/* file-mp4.c
 * routines for dissection of MP4 files
 * Copyright 2013-2014, Martin Kaiser <martin@kaiser.cx>
 *
 * Wireshark - Network traffic analyzer
 * By Gerald Combs <gerald@wireshark.org>
 * Copyright 1998 Gerald Combs
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 */

/* this dissector is based on
 * ISO/IEC 14496-12 (ISO base media file format) and
 * ISO/IEC 14496-14 (MP4 file format)
 *
 * at the moment, it dissects the basic box structure and the payload of
 * some simple boxes */


#include "config.h"

#include <math.h>

#include <epan/packet.h>
#include <epan/expert.h>

#define MAKE_TYPE_VAL(a, b, c, d)   ((a)<<24 | (b)<<16 | (c)<<8 | (d))

/* Although the dissection of each box consumes a couple of bytes, it's
   possible to craft a file whose boxes recurse so deeply that wireshark
   crashes before we processed all data. Therefore, we limit the
   recursion level for boxes to a reasonable depth. */
#define MP4_BOX_MAX_REC_LVL  20

void proto_register_mp4(void);
void proto_reg_handoff_mp4(void);

static gint dissect_mp4_box(guint32 parent_box_type _U_, guint depth,
        tvbuff_t *tvb, gint offset, packet_info *pinfo, proto_tree *tree);

static int proto_mp4 = -1;

static gint ett_mp4 = -1;
static gint ett_mp4_box = -1;

static int hf_mp4_box_size = -1;
static int hf_mp4_box_type_str = -1;
static int hf_mp4_box_largesize = -1;
static int hf_mp4_full_box_ver = -1;
static int hf_mp4_full_box_flags = -1;
static int hf_mp4_full_box_flags_media_data_location = -1;
static int hf_mp4_ftyp_brand = -1;
static int hf_mp4_ftyp_ver = -1;
static int hf_mp4_ftyp_add_brand = -1;
static int hf_mp4_stsz_sample_size = -1;
static int hf_mp4_stsz_sample_count = -1;
static int hf_mp4_stsz_entry_size = -1;
static int hf_mp4_mvhd_creat_time = -1;
static int hf_mp4_mvhd_mod_time = -1;
static int hf_mp4_mvhd_timescale = -1;
static int hf_mp4_mvhd_duration = -1;
static int hf_mp4_mvhd_rate = -1;
static int hf_mp4_mvhd_vol = -1;
static int hf_mp4_mvhd_next_tid = -1;
static int hf_mp4_mfhd_seq_num = -1;
static int hf_mp4_tkhd_creat_time = -1;
static int hf_mp4_tkhd_mod_time = -1;
static int hf_mp4_tkhd_track_id = -1;
static int hf_mp4_tkhd_duration = -1;
static int hf_mp4_tkhd_width = -1;
static int hf_mp4_tkhd_height = -1;
static int hf_mp4_hdlr_type = -1;
static int hf_mp4_hdlr_name = -1;
static int hf_mp4_dref_entry_cnt = -1;
static int hf_mp4_stsd_entry_cnt = -1;

static expert_field ei_mp4_box_too_large = EI_INIT;
static expert_field ei_mp4_too_many_rec_lvls = EI_INIT;
static expert_field ei_mp4_mvhd_next_tid_unknown = EI_INIT;

/* a box must at least have a 32bit len field and a 32bit type */
#define MIN_BOX_SIZE 8
/* an extended box has the first length field set to 1 */
#define BOX_SIZE_EXTENDED 1

/* the box type is stored as four text characters
   it is in network byte order and contains only printable characters
   for our internal handling, we convert this to a 32bit value */

#define BOX_TYPE_NONE  0x0 /* used for parent_box_type of a top-level box */
#define BOX_TYPE_FTYP  MAKE_TYPE_VAL('f', 't', 'y', 'p')
#define BOX_TYPE_MOOV  MAKE_TYPE_VAL('m', 'o', 'o', 'v')
#define BOX_TYPE_MVHD  MAKE_TYPE_VAL('m', 'v', 'h', 'd')
#define BOX_TYPE_TRAK  MAKE_TYPE_VAL('t', 'r', 'a', 'k')
#define BOX_TYPE_TKHD  MAKE_TYPE_VAL('t', 'k', 'h', 'd')
#define BOX_TYPE_MDIA  MAKE_TYPE_VAL('m', 'd', 'i', 'a')
#define BOX_TYPE_MDHD  MAKE_TYPE_VAL('m', 'd', 'h', 'd')
#define BOX_TYPE_HDLR  MAKE_TYPE_VAL('h', 'd', 'l', 'r')
#define BOX_TYPE_MINF  MAKE_TYPE_VAL('m', 'i', 'n', 'f')
#define BOX_TYPE_VMHD  MAKE_TYPE_VAL('v', 'm', 'h', 'd')
#define BOX_TYPE_SMHD  MAKE_TYPE_VAL('s', 'm', 'h', 'd')
#define BOX_TYPE_DINF  MAKE_TYPE_VAL('d', 'i', 'n', 'f')
#define BOX_TYPE_DREF  MAKE_TYPE_VAL('d', 'r', 'e', 'f')
#define BOX_TYPE_STBL  MAKE_TYPE_VAL('s', 't', 'b', 'l')
#define BOX_TYPE_STTS  MAKE_TYPE_VAL('s', 't', 't', 's')
#define BOX_TYPE_CTTS  MAKE_TYPE_VAL('c', 't', 't', 's')
#define BOX_TYPE_STSD  MAKE_TYPE_VAL('s', 't', 's', 'd')
#define BOX_TYPE_STSZ  MAKE_TYPE_VAL('s', 't', 's', 'z')
#define BOX_TYPE_STZ2  MAKE_TYPE_VAL('s', 't', 'z', '2')
#define BOX_TYPE_STSC  MAKE_TYPE_VAL('s', 't', 's', 'c')
#define BOX_TYPE_STCO  MAKE_TYPE_VAL('s', 't', 'c', 'o')
#define BOX_TYPE_STSS  MAKE_TYPE_VAL('s', 't', 's', 's')
#define BOX_TYPE_MVEX  MAKE_TYPE_VAL('m', 'v', 'e', 'x')
#define BOX_TYPE_MOOF  MAKE_TYPE_VAL('m', 'o', 'o', 'f')
#define BOX_TYPE_MEHD  MAKE_TYPE_VAL('m', 'e', 'h', 'd')
#define BOX_TYPE_TREX  MAKE_TYPE_VAL('t', 'r', 'e', 'x')
#define BOX_TYPE_MFHD  MAKE_TYPE_VAL('m', 'f', 'h', 'd')
#define BOX_TYPE_TRAF  MAKE_TYPE_VAL('t', 'r', 'a', 'f')
#define BOX_TYPE_TFHD  MAKE_TYPE_VAL('t', 'f', 'h', 'd')
#define BOX_TYPE_TRUN  MAKE_TYPE_VAL('t', 'r', 'u', 'n')
#define BOX_TYPE_MDAT  MAKE_TYPE_VAL('m', 'd', 'a', 't')
#define BOX_TYPE_UDTA  MAKE_TYPE_VAL('u', 'd', 't', 'a')
/* the box name is url + <space>, all names must be 4 characters long */
#define BOX_TYPE_URL_  MAKE_TYPE_VAL('u', 'r', 'l', ' ')

/* the location for this URL box is the same as in the upper-level movie box */
#define ENTRY_FLAG_MOVIE 0x000001

static const value_string box_types[] = {
    { BOX_TYPE_FTYP, "File Type Box" },
    { BOX_TYPE_MOOV, "Movie Box" },
    { BOX_TYPE_MVHD, "Movie Header Box" },
    { BOX_TYPE_TRAK, "Track Box" },
    { BOX_TYPE_TKHD, "Track Header Box" },
    { BOX_TYPE_MDIA, "Media Box" },
    { BOX_TYPE_MDHD, "Media Header Box" },
    { BOX_TYPE_HDLR, "Handler Reference Box" },
    { BOX_TYPE_MINF, "Media Information Box" },
    { BOX_TYPE_VMHD, "Video Media Header Box" },
    { BOX_TYPE_SMHD, "Sound Media Header Box" },
    { BOX_TYPE_DINF, "Data Information Box" },
    { BOX_TYPE_DREF, "Data Reference Box" },
    { BOX_TYPE_STBL, "Sample to Group Box" },
    { BOX_TYPE_STTS, "Decoding Time To Sample Box" },
    { BOX_TYPE_CTTS, "Composition Time To Sample Box" },
    { BOX_TYPE_STSD, "Sample Description Box" },
    { BOX_TYPE_STSZ, "Sample Size Box" },
    { BOX_TYPE_STZ2, "Compact Sample Size Box" },
    { BOX_TYPE_STSC, "Sample To Chunk Box" },
    { BOX_TYPE_STCO, "Chunk Offset Box" },
    { BOX_TYPE_STSS, "Sync Sample Table" },
    { BOX_TYPE_MVEX, "Movie Extends Box" },
    { BOX_TYPE_MOOF, "Movie Fragment Box" },
    { BOX_TYPE_MEHD, "Movie Extends Header Box" },
    { BOX_TYPE_TREX, "Track Extends Box" },
    { BOX_TYPE_MFHD, "Movie Fragment Header Box" },
    { BOX_TYPE_TRAF, "Track Fragment Box" },
    { BOX_TYPE_TFHD, "Track Fragment Header Box" },
    { BOX_TYPE_TRUN, "Track Fragment Run Box" },
    { BOX_TYPE_MDAT, "Media Data Box" },
    { BOX_TYPE_UDTA, "User Data Box" },
    { BOX_TYPE_URL_, "URL Box" },
    { 0, NULL }
};

/* convert a decimal number x into a double 0.x (e.g. 123 becomes 0.123) */
static inline double
make_fract(guint x)
{
    if (x==0)
        return 0.0;

    return (double)(x / exp(log(10.0)*(1+floor(log((double)x)/log(10.0)))));
}

static gint
dissect_mp4_mvhd_body(tvbuff_t *tvb, gint offset, gint len _U_,
        packet_info *pinfo, guint depth _U_, proto_tree *tree)
{
    gint        offset_start;
    guint8      version;
    guint8      time_len;
    double      rate, vol;
    guint16     fract_dec;
    guint32     next_tid;
    proto_item *next_tid_it;

    offset_start = offset;

    version = tvb_get_guint8(tvb, offset);
    proto_tree_add_item(tree, hf_mp4_full_box_ver,
            tvb, offset, 1, ENC_BIG_ENDIAN);
    offset += 1;
    proto_tree_add_item(tree, hf_mp4_full_box_flags,
            tvb, offset, 3, ENC_BIG_ENDIAN);
    offset += 3;

    time_len = (version==0) ? 4 : 8;
    proto_tree_add_item(tree, hf_mp4_mvhd_creat_time,
            tvb, offset, time_len, ENC_BIG_ENDIAN);
    offset += time_len;
    proto_tree_add_item(tree, hf_mp4_mvhd_mod_time,
            tvb, offset, time_len, ENC_BIG_ENDIAN);
    offset += time_len;
    proto_tree_add_item(tree, hf_mp4_mvhd_timescale,
            tvb, offset, 4, ENC_BIG_ENDIAN);
    offset += 4;
    proto_tree_add_item(tree, hf_mp4_mvhd_duration,
            tvb, offset, time_len, ENC_BIG_ENDIAN);
    offset += time_len;

    rate = tvb_get_ntohs(tvb, offset);
    fract_dec = tvb_get_ntohs(tvb, offset+2);
    rate += make_fract(fract_dec);
    proto_tree_add_double(tree, hf_mp4_mvhd_rate, tvb, offset, 4, rate);
    offset += 4;

    vol = tvb_get_guint8(tvb, offset);
    fract_dec = tvb_get_guint8(tvb, offset+1);
    vol += make_fract(fract_dec);
    proto_tree_add_double(tree, hf_mp4_mvhd_vol, tvb, offset, 4, vol);
    offset += 2;

    offset += 2;   /* 16 bits reserved */
    offset += 2*4; /* 2 * uint32 reserved */

    offset += 9*4; /* XXX - unity matrix */
    offset += 6*4; /* 6 * 32 bits predefined = 0 */

    next_tid = tvb_get_ntohl(tvb, offset);
    next_tid_it = proto_tree_add_item(tree, hf_mp4_mvhd_next_tid,
            tvb, offset, 4, ENC_BIG_ENDIAN);
    if (next_tid == G_MAXUINT32)
        expert_add_info(pinfo, next_tid_it, &ei_mp4_mvhd_next_tid_unknown);
    offset += 4;

    return offset-offset_start;
}

static gint
dissect_mp4_mfhd_body(tvbuff_t *tvb, gint offset, gint len _U_,
        packet_info *pinfo _U_, guint depth _U_, proto_tree *tree)
{
    gint offset_start;

    offset_start = offset;
    proto_tree_add_item(tree, hf_mp4_full_box_ver,
            tvb, offset, 1, ENC_BIG_ENDIAN);
    offset += 1;
    proto_tree_add_item(tree, hf_mp4_full_box_flags,
            tvb, offset, 3, ENC_BIG_ENDIAN);
    offset += 3;

    proto_tree_add_item(tree, hf_mp4_mfhd_seq_num,
            tvb, offset, 4, ENC_BIG_ENDIAN);
    offset += 4;

    return offset-offset_start;
}


static gint
dissect_mp4_tkhd_body(tvbuff_t *tvb, gint offset, gint len _U_,
        packet_info *pinfo _U_, guint depth _U_, proto_tree *tree)
{
    gint     offset_start;
    guint8   version;
    guint8   time_len;
    double   width, height;
    guint16  fract_dec;

    offset_start = offset;

    version = tvb_get_guint8(tvb, offset);
    proto_tree_add_item(tree, hf_mp4_full_box_ver,
            tvb, offset, 1, ENC_BIG_ENDIAN);
    offset += 1;
    proto_tree_add_item(tree, hf_mp4_full_box_flags,
            tvb, offset, 3, ENC_BIG_ENDIAN);
    offset += 3;

    time_len = (version==0) ? 4 : 8;
    proto_tree_add_item(tree, hf_mp4_tkhd_creat_time,
            tvb, offset, time_len, ENC_BIG_ENDIAN);
    offset += time_len;
    proto_tree_add_item(tree, hf_mp4_tkhd_mod_time,
            tvb, offset, time_len, ENC_BIG_ENDIAN);
    offset += time_len;

    proto_tree_add_item(tree, hf_mp4_tkhd_track_id,
            tvb, offset, 4, ENC_BIG_ENDIAN);
    offset += 4;

    offset += 4;   /* 32bit reserved */

    proto_tree_add_item(tree, hf_mp4_tkhd_duration,
            tvb, offset, time_len, ENC_BIG_ENDIAN);
    offset += time_len;

    offset += 2*4; /* 2*32bit reserved */
    offset += 2;   /* 16bit layer */
    offset += 2;   /* 16bit alternate_group */
    offset += 2;   /* 16bit volume */
    offset += 2;   /* 16bit reserved */
    offset += 9*4; /* 9*32bit matrix */

    width = tvb_get_ntohs(tvb, offset);
    fract_dec = tvb_get_ntohs(tvb, offset+2);
    width += make_fract(fract_dec);
    proto_tree_add_double(tree, hf_mp4_tkhd_width, tvb, offset, 4, width);
    offset += 4;

    height = tvb_get_ntohs(tvb, offset);
    fract_dec = tvb_get_ntohs(tvb, offset+2);
    height += make_fract(fract_dec);
    proto_tree_add_double(tree, hf_mp4_tkhd_height, tvb, offset, 4, height);
    offset += 4;

    return offset-offset_start;
}


static gint
dissect_mp4_ftyp_body(tvbuff_t *tvb, gint offset, gint len,
        packet_info *pinfo _U_, guint depth _U_, proto_tree *tree)
{
    gint offset_start;

    offset_start = offset;
    proto_tree_add_item(tree, hf_mp4_ftyp_brand,
            tvb, offset, 4, ENC_ASCII|ENC_NA);
    offset += 4;
    proto_tree_add_item(tree, hf_mp4_ftyp_ver,
            tvb, offset, 4, ENC_BIG_ENDIAN);
    offset += 4;

    while ((offset-offset_start) < len) {
        proto_tree_add_item(tree, hf_mp4_ftyp_add_brand,
                tvb, offset, 4, ENC_ASCII|ENC_NA);
        offset += 4;
    }

    return offset - offset_start;
}


static gint
dissect_mp4_stsz_body(tvbuff_t *tvb, gint offset, gint len _U_,
        packet_info *pinfo _U_, guint depth _U_, proto_tree *tree)
{
    gint offset_start;
    guint32  sample_size, sample_count, i;

    offset_start = offset;
    sample_size = tvb_get_ntohl(tvb, offset);

    proto_tree_add_item(tree, hf_mp4_stsz_sample_size,
            tvb, offset, 4, ENC_BIG_ENDIAN);
    /* XXX - expert info for sample size == 0 */
    offset += 4;

    sample_count = tvb_get_ntohl(tvb, offset);
    proto_tree_add_item(tree, hf_mp4_stsz_sample_count,
            tvb, offset, 4, ENC_BIG_ENDIAN);
    offset += 4;

    if (sample_size != 0)
        return offset - offset_start;

    for (i=0; i<sample_count; i++) {
        proto_tree_add_item(tree, hf_mp4_stsz_entry_size,
                tvb, offset, 4, ENC_BIG_ENDIAN);
        offset += 4;
    }

    return offset - offset_start;
}

 
static gint
dissect_mp4_hdlr_body(tvbuff_t *tvb, gint offset, gint len _U_,
        packet_info *pinfo _U_, guint depth _U_, proto_tree *tree)
{
    gint   offset_start;
    guint  hdlr_name_len;

    offset_start = offset;

    proto_tree_add_item(tree, hf_mp4_full_box_ver,
            tvb, offset, 1, ENC_BIG_ENDIAN);
    /* XXX - put up an expert info if version!=0 */
    offset += 1;
    proto_tree_add_item(tree, hf_mp4_full_box_flags,
            tvb, offset, 3, ENC_BIG_ENDIAN);
    offset += 3;

    offset += 4;   /* four reserved 0 bytes */

    proto_tree_add_item(tree, hf_mp4_hdlr_type,
            tvb, offset, 4, ENC_ASCII|ENC_NA);
    offset += 4;

    offset += 12;   /* 3x32bit reserved */

    /* name is a 0-terminated UTF-8 string, len includes the final 0 */
    hdlr_name_len = tvb_strsize(tvb, offset);
    proto_tree_add_item(tree, hf_mp4_hdlr_name,
            tvb, offset, hdlr_name_len, ENC_UTF_8|ENC_NA);
    offset += hdlr_name_len;

    return offset-offset_start;
}


static gint
dissect_mp4_dref_body(tvbuff_t *tvb, gint offset, gint len _U_,
        packet_info *pinfo, guint depth, proto_tree *tree)
{
    gint     offset_start;
    guint32  entry_cnt, i;
    gint     ret;

    offset_start = offset;

    proto_tree_add_item(tree, hf_mp4_full_box_ver,
            tvb, offset, 1, ENC_BIG_ENDIAN);
    /* XXX - put up an expert info if version!=0 */
    offset += 1;
    proto_tree_add_item(tree, hf_mp4_full_box_flags,
            tvb, offset, 3, ENC_BIG_ENDIAN);
    offset += 3;

    entry_cnt = tvb_get_ntohl(tvb, offset);
    proto_tree_add_item(tree, hf_mp4_dref_entry_cnt,
            tvb, offset, 4, ENC_BIG_ENDIAN);
    offset += 4;

    for(i=0; i<entry_cnt; i++) {
        ret = dissect_mp4_box(BOX_TYPE_DREF, depth, tvb, offset, pinfo, tree);
        if (ret<=0)
            break;

        offset += ret;
    }

    return offset-offset_start;
}


static gint
dissect_mp4_url_body(tvbuff_t *tvb, gint offset, gint len,
        packet_info *pinfo _U_, guint depth _U_, proto_tree *tree)
{
#if 0
    guint32  flags;
#endif

    proto_tree_add_item(tree, hf_mp4_full_box_ver,
            tvb, offset, 1, ENC_BIG_ENDIAN);
    /* XXX - put up an expert info if version!=0 */
    offset += 1;

#if 0
    flags = tvb_get_ntoh24(tvb, offset);
#endif
    proto_tree_add_item(tree, hf_mp4_full_box_flags,
            tvb, offset, 3, ENC_BIG_ENDIAN);
    proto_tree_add_item(tree, hf_mp4_full_box_flags_media_data_location, tvb, offset, 3, ENC_BIG_ENDIAN);
    /*offset += 3;*/

#if 0
    if (flags&ENTRY_FLAG_MOVIE) {
    }
    else {
        /* XXX - dissect location string */
    }
#endif

    return len;
}


static gint
dissect_mp4_stsd_body(tvbuff_t *tvb, gint offset, gint len,
        packet_info *pinfo, guint depth, proto_tree *tree)
{
    guint32  entry_cnt, i;
    gint     ret;

    proto_tree_add_item(tree, hf_mp4_full_box_ver,
            tvb, offset, 1, ENC_BIG_ENDIAN);
    /* XXX - put up an expert info if version!=0 */
    offset += 1;
    proto_tree_add_item(tree, hf_mp4_full_box_flags,
            tvb, offset, 3, ENC_BIG_ENDIAN);
    offset += 3;

    entry_cnt = tvb_get_ntohl(tvb, offset);
    proto_tree_add_item(tree, hf_mp4_stsd_entry_cnt,
            tvb, offset, 4, ENC_BIG_ENDIAN);
    offset += 4;

    for(i=0; i<entry_cnt; i++) {
        /* a sample entry has the same format as an mp4 box
           we call dissect_mp4_box() to dissect it
           alternatively, we could parse it ourselves, we'd then have to
           handle the extended lengths etc */

        /* XXX - dissect the content of each Sample Entry,
           this depends on the handler_type, we could add an optional
           void *data parameter to dissect_mp4_box() and handle sample
           entry boxes based on parent box and data parameter */
        ret = dissect_mp4_box(BOX_TYPE_STSD, depth, tvb, offset, pinfo, tree);
        if (ret<=0)
            break;

        offset += ret;
    }

    return len;
}

 
/* dissect a box, return its (standard or extended) length or 0 for error
   depth is the recursion level of the parent box */
static gint
dissect_mp4_box(guint32 parent_box_type _U_, guint depth,
        tvbuff_t *tvb, gint offset, packet_info *pinfo, proto_tree *tree)
{
    gint        offset_start;
    guint64     box_size;
    guint32     box_type;
    guint8     *box_type_str;
    proto_item *type_pi, *size_pi, *ext_size_pi = NULL;
    proto_tree *box_tree;
    gint        ret;
    gint        body_size;


    offset_start = offset;

    /* the following mechanisms are not supported for now
       - size==0, indicating that the box extends to the end of the file
       - extended box types */

    box_size = (guint64)tvb_get_ntohl(tvb, offset);
    if ((box_size != BOX_SIZE_EXTENDED) && (box_size < MIN_BOX_SIZE))
        return -1;

    box_type = tvb_get_ntohl(tvb, offset+4);
    box_type_str = tvb_get_string_enc(wmem_packet_scope(), tvb,
            offset+4, 4, ENC_ASCII|ENC_NA);

    box_tree = proto_tree_add_subtree_format(tree, tvb, offset, -1, ett_mp4_box, &type_pi, "%s (%s)",
            val_to_str_const(box_type, box_types, "unknown"), box_type_str);

    size_pi = proto_tree_add_item(box_tree, hf_mp4_box_size,
            tvb, offset, 4, ENC_BIG_ENDIAN);
    if (box_size == BOX_SIZE_EXTENDED)
        proto_item_append_text(size_pi, " (actual size is in largesize)");

    offset += 4;
    proto_tree_add_item(box_tree, hf_mp4_box_type_str,
            tvb, offset, 4, ENC_ASCII|ENC_NA);
    offset += 4;

    if (box_size == BOX_SIZE_EXTENDED) {
        box_size = tvb_get_ntoh64(tvb, offset);
        ext_size_pi = proto_tree_add_item(box_tree, hf_mp4_box_largesize,
                tvb, offset, 8, ENC_BIG_ENDIAN);
        offset += 8;
    }

    if (box_size > G_MAXINT) {
        /* this should be ok for ext_size_pi==NULL */
        expert_add_info(pinfo, ext_size_pi, &ei_mp4_box_too_large);
        return -1;
    }
    proto_item_set_len(type_pi, (gint)box_size);
    body_size = (gint)box_size - (offset-offset_start);

    depth++;
    if (depth > MP4_BOX_MAX_REC_LVL) {
        proto_tree_add_expert(tree, pinfo, &ei_mp4_too_many_rec_lvls,
                tvb, offset_start, (gint)box_size);
        return -1;
    }

    /* we do not dissect full box version and flags here
       these two components are required by the function dissecting the body
       some fields of the body depend on the version and flags */

    /* XXX - check parent box if supplied */
    switch (box_type) {
        case BOX_TYPE_FTYP:
            dissect_mp4_ftyp_body(tvb, offset, body_size, pinfo, depth, box_tree);
            break;
        case BOX_TYPE_MVHD:
            dissect_mp4_mvhd_body(tvb, offset, body_size, pinfo, depth, box_tree);
            break;
        case BOX_TYPE_MFHD:
            dissect_mp4_mfhd_body(tvb, offset, body_size, pinfo, depth, box_tree);
            break;
        case BOX_TYPE_TKHD:
            dissect_mp4_tkhd_body(tvb, offset, body_size, pinfo, depth, box_tree);
            break;
        case BOX_TYPE_STSZ:
            dissect_mp4_stsz_body(tvb, offset, body_size, pinfo, depth, box_tree);
            break;
        case BOX_TYPE_HDLR:
            dissect_mp4_hdlr_body(tvb, offset, body_size, pinfo, depth, box_tree);
            break;
        case BOX_TYPE_DREF:
            dissect_mp4_dref_body(tvb, offset, body_size, pinfo, depth, box_tree);
            break;
        case BOX_TYPE_URL_:
            dissect_mp4_url_body(tvb, offset, body_size, pinfo, depth, box_tree);
            break;
        case BOX_TYPE_STSD:
            dissect_mp4_stsd_body(tvb, offset, body_size, pinfo, depth, box_tree);
            break;
        case BOX_TYPE_MOOV:
        case BOX_TYPE_MOOF:
        case BOX_TYPE_STBL:
        case BOX_TYPE_MDIA:
        case BOX_TYPE_TRAK:
        case BOX_TYPE_TRAF:
        case BOX_TYPE_MINF:
        case BOX_TYPE_MVEX:
        case BOX_TYPE_DINF:
        case BOX_TYPE_UDTA:
            while (offset-offset_start < (gint)box_size) {
                ret = dissect_mp4_box(box_type, depth,
                        tvb, offset, pinfo, box_tree);
                if (ret <= 0)
                    break;
                offset += ret;
            }
            break;
        default:
            break;
    }

    return (gint)box_size;
}


static int
dissect_mp4(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
{
    gint        offset = 0;
    guint32     box_type;
    proto_item *pi;
    proto_tree *mp4_tree;
    gint        ret;

    /* to make sure that we have an mp4 file, we check that it starts with
        a box of a known type
       please note that we do not allow the first box to be an extended box
       this detection should be safe as long as the dissector is only called for
        the video/mp4 mime type
       when we read mp4 files directly, we might need stricter checks here */
    if (tvb_reported_length(tvb) < MIN_BOX_SIZE)
        return 0;
    box_type = tvb_get_ntohl(tvb, 4);
    if (try_val_to_str(box_type, box_types) == NULL)
        return 0;

    col_set_str(pinfo->cinfo, COL_PROTOCOL, "MP4");
    col_clear(pinfo->cinfo, COL_INFO);

    pi = proto_tree_add_protocol_format(tree, proto_mp4,
            tvb, 0, (gint)tvb_reported_length(tvb), "MP4");
    mp4_tree = proto_item_add_subtree(pi, ett_mp4);

    while (tvb_reported_length_remaining(tvb, offset) > 0) {
        ret = dissect_mp4_box(BOX_TYPE_NONE, 0, tvb, offset, pinfo, mp4_tree);
        if (ret <= 0)
            break;
        offset += ret;
    }

    return offset;
}

void
proto_register_mp4(void)
{
    static hf_register_info hf[] = {
        { &hf_mp4_box_size,
            { "Box size", "mp4.box.size", FT_UINT32, BASE_DEC,
                NULL, 0, NULL, HFILL } },
        { &hf_mp4_box_type_str,
            { "Box type", "mp4.box.type_str", FT_STRING, BASE_NONE,
                NULL, 0, NULL, HFILL } },
        { &hf_mp4_box_largesize,
            { "Box size (largesize)", "mp4.box.largesize", FT_UINT64, BASE_DEC,
                NULL, 0, NULL, HFILL } },
        { &hf_mp4_full_box_ver,
            { "Box version", "mp4.full_box.version", FT_UINT8, BASE_DEC,
                NULL, 0, NULL, HFILL } },
        { &hf_mp4_full_box_flags,
            { "Flags", "mp4.full_box.flags", FT_UINT24, BASE_HEX,
                NULL, 0, NULL, HFILL } },
        { &hf_mp4_full_box_flags_media_data_location,
            { "Media data location is defined in the movie box", "mp4.full_box.flags.media_data_location", FT_BOOLEAN, 24,
                NULL, ENTRY_FLAG_MOVIE, NULL, HFILL } },
        { &hf_mp4_ftyp_brand,
            { "Brand", "mp4.ftyp.brand", FT_STRING, BASE_NONE,
                NULL, 0, NULL, HFILL } },
        { &hf_mp4_ftyp_ver,
            { "Version", "mp4.ftyp.version", FT_UINT32, BASE_DEC,
                NULL, 0, NULL, HFILL } },
        { &hf_mp4_ftyp_add_brand,
            { "Additional brand", "mp4.ftyp.additional_brand", FT_STRING,
                BASE_NONE, NULL, 0, NULL, HFILL } },
        { &hf_mp4_stsz_sample_size,
            { "Sample size", "mp4.stsz.sample_size", FT_UINT32,
                BASE_DEC, NULL, 0, NULL, HFILL } },
        { &hf_mp4_stsz_sample_count,
            { "Sample count", "mp4.stsz.sample_count", FT_UINT32,
                BASE_DEC, NULL, 0, NULL, HFILL } },
        { &hf_mp4_stsz_entry_size,
            { "Entry size", "mp4.stsz.entry_size", FT_UINT32,
                BASE_DEC, NULL, 0, NULL, HFILL } },
        { &hf_mp4_mvhd_creat_time,
            { "Creation time", "mp4.mvhd.creation_time", FT_UINT64,
                BASE_DEC, NULL, 0, NULL, HFILL } },
        { &hf_mp4_mvhd_mod_time,
            { "Modification time", "mp4.mvhd.modification_time", FT_UINT64,
                BASE_DEC, NULL, 0, NULL, HFILL } },
        { &hf_mp4_mvhd_timescale,
            { "Timescale", "mp4.mvhd.timescale", FT_UINT32,
                BASE_DEC, NULL, 0, NULL, HFILL } },
        { &hf_mp4_mvhd_duration,
            { "Duration", "mp4.mvhd.duration", FT_UINT64,
                BASE_DEC, NULL, 0, NULL, HFILL } },
        { &hf_mp4_mvhd_rate,
            { "Rate", "mp4.mvhd.rate", FT_DOUBLE,
                BASE_NONE, NULL, 0, NULL, HFILL } },
        { &hf_mp4_mvhd_vol,
            { "Volume", "mp4.mvhd.volume", FT_DOUBLE,
                BASE_NONE, NULL, 0, NULL, HFILL } },
        { &hf_mp4_mvhd_next_tid,
            { "Next Track ID", "mp4.mvhd.next_track_id", FT_UINT32,
                BASE_HEX, NULL, 0, NULL, HFILL } },
        { &hf_mp4_mfhd_seq_num,
            { "Sequence number", "mp4.mfhd.sequence_number", FT_UINT32,
                BASE_DEC, NULL, 0, NULL, HFILL } },
        { &hf_mp4_tkhd_creat_time,
            { "Creation time", "mp4.tkhd.creation_time", FT_UINT64,
                BASE_DEC, NULL, 0, NULL, HFILL } },
        { &hf_mp4_tkhd_mod_time,
            { "Modification time", "mp4.tkhd.modification_time", FT_UINT64,
                BASE_DEC, NULL, 0, NULL, HFILL } },
        { &hf_mp4_tkhd_track_id,
            { "Track ID", "mp4.tkhd.track_id", FT_UINT32,
                BASE_DEC, NULL, 0, NULL, HFILL } },
        { &hf_mp4_tkhd_duration,
            { "Duration", "mp4.tkhd.duration", FT_UINT64,
                BASE_DEC, NULL, 0, NULL, HFILL } },
        { &hf_mp4_tkhd_width,
            { "Width", "mp4.tkhd.width", FT_DOUBLE,
                BASE_NONE, NULL, 0, NULL, HFILL } },
        { &hf_mp4_tkhd_height,
            { "Height", "mp4.tkhd.height", FT_DOUBLE,
                BASE_NONE, NULL, 0, NULL, HFILL } },
        { &hf_mp4_hdlr_type,
            { "Handler type", "mp4.hdlr.type", FT_STRING,
                BASE_NONE, NULL, 0, NULL, HFILL } },
        { &hf_mp4_hdlr_name,
            { "Handler name", "mp4.hdlr.name", FT_STRINGZ,
                BASE_NONE, NULL, 0, NULL, HFILL } },
        { &hf_mp4_dref_entry_cnt,
            { "Number of entries", "mp4.dref.entry_count", FT_UINT32,
                BASE_DEC, NULL, 0, NULL, HFILL } },
        { &hf_mp4_stsd_entry_cnt,
            { "Number of entries", "mp4.stsd.entry_count", FT_UINT32,
                BASE_DEC, NULL, 0, NULL, HFILL } }
    };

    static gint *ett[] = {
        &ett_mp4,
        &ett_mp4_box
    };

    static ei_register_info ei[] = {
        { &ei_mp4_box_too_large,
            { "mp4.box_too_large", PI_PROTOCOL, PI_WARN,
                "box size too large, dissection of this box is not supported", EXPFILL }},
        { &ei_mp4_too_many_rec_lvls,
            { "mp4.too_many_levels", PI_UNDECODED, PI_WARN,
                "too many recursion levels", EXPFILL }},
        { &ei_mp4_mvhd_next_tid_unknown,
            { "mp4.mvhd.next_tid_unknown", PI_PROTOCOL, PI_CHAT,
                "Next track ID is unknown. Search for an unused track ID if you want to insert a new track.", EXPFILL }}
    };

    expert_module_t *expert_mp4;

    proto_mp4 = proto_register_protocol("MP4 / ISOBMFF file format", "mp4", "mp4");

    proto_register_field_array(proto_mp4, hf, array_length(hf));
    proto_register_subtree_array(ett, array_length(ett));
    expert_mp4 = expert_register_protocol(proto_mp4);
    expert_register_field_array(expert_mp4, ei, array_length(ei));
}

void
proto_reg_handoff_mp4(void)
{
    dissector_handle_t mp4_handle = create_dissector_handle(dissect_mp4, proto_mp4);
    dissector_add_string("media_type", "video/mp4", mp4_handle);
    dissector_add_string("media_type", "audio/mp4", mp4_handle);
}


/*
 * Editor modelines  -  http://www.wireshark.org/tools/modelines.html
 *
 * Local variables:
 * c-basic-offset: 4
 * tab-width: 8
 * indent-tabs-mode: nil
 * End:
 *
 * vi: set shiftwidth=4 tabstop=8 expandtab:
 * :indentSize=4:tabSize=8:noTabs=true:
 */
