [43] = "Punk",
    [44] = "Space",
    [45] = "Meditative",
    [46] = "Instrumental Pop",
    [47] = "Instrumental Rock",
    [48] = "Ethnic",
    [49] = "Gothic",
    [50] = "Darkwave",
    [51] = "Techno-Industrial",
    [52] = "Electronic",
    [53] = "Pop-Folk",
    [54] = "Eurodance",
    [55] = "Dream",
    [56] = "Southern Rock",
    [57] = "Comedy",
    [58] = "Cult",
    [59] = "Gangsta",
    [60] = "Top 40",
    [61] = "Christian Rap",
    [62] = "Pop/Funk",
    [63] = "Jungle",
    [64] = "Native American",
    [65] = "Cabaret",
    [66] = "New Wave",
    [67] = "Psychadelic",
    [68] = "Rave",
    [69] = "Showtunes",
    [70] = "Trailer",
    [71] = "Lo-Fi",
    [72] = "Tribal",
    [73] = "Acid Punk",
    [74] = "Acid Jazz",
    [75] = "Polka",
    [76] = "Retro",
    [77] = "Musical",
    [78] = "Rock & Roll",
    [79] = "Hard Rock",
    [80] = "Folk",
    [81] = "Folk-Rock",
    [82] = "National Folk",
    [83] = "Swing",
    [84] = "Fast Fusion",
    [85] = "Bebob",
    [86] = "Latin",
    [87] = "Revival",
    [88] = "Celtic",
    [89] = "Bluegrass",
    [90] = "Avantgarde",
    [91] = "Gothic Rock",
    [92] = "Progressive Rock",
    [93] = "Psychedelic Rock",
    [94] = "Symphonic Rock",
    [95] = "Slow Rock",
    [96] = "Big Band",
    [97] = "Chorus",
    [98] = "Easy Listening",
    [99] = "Acoustic",
    [100] = "Humour",
    [101] = "Speech",
    [102] = "Chanson",
    [103] = "Opera",
    [104] = "Chamber Music",
    [105] = "Sonata",
    [106] = "Symphony",
    [107] = "Booty Bass",
    [108] = "Primus",
    [109] = "Porn Groove",
    [110] = "Satire",
    [111] = "Slow Jam",
    [112] = "Club",
    [113] = "Tango",
    [114] = "Samba",
    [115] = "Folklore",
    [116] = "Ballad",
    [117] = "Power Ballad",
    [118] = "Rhythmic Soul",
    [119] = "Freestyle",
    [120] = "Duet",
    [121] = "Punk Rock",
    [122] = "Drum Solo",
    [123] = "A capella",
    [124] = "Euro-House",
    [125] = "Dance Hall",
};

/* buf must be ID3v2_HEADER_SIZE byte long */
static int id3v2_match(const uint8_t *buf)
{
    return (buf[0] == 'I' &&
            buf[1] == 'D' &&
            buf[2] == '3' &&
            buf[3] != 0xff &&
            buf[4] != 0xff &&
            (buf[6] & 0x80) == 0 &&
            (buf[7] & 0x80) == 0 &&
            (buf[8] & 0x80) == 0 &&
            (buf[9] & 0x80) == 0);
}

static unsigned int id3v2_get_size(ByteIOContext *s, int len)
{
    int v=0;
    while(len--)
        v= (v<<7) + (get_byte(s)&0x7F);
    return v;
}

static void id3v2_read_ttag(AVFormatContext *s, int taglen, char *dst, int dstlen)
{
    char *q;
    int len;

    if(taglen < 1)
        return;

    taglen--; /* account for encoding type byte */
    dstlen--; /* Leave space for zero terminator */

    switch(get_byte(&s->pb)) { /* encoding type */

    case 0:  /* ISO-8859-1 (0 - 255 maps directly into unicode) */
        q = dst;
        while(taglen--) {
            uint8_t tmp;
            PUT_UTF8(get_byte(&s->pb), tmp, if (q - dst < dstlen - 1) *q++ = tmp;)
        }
        *q = '\0';
        break;

    case 3:  /* UTF-8 */
        len = FFMIN(taglen, dstlen);
        get_buffer(&s->pb, dst, len);
        dst[len] = 0;
        break;
    }
}

/**
 * ID3v2 parser
 *
 * Handles ID3v2.2, 2.3 and 2.4.
 *
 */

static void id3v2_parse(AVFormatContext *s, int len, uint8_t version, uint8_t flags)
{
    int isv34, tlen;
    uint32_t tag;
    offset_t next;
    char tmp[16];
    int taghdrlen;
    const char *reason;

    switch(version) {
    case 2:
        if(flags & 0x40) {
            reason = "compression";
            goto error;
        }
        isv34 = 0;
        taghdrlen = 6;
        break;

    case 3:
    case 4:
        isv34 = 1;
        taghdrlen = 10;
        break;

    default:
        reason = "version";
        goto error;
    }

    if(flags & 0x80) {
        reason = "unsynchronization";
        goto error;
    }

    if(isv34 && flags & 0x40) /* Extended header present, just skip over it */
        url_fskip(&s->pb, id3v2_get_size(&s->pb, 4));

    while(len >= taghdrlen) {
        if(isv34) {
            tag  = get_be32(&s->pb);
            tlen = id3v2_get_size(&s->pb, 4);
            get_be16(&s->pb); /* flags */
        } else {
            tag  = get_be24(&s->pb);
            tlen = id3v2_get_size(&s->pb, 3);
        }
        len -= taghdrlen + tlen;

        if(len < 0)
            break;

        next = url_ftell(&s->pb) + tlen;

        switch(tag) {
        case MKBETAG('T', 'I', 'T', '2'):
        case MKBETAG(0,   'T', 'T', '2'):
            id3v2_read_ttag(s, tlen, s->title, sizeof(s->title));
            break;
        case MKBETAG('T', 'P', 'E', '1'):
        case MKBETAG(0,   'T', 'P', '1'):
            id3v2_read_ttag(s, tlen, s->author, sizeof(s->author));
            break;
        case MKBETAG('T', 'A', 'L', 'B'):
        case MKBETAG(0,   'T', 'A', 'L'):
            id3v2_read_ttag(s, tlen, s->album, sizeof(s->album));
            break;
        case MKBETAG('T', 'C', 'O', 'N'):
        case MKBETAG(0,   'T', 'C', 'O'):
            id3v2_read_ttag(s, tlen, s->genre, sizeof(s->genre));
            break;
        case MKBETAG('T', 'C', 'O', 'P'):
        case MKBETAG(0,   'T', 'C', 'R'):
            id3v2_read_ttag(s, tlen, s->copyright, sizeof(s->copyright));
            break;
        case MKBETAG('T', 'R', 'C', 'K'):
        case MKBETAG(0,   'T', 'R', 'K'):
            id3v2_read_ttag(s, tlen, tmp, sizeof(tmp));
            s->track = atoi(tmp);
            break;
        case 0:
            /* padding, skip to end */
            url_fskip(&s->pb, len);
            len = 0;
            continue;
        }
        /* Skip to end of tag */
        url_fseek(&s->pb, next, SEEK_SET);
    }

    if(version == 4 && flags & 0x10) /* Footer preset, always 10 bytes, skip over it */
        url_fskip(&s->pb, 10);
    return;

  error:
    av_log(s, AV_LOG_INFO, "ID3v2.%d tag skipped, cannot handle %s\n", version, reason);
    url_fskip(&s->pb, len);
}