Quelle  matroska_segment.cpp   Sprache: C

/*****************************************************************************
 * matroska_segment.cpp : matroska demuxer
 *****************************************************************************
 * Copyright (C) 2003-2010 VLC authors and VideoLAN
 *
 * Authors: Laurent Aimar <fenrir@via.ecp.fr>
 *          Steve Lhomme <steve.lhomme@free.fr>
 *
 * This program 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.
 *
 * This program 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 this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
 *****************************************************************************/

#include "matroska_segment.hpp"
#include "chapters.hpp"
#include "demux.hpp"
#include "util.hpp"
#include "Ebml_dispatcher.hpp"

#include <vlc_arrays.h>

#include <new>
#include <iterator>
#include <limits>

namespace mkv {

matroska_segment_c::matroska_segment_c( demux_sys_t & demuxer, matroska_iostream_c & estream, KaxSegment *p_seg )
    :segment(p_seg)
    ,es(estream)
    ,i_timescale(MKVD_TIMECODESCALE)
    ,i_duration(-1)
    ,i_mk_start_time(0)
    ,i_seekhead_count(0)
    ,i_seekhead_position(-1)
    ,i_cues_position(-1)
    ,i_tracks_position(-1)
    ,i_info_position(-1)
    ,i_chapters_position(-1)
    ,i_attachments_position(-1)
    ,cluster(NULL)
    ,i_block_pos(0)
    ,p_segment_uid(NULL)
    ,p_prev_segment_uid(NULL)
    ,p_next_segment_uid(NULL)
    ,b_cues(false)
    ,psz_muxing_application(NULL)
    ,psz_writing_application(NULL)
    ,psz_title(NULL)
    ,i_default_edition(0)
    ,sys(demuxer)
    ,ep( EbmlParser(&estream, p_seg, &demuxer.demuxer ))
    ,b_preloaded(false)
    ,b_ref_external_segments(false)
{
}

matroska_segment_c::~matroska_segment_c()
{
    free( psz_writing_application );
    free( psz_muxing_application );
    free( psz_title );

    delete segment;
    delete p_segment_uid;
    delete p_prev_segment_uid;
    delete p_next_segment_uid;

    vlc_delete_all( stored_editions );
    vlc_delete_all( translations );
    vlc_delete_all( families );
}


/*****************************************************************************
 * Tools                                                                     *
 *****************************************************************************
 *  * LoadCues : load the cues element and update index
 *  * LoadTags : load ... the tags element
 *  * InformationCreate : create all information, load tags if present
 *****************************************************************************/
void matroska_segment_c::LoadCues( KaxCues *cues )
{
    EbmlElement *el;

    if( b_cues )
    {
        msg_Warn( &sys.demuxer, "There can be only 1 Cues per section." );
        return;
    }

    EbmlParser eparser (&es, cues, &sys.demuxer );
    while( ( el = eparser.Get() ) != NULL )
    {
        if( MKV_IS_ID( el, KaxCuePoint ) )
        {
            uint64_t cue_position = -1;
            vlc_tick_t  cue_mk_time = -1;

            unsigned int track_id = 0;
            bool b_invalid_cue = false;

            eparser.Down();
            while( ( el = eparser.Get() ) != NULL )
            {
                if ( MKV_CHECKED_PTR_DECL( cuetime, KaxCueTime, el ) )
                {
                    try
                    {
                        if( unlikely( !cuetime->ValidateSize() ) )
                        {
                            msg_Err( &sys.demuxer, "CueTime size too big");
                            b_invalid_cue = true;
                            break;
                        }
                        cuetime->ReadData( es.I_O() );
                    }
                    catch(...)
                    {
                        msg_Err( &sys.demuxer, "Error while reading CueTime" );
                        b_invalid_cue = true;
                        break;
                    }
                    cue_mk_time = VLC_TICK_FROM_NS(static_cast<uint64_t>( *cuetime ) * i_timescale);
                }
                else if( MKV_IS_ID( el, KaxCueTrackPositions ) )
                {
                    eparser.Down();
                    try
                    {
                        while( ( el = eparser.Get() ) != NULL )
                        {
                            if( unlikely( !el->ValidateSize() ) )
                            {
                                eparser.Up();
                                msg_Err( &sys.demuxer, "Error %s too big, aborting", EBML_NAME(el) );
                                b_invalid_cue = true;
                                break;
                            }

                            if( MKV_CHECKED_PTR_DECL ( kct_ptr, KaxCueTrack, el ) )
                            {
                                kct_ptr->ReadData( es.I_O() );
                                track_id = static_cast<uint16_t>( *kct_ptr );
                            }
                            else if( MKV_CHECKED_PTR_DECL ( kccp_ptr, KaxCueClusterPosition, el ) )
                            {
                                kccp_ptr->ReadData( es.I_O() );
                                cue_position = segment->GetGlobalPosition( static_cast<uint64_t>( *kccp_ptr ) );

                                _seeker.add_cluster_position( cue_position );
                            }
                            else if( MKV_CHECKED_PTR_DECL ( kcbn_ptr, KaxCueBlockNumber, el ) )
                            {
                                VLC_UNUSED( kcbn_ptr );
                            }
#if LIBMATROSKA_VERSION >= 0x010401
                            else if( MKV_CHECKED_PTR_DECL( cuerelative, KaxCueRelativePosition, el ) )
                            {
                                VLC_UNUSED( cuerelative );
                            }
                            else if( MKV_CHECKED_PTR_DECL( cueblock, KaxCueBlockNumber, el ) )
                            {
                                VLC_UNUSED( cueblock );
                            }
                            else if( MKV_CHECKED_PTR_DECL( cueref, KaxCueReference, el ) )
                            {
                                VLC_UNUSED( cueref );
                            }
                            else if( MKV_CHECKED_PTR_DECL( cueduration, KaxCueDuration, el ) )
                            {
                                VLC_UNUSED( cueduration );
                            }
#endif
                            else
                            {
                                msg_Dbg( &sys.demuxer, "         * Unknown (%s)", EBML_NAME(el) );
                            }
                        }
                    }
                    catch(...)
                    {
                        eparser.Up();
                        msg_Err( &sys.demuxer, "Error while reading %s", EBML_NAME(el) );
                        b_invalid_cue = true;
                        break;
                    }
                    eparser.Up();
                }
                else
                {
                    msg_Dbg( &sys.demuxer, "     * Unknown (%s)", EBML_NAME(el) );
                }
            }
            eparser.Up();

            if( track_id != 0 && cue_mk_time != -1 && cue_position != static_cast<uint64_t>( -1 ) ) {

                SegmentSeeker::Seekpoint::TrustLevel level = SegmentSeeker::Seekpoint::DISABLED;

                if( ! b_invalid_cue && tracks.find( track_id ) != tracks.end() )
                {
                    level = sys.trust_cues ?
                            SegmentSeeker::Seekpoint::TRUSTED :
                            SegmentSeeker::Seekpoint::QUESTIONABLE;
                }

                _seeker.add_seekpoint( track_id,
                    SegmentSeeker::Seekpoint( cue_position, cue_mk_time, level ) );
            }
        }
        else
        {
            msg_Dbg( &sys.demuxer, " * Unknown (%s)", EBML_NAME(el) );
        }
    }
    b_cues = true;
    msg_Dbg( &sys.demuxer, "|   - loading cues done." );
}


static const struct {
    vlc_meta_type_t type;
    const char *key;
    int target_type; /* 0 is valid for all target_type */
} metadata_map[] = {
                     {vlc_meta_ShowName,    "TITLE",         70},
                     {vlc_meta_Album,       "TITLE",         50},
                     {vlc_meta_Title,       "TITLE",         30},
                     {vlc_meta_DiscNumber,  "PART_NUMBER",   60},
                     {vlc_meta_Season,      "PART_NUMBER",   60},
                     {vlc_meta_Episode,     "PART_NUMBER",   50},
                     {vlc_meta_TrackNumber, "PART_NUMBER",   30},
                     {vlc_meta_DiscTotal,   "TOTAL_PARTS",   70},
                     {vlc_meta_TrackTotal,  "TOTAL_PARTS",   30},
                     {vlc_meta_Setting,     "ENCODER_SETTINGS", 0},
                     /* TODO read TagLanguage {vlc_meta_Language} */
                     /* TODO read tags targeting attachments {vlc_meta_ArtworkURL, */
                     {vlc_meta_AlbumArtist, "ARTIST",        50},
                     {vlc_meta_Artist,      "ARTIST",        0},
                     {vlc_meta_Director,    "DIRECTOR",      0},
                     {vlc_meta_Actors,      "ACTOR",         0},
                     {vlc_meta_Genre,       "GENRE",         0},
                     {vlc_meta_Copyright,   "COPYRIGHT",     0},
                     {vlc_meta_Description, "DESCRIPTION",   0},
                     {vlc_meta_Description, "COMMENT",       0},
                     {vlc_meta_Rating,      "RATING",        0},
                     {vlc_meta_Date,        "DATE_RELEASED", 0},
                     {vlc_meta_Date,        "DATE_RELEASE",  0},
                     {vlc_meta_Date,        "DATE_RECORDED", 0},
                     {vlc_meta_URL,         "URL",           0},
                     {vlc_meta_Publisher,   "PUBLISHER",     0},
                     {vlc_meta_EncodedBy,   "ENCODED_BY",    0},
                     {vlc_meta_Album,       "ALBUM",         0}, /* invalid tag */
                     {vlc_meta_Title,       NULL,            0},
};

bool matroska_segment_c::ParseSimpleTags( SimpleTag* pout_simple, KaxTagSimple *tag, int target_type )
{
    msg_Dbg( &sys.demuxer, "|   + Simple Tag ");
    struct SimpleTagHandlerPayload
    {
        matroska_segment_c * const obj;
        EbmlParser         * const ep;
        demux_sys_t        & sys;
        SimpleTag          & out;
        int                target_type;
    } payload = { this, &ep, sys, *pout_simple, 50 };
    MKV_SWITCH_CREATE( EbmlTypeDispatcher, SimpleTagHandler, SimpleTagHandlerPayload )
    {
        MKV_SWITCH_INIT();
        E_CASE( KaxTagName, entry )
        {
            vars.out.tag_name = UTFstring( entry ).GetUTF8().c_str();
        }
        E_CASE( KaxTagString, entry )
        {
            vars.out.value = UTFstring( entry ).GetUTF8().c_str();
        }
        E_CASE( KaxTagLangue, entry )
        {
            vars.out.lang = entry.GetValue();
        }
        E_CASE( KaxTagDefault, unused )
        {
            VLC_UNUSED(unused);
            VLC_UNUSED(vars);
        }
        E_CASE( KaxTagSimple, simple )
        {
            SimpleTag st; // ParseSimpleTags will write to this variable
                          // the SimpleTag is valid if ParseSimpleTags returns `true`

            if (vars.obj->ParseSimpleTags( &st, &simple, vars.target_type ))
              vars.out.sub_tags.push_back( std::move(st) );
        }
    };
    SimpleTagHandler::Dispatcher().iterate( tag->begin(), tag->end(), &payload );

    if( pout_simple->tag_name.empty() )
    {
        msg_Warn( &sys.demuxer, "Invalid MKV SimpleTag found.");
        return false;
    }
    if( !sys.meta )
        sys.meta = vlc_meta_New();
    for( int i = 0; metadata_map[i].key; i++ )
    {
        if( pout_simple->tag_name == metadata_map[i].key &&
            (metadata_map[i].target_type == 0 || target_type == metadata_map[i].target_type ) )
        {
            vlc_meta_Set( sys.meta, metadata_map[i].type, pout_simple->value.c_str () );
            msg_Dbg( &sys.demuxer, "|   |   + Meta %s: %s", pout_simple->tag_name.c_str (), pout_simple->value.c_str ());
            goto done;
        }
    }
    msg_Dbg( &sys.demuxer, "|   |   + Meta %s: %s", pout_simple->tag_name.c_str (), pout_simple->value.c_str ());
    vlc_meta_SetExtra( sys.meta, pout_simple->tag_name.c_str (), pout_simple->value.c_str ());
done:
    return true;
}

void matroska_segment_c::LoadTags( KaxTags *tags_ )
{
    if ( !ReadMaster( *tags_ ) )
        return;

    struct TagsHandlerPayload
    {
        matroska_segment_c * const obj;
        EbmlParser         * const ep;
        demux_sys_t        & sys;
        int                target_type;
    } payload = { this, &ep, sys, 50 };
    MKV_SWITCH_CREATE( EbmlTypeDispatcher, KaxTagsHandler, TagsHandlerPayload )
    {
        MKV_SWITCH_INIT();
        E_CASE( KaxTag, entry )
        {
            msg_Dbg( &vars.sys.demuxer, "+ Tag" );
            Tag tag;
            struct TagHandlerPayload
            {
                matroska_segment_c * const obj;
                EbmlParser         * const ep;
                demux_sys_t        & sys;
                Tag                & tag;
                int                target_type;
            } payload = { vars.obj, vars.ep, vars.sys, tag, 50 };
            MKV_SWITCH_CREATE( EbmlTypeDispatcher, TagHandler, TagHandlerPayload )
            {
                MKV_SWITCH_INIT();
                E_CASE( KaxTagTargets, targets )
                {
                    msg_Dbg( &vars.sys.demuxer, "|   + Targets" );

                    MKV_SWITCH_CREATE( EbmlTypeDispatcher, TargetsHandler, TagHandlerPayload )
                    {
                        MKV_SWITCH_INIT();
                        E_CASE( KaxTagTargetTypeValue, entry )
                        {
                            vars.target_type = static_cast<uint32_t>( entry );
                            msg_Dbg( &vars.sys.demuxer, "|   |   + TargetTypeValue: %u", vars.target_type);
                        }
                        E_CASE( KaxTagTrackUID, entry )
                        {
                            vars.tag.i_tag_type = TRACK_UID;
                            vars.tag.i_uid = static_cast<uint64_t>( entry );
                            msg_Dbg( &vars.sys.demuxer, "|   |   + TrackUID: %" PRIu64, vars.tag.i_uid);
                        }
                        E_CASE( KaxTagEditionUID, entry )
                        {
                            vars.tag.i_tag_type = EDITION_UID;
                            vars.tag.i_uid = static_cast<uint64_t>( entry );
                            msg_Dbg( &vars.sys.demuxer, "|   |   + EditionUID: %" PRIu64, vars.tag.i_uid);
                        }
                        E_CASE( KaxTagChapterUID, entry )
                        {
                            vars.tag.i_tag_type = CHAPTER_UID;
                            vars.tag.i_uid = static_cast<uint64_t>( entry );
                            msg_Dbg( &vars.sys.demuxer, "|   |   + ChapterUID: %" PRIu64, vars.tag.i_uid);
                        }
                        E_CASE( KaxTagAttachmentUID, entry )
                        {
                            vars.tag.i_tag_type = ATTACHMENT_UID;
                            vars.tag.i_uid = static_cast<uint64_t>( entry );
                            msg_Dbg( &vars.sys.demuxer, "|   |   + AttachmentUID: %" PRIu64, vars.tag.i_uid);
                        }
                        E_CASE( KaxTagTargetType, entry )
                        {
                            msg_Dbg( &vars.sys.demuxer, "|   |   + TargetType: %s", entry.GetValue().c_str());
                        }
                        E_CASE_DEFAULT( el )
                        {
                            msg_Dbg( &vars.sys.demuxer, "|   |   + Unknown (%s)", EBML_NAME(&el) );
                        }
                    };

                    TargetsHandler::Dispatcher().iterate( targets.begin(), targets.end(), &vars );
                }
                E_CASE( KaxTagSimple, entry )
                {
                    SimpleTag simple;

                    if (vars.obj->ParseSimpleTags( &simple, &entry, vars.target_type ))
                        vars.tag.simple_tags.push_back( std::move(simple) );
                }
                E_CASE_DEFAULT( el )
                {
                    msg_Dbg( &vars.sys.demuxer, "|   |   + Unknown (%s)", EBML_NAME(&el) );
                }
            };

            TagHandler::Dispatcher().iterate( entry.begin(), entry.end(), &payload );
            vars.obj->tags.push_back(std::move(tag));
        }
        E_CASE_DEFAULT( el )
        {
            msg_Dbg( &vars.sys.demuxer, "|   + LoadTag Unknown (%s)", EBML_NAME(&el) );
        }
    };

    KaxTagsHandler::Dispatcher().iterate( tags_->begin(), tags_->end(), &payload );
    msg_Dbg( &sys.demuxer, "loading tags done." );
}

/*****************************************************************************
 * InformationCreate:
 *****************************************************************************/
void matroska_segment_c::InformationCreate( )
{
    if( !sys.meta )
        sys.meta = vlc_meta_New();

    if( psz_title )
    {
        vlc_meta_SetTitle( sys.meta, psz_title );
    }
}


/*****************************************************************************
 * Misc
 *****************************************************************************/

bool matroska_segment_c::PreloadClusters(uint64_t i_cluster_pos)
{
    struct ClusterHandlerPayload
    {
        matroska_segment_c * const obj;
        bool stop_parsing;

    } payload = { this, false };

    MKV_SWITCH_CREATE(EbmlTypeDispatcher, ClusterHandler, ClusterHandlerPayload )
    {
        MKV_SWITCH_INIT();

        E_CASE( KaxCluster, kcluster )
        {
            vars.obj->ParseCluster( &kcluster, false );
        }

        E_CASE_DEFAULT( el )
        {
            VLC_UNUSED( el );
            vars.stop_parsing = true;
        }
    };

    {
        es.I_O().setFilePointer( i_cluster_pos );

        while (payload.stop_parsing == false)
        {
            EbmlParser parser ( &es, segment, &sys.demuxer );
            EbmlElement* el = parser.Get();

            if( el == NULL )
                break;

            ClusterHandler::Dispatcher().send( el, &payload );
        }
    }

    return true;
}

bool matroska_segment_c::PreloadFamily( const matroska_segment_c & of_segment )
{
    if ( b_preloaded )
        return false;

    if ( SameFamily( of_segment ) )
        return Preload( );

    return false;
}

bool matroska_segment_c::CompareSegmentUIDs( const matroska_segment_c * p_item_a, const matroska_segment_c * p_item_b )
{
    EbmlBinary *p_tmp;

    if ( p_item_a == NULL || p_item_b == NULL )
        return false;

    p_tmp = static_cast<EbmlBinary *>( p_item_a->p_segment_uid );
    if ( !p_tmp )
        return false;
    if ( p_item_b->p_prev_segment_uid != NULL
          && *p_tmp == *p_item_b->p_prev_segment_uid )
        return true;

    p_tmp = static_cast<EbmlBinary *>( p_item_a->p_next_segment_uid );
    if ( !p_tmp )
        return false;

    if ( p_item_b->p_segment_uid != NULL
          && *p_tmp == *p_item_b->p_segment_uid )
        return true;

    if ( p_item_b->p_prev_segment_uid != NULL
          && *p_tmp == *p_item_b->p_prev_segment_uid )
        return true;

    return false;
}

bool matroska_segment_c::SameFamily( const matroska_segment_c & of_segment ) const
{
    for (size_t i=0; i<families.size(); i++)
    {
        for (size_t j=0; j<of_segment.families.size(); j++)
        {
            if ( *(families[i]) == *(of_segment.families[j]) )
                return true;
        }
    }
    return false;
}

bool matroska_segment_c::Preload( )
{
    if ( b_preloaded )
        return false;

    EbmlElement *el = NULL;

    ep.Reset( &sys.demuxer );

    while( ( el = ep.Get() ) != NULL )
    {
        if( MKV_IS_ID( el, KaxSeekHead ) )
        {
            /* Multiple allowed */
            /* We bail at 10, to prevent possible recursion */
            msg_Dbg(  &sys.demuxer, "|   + Seek head" );
            if( i_seekhead_count < 10 )
            {
                i_seekhead_position = el->GetElementPosition();
                ParseSeekHead( static_cast<KaxSeekHead*>( el ) );
            }
        }
        else if( MKV_IS_ID( el, KaxInfo ) )
        {
            /* Multiple allowed, mandatory */
            msg_Dbg(  &sys.demuxer, "|   + Information" );
            if( i_info_position < 0 )
            {
                ParseInfo( static_cast<KaxInfo*>( el ) );
                i_info_position = el->GetElementPosition();
            }
        }
        else if( MKV_CHECKED_PTR_DECL ( kt_ptr, KaxTracks, el ) )
        {
            /* Multiple allowed */
            msg_Dbg(  &sys.demuxer, "|   + Tracks" );
            if( i_tracks_position < 0 )
            {
                ParseTracks( kt_ptr );
            }
            if ( tracks.size() == 0 )
            {
                msg_Err( &sys.demuxer, "No tracks supported" );
            }
            i_tracks_position = el->GetElementPosition();
        }
        else if( MKV_CHECKED_PTR_DECL ( cues, KaxCues, el ) )
        {
            msg_Dbg(  &sys.demuxer, "|   + Cues" );
            if( i_cues_position < 0 )
            {
                LoadCues( cues );
                i_cues_position = el->GetElementPosition();
            }
        }
        else if( MKV_CHECKED_PTR_DECL ( cluster_, KaxCluster, el ) )
        {
            if( sys.b_seekable &&
                var_InheritBool( &sys.demuxer, "mkv-preload-clusters" ) )
            {
                PreloadClusters        ( cluster_->GetElementPosition() );
                es.I_O().setFilePointer( cluster_->GetElementPosition() );
            }
            msg_Dbg( &sys.demuxer, "|   + Cluster" );


            if (EnsureDuration(*cluster_))
            {
                cluster = cluster_;

                // add first cluster as trusted seekpoint for all tracks
                for( tracks_map_t::const_iterator it = tracks.begin();
                     it != tracks.end(); ++it )
                {
                    _seeker.add_seekpoint( it->first,
                    SegmentSeeker::Seekpoint( cluster->GetElementPosition(), -1,
                                              SegmentSeeker::Seekpoint::TrustLevel::QUESTIONABLE ) );
                }

                /* stop pre-parsing the stream */
                break;
            }
        }
        else if( MKV_CHECKED_PTR_DECL ( ka_ptr, KaxAttachments, el ) )
        {
            msg_Dbg( &sys.demuxer, "|   + Attachments" );
            if( i_attachments_position < 0 )
            {
                ParseAttachments( ka_ptr );
                i_attachments_position = el->GetElementPosition();
            }
        }
        else if( MKV_CHECKED_PTR_DECL ( chapters, KaxChapters, el ) )
        {
            msg_Dbg( &sys.demuxer, "|   + Chapters" );
            if( i_chapters_position < 0 )
            {
                ParseChapters( chapters );
                i_chapters_position = el->GetElementPosition();
            }
        }
        else if( MKV_CHECKED_PTR_DECL ( tags_, KaxTags, el ) )
        {
            msg_Dbg( &sys.demuxer, "|   + Tags" );
            if(tags.empty ())
            {
                LoadTags( tags_ );
            }
        }
        else if( MKV_IS_ID ( el, EbmlVoid ) )
            msg_Dbg( &sys.demuxer, "|   + Void" );
        else
            msg_Dbg( &sys.demuxer, "|   + Preload Unknown (%s)", EBML_NAME(el) );
    }

    ComputeTrackPriority();

    b_preloaded = true;

    return true;
}

/* Here we try to load elements that were found in Seek Heads, but not yet parsed */
bool matroska_segment_c::LoadSeekHeadItem( const EbmlCallbacks & ClassInfos, int64_t i_element_position )
{
    int64_t     i_sav_position = static_cast<int64_t>( es.I_O().getFilePointer() );
    EbmlElement *el;

    es.I_O().setFilePointer( i_element_position, seek_beginning );
    el = es.FindNextID( ClassInfos, 0xFFFFFFFFL);

    if( el == nullptr || el->IsDummy() )
    {
        msg_Err( &sys.demuxer, "cannot load some cues/chapters/tags etc. (broken seekhead or file)" );
        es.I_O().setFilePointer( i_sav_position, seek_beginning );
        delete el;
        return false;
    }

    if( MKV_CHECKED_PTR_DECL ( ksh_ptr, KaxSeekHead, el ) )
    {
        /* Multiple allowed */
        msg_Dbg( &sys.demuxer, "|   + Seek head" );
        if( i_seekhead_count < 10 )
        {
            if ( i_seekhead_position != i_element_position )
            {
                i_seekhead_position = i_element_position;
                ParseSeekHead( ksh_ptr );
            }
        }
    }
    else if( MKV_CHECKED_PTR_DECL ( ki_ptr, KaxInfo, el ) ) // FIXME
    {
        /* Multiple allowed, mandatory */
        msg_Dbg( &sys.demuxer, "|   + Information" );
        if( i_info_position < 0 )
        {
            ParseInfo( ki_ptr );
            i_info_position = i_element_position;
        }
    }
    else if( MKV_CHECKED_PTR_DECL ( kt_ptr, KaxTracks, el ) ) // FIXME
    {
        /* Multiple allowed */
        msg_Dbg( &sys.demuxer, "|   + Tracks" );
        if( i_tracks_position < 0 )
            ParseTracks( kt_ptr );
        if ( tracks.size() == 0 )
        {
            msg_Err( &sys.demuxer, "No tracks supported" );
            delete el;
            es.I_O().setFilePointer( i_sav_position, seek_beginning );
            return false;
        }
        i_tracks_position = i_element_position;
    }
    else if( MKV_CHECKED_PTR_DECL ( kc_ptr, KaxCues, el ) )
    {
        msg_Dbg( &sys.demuxer, "|   + Cues" );
        if( i_cues_position < 0 )
        {
            LoadCues( kc_ptr );
            i_cues_position = i_element_position;
        }
    }
    else if( MKV_CHECKED_PTR_DECL ( ka_ptr, KaxAttachments, el ) )
    {
        msg_Dbg( &sys.demuxer, "|   + Attachments" );
        if( i_attachments_position < 0 )
        {
            ParseAttachments( ka_ptr );
            i_attachments_position = i_element_position;
        }
    }
    else if( MKV_CHECKED_PTR_DECL ( chapters, KaxChapters, el ) )
    {
        msg_Dbg( &sys.demuxer, "|   + Chapters" );
        if( i_chapters_position < 0 )
        {
            ParseChapters( chapters );
            i_chapters_position = i_element_position;
        }
    }
    else if( MKV_CHECKED_PTR_DECL ( tags_, KaxTags, el ) )
    {
        msg_Dbg( &sys.demuxer, "|   + Tags" );
        if(tags.empty ())
        {
            LoadTags( tags_ );
        }
    }
    else
    {
        msg_Dbg( &sys.demuxer, "|   + LoadSeekHeadItem Unknown (%s)", EBML_NAME(el) );
    }
    delete el;

    es.I_O().setFilePointer( i_sav_position, seek_beginning );
    return true;
}

bool matroska_segment_c::Seek( demux_t &demuxer, vlc_tick_t i_absolute_mk_date, vlc_tick_t i_mk_time_offset, bool b_accurate )
{
    SegmentSeeker::tracks_seekpoint_t seekpoints;

    SegmentSeeker::fptr_t i_seek_position = std::numeric_limits<SegmentSeeker::fptr_t>::max();
    vlc_tick_t i_mk_seek_time = -1;
    vlc_tick_t i_mk_date = i_absolute_mk_date - i_mk_time_offset;
    SegmentSeeker::track_ids_t selected_tracks;
    SegmentSeeker::track_ids_t priority;

    // reset information for all tracks //

    for( tracks_map_t::iterator it = tracks.begin(); it != tracks.end(); ++it )
    {
        mkv_track_t &track = *it->second;

        track.i_skip_until_fpos = std::numeric_limits<uint64_t>::max();
        if( track.i_last_dts != VLC_TICK_INVALID )
            track.b_discontinuity = true;
        track.i_last_dts        = VLC_TICK_INVALID;

        bool selected;
        if (track.p_es == NULL)
            selected = false;
        else
            es_out_Control( demuxer.out, ES_OUT_GET_ES_STATE, track.p_es, &selected );
        if ( selected )
            selected_tracks.push_back( track.i_number );
    }

    if ( selected_tracks.empty() )
    {
        selected_tracks = priority_tracks;
        priority = priority_tracks;
    }
    else
    {
        std::set_intersection(priority_tracks.begin(),priority_tracks.end(),
                              selected_tracks.begin(),selected_tracks.end(),
                              std::back_inserter(priority));
        if (priority.empty()) // no video selected ?
            priority = selected_tracks;
    }

    // find appropriate seekpoints //

    try {
        seekpoints = _seeker.get_seekpoints( *this, i_mk_date, priority, selected_tracks );
    }
    catch( std::exception const& e )
    {
        msg_Err( &sys.demuxer, "error during seek: \"%s\", aborting!", e.what() );
        return false;
    }

    // initialize seek information in order to set up playback //

    for( SegmentSeeker::tracks_seekpoint_t::const_iterator it = seekpoints.begin(); it != seekpoints.end(); ++it )
    {
        tracks_map_t::iterator trackit = tracks.find( it->first );
        if ( trackit == tracks.end() )
            continue; // there were blocks with unknown tracks

        if( i_seek_position > it->second.fpos )
        {
            i_seek_position = it->second.fpos;
            i_mk_seek_time  = it->second.pts;
        }

        // blocks that will be not be read until this fpos
        if ( b_accurate )
            trackit->second->i_skip_until_fpos = it->second.fpos;
        else
            trackit->second->i_skip_until_fpos = std::numeric_limits<uint64_t>::max();
        if (it->second.pts != -1)
            trackit->second->i_last_dts        = it->second.pts + i_mk_time_offset;

        msg_Dbg( &sys.demuxer, "seek: preroll{ track: %u, pts: %" PRId64 ", fpos: %" PRIu64 " skip: %" PRIu64 "} ",
          it->first, it->second.pts, it->second.fpos, trackit->second->i_skip_until_fpos );
    }

    if ( i_seek_position == std::numeric_limits<SegmentSeeker::fptr_t>::max() )
        return false;

    // propagate seek information //

    sys.i_pcr           = VLC_TICK_INVALID;
    sys.i_pts           = VLC_TICK_0 + i_mk_seek_time + i_mk_time_offset;
    if (b_accurate)
        sys.i_start_pts = VLC_TICK_0 + i_absolute_mk_date;
    else
        sys.i_start_pts = sys.i_pts;

    // make the jump //

    _seeker.mkv_jump_to( *this, i_seek_position );

    // debug diagnostics //

    msg_Dbg( &sys.demuxer, "seek: preroll{ req: %" PRId64 ", start-pts: %" PRId64 ", start-fpos: %" PRIu64 "} ",
      sys.i_start_pts, sys.i_pts, i_seek_position );

    // blocks that will be read and decoded but discarded until this pts
    es_out_Control( sys.demuxer.out, ES_OUT_SET_NEXT_DISPLAY_TIME, sys.i_start_pts );
    return true;
}


mkv_track_t * matroska_segment_c::FindTrackByBlock(
                                             const KaxBlock *p_block, const KaxSimpleBlock *p_simpleblock )
{
    tracks_map_t::iterator track_it;

    if (p_block != NULL)
        track_it = tracks.find( p_block->TrackNum() );
    else if( p_simpleblock != NULL)
        track_it = tracks.find( p_simpleblock->TrackNum() );
    else
        track_it = tracks.end();

    if (track_it == tracks.end())
        return NULL;

    return track_it->second.get();
}

void matroska_segment_c::ComputeTrackPriority()
{
    bool b_has_default_video = false;
    bool b_has_default_audio = false;
    /* check for default */
    for( tracks_map_t::const_iterator it = tracks.begin(); it != tracks.end();
         ++it )
    {
        mkv_track_t &track = *it->second;

        bool flag = track.b_enabled && ( track.b_default || track.b_forced );

        switch( track.fmt.i_cat )
        {
            case VIDEO_ES: b_has_default_video |= flag; break;
            case AUDIO_ES: b_has_default_audio |= flag; break;
            default: break; // ignore
        }
    }

    for( tracks_map_t::iterator it = tracks.begin(); it != tracks.end(); ++it )
    {
        tracks_map_t::key_type track_id = it->first;
        mkv_track_t          & track    = *it->second;

        if( unlikely( track.fmt.i_cat == UNKNOWN_ES || track.codec.empty() ) )
        {
            msg_Warn( &sys.demuxer, "invalid track[%d]", static_cast<int>( track_id ) );
            track.p_es = NULL;
            continue;
        }
        else if( unlikely( !b_has_default_video && track.fmt.i_cat == VIDEO_ES ) )
        {
            track.b_default = true;
            b_has_default_video = true;
        }
        else if( unlikely( !b_has_default_audio &&  track.fmt.i_cat == AUDIO_ES ) )
        {
            track.b_default = true;
            b_has_default_audio = true;
        }
        if( unlikely( !track.b_enabled ) )
            track.fmt.i_priority = ES_PRIORITY_NOT_SELECTABLE;
        else if( track.b_forced )
            track.fmt.i_priority = ES_PRIORITY_SELECTABLE_MIN + 2;
        else if( track.b_default )
            track.fmt.i_priority = ES_PRIORITY_SELECTABLE_MIN + 1;
        else
            track.fmt.i_priority = ES_PRIORITY_SELECTABLE_MIN;

        /* Avoid multivideo tracks when unnecessary */
        if( track.fmt.i_cat == VIDEO_ES )
            track.fmt.i_priority--;
    }

    // find track(s) with highest priority //
    {
        int   score = -1;
        int es_type = -1;

        for( tracks_map_t::const_iterator it = this->tracks.begin(); it != this->tracks.end(); ++it )
        {
            int track_score = -1;

            switch( it->second->fmt.i_cat )
            {
                case VIDEO_ES: ++track_score;
                /* fallthrough */
                case AUDIO_ES: ++track_score;
                /* fallthrough */
                case   SPU_ES: ++track_score;
                /* fallthrough */
                default:
                  if( score < track_score )
                  {
                      es_type = it->second->fmt.i_cat;
                      score   = track_score;
                  }
            }
        }

        for( tracks_map_t::const_iterator it = this->tracks.begin(); it != this->tracks.end(); ++it )
        {
            if( it->second->fmt.i_cat == es_type )
                priority_tracks.push_back( it->first );
        }
    }
}

bool matroska_segment_c::EnsureDuration(KaxCluster & fromCluster)
{
    if ( i_duration > 0 )
        return true;

    i_duration = -1;

    if( !sys.b_fastseekable )
    {
        msg_Warn( &sys.demuxer, "could not look for the segment duration" );
        return true;
    }

    uint64_t i_current_position = es.I_O().getFilePointer();
    uint64_t i_last_cluster_pos = fromCluster.GetElementPosition();

    // find the last Cluster from the Cues

    if ( b_cues && _seeker._cluster_positions.size() )
        i_last_cluster_pos = *_seeker._cluster_positions.rbegin();
    else if( !fromCluster.IsFiniteSize() )
    {
        // make sure our first Cluster has a timestamp
        return ParseCluster( &fromCluster, false, SCOPE_PARTIAL_DATA );
    }

    es.I_O().setFilePointer( i_last_cluster_pos, seek_beginning );

    EbmlParser eparser ( &es, segment, &sys.demuxer );

    // locate the definitely last cluster in the stream

    while( EbmlElement* el = eparser.Get() )
    {
        if( !el->IsFiniteSize() && el->GetElementPosition() != i_last_cluster_pos )
        {
            es.I_O().setFilePointer( i_current_position, seek_beginning );
            return true;
        }

        if( MKV_IS_ID( el, KaxCluster ) )
        {
            i_last_cluster_pos = el->GetElementPosition();
            if ( i_last_cluster_pos == fromCluster.GetElementPosition() )
            {
                // make sure our first Cluster has a timestamp
                if (!ParseCluster( &fromCluster, true, SCOPE_PARTIAL_DATA ))
                    return false;
            }
        }
    }

    // find the last timecode in the Cluster

    eparser.Reset( &sys.demuxer );
    es.I_O().setFilePointer( i_last_cluster_pos, seek_beginning );

    EbmlElement* el = eparser.Get();
    MKV_CHECKED_PTR_DECL( p_last_cluster, KaxCluster, el );

    if( p_last_cluster &&
        ParseCluster( p_last_cluster, false, SCOPE_PARTIAL_DATA ) )
    {
        // use the last block + duration
        uint64_t i_last_timecode = p_last_cluster->GlobalTimestamp();
        for (auto l : *p_last_cluster)
        {
            if( MKV_CHECKED_PTR_DECL ( simpleblock, KaxSimpleBlock, l ) )
            {
                simpleblock->SetParent( *p_last_cluster );
                i_last_timecode = std::max(i_last_timecode, simpleblock->GlobalTimestamp());
            }
            else if( MKV_CHECKED_PTR_DECL_CONST ( group, KaxBlockGroup, l ) )
            {
                uint64_t i_group_timecode = 0;
                for (auto g : *group)
                {
                    if( MKV_CHECKED_PTR_DECL ( block, KaxBlock, g ) )
                    {
                        block->SetParent( *p_last_cluster );
                        i_group_timecode += block->GlobalTimestamp();
                    }
                    else if( MKV_CHECKED_PTR_DECL_CONST ( kbd_ptr, KaxBlockDuration, g ) )
                    {
                        i_group_timecode += static_cast<uint64_t>( *kbd_ptr );
                    }
                }
                i_last_timecode = std::max(i_last_timecode, i_group_timecode);
            }
        }

        i_duration = VLC_TICK_FROM_NS( i_last_timecode - fromCluster.GlobalTimestamp() );
        msg_Dbg( &sys.demuxer, " extracted Duration=%" PRId64, SEC_FROM_VLC_TICK(i_duration) );
    }

    // get back to the reading position we were at before looking for a duration
    es.I_O().setFilePointer( i_current_position, seek_beginning );
    return true;
}

bool matroska_segment_c::ESCreate()
{
    /* add all es */
    msg_Dbg( &sys.demuxer, "found %d es", static_cast<int>( tracks.size() ) );

    mkv_track_t *default_tracks[ES_CATEGORY_COUNT] = {};
    for( tracks_map_t::iterator it = tracks.begin(); it != tracks.end(); ++it )
    {
        tracks_map_t::key_type   track_id = it->first;
        mkv_track_t            & track    = *it->second;

        if( unlikely( track.fmt.i_cat == UNKNOWN_ES || track.codec.empty() ) )
        {
            msg_Warn( &sys.demuxer, "invalid track[%d]", static_cast<int>( track_id ) );
            track.p_es = NULL;
            continue;
        }
        track.fmt.i_id = static_cast<int>( track_id );

        if( !track.p_es )
        {
            track.p_es = es_out_Add( sys.demuxer.out, &track.fmt );

            if( track.p_es &&
                !sys.ev.AddTrack( track ) )
            {
                msg_Warn( &sys.demuxer, "Could not register events, interactive menus will not work");
            }
        }

        /* Turn on a subtitles track if it has been flagged as default -
         * but only do this if no subtitles track has already been engaged,
         * either by an earlier 'default track' (??) or by default
         * language choice behaviour.
         */
        if( track.b_default || track.b_forced )
        {
            mkv_track_t *&default_track = default_tracks[track.fmt.i_cat];
            if( !default_track || track.b_default )
                default_track = &track;
        }
    }

    for( mkv_track_t *track : default_tracks )
    {
        if( track )
            es_out_Control( sys.demuxer.out, ES_OUT_SET_ES_DEFAULT, track->p_es );
    }

    return true;
}

void matroska_segment_c::ESDestroy( )
{
    sys.ev.AbortThread();

    for( tracks_map_t::iterator it = tracks.begin(); it != tracks.end(); ++it )
    {
        mkv_track_t & track = *it->second;

        if( track.p_es != NULL )
        {
            es_out_Del( sys.demuxer.out, track.p_es );
            sys.ev.DelTrack( track );
            track.p_es = NULL;
        }
    }
}

int matroska_segment_c::BlockGet( KaxBlock * & pp_block, KaxSimpleBlock * & pp_simpleblock,
                                  KaxBlockAdditions * & pp_additions,
                                  bool *pb_key_picture, bool *pb_discardable_picture,
                                  uint64_t *pi_duration )
{
    pp_simpleblock = NULL;
    pp_block = NULL;
    pp_additions = NULL;

    *pb_key_picture         = true;
    *pb_discardable_picture = false;
    *pi_duration = 0;

    uint64_t duration = 0;
    int64_t duration_padding = 0;

    struct BlockPayload {
        matroska_segment_c * const obj;
        EbmlParser         * const ep;
        demux_t            * const p_demuxer;
        KaxBlock          *& block;
        KaxSimpleBlock    *& simpleblock;
        KaxBlockAdditions *& additions;

        uint64_t           & i_duration;
        int64_t            & duration_padding;
        bool               & b_key_picture;
        bool               & b_discardable_picture;
        bool                 b_cluster_timecode;

    } payload = {
        this, &ep, &sys.demuxer, pp_block, pp_simpleblock, pp_additions,
        duration, duration_padding, *pb_key_picture, *pb_discardable_picture, true
    };

    MKV_SWITCH_CREATE( EbmlTypeDispatcher, BlockGetHandler_l1, BlockPayload )
    {
        MKV_SWITCH_INIT();

        E_CASE( KaxCluster, kcluster )
        {
            vars.obj->cluster = &kcluster;
            vars.b_cluster_timecode = false;
            vars.ep->Down ();
        }
        E_CASE( KaxCues, kcue )
        {
            VLC_UNUSED( kcue );
            msg_Warn( vars.p_demuxer, "find KaxCues FIXME" );
        }
        E_CASE_DEFAULT(element)
        {
            msg_Dbg( vars.p_demuxer, "Unknown (%s)", EBML_NAME(&element) );
        }
    };

    MKV_SWITCH_CREATE( EbmlTypeDispatcher, BlockGetHandler_l2, BlockPayload )
    {
        MKV_SWITCH_INIT();

        E_CASE( KaxClusterTimestamp, ktimecode )
        {
            ktimecode.ReadData( vars.obj->es.I_O(), SCOPE_ALL_DATA );
            vars.obj->cluster->InitTimestamp( static_cast<uint64_t>( ktimecode ), vars.obj->i_timescale );
            vars.obj->_seeker.add_cluster( vars.obj->cluster );
            vars.b_cluster_timecode = true;
        }
        E_CASE( KaxClusterSilentTracks, ksilent )
        {
            vars.ep->Down ();

            VLC_UNUSED( ksilent );
        }
        E_CASE( KaxBlockGroup, kbgroup )
        {
            if( vars.b_cluster_timecode == false )
            {
                msg_Warn( vars.p_demuxer, "ignoring KaxBlockGroup prior to mandatory Timecode" );
                return;
            }

            vars.obj->i_block_pos = kbgroup.GetElementPosition();
            vars.ep->Down ();
        }
        E_CASE( KaxSimpleBlock, ksblock )
        {
            if( vars.b_cluster_timecode == false )
            {
                msg_Warn( vars.p_demuxer, "ignoring SimpleBlock prior to mandatory Timecode" );
                return;
            }

            filepos_t read = 0;
            try {
                read = ksblock.ReadData( vars.obj->es.I_O() );
            } catch(...) {
            }
            if (read == 0 && ksblock.GetSize() != 0) {
                msg_Err( vars.p_demuxer,"Error while reading %s",  EBML_NAME(&ksblock) );
                ksblock.ReleaseFrames();
                return;
            }
            vars.simpleblock = &ksblock;
            vars.simpleblock->SetParent( *vars.obj->cluster );

            if( ksblock.IsKeyframe() )
            {
                bool const b_valid_track = vars.obj->FindTrackByBlock( NULL, &ksblock ) != NULL;
                if (b_valid_track)
                    vars.obj->_seeker.add_seekpoint( ksblock.TrackNum(),
                        SegmentSeeker::Seekpoint( ksblock.GetElementPosition(), VLC_TICK_FROM_NS(ksblock.GlobalTimestamp()) ) );
            }
        }
    };

    MKV_SWITCH_CREATE( EbmlTypeDispatcher, BlockGetHandler_l3, BlockPayload )
    {
        MKV_SWITCH_INIT();

        E_CASE( KaxBlock, kblock )
        {
            filepos_t read = 0;
            try {
                read = kblock.ReadData( vars.obj->es.I_O() );
            } catch(...) {
            }
            if (unlikely(read == 0) && kblock.GetSize() != 0) {
                msg_Err( vars.p_demuxer,"Error while reading %s",  EBML_NAME(&kblock) );
                kblock.ReleaseFrames();
                return;
            }
            vars.block = &kblock;
            vars.block->SetParent( *vars.obj->cluster );

            const mkv_track_t *p_track = vars.obj->FindTrackByBlock( &kblock, NULL );
            if( p_track != NULL && p_track->fmt.i_cat == SPU_ES )
            {
                vars.obj->_seeker.add_seekpoint( kblock.TrackNum(),
                    SegmentSeeker::Seekpoint( kblock.GetElementPosition(), VLC_TICK_FROM_NS(kblock.GlobalTimestamp()) ) );
            }

            vars.ep->Keep ();
        }
        E_CASE( KaxBlockAdditions, kadditions )
        {
            if ( vars.obj->ReadMaster( kadditions ) )
            {
                vars.additions = &kadditions;
                vars.ep->Keep ();
            }
        }
        E_CASE( KaxBlockDuration, kduration )
        {
            kduration.ReadData( vars.obj->es.I_O() );
            vars.i_duration = static_cast<uint64_t>( kduration );
        }
        E_CASE( KaxReferenceBlock, kreference )
        {
           kreference.ReadData( vars.obj->es.I_O() );

           if( vars.b_key_picture )
               vars.b_key_picture = false;
           else if( static_cast<int64_t>( kreference ) )
               vars.b_discardable_picture = true;
        }
        E_CASE( KaxClusterSilentTrackNumber, kstrackn )
        {
            VLC_UNUSED( kstrackn );
            VLC_UNUSED( vars );
        }
#if LIBMATROSKA_VERSION >= 0x010401
        E_CASE( KaxDiscardPadding, kdiscardp )
        {
            kdiscardp.ReadData( vars.obj->es.I_O() );
            vars.duration_padding = static_cast<int64_t>( kdiscardp );
        }
#endif
        E_CASE_DEFAULT( element )
        {
            VLC_UNUSED(element);

            msg_Warn( vars.p_demuxer, "unknown element at { fpos: %" PRId64 ", '%s' }",
              element.GetElementPosition(), EBML_NAME( &element ) );
        }
    };

    static EbmlTypeDispatcher const * const dispatchers[] = {
        &BlockGetHandler_l1::Dispatcher(),
        &BlockGetHandler_l2::Dispatcher(),
        &BlockGetHandler_l3::Dispatcher()
    };

    for( ;; )
    {
        EbmlElement *el = NULL;
        int         i_level;

        if( pp_simpleblock != NULL || ((el = ep.Get()) == NULL && pp_block != NULL) )
        {
            /* Check blocks validity to protect against broken files */
            const mkv_track_t *p_track = FindTrackByBlock( pp_block , pp_simpleblock );
            if( p_track == NULL )
            {
                ep.Unkeep();
                pp_simpleblock = NULL;
                pp_block = NULL;
                continue;
            }
            if( pp_simpleblock != NULL )
            {
                *pb_key_picture         = pp_simpleblock->IsKeyframe();
                *pb_discardable_picture = pp_simpleblock->IsDiscardable();
            }
            /* We have block group let's check if the picture is a keyframe */
            else if( *pb_key_picture )
            {
                if( p_track->fmt.i_codec == VLC_CODEC_THEORA )
                {
                    DataBuffer *    p_data = &pp_block->GetBuffer(0);
                    const uint8_t * p_buff = p_data->Buffer();
                    /* if the second bit of a Theora frame is 1
                       it's not a keyframe */
                    if( p_data->Size() && p_buff )
                    {
                        if( p_buff[0] & 0x40 )
                            *pb_key_picture = false;
                    }
                    else
                        *pb_key_picture = false;
                }
            }

            /* A negative DiscardPadding designates padding at the start of
             * the block, which we don't handle; some files in the wild also
             * carry bogus negative values due to encoder bugs. Never let it
             * extend the block duration. */
            if ( duration_padding < 0)
            {
                msg_Warn( &sys.demuxer, "ignoring negative DiscardPadding (%" PRId64 ")", duration_padding );
                *pi_duration = duration;
            }
            else if( duration < (uint64_t)duration_padding )
                *pi_duration = 0;
            else
                *pi_duration = duration - duration_padding;

            return VLC_SUCCESS;
        }

        i_level = ep.GetLevel();

        if( el == NULL )
        {
            if( i_level > 1 )
            {
                ep.Up();
                continue;
            }
            msg_Warn( &sys.demuxer, "EOF" );
            return VLC_EGENERIC;
        }

        /* Verify that we are still inside our cluster
         * It can happens with broken files and when seeking
         * without index */
        if( i_level > 1 )
        {
            if( cluster && !ep.IsTopPresent( cluster ) )
            {
                msg_Warn( &sys.demuxer, "Unexpected escape from current cluster" );
                cluster = NULL;
            }
            if( !cluster )
                continue;
        }

        /* do parsing */

        try {
            switch( i_level )
            {
                case 2:
                /* fallthrough */
                case 3:
                    if( unlikely( !el->ValidateSize() || ( el->IsFiniteSize() && el->GetSize() >= SIZE_MAX ) ) )
                    {
                        msg_Err( &sys.demuxer, "Error while reading %s... upping level", EBML_NAME(el));
                        ep.Up();

                        if ( i_level == 2 )
                            break;

                        ep.Unkeep();
                        pp_simpleblock = NULL;
                        pp_block = NULL;

                        break;
                    }
                    /* fallthrough */
                case 1:
                    {
                        EbmlTypeDispatcher const * dispatcher = dispatchers[i_level - 1];
                        dispatcher->send( el, &payload );
                    }
                    break;

                default:
                    msg_Err( &sys.demuxer, "invalid level = %d", i_level );
                    return VLC_EGENERIC;
            }
        }
        catch (int ret_code)
        {
            return ret_code;
        }
        catch (...)
        {
            msg_Err( &sys.demuxer, "Error while reading %s... upping level", EBML_NAME(el));
            ep.Up();
            ep.Unkeep();
            pp_simpleblock = NULL;
            pp_block = NULL;
        }
    }
}

} // namespace