dvdio.cc

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/*
 * Copyright (C) 2017-2023 Norbert Schlia (nschlia@oblivion-software.de)
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * On Debian systems, the complete text of the GNU General Public License
 * Version 3 can be found in `/usr/share/common-licenses/GPL-3'.
 */
 
#ifdef USE_LIBDVD
 
#include "dvdio.h"
#include "logging.h"
 
#include <cstring>
 
#include <dvdread/dvd_reader.h>
#include <dvdread/nav_read.h>
 
DvdIO::DvdIO()
    : m_dvd(nullptr)
    , m_dvd_title(nullptr)
    , m_vmg_file(nullptr)
    , m_vts_file(nullptr)
    , m_cur_pgc(nullptr)
    , m_start_cell(0)
    , m_end_cell(0)
    , m_cur_cell(0)
    , m_next_cell(0)
    , m_goto_next_cell(false)
    , m_cur_block(0)
    , m_is_eof(false)
    , m_errno(0)
    , m_rest_size(0)
    , m_rest_pos(0)
    , m_cur_pos(0)
    , m_full_title(false)
    , m_title_idx(0)
    , m_chapter_idx(0)
    , m_angle_idx(0)
    , m_duration(AV_NOPTS_VALUE)
    , m_size(0)
{
    std::memset(&m_data, 0, sizeof(m_data));
    std::memset(&m_buffer, 0, sizeof(m_buffer));
}
 
DvdIO::~DvdIO()
{
    pvt_close();
}
 
VIRTUALTYPE DvdIO::type() const
{
    return VIRTUALTYPE_DVD;
}
 
size_t DvdIO::bufsize() const
{
    return sizeof(m_data);
}
 
int DvdIO::openio(LPVIRTUALFILE virtualfile)
{
    int pgc_id;
    int ttn;
    int pgn;
    tt_srpt_t *tt_srpt;
    vts_ptt_srpt_t *vts_ptt_srpt;
 
    set_virtualfile(virtualfile);
 
    if (virtualfile != nullptr)
    {
        m_full_title    = virtualfile->m_full_title;
        m_title_idx     = virtualfile->m_dvd.m_title_no - 1;
        m_chapter_idx   = virtualfile->m_dvd.m_chapter_no - 1;
        m_angle_idx     = virtualfile->m_dvd.m_angle_no - 1;
        m_duration      = virtualfile->m_duration;
    }
    else
    {
        m_full_title    = false;
        m_title_idx     = 0;
        m_chapter_idx   = 0;
        m_angle_idx     = 0;
        m_duration      = AV_NOPTS_VALUE;
    }
 
    Logging::debug(path(), "Opening the input DVD.");
 
    // Open the disc.
    m_dvd = DVDOpen(path().c_str());
    if (m_dvd == nullptr)
    {
        Logging::error(path(), "Couldn't open the DVD.");
        return EINVAL;
    }
 
    // Load the video manager to find out the information about the titles on this disc.
    m_vmg_file = ifoOpen(m_dvd, 0);
    if (m_vmg_file == nullptr)
    {
        Logging::error(path(), "Can't open VMG info.");
        DVDClose(m_dvd);
        return EINVAL;
    }
    tt_srpt = m_vmg_file->tt_srpt;
 
    // Make sure our title number is valid.
    Logging::trace(path(), "There are %1 titles on this DVD.", static_cast<uint16_t>(tt_srpt->nr_of_srpts));
 
    if (m_title_idx < 0 || m_title_idx >= tt_srpt->nr_of_srpts)
    {
        Logging::error(path(), "Invalid title %1.", m_title_idx + 1);
        ifoClose(m_vmg_file);
        DVDClose(m_dvd);
        return EINVAL;
    }
 
    // Make sure the chapter number is valid for this title.
    Logging::trace(nullptr, "There are %1 chapters in this title.", static_cast<uint16_t>(tt_srpt->title[m_title_idx].nr_of_ptts));
 
    if (m_chapter_idx < 0 || m_chapter_idx >= tt_srpt->title[m_title_idx].nr_of_ptts)
    {
        Logging::error(path(), "Invalid chapter %1.", m_chapter_idx + 1);
        ifoClose(m_vmg_file);
        DVDClose(m_dvd);
        return EINVAL;
    }
 
    // Make sure the angle number is valid for this title.
    Logging::trace(path(), "There are %1 angles in this title.", tt_srpt->title[m_title_idx].nr_of_angles);
 
    if (m_angle_idx < 0 || m_angle_idx >= tt_srpt->title[m_title_idx].nr_of_angles)
    {
        Logging::error(nullptr, "Invalid angle %1.", m_angle_idx + 1);
        ifoClose(m_vmg_file);
        DVDClose(m_dvd);
        return EINVAL;
    }
 
    // Load the VTS information for the title set our title is in.
    m_vts_file = ifoOpen(m_dvd, tt_srpt->title[m_title_idx].title_set_nr);
    if (m_vts_file == nullptr)
    {
        Logging::error(path(), "Can't open the title %1 info file.", tt_srpt->title[m_title_idx].title_set_nr);
        ifoClose(m_vmg_file);
        DVDClose(m_dvd);
        return EINVAL;
    }
 
    // Determine which program chain we want to watch.  This is based on the chapter number.
    ttn                 = tt_srpt->title[m_title_idx].vts_ttn;
    vts_ptt_srpt        = m_vts_file->vts_ptt_srpt;
    pgc_id              = vts_ptt_srpt->title[ttn - 1].ptt[m_chapter_idx].pgcn;
    pgn                 = vts_ptt_srpt->title[ttn - 1].ptt[m_chapter_idx].pgn;
    m_cur_pgc           = m_vts_file->vts_pgcit->pgci_srp[pgc_id - 1].pgc;
    m_start_cell        = m_cur_pgc->program_map[pgn - 1] - 1;
 
    if (pgn < m_cur_pgc->nr_of_programs)
    {
        m_end_cell      = m_cur_pgc->program_map[pgn] - 1;
    }
    else
    {
        m_end_cell      = m_cur_pgc->nr_of_cells;
    }
 
    // We've got enough info, time to open the title set data.
    m_dvd_title = DVDOpenFile(m_dvd, tt_srpt->title[m_title_idx].title_set_nr, DVD_READ_TITLE_VOBS);
    if (m_dvd_title == nullptr)
    {
        Logging::error(path(), "Can't open title VOBS (VTS_%<%02d>1_X.VOB).", tt_srpt->title[m_title_idx].title_set_nr);
        ifoClose(m_vts_file);
        ifoClose(m_vmg_file);
        DVDClose(m_dvd);
        return EINVAL;
    }
 
    rewind();
 
    // Determine the net file size
    m_size = 0;
    size_t bytes_read;
 
    while ((bytes_read = readio(nullptr, ULONG_MAX)) != 0 && !eof())
    {
        m_size += bytes_read;
    }
 
    rewind();
 
    return 0;
}
 
// Demux and cell navigation nicked from https://www.videolan.org/vlc/download-sources.html
// More details see http://stnsoft.com/DVD/vobov.html
 
#define PS_STREAM_ID_END_STREAM         0xB9    
#define PS_STREAM_ID_PACK_HEADER        0xBA    
#define PS_STREAM_ID_SYSTEM_HEADER      0xBB    
#define PS_STREAM_ID_MAP                0xBC    
#define PS_STREAM_ID_PRIVATE_STREAM1    0xBD    
#define PS_STREAM_ID_PADDING            0xBE    
#define PS_STREAM_ID_PRIVATE            0xBF    
#define PS_STREAM_ID_AUDIO              0xC0    
#define PS_STREAM_ID_VIDEO              0xE0    
#define PS_STREAM_ID_EXTENDED           0xFD    
#define PS_STREAM_ID_DIRECTORY          0xFF    
#define PS_STREAM_ID                    3       
bool DvdIO::get_packet_size(const uint8_t *p, size_t peek, size_t *size) const
{
    if (peek < 4)
    {
        return false;   // Invalid size
    }
 
    switch (p[PS_STREAM_ID])
    {
    case PS_STREAM_ID_END_STREAM:
    {
        *size = 4;
        return true;
    }
    case PS_STREAM_ID_PACK_HEADER:
    {
        // MPEG-2 pack header, see http://stnsoft.com/DVD/packhdr.html
        if (peek > 4)
        {
            if (peek >= 14 && (p[4] >> 6) == 0x01)
            {
                *size = 14 + static_cast<size_t>(p[13] & 0x07); // Byte 13 Bit 0..2: Pack stuffing length
                return true;
            }
            else if (peek >= 12 && (p[4] >> 4) == 0x02)
            {
                *size = 12;                  // unclear what this is for
                return true;
            }
        }
        break;
    }
    case PS_STREAM_ID_SYSTEM_HEADER:        // http://stnsoft.com/DVD/sys_hdr.html, see http://stnsoft.com/DVD/sys_hdr.html
    case PS_STREAM_ID_MAP:                  // ???
    case PS_STREAM_ID_DIRECTORY:            // ???
    default:
    {
        if (peek >= 6)
        {
            *size = (6 + ((static_cast<unsigned int>(p[4]) << 8) | p[5]));  // Byte 4/5: header length
            return true;
        }
        break;
    }
    }
    return false;   // unknown ID
}
 
int DvdIO::get_pes_id(const uint8_t *buffer, size_t size) const
{
    if (buffer[PS_STREAM_ID] == PS_STREAM_ID_PRIVATE_STREAM1)
    {
        uint8_t sub_id = 0;
        if (size >= 9 && size >= static_cast<unsigned int>(9 + buffer[8]))
        {
            const size_t start = static_cast<size_t>(9 + buffer[8]);
            sub_id = buffer[start];
 
            if ((sub_id & 0xfe) == 0xa0 &&
                    size >= start + 7 &&
                    (buffer[start + 5] >= 0xc0 ||
                     buffer[start + 6] != 0x80))
            {
                // AOB LPCM/MLP extension
                // XXX for MLP I think that the !=0x80 test is not good and
                // will fail for some valid files
                return (0xa000 | (sub_id & 0x01));
            }
        }
 
        // VOB extension
        return (0xbd00 | sub_id);
    }
    else if (buffer[PS_STREAM_ID] == PS_STREAM_ID_EXTENDED &&
             size >= 9 &&
             (buffer[6] & 0xC0) == 0x80 &&    // mpeg2
             (buffer[7] & 0x01) == 0x01)      // extension_flag
    {
        // ISO 13818 amendment 2 and SMPTE RP 227
        const uint8_t flags = buffer[7];
        size_t skip = 9;
 
        // Find PES extension
        if ((flags & 0x80))
        {
            skip += 5;        // pts
            if ((flags & 0x40))
            {
                skip += 5;    // dts
            }
        }
        if ((flags & 0x20))
        {
            skip += 6;
        }
        if ((flags & 0x10))
        {
            skip += 3;
        }
        if ((flags & 0x08))
        {
            skip += 1;
        }
        if ((flags & 0x04))
        {
            skip += 1;
        }
        if ((flags & 0x02))
        {
            skip += 2;
        }
 
        if (skip < size && (buffer[skip] & 0x01))
        {
            const uint8_t flags2 = buffer[skip];
 
            // Find PES extension 2
            skip += 1;
            if (flags2 & 0x80)
            {
                skip += 16;
            }
            if ((flags2 & 0x40) && skip < size)
            {
                skip += static_cast<size_t>(1 + buffer[skip]);
            }
            if (flags2 & 0x20)
            {
                skip += 2;
            }
            if (flags2 & 0x10)
            {
                skip += 2;
            }
 
            if (skip + 1 < size)
            {
                const int i_extension_field_length = buffer[skip] & 0x7f;
                if (i_extension_field_length >=1)
                {
                    int i_stream_id_extension_flag = (buffer[skip+1] >> 7) & 0x1;
                    if (i_stream_id_extension_flag == 0)
                    {
                        return (0xfd00 | (buffer[skip+1] & 0x7f));
                    }
                }
            }
        }
    }
    return buffer[PS_STREAM_ID];
}
 
size_t DvdIO::demux_pes(uint8_t *out, const uint8_t *in, size_t len) const
{
    size_t netsize = 0;
    while (len > 0)
    {
        size_t pktsize = 0;
        if (!get_packet_size(in, len, &pktsize) || pktsize > len)
        {
            break;
        }
 
        // Parse block and copy to buffer
        switch (0x100 | in[PS_STREAM_ID])
        {
        // Ignore thesse...
        case (0x100 | PS_STREAM_ID_END_STREAM):
        case (0x100 | PS_STREAM_ID_SYSTEM_HEADER):
        case (0x100 | PS_STREAM_ID_MAP):
        {
            break;
        }
        case (0x100 | PS_STREAM_ID_PACK_HEADER):    // MPEG-2 Pack Header
        {
            std::memcpy(out, in, pktsize);
            out += pktsize;
            netsize += pktsize;
            break;
        }
        default:
        {
            int id = get_pes_id(in, pktsize);
            if (id >= PS_STREAM_ID_AUDIO)           // Audio/Video/Extended or Directory
            {
                // Probably this is sufficient here:
                // 110x xxxx    0xC0 - 0xDF MPEG-1 or MPEG-2 audio stream number x xxxx
                // 1110 xxxx    0xE0 - 0xEF MPEG-1 or MPEG-2 video stream number xxxx
                std::memcpy(out, in, pktsize);
                out += pktsize;
                netsize += pktsize;
            }
            break;
        }
        }
 
        in += pktsize;
        len -= pktsize;
    }
 
    return netsize;
}
 
DvdIO::DSITYPE DvdIO::handle_DSI(void *_dsi_pack, size_t * cur_output_size, unsigned int *next_block, uint8_t *data)
{
    dsi_t * dsi_pack = reinterpret_cast<dsi_t*>(_dsi_pack);
    DSITYPE dsitype = DSITYPE_CONTINUE;
    bool end_of_cell;
 
    navRead_DSI(dsi_pack, &data[DSI_START_BYTE]);
 
    // Determine where we go next.  These values are the ones we mostly
    // care about.
    m_cur_block         = dsi_pack->dsi_gi.nv_pck_lbn;
    *cur_output_size    = dsi_pack->dsi_gi.vobu_ea;
 
    // If we're not at the end of this cell, we can determine the next
    // VOBU to display using the VOBU_SRI information section of the
    // DSI.  Using this value correctly follows the current angle,
    // avoiding the doubled scenes in The Matrix, and makes our life
    // really happy.
 
    *next_block = m_cur_block + (dsi_pack->vobu_sri.next_vobu & 0x7fffffff);
    end_of_cell = (dsi_pack->vobu_sri.next_vobu == SRI_END_OF_CELL || *next_block >= m_cur_pgc->cell_playback[m_cur_cell].last_sector); // Double check end of cell: DVD transcoding stops in the middle of the chapter #48
 
    if (!end_of_cell && m_angle_idx > 1)
    {
        switch ((dsi_pack->sml_pbi.category & 0xf000) >> 12)
        {
        case 0x4:
        {
            // Interleaved unit with no angle
            // dsi_pack->sml_pbi.ilvu_sa
            // relative offset to the next ILVU block (not VOBU) for this angle or scene.
            // 00 00 00 00 for PREU and non-interleaved blocks
            // ff ff ff ff for the last interleaved block, indicating the end of interleaving
            if (dsi_pack->sml_pbi.ilvu_sa != 0 && dsi_pack->sml_pbi.ilvu_sa != 0xffffffff)
            {
                *next_block = m_cur_block + dsi_pack->sml_pbi.ilvu_sa;
                *cur_output_size = dsi_pack->sml_pbi.ilvu_ea;
            }
            else
            {
                *next_block = m_cur_block + dsi_pack->dsi_gi.vobu_ea + 1;
            }
            break;
        }
        case 0x5:
        {
            // vobu is end of ilvu
            if (dsi_pack->sml_agli.data[m_angle_idx].address)
            {
                *next_block = m_cur_block + dsi_pack->sml_agli.data[m_angle_idx].address;
                *cur_output_size = dsi_pack->sml_pbi.ilvu_ea;
                break;
            }
        }
            // fall through
        case 0x6:   // vobu is beginning of ilvu
        case 0x9:   // next scr is 0
        case 0xa:   // entering interleaved section
        case 0x8:   // non interleaved cells in interleaved section
        default:
        {
            *next_block = m_cur_block + (dsi_pack->vobu_sri.next_vobu & 0x7fffffff);
            break;
        }
        }
    }
    else if (end_of_cell)
    {
        if (m_next_cell >= m_cur_pgc->nr_of_cells)
        {
            *next_block = 0;
            dsitype = DSITYPE_EOF_TITLE;
        }
        else
        {
            m_cur_cell = m_next_cell;
 
            next_cell();
 
            if (m_cur_cell >= m_end_cell)
            {
                dsitype = DSITYPE_EOF_CHAPTER;
            }
 
            *next_block = m_cur_pgc->cell_playback[m_cur_cell].first_sector;
        }
    }
 
    return dsitype;
}
 
void DvdIO::next_cell()
{
    // Check if we're entering an angle block
    if (m_cur_pgc->cell_playback[m_cur_cell].block_type == static_cast<unsigned int>(BLOCK_TYPE_ANGLE_BLOCK))
    {
        m_cur_cell += m_angle_idx;
 
        for (int i = 0;; ++i)
        {
            if (m_cur_pgc->cell_playback[m_cur_cell + i].block_mode == static_cast<unsigned int>(BLOCK_MODE_LAST_CELL))
            {
                m_next_cell = m_cur_cell + i + 1;
                break;
            }
        }
    }
    else
    {
        m_next_cell = m_cur_cell + 1;
    }
}
 
size_t DvdIO::readio(void * data, size_t size)
{
    size_t cur_output_size;
    size_t result_len = 0;
    DSITYPE dsitype;
 
    if (m_rest_size)
    {
        size_t rest_size = m_rest_size;
 
        if (m_rest_size > size)
        {
            errno = EINVAL;
            return 0;
        }
 
        if (data != nullptr)
        {
            std::memcpy(data, &m_data[m_rest_pos], rest_size);
        }
 
        m_rest_size = m_rest_pos = 0;
 
        return rest_size;
    }
 
    // Playback by cell in this pgc, starting at the cell for our chapter.
    //while (next_cell < last_cell)
    {
        if (m_goto_next_cell)
        {
            m_goto_next_cell = false;
 
            m_cur_cell = m_next_cell;
 
            next_cell();
 
            m_cur_block = m_cur_pgc->cell_playback[m_cur_cell].first_sector;
        }
 
        if (m_cur_block >= m_cur_pgc->cell_playback[m_cur_cell].last_sector)
        {
            m_is_eof = false;
            return 0;
        }
 
        // We loop until we're out of this cell.
        //for(cur_pack = cur_pgc->cell_playback[cur_cell].first_sector;
        //     cur_pack < cur_pgc->cell_playback[cur_cell].last_sector;)
        {
            dsi_t dsi_pack;
            unsigned int next_block;
            ssize_t maxlen;
 
            // Read NAV packet.
            maxlen = DVDReadBlocks(m_dvd_title, static_cast<int>(m_cur_block), 1, m_buffer);
            if (maxlen != 1)
            {
                Logging::error(path(), "Read failed for block at %1.", m_cur_block);
                m_errno = EIO;
                return 0;
            }
 
            if (!is_nav_pack(m_buffer))
            {
                Logging::warning(path(), "Block at %1 is probably not a NAV packet. Transcode may fail.", m_cur_block);
            }
 
            // Parse the contained dsi packet.
            dsitype = handle_DSI(&dsi_pack, &cur_output_size, &next_block, m_buffer);
            if (m_cur_block != dsi_pack.dsi_gi.nv_pck_lbn)
            {
                Logging::error(path(), "Read failed at %1 because current block != dsi_pack.dsi_gi.nv_pck_lbn.", m_cur_block);
                m_errno = EIO;
                return 0;
            }
 
            if (cur_output_size >= 1024)
            {
                Logging::error(path(), "Read failed at %1 because current output size %2 >= 1024.", m_cur_block, cur_output_size);
                m_errno = EIO;
                return 0;
            }
 
            m_cur_block++;
 
            // Read in and output cur_output_size packs.
            maxlen = DVDReadBlocks(m_dvd_title, static_cast<int>(m_cur_block), cur_output_size, m_buffer);
 
            if (maxlen != static_cast<int>(cur_output_size))
            {
                Logging::error(path(), "Read failed for %1 blocks at %2.", cur_output_size, m_cur_block);
                m_errno = EIO;
                return 0;
            }
 
            size_t netsize = cur_output_size * DVD_VIDEO_LB_LEN;
 
            netsize = demux_pes(m_data, m_buffer, netsize);
 
            if (data != nullptr)
            {
                if (netsize > size)
                {
                    result_len = size;
 
                    std::memcpy(data, m_data, result_len);
 
                    m_rest_size = netsize - size;
                    m_rest_pos = size;
                }
                else
                {
                    result_len = netsize;
 
                    std::memcpy(data, m_data, result_len);
                }
            }
            else
            {
                if (netsize > size)
                {
                    result_len = size;
                }
                else
                {
                    result_len = netsize;
                }
            }
 
            m_cur_block = next_block;
        }
 
        //break;
    }
 
    // DSITYPE_EOF_TITLE - end of title
    // DSITYPE_EOF_CHAPTER - end of chapter
    if ((dsitype != DSITYPE_CONTINUE && !m_full_title) ||   // Stop at end of chapter/title
            (dsitype == DSITYPE_EOF_TITLE))                 // Stop at end of title
    {
        m_is_eof = true;
    }
 
    m_cur_pos += result_len;
 
    return result_len;
}
 
int DvdIO::error() const
{
    return m_errno;
}
 
int64_t DvdIO::duration() const
{
    return m_duration;
}
 
size_t DvdIO::size() const
{
    return m_size;
}
 
size_t DvdIO::tell() const
{
    return m_cur_pos;
}
 
void DvdIO::rewind()
{
    m_next_cell         = m_start_cell;
    m_cur_cell          = m_start_cell;
 
    m_goto_next_cell    = true;
    m_is_eof            = false;
    m_errno             = 0;
    m_rest_size         = 0;
    m_rest_pos          = 0;
    m_cur_pos           = 0;
}
 
int DvdIO::seek(int64_t offset, int whence)
{
    errno = 0;
 
    if (whence == SEEK_SET && !offset)
    {
        // Only rewind (seek(0, SEEK_SET) is implemented yet
        rewind();
        return 0;
    }
    size_t cur_pos = tell();
    size_t abs_offset = 0;
 
    switch (whence)
    {
    case SEEK_SET:
        abs_offset = static_cast<size_t>(offset);
        break;
    case SEEK_CUR:
        abs_offset += cur_pos;
        break;
    case SEEK_END:
        abs_offset = size() - abs_offset;
        break;
    default:
        errno = EINVAL;
        return (EOF);
    }
 
    if (cur_pos == abs_offset)
    {
        // Already at right position
        return static_cast<int>(abs_offset);
    }
 
    if (cur_pos > abs_offset)
    {
        // Need to start from beginning to find byte position
        rewind();
        cur_pos = 0;
    }
 
    size_t total_read = 0;
    size_t bytes_read;
    while ((bytes_read = readio(nullptr, abs_offset - total_read - cur_pos)) != 0 && total_read < abs_offset && !eof())
    {
        total_read += bytes_read;
    }
 
    if (total_read)
    {
        return static_cast<int>(cur_pos + total_read);
    }
 
    errno = EPERM;
    return (EOF);
}
 
bool DvdIO::eof() const
{
    return m_is_eof;
}
 
void DvdIO::closeio()
{
    pvt_close();
}
 
void DvdIO::pvt_close()
{
    ifo_handle_t *  vts_file = m_vts_file;
    if (vts_file != nullptr)
    {
        m_vts_file = nullptr;
        ifoClose(vts_file);
    }
    ifo_handle_t *  vmg_file  = m_vmg_file;
    if (vmg_file != nullptr)
    {
        m_vmg_file = nullptr;
        ifoClose(vmg_file);
    }
    dvd_file_t *    dvd_title = m_dvd_title;
    if (dvd_title != nullptr)
    {
        m_dvd_title = nullptr;
        DVDCloseFile(dvd_title);
    }
    dvd_reader_t *  dvd = m_dvd;
    if (dvd != nullptr)
    {
        m_dvd = nullptr;
        DVDClose(dvd);
    }
}
 
// Code nicked from Handbrake (https://github.com/HandBrake/HandBrake/blob/master/libhb/dvd.c)
bool DvdIO::is_nav_pack(const unsigned char *buffer) const
{
    /*
     * The NAV Pack is comprised of the PCI Packet and DSI Packet, both
     * of these start at known offsets and start with a special identifier.
     *
     * NAV = {
     *  PCI = { 00 00 01 bf  # private stream header
     *          ?? ??        # length
     *          00           # substream
     *          ...
     *        }
     *  DSI = { 00 00 01 bf  # private stream header
     *          ?? ??        # length
     *          01           # substream
     *          ...
     *        }
     *
     * The PCI starts at offset 0x26 into the sector, and the DSI starts at 0x400
     *
     * This information from: http://dvd.sourceforge.net/dvdinfo/
     */
    if ((buffer[0x26] == 0x00 &&      // PCI
         buffer[0x27] == 0x00 &&
         buffer[0x28] == 0x01 &&
         buffer[0x29] == 0xbf &&
         buffer[0x2c] == 0x00) &&
            (buffer[0x400] == 0x00 &&     // DSI
             buffer[0x401] == 0x00 &&
             buffer[0x402] == 0x01 &&
             buffer[0x403] == 0xbf &&
             buffer[0x406] == 0x01))
    {
        return true;
    }
    else
    {
        return false;
    }
}
 
#endif // USE_LIBDVD