id3v2.c

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/*
 * 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
 */

/**
 * @file
 * ID3v2 header parser
 *
 * Specifications available at:
 * http://id3.org/Developer_Information
 */

#include "config.h"

#if CONFIG_ZLIB
#include <zlib.h>
#endif

#include "libavutil/avstring.h"
#include "libavutil/dict.h"
#include "libavutil/intreadwrite.h"
#include "avio_internal.h"
#include "internal.h"
#include "id3v1.h"
#include "id3v2.h"

const AVMetadataConv ff_id3v2_34_metadata_conv[] = {
    { "TALB", "album"        },
    { "TCOM", "composer"     },
    { "TCON", "genre"        },
    { "TCOP", "copyright"    },
    { "TENC", "encoded_by"   },
    { "TIT2", "title"        },
    { "TLAN", "language"     },
    { "TPE1", "artist"       },
    { "TPE2", "album_artist" },
    { "TPE3", "performer"    },
    { "TPOS", "disc"         },
    { "TPUB", "publisher"    },
    { "TRCK", "track"        },
    { "TSSE", "encoder"      },
    { "USLT", "lyrics"       },
    { 0 }
};

const AVMetadataConv ff_id3v2_4_metadata_conv[] = {
    { "TCMP", "compilation"   },
    { "TDRC", "date"          },
    { "TDRL", "date"          },
    { "TDEN", "creation_time" },
    { "TSOA", "album-sort"    },
    { "TSOP", "artist-sort"   },
    { "TSOT", "title-sort"    },
    { 0 }
};

static const AVMetadataConv id3v2_2_metadata_conv[] = {
    { "TAL", "album"        },
    { "TCO", "genre"        },
    { "TCP", "compilation"  },
    { "TT2", "title"        },
    { "TEN", "encoded_by"   },
    { "TP1", "artist"       },
    { "TP2", "album_artist" },
    { "TP3", "performer"    },
    { "TRK", "track"        },
    { 0 }
};

const char ff_id3v2_tags[][4] = {
    "TALB", "TBPM", "TCOM", "TCON", "TCOP", "TDLY", "TENC", "TEXT",
    "TFLT", "TIT1", "TIT2", "TIT3", "TKEY", "TLAN", "TLEN", "TMED",
    "TOAL", "TOFN", "TOLY", "TOPE", "TOWN", "TPE1", "TPE2", "TPE3",
    "TPE4", "TPOS", "TPUB", "TRCK", "TRSN", "TRSO", "TSRC", "TSSE",
    { 0 },
};

const char ff_id3v2_4_tags[][4] = {
    "TDEN", "TDOR", "TDRC", "TDRL", "TDTG", "TIPL", "TMCL", "TMOO",
    "TPRO", "TSOA", "TSOP", "TSOT", "TSST",
    { 0 },
};

const char ff_id3v2_3_tags[][4] = {
    "TDAT", "TIME", "TORY", "TRDA", "TSIZ", "TYER",
    { 0 },
};

const char * const ff_id3v2_picture_types[21] = {
    "Other",
    "32x32 pixels 'file icon'",
    "Other file icon",
    "Cover (front)",
    "Cover (back)",
    "Leaflet page",
    "Media (e.g. label side of CD)",
    "Lead artist/lead performer/soloist",
    "Artist/performer",
    "Conductor",
    "Band/Orchestra",
    "Composer",
    "Lyricist/text writer",
    "Recording Location",
    "During recording",
    "During performance",
    "Movie/video screen capture",
    "A bright coloured fish",
    "Illustration",
    "Band/artist logotype",
    "Publisher/Studio logotype",
};

const CodecMime ff_id3v2_mime_tags[] = {
    { "image/gif",  AV_CODEC_ID_GIF   },
    { "image/jpeg", AV_CODEC_ID_MJPEG },
    { "image/jpg",  AV_CODEC_ID_MJPEG },
    { "image/png",  AV_CODEC_ID_PNG   },
    { "image/tiff", AV_CODEC_ID_TIFF  },
    { "image/bmp",  AV_CODEC_ID_BMP   },
    { "JPG",        AV_CODEC_ID_MJPEG }, /* ID3v2.2  */
    { "PNG",        AV_CODEC_ID_PNG   }, /* ID3v2.2  */
    { "",           AV_CODEC_ID_NONE  },
};

int ff_id3v2_match(const uint8_t *buf, const char *magic)
{
    return  buf[0]         == magic[0] &&
            buf[1]         == magic[1] &&
            buf[2]         == magic[2] &&
            buf[3]         != 0xff     &&
            buf[4]         != 0xff     &&
           (buf[6] & 0x80) == 0        &&
           (buf[7] & 0x80) == 0        &&
           (buf[8] & 0x80) == 0        &&
           (buf[9] & 0x80) == 0;
}

int ff_id3v2_tag_len(const uint8_t *buf)
{
    int len = ((buf[6] & 0x7f) << 21) +
              ((buf[7] & 0x7f) << 14) +
              ((buf[8] & 0x7f) << 7) +
              (buf[9] & 0x7f) +
              ID3v2_HEADER_SIZE;
    if (buf[5] & 0x10)
        len += ID3v2_HEADER_SIZE;
    return len;
}

static unsigned int get_size(AVIOContext *s, int len)
{
    int v = 0;
    while (len--)
        v = (v << 7) + (avio_r8(s) & 0x7F);
    return v;
}

static unsigned int size_to_syncsafe(unsigned int size)
{
    return (((size) & (0x7f <<  0)) >> 0) +
           (((size) & (0x7f <<  8)) >> 1) +
           (((size) & (0x7f << 16)) >> 2) +
           (((size) & (0x7f << 24)) >> 3);
}

/* No real verification, only check that the tag consists of
 * a combination of capital alpha-numerical characters */
static int is_tag(const char *buf, unsigned int len)
{
    if (!len)
        return 0;

    while (len--)
        if ((buf[len] < 'A' ||
             buf[len] > 'Z') &&
            (buf[len] < '0' ||
             buf[len] > '9'))
            return 0;

    return 1;
}

/**
 * Return 1 if the tag of length len at the given offset is valid, 0 if not, -1 on error
 */
static int check_tag(AVIOContext *s, int offset, unsigned int len)
{
    char tag[4];

    if (len > 4 ||
        avio_seek(s, offset, SEEK_SET) < 0 ||
        avio_read(s, tag, len) < (int)len)
        return -1;
    else if (!AV_RB32(tag) || is_tag(tag, len))
        return 1;

    return 0;
}

/**
 * Free GEOB type extra metadata.
 */
static void free_geobtag(void *obj)
{
    ID3v2ExtraMetaGEOB *geob = obj;
    av_freep(&geob->mime_type);
    av_freep(&geob->file_name);
    av_freep(&geob->description);
    av_freep(&geob->data);
    av_free(geob);
}

/**
 * Decode characters to UTF-8 according to encoding type. The decoded buffer is
 * always null terminated. Stop reading when either *maxread bytes are read from
 * pb or U+0000 character is found.
 *
 * @param dst Pointer where the address of the buffer with the decoded bytes is
 * stored. Buffer must be freed by caller.
 * @param maxread Pointer to maximum number of characters to read from the
 * AVIOContext. After execution the value is decremented by the number of bytes
 * actually read.
 * @returns 0 if no error occurred, dst is uninitialized on error
 */
static int decode_str(AVFormatContext *s, AVIOContext *pb, int encoding,
                      uint8_t **dst, int *maxread)
{
    int ret;
    uint8_t tmp;
    uint32_t ch = 1;
    int left = *maxread;
    unsigned int (*get)(AVIOContext*) = avio_rb16;
    AVIOContext *dynbuf;

    if ((ret = avio_open_dyn_buf(&dynbuf)) < 0) {
        av_log(s, AV_LOG_ERROR, "Error opening memory stream\n");
        return ret;
    }

    switch (encoding) {
    case ID3v2_ENCODING_ISO8859:
        while (left && ch) {
            ch = avio_r8(pb);
            PUT_UTF8(ch, tmp, avio_w8(dynbuf, tmp);)
            left--;
        }
        break;

    case ID3v2_ENCODING_UTF16BOM:
        if ((left -= 2) < 0) {
            av_log(s, AV_LOG_ERROR, "Cannot read BOM value, input too short\n");
            ffio_free_dyn_buf(&dynbuf);
            *dst = NULL;
            return AVERROR_INVALIDDATA;
        }
        switch (avio_rb16(pb)) {
        case 0xfffe:
            get = avio_rl16;
        case 0xfeff:
            break;
        default:
            av_log(s, AV_LOG_ERROR, "Incorrect BOM value\n");
            ffio_free_dyn_buf(&dynbuf);
            *dst = NULL;
            *maxread = left;
            return AVERROR_INVALIDDATA;
        }
        // fall-through

    case ID3v2_ENCODING_UTF16BE:
        while ((left > 1) && ch) {
            GET_UTF16(ch, ((left -= 2) >= 0 ? get(pb) : 0), break;)
            PUT_UTF8(ch, tmp, avio_w8(dynbuf, tmp);)
        }
        if (left < 0)
            left += 2;  /* did not read last char from pb */
        break;

    case ID3v2_ENCODING_UTF8:
        while (left && ch) {
            ch = avio_r8(pb);
            avio_w8(dynbuf, ch);
            left--;
        }
        break;
    default:
        av_log(s, AV_LOG_WARNING, "Unknown encoding\n");
    }

    if (ch)
        avio_w8(dynbuf, 0);

    avio_close_dyn_buf(dynbuf, dst);
    *maxread = left;

    return 0;
}

/**
 * Parse a text tag.
 */
static void read_ttag(AVFormatContext *s, AVIOContext *pb, int taglen,
                      AVDictionary **metadata, const char *key)
{
    uint8_t *dst;
    int encoding, dict_flags = AV_DICT_DONT_OVERWRITE | AV_DICT_DONT_STRDUP_VAL;
    unsigned genre;

    if (taglen < 1)
        return;

    encoding = avio_r8(pb);
    taglen--; /* account for encoding type byte */

    if (decode_str(s, pb, encoding, &dst, &taglen) < 0) {
        av_log(s, AV_LOG_ERROR, "Error reading frame %s, skipped\n", key);
        return;
    }

    if (!(strcmp(key, "TCON") && strcmp(key, "TCO"))                         &&
        (sscanf(dst, "(%d)", &genre) == 1 || sscanf(dst, "%d", &genre) == 1) &&
        genre <= ID3v1_GENRE_MAX) {
        av_freep(&dst);
        dst = av_strdup(ff_id3v1_genre_str[genre]);
    } else if (!(strcmp(key, "TXXX") && strcmp(key, "TXX"))) {
        /* dst now contains the key, need to get value */
        key = dst;
        if (decode_str(s, pb, encoding, &dst, &taglen) < 0) {
            av_log(s, AV_LOG_ERROR, "Error reading frame %s, skipped\n", key);
            av_freep(&key);
            return;
        }
        dict_flags |= AV_DICT_DONT_STRDUP_KEY;
    } else if (!*dst)
        av_freep(&dst);

    if (dst)
        av_dict_set(metadata, key, dst, dict_flags);
}

static void read_uslt(AVFormatContext *s, AVIOContext *pb, int taglen,
                      AVDictionary **metadata)
{
    uint8_t lang[4];
    uint8_t *descriptor = NULL; // 'Content descriptor'
    uint8_t *text = NULL;
    char *key = NULL;
    int encoding;
    int ok = 0;

    if (taglen < 1)
        goto error;

    encoding = avio_r8(pb);
    taglen--;

    if (avio_read(pb, lang, 3) < 3)
        goto error;
    lang[3] = '\0';
    taglen -= 3;

    if (decode_str(s, pb, encoding, &descriptor, &taglen) < 0)
        goto error;

    if (decode_str(s, pb, encoding, &text, &taglen) < 0)
        goto error;

    // FFmpeg does not support hierarchical metadata, so concatenate the keys.
    key = av_asprintf("lyrics-%s%s%s", descriptor[0] ? (char *)descriptor : "",
                                       descriptor[0] ? "-" : "",
                                       lang);
    if (!key)
        goto error;

    av_dict_set(metadata, key, text, 0);

    ok = 1;
error:
    if (!ok)
        av_log(s, AV_LOG_ERROR, "Error reading lyrics, skipped\n");
    av_free(descriptor);
    av_free(text);
    av_free(key);
}

/**
 * Parse a comment tag.
 */
static void read_comment(AVFormatContext *s, AVIOContext *pb, int taglen,
                      AVDictionary **metadata)
{
    const char *key = "comment";
    uint8_t *dst;
    int encoding, dict_flags = AV_DICT_DONT_OVERWRITE | AV_DICT_DONT_STRDUP_VAL;
    av_unused int language;

    if (taglen < 4)
        return;

    encoding = avio_r8(pb);
    language = avio_rl24(pb);
    taglen -= 4;

    if (decode_str(s, pb, encoding, &dst, &taglen) < 0) {
        av_log(s, AV_LOG_ERROR, "Error reading comment frame, skipped\n");
        return;
    }

    if (dst && !*dst)
        av_freep(&dst);

    if (dst) {
        key = (const char *) dst;
        dict_flags |= AV_DICT_DONT_STRDUP_KEY;
    }

    if (decode_str(s, pb, encoding, &dst, &taglen) < 0) {
        av_log(s, AV_LOG_ERROR, "Error reading comment frame, skipped\n");
        if (dict_flags & AV_DICT_DONT_STRDUP_KEY)
            av_freep((void*)&key);
        return;
    }

    if (dst)
        av_dict_set(metadata, key, (const char *) dst, dict_flags);
}

/**
 * Parse GEOB tag into a ID3v2ExtraMetaGEOB struct.
 */
static void read_geobtag(AVFormatContext *s, AVIOContext *pb, int taglen,
                         const char *tag, ID3v2ExtraMeta **extra_meta,
                         int isv34)
{
    ID3v2ExtraMetaGEOB *geob_data = NULL;
    ID3v2ExtraMeta *new_extra     = NULL;
    char encoding;
    unsigned int len;

    if (taglen < 1)
        return;

    geob_data = av_mallocz(sizeof(ID3v2ExtraMetaGEOB));
    if (!geob_data) {
        av_log(s, AV_LOG_ERROR, "Failed to alloc %"SIZE_SPECIFIER" bytes\n",
               sizeof(ID3v2ExtraMetaGEOB));
        return;
    }

    new_extra = av_mallocz(sizeof(ID3v2ExtraMeta));
    if (!new_extra) {
        av_log(s, AV_LOG_ERROR, "Failed to alloc %"SIZE_SPECIFIER" bytes\n",
               sizeof(ID3v2ExtraMeta));
        goto fail;
    }

    /* read encoding type byte */
    encoding = avio_r8(pb);
    taglen--;

    /* read MIME type (always ISO-8859) */
    if (decode_str(s, pb, ID3v2_ENCODING_ISO8859, &geob_data->mime_type,
                   &taglen) < 0 ||
        taglen <= 0)
        goto fail;

    /* read file name */
    if (decode_str(s, pb, encoding, &geob_data->file_name, &taglen) < 0 ||
        taglen <= 0)
        goto fail;

    /* read content description */
    if (decode_str(s, pb, encoding, &geob_data->description, &taglen) < 0 ||
        taglen < 0)
        goto fail;

    if (taglen) {
        /* save encapsulated binary data */
        geob_data->data = av_malloc(taglen);
        if (!geob_data->data) {
            av_log(s, AV_LOG_ERROR, "Failed to alloc %d bytes\n", taglen);
            goto fail;
        }
        if ((len = avio_read(pb, geob_data->data, taglen)) < taglen)
            av_log(s, AV_LOG_WARNING,
                   "Error reading GEOB frame, data truncated.\n");
        geob_data->datasize = len;
    } else {
        geob_data->data     = NULL;
        geob_data->datasize = 0;
    }

    /* add data to the list */
    new_extra->tag  = "GEOB";
    new_extra->data = geob_data;
    new_extra->next = *extra_meta;
    *extra_meta     = new_extra;

    return;

fail:
    av_log(s, AV_LOG_ERROR, "Error reading frame %s, skipped\n", tag);
    free_geobtag(geob_data);
    av_free(new_extra);
    return;
}

static int is_number(const char *str)
{
    while (*str >= '0' && *str <= '9')
        str++;
    return !*str;
}

static AVDictionaryEntry *get_date_tag(AVDictionary *m, const char *tag)
{
    AVDictionaryEntry *t;
    if ((t = av_dict_get(m, tag, NULL, AV_DICT_MATCH_CASE)) &&
        strlen(t->value) == 4 && is_number(t->value))
        return t;
    return NULL;
}

static void merge_date(AVDictionary **m)
{
    AVDictionaryEntry *t;
    char date[17] = { 0 };      // YYYY-MM-DD hh:mm

    if (!(t = get_date_tag(*m, "TYER")) &&
        !(t = get_date_tag(*m, "TYE")))
        return;
    av_strlcpy(date, t->value, 5);
    av_dict_set(m, "TYER", NULL, 0);
    av_dict_set(m, "TYE", NULL, 0);

    if (!(t = get_date_tag(*m, "TDAT")) &&
        !(t = get_date_tag(*m, "TDA")))
        goto finish;
    snprintf(date + 4, sizeof(date) - 4, "-%.2s-%.2s", t->value + 2, t->value);
    av_dict_set(m, "TDAT", NULL, 0);
    av_dict_set(m, "TDA", NULL, 0);

    if (!(t = get_date_tag(*m, "TIME")) &&
        !(t = get_date_tag(*m, "TIM")))
        goto finish;
    snprintf(date + 10, sizeof(date) - 10,
             " %.2s:%.2s", t->value, t->value + 2);
    av_dict_set(m, "TIME", NULL, 0);
    av_dict_set(m, "TIM", NULL, 0);

finish:
    if (date[0])
        av_dict_set(m, "date", date, 0);
}

static void free_apic(void *obj)
{
    ID3v2ExtraMetaAPIC *apic = obj;
    av_buffer_unref(&apic->buf);
    av_freep(&apic->description);
    av_freep(&apic);
}

static void rstrip_spaces(char *buf)
{
    size_t len = strlen(buf);
    while (len > 0 && buf[len - 1] == ' ')
        buf[--len] = 0;
}

static void read_apic(AVFormatContext *s, AVIOContext *pb, int taglen,
                      const char *tag, ID3v2ExtraMeta **extra_meta,
                      int isv34)
{
    int enc, pic_type;
    char mimetype[64];
    const CodecMime *mime     = ff_id3v2_mime_tags;
    enum AVCodecID id         = AV_CODEC_ID_NONE;
    ID3v2ExtraMetaAPIC *apic  = NULL;
    ID3v2ExtraMeta *new_extra = NULL;
    int64_t end               = avio_tell(pb) + taglen;

    if (taglen <= 4 || (!isv34 && taglen <= 6))
        goto fail;

    new_extra = av_mallocz(sizeof(*new_extra));
    apic      = av_mallocz(sizeof(*apic));
    if (!new_extra || !apic)
        goto fail;

    enc = avio_r8(pb);
    taglen--;

    /* mimetype */
    if (isv34) {
        taglen -= avio_get_str(pb, taglen, mimetype, sizeof(mimetype));
    } else {
        avio_read(pb, mimetype, 3);
        mimetype[3] = 0;
        taglen    -= 3;
    }

    while (mime->id != AV_CODEC_ID_NONE) {
        if (!av_strncasecmp(mime->str, mimetype, sizeof(mimetype))) {
            id = mime->id;
            break;
        }
        mime++;
    }
    if (id == AV_CODEC_ID_NONE) {
        av_log(s, AV_LOG_WARNING,
               "Unknown attached picture mimetype: %s, skipping.\n", mimetype);
        goto fail;
    }
    apic->id = id;

    /* picture type */
    pic_type = avio_r8(pb);
    taglen--;
    if (pic_type < 0 || pic_type >= FF_ARRAY_ELEMS(ff_id3v2_picture_types)) {
        av_log(s, AV_LOG_WARNING, "Unknown attached picture type %d.\n",
               pic_type);
        pic_type = 0;
    }
    apic->type = ff_id3v2_picture_types[pic_type];

    /* description and picture data */
    if (decode_str(s, pb, enc, &apic->description, &taglen) < 0) {
        av_log(s, AV_LOG_ERROR,
               "Error decoding attached picture description.\n");
        goto fail;
    }

    apic->buf = av_buffer_alloc(taglen + AV_INPUT_BUFFER_PADDING_SIZE);
    if (!apic->buf || !taglen || avio_read(pb, apic->buf->data, taglen) != taglen)
        goto fail;
    memset(apic->buf->data + taglen, 0, AV_INPUT_BUFFER_PADDING_SIZE);

    new_extra->tag  = "APIC";
    new_extra->data = apic;
    new_extra->next = *extra_meta;
    *extra_meta     = new_extra;

    // The description must be unique, and some ID3v2 tag writers add spaces
    // to write several APIC entries with the same description.
    rstrip_spaces(apic->description);

    return;

fail:
    if (apic)
        free_apic(apic);
    av_freep(&new_extra);
    avio_seek(pb, end, SEEK_SET);
}

static void free_chapter(void *obj)
{
    ID3v2ExtraMetaCHAP *chap = obj;
    av_freep(&chap->element_id);
    av_dict_free(&chap->meta);
    av_freep(&chap);
}

static void read_chapter(AVFormatContext *s, AVIOContext *pb, int len, const char *ttag, ID3v2ExtraMeta **extra_meta, int isv34)
{
    int taglen;
    char tag[5];
    ID3v2ExtraMeta *new_extra = NULL;
    ID3v2ExtraMetaCHAP *chap  = NULL;

    new_extra = av_mallocz(sizeof(*new_extra));
    chap      = av_mallocz(sizeof(*chap));

    if (!new_extra || !chap)
        goto fail;

    if (decode_str(s, pb, 0, &chap->element_id, &len) < 0)
        goto fail;

    if (len < 16)
        goto fail;

    chap->start = avio_rb32(pb);
    chap->end   = avio_rb32(pb);
    avio_skip(pb, 8);

    len -= 16;
    while (len > 10) {
        if (avio_read(pb, tag, 4) < 4)
            goto fail;
        tag[4] = 0;
        taglen = avio_rb32(pb);
        avio_skip(pb, 2);
        len -= 10;
        if (taglen < 0 || taglen > len)
            goto fail;
        if (tag[0] == 'T')
            read_ttag(s, pb, taglen, &chap->meta, tag);
        else
            avio_skip(pb, taglen);
        len -= taglen;
    }

    ff_metadata_conv(&chap->meta, NULL, ff_id3v2_34_metadata_conv);
    ff_metadata_conv(&chap->meta, NULL, ff_id3v2_4_metadata_conv);

    new_extra->tag  = "CHAP";
    new_extra->data = chap;
    new_extra->next = *extra_meta;
    *extra_meta     = new_extra;

    return;

fail:
    if (chap)
        free_chapter(chap);
    av_freep(&new_extra);
}

static void free_priv(void *obj)
{
    ID3v2ExtraMetaPRIV *priv = obj;
    av_freep(&priv->owner);
    av_freep(&priv->data);
    av_freep(&priv);
}

static void read_priv(AVFormatContext *s, AVIOContext *pb, int taglen,
                      const char *tag, ID3v2ExtraMeta **extra_meta, int isv34)
{
    ID3v2ExtraMeta *meta;
    ID3v2ExtraMetaPRIV *priv;

    meta = av_mallocz(sizeof(*meta));
    priv = av_mallocz(sizeof(*priv));

    if (!meta || !priv)
        goto fail;

    if (decode_str(s, pb, ID3v2_ENCODING_ISO8859, &priv->owner, &taglen) < 0)
        goto fail;

    priv->data = av_malloc(taglen);
    if (!priv->data)
        goto fail;

    priv->datasize = taglen;

    if (avio_read(pb, priv->data, priv->datasize) != priv->datasize)
        goto fail;

    meta->tag   = "PRIV";
    meta->data  = priv;
    meta->next  = *extra_meta;
    *extra_meta = meta;

    return;

fail:
    if (priv)
        free_priv(priv);
    av_freep(&meta);
}

typedef struct ID3v2EMFunc {
    const char *tag3;
    const char *tag4;
    void (*read)(AVFormatContext *s, AVIOContext *pb, int taglen,
                 const char *tag, ID3v2ExtraMeta **extra_meta,
                 int isv34);
    void (*free)(void *obj);
} ID3v2EMFunc;

static const ID3v2EMFunc id3v2_extra_meta_funcs[] = {
    { "GEO", "GEOB", read_geobtag, free_geobtag },
    { "PIC", "APIC", read_apic,    free_apic    },
    { "CHAP","CHAP", read_chapter, free_chapter },
    { "PRIV","PRIV", read_priv,    free_priv    },
    { NULL }
};

/**
 * Get the corresponding ID3v2EMFunc struct for a tag.
 * @param isv34 Determines if v2.2 or v2.3/4 strings are used
 * @return A pointer to the ID3v2EMFunc struct if found, NULL otherwise.
 */
static const ID3v2EMFunc *get_extra_meta_func(const char *tag, int isv34)
{
    int i = 0;
    while (id3v2_extra_meta_funcs[i].tag3) {
        if (tag && !memcmp(tag,
                    (isv34 ? id3v2_extra_meta_funcs[i].tag4 :
                             id3v2_extra_meta_funcs[i].tag3),
                    (isv34 ? 4 : 3)))
            return &id3v2_extra_meta_funcs[i];
        i++;
    }
    return NULL;
}

static void id3v2_parse(AVIOContext *pb, AVDictionary **metadata,
                        AVFormatContext *s, int len, uint8_t version,
                        uint8_t flags, ID3v2ExtraMeta **extra_meta)
{
    int isv34, unsync;
    unsigned tlen;
    char tag[5];
    int64_t next, end = avio_tell(pb) + len;
    int taghdrlen;
    const char *reason = NULL;
    AVIOContext pb_local;
    AVIOContext *pbx;
    unsigned char *buffer = NULL;
    int buffer_size       = 0;
    const ID3v2EMFunc *extra_func = NULL;
    unsigned char *uncompressed_buffer = NULL;
    av_unused int uncompressed_buffer_size = 0;
    const char *comm_frame;

    av_log(s, AV_LOG_DEBUG, "id3v2 ver:%d flags:%02X len:%d\n", version, flags, len);

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

    case 3:
    case 4:
        isv34     = 1;
        taghdrlen = 10;
        comm_frame = "COMM";
        break;

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

    unsync = flags & 0x80;

    if (isv34 && flags & 0x40) { /* Extended header present, just skip over it */
        int extlen = get_size(pb, 4);
        if (version == 4)
            /* In v2.4 the length includes the length field we just read. */
            extlen -= 4;

        if (extlen < 0) {
            reason = "invalid extended header length";
            goto error;
        }
        avio_skip(pb, extlen);
        len -= extlen + 4;
        if (len < 0) {
            reason = "extended header too long.";
            goto error;
        }
    }

    while (len >= taghdrlen) {
        unsigned int tflags = 0;
        int tunsync         = 0;
        int tcomp           = 0;
        int tencr           = 0;
        unsigned long av_unused dlen;

        if (isv34) {
            if (avio_read(pb, tag, 4) < 4)
                break;
            tag[4] = 0;
            if (version == 3) {
                tlen = avio_rb32(pb);
            } else {
                /* some encoders incorrectly uses v3 sizes instead of syncsafe ones
                 * so check the next tag to see which one to use */
                tlen = avio_rb32(pb);
                if (tlen > 0x7f) {
                    if (tlen < len) {
                        int64_t cur = avio_tell(pb);

                        if (ffio_ensure_seekback(pb, 2 /* tflags */ + tlen + 4 /* next tag */))
                            break;

                        if (check_tag(pb, cur + 2 + size_to_syncsafe(tlen), 4) == 1)
                            tlen = size_to_syncsafe(tlen);
                        else if (check_tag(pb, cur + 2 + tlen, 4) != 1)
                            break;
                        avio_seek(pb, cur, SEEK_SET);
                    } else
                        tlen = size_to_syncsafe(tlen);
                }
            }
            tflags  = avio_rb16(pb);
            tunsync = tflags & ID3v2_FLAG_UNSYNCH;
        } else {
            if (avio_read(pb, tag, 3) < 3)
                break;
            tag[3] = 0;
            tlen   = avio_rb24(pb);
        }
        if (tlen > (1<<28))
            break;
        len -= taghdrlen + tlen;

        if (len < 0)
            break;

        next = avio_tell(pb) + tlen;

        if (!tlen) {
            if (tag[0])
                av_log(s, AV_LOG_DEBUG, "Invalid empty frame %s, skipping.\n",
                       tag);
            continue;
        }

        if (tflags & ID3v2_FLAG_DATALEN) {
            if (tlen < 4)
                break;
            dlen = avio_rb32(pb);
            tlen -= 4;
        } else
            dlen = tlen;

        tcomp = tflags & ID3v2_FLAG_COMPRESSION;
        tencr = tflags & ID3v2_FLAG_ENCRYPTION;

        /* skip encrypted tags and, if no zlib, compressed tags */
        if (tencr || (!CONFIG_ZLIB && tcomp)) {
            const char *type;
            if (!tcomp)
                type = "encrypted";
            else if (!tencr)
                type = "compressed";
            else
                type = "encrypted and compressed";

            av_log(s, AV_LOG_WARNING, "Skipping %s ID3v2 frame %s.\n", type, tag);
            avio_skip(pb, tlen);
        /* check for text tag or supported special meta tag */
        } else if (tag[0] == 'T' ||
                   !memcmp(tag, "USLT", 4) ||
                   !strcmp(tag, comm_frame) ||
                   (extra_meta &&
                    (extra_func = get_extra_meta_func(tag, isv34)))) {
            pbx = pb;

            if (unsync || tunsync || tcomp) {
                av_fast_malloc(&buffer, &buffer_size, tlen);
                if (!buffer) {
                    av_log(s, AV_LOG_ERROR, "Failed to alloc %d bytes\n", tlen);
                    goto seek;
                }
            }
            if (unsync || tunsync) {
                int64_t end = avio_tell(pb) + tlen;
                uint8_t *b;

                b = buffer;
                while (avio_tell(pb) < end && b - buffer < tlen && !pb->eof_reached) {
                    *b++ = avio_r8(pb);
                    if (*(b - 1) == 0xff && avio_tell(pb) < end - 1 &&
                        b - buffer < tlen &&
                        !pb->eof_reached ) {
                        uint8_t val = avio_r8(pb);
                        *b++ = val ? val : avio_r8(pb);
                    }
                }
                ffio_init_context(&pb_local, buffer, b - buffer, 0, NULL, NULL, NULL,
                                  NULL);
                tlen = b - buffer;
                pbx  = &pb_local; // read from sync buffer
            }

#if CONFIG_ZLIB
                if (tcomp) {
                    int err;

                    av_log(s, AV_LOG_DEBUG, "Compresssed frame %s tlen=%d dlen=%ld\n", tag, tlen, dlen);

                    av_fast_malloc(&uncompressed_buffer, &uncompressed_buffer_size, dlen);
                    if (!uncompressed_buffer) {
                        av_log(s, AV_LOG_ERROR, "Failed to alloc %ld bytes\n", dlen);
                        goto seek;
                    }

                    if (!(unsync || tunsync)) {
                        err = avio_read(pb, buffer, tlen);
                        if (err < 0) {
                            av_log(s, AV_LOG_ERROR, "Failed to read compressed tag\n");
                            goto seek;
                        }
                        tlen = err;
                    }

                    err = uncompress(uncompressed_buffer, &dlen, buffer, tlen);
                    if (err != Z_OK) {
                        av_log(s, AV_LOG_ERROR, "Failed to uncompress tag: %d\n", err);
                        goto seek;
                    }
                    ffio_init_context(&pb_local, uncompressed_buffer, dlen, 0, NULL, NULL, NULL, NULL);
                    tlen = dlen;
                    pbx = &pb_local; // read from sync buffer
                }
#endif
            if (tag[0] == 'T')
                /* parse text tag */
                read_ttag(s, pbx, tlen, metadata, tag);
            else if (!memcmp(tag, "USLT", 4))
                read_uslt(s, pbx, tlen, metadata);
            else if (!strcmp(tag, comm_frame))
                read_comment(s, pbx, tlen, metadata);
            else
                /* parse special meta tag */
                extra_func->read(s, pbx, tlen, tag, extra_meta, isv34);
        } else if (!tag[0]) {
            if (tag[1])
                av_log(s, AV_LOG_WARNING, "invalid frame id, assuming padding\n");
            avio_skip(pb, tlen);
            break;
        }
        /* Skip to end of tag */
seek:
        avio_seek(pb, next, SEEK_SET);
    }

    /* Footer preset, always 10 bytes, skip over it */
    if (version == 4 && flags & 0x10)
        end += 10;

error:
    if (reason)
        av_log(s, AV_LOG_INFO, "ID3v2.%d tag skipped, cannot handle %s\n",
               version, reason);
    avio_seek(pb, end, SEEK_SET);
    av_free(buffer);
    av_free(uncompressed_buffer);
    return;
}

static void id3v2_read_internal(AVIOContext *pb, AVDictionary **metadata,
                                AVFormatContext *s, const char *magic,
                                ID3v2ExtraMeta **extra_meta, int64_t max_search_size)
{
    int len, ret;
    uint8_t buf[ID3v2_HEADER_SIZE];
    int found_header;
    int64_t start, off;

    if (max_search_size && max_search_size < ID3v2_HEADER_SIZE)
        return;

    start = avio_tell(pb);
    do {
        /* save the current offset in case there's nothing to read/skip */
        off = avio_tell(pb);
        if (max_search_size && off - start >= max_search_size - ID3v2_HEADER_SIZE) {
            avio_seek(pb, off, SEEK_SET);
            break;
        }

        ret = ffio_ensure_seekback(pb, ID3v2_HEADER_SIZE);
        if (ret >= 0)
            ret = avio_read(pb, buf, ID3v2_HEADER_SIZE);
        if (ret != ID3v2_HEADER_SIZE) {
            avio_seek(pb, off, SEEK_SET);
            break;
        }
        found_header = ff_id3v2_match(buf, magic);
        if (found_header) {
            /* parse ID3v2 header */
            len = ((buf[6] & 0x7f) << 21) |
                  ((buf[7] & 0x7f) << 14) |
                  ((buf[8] & 0x7f) << 7) |
                   (buf[9] & 0x7f);
            id3v2_parse(pb, metadata, s, len, buf[3], buf[5], extra_meta);
        } else {
            avio_seek(pb, off, SEEK_SET);
        }
    } while (found_header);
    ff_metadata_conv(metadata, NULL, ff_id3v2_34_metadata_conv);
    ff_metadata_conv(metadata, NULL, id3v2_2_metadata_conv);
    ff_metadata_conv(metadata, NULL, ff_id3v2_4_metadata_conv);
    merge_date(metadata);
}

void ff_id3v2_read_dict(AVIOContext *pb, AVDictionary **metadata,
                        const char *magic, ID3v2ExtraMeta **extra_meta)
{
    id3v2_read_internal(pb, metadata, NULL, magic, extra_meta, 0);
}

void ff_id3v2_read(AVFormatContext *s, const char *magic,
                   ID3v2ExtraMeta **extra_meta, unsigned int max_search_size)
{
    id3v2_read_internal(s->pb, &s->metadata, s, magic, extra_meta, max_search_size);
}

void ff_id3v2_free_extra_meta(ID3v2ExtraMeta **extra_meta)
{
    ID3v2ExtraMeta *current = *extra_meta, *next;
    const ID3v2EMFunc *extra_func;

    while (current) {
        if ((extra_func = get_extra_meta_func(current->tag, 1)))
            extra_func->free(current->data);
        next = current->next;
        av_freep(&current);
        current = next;
    }

    *extra_meta = NULL;
}

int ff_id3v2_parse_apic(AVFormatContext *s, ID3v2ExtraMeta **extra_meta)
{
    ID3v2ExtraMeta *cur;

    for (cur = *extra_meta; cur; cur = cur->next) {
        ID3v2ExtraMetaAPIC *apic;
        AVStream *st;

        if (strcmp(cur->tag, "APIC"))
            continue;
        apic = cur->data;

        if (!(st = avformat_new_stream(s, NULL)))
            return AVERROR(ENOMEM);

        st->disposition      |= AV_DISPOSITION_ATTACHED_PIC;
        st->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
        st->codecpar->codec_id   = apic->id;

        if (AV_RB64(apic->buf->data) == 0x89504e470d0a1a0a)
            st->codecpar->codec_id = AV_CODEC_ID_PNG;

        if (apic->description[0])
            av_dict_set(&st->metadata, "title", apic->description, 0);

        av_dict_set(&st->metadata, "comment", apic->type, 0);

        av_init_packet(&st->attached_pic);
        st->attached_pic.buf          = apic->buf;
        st->attached_pic.data         = apic->buf->data;
        st->attached_pic.size         = apic->buf->size - AV_INPUT_BUFFER_PADDING_SIZE;
        st->attached_pic.stream_index = st->index;
        st->attached_pic.flags       |= AV_PKT_FLAG_KEY;

        apic->buf = NULL;
    }

    return 0;
}

int ff_id3v2_parse_chapters(AVFormatContext *s, ID3v2ExtraMeta **extra_meta)
{
    int ret = 0;
    ID3v2ExtraMeta *cur;
    AVRational time_base = {1, 1000};
    ID3v2ExtraMetaCHAP **chapters = NULL;
    int num_chapters = 0;
    int i;

    // since extra_meta is a linked list where elements are prepended,
    // we need to reverse the order of chapters
    for (cur = *extra_meta; cur; cur = cur->next) {
        ID3v2ExtraMetaCHAP *chap;

        if (strcmp(cur->tag, "CHAP"))
            continue;
        chap = cur->data;

        if ((ret = av_dynarray_add_nofree(&chapters, &num_chapters, chap)) < 0)
            goto end;
    }

    for (i = 0; i < (num_chapters / 2); i++) {
        ID3v2ExtraMetaCHAP *right;
        int right_index;

        right_index = (num_chapters - 1) - i;
        right = chapters[right_index];

        chapters[right_index] = chapters[i];
        chapters[i] = right;
    }

    for (i = 0; i < num_chapters; i++) {
        ID3v2ExtraMetaCHAP *chap;
        AVChapter *chapter;

        chap = chapters[i];
        chapter = avpriv_new_chapter(s, i, time_base, chap->start, chap->end, chap->element_id);
        if (!chapter)
            continue;

        if ((ret = av_dict_copy(&chapter->metadata, chap->meta, 0)) < 0)
            goto end;
    }

end:
    av_freep(&chapters);
    return ret;
}