source: vbox/trunk/src/VBox/Main/src-client/EbmlWriter.cpp@ 63013

/* $Id: EbmlWriter.cpp 62485 2016-07-22 18:36:43Z vboxsync $ */
/** @file
 * EbmlWriter.cpp - EBML writer + WebM container
 */

/*
 * Copyright (C) 2013-2016 Oracle Corporation
 *
 * This file is part of VirtualBox Open Source Edition (OSE), as
 * available from http://www.virtualbox.org. This file is free software;
 * you can redistribute it and/or modify it under the terms of the GNU
 * General Public License (GPL) as published by the Free Software
 * Foundation, in version 2 as it comes in the "COPYING" file of the
 * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
 * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
 */

/*
 * This code is based on:
 *
 * Copyright (c) 2010 The WebM project authors. All Rights Reserved.
 *
 * Use of this source code is governed by a BSD-style license
 * that can be found in the LICENSE file in the root of the source
 * tree. An additional intellectual property rights grant can be found
 * in the file PATENTS.  All contributing project authors may
 * be found in the AUTHORS file in the root of the source tree.
 */

#include <list>
#include <stack>
#include <iprt/string.h>
#include <iprt/file.h>
#include <iprt/asm.h>
#include <iprt/cdefs.h>
#include <iprt/err.h>
#include <VBox/log.h>
#include "EbmlWriter.h"

/* Matroska EBML Class IDs supported by WebM */
 enum Mkv
 {
     EBML = 0x1A45DFA3,
     EBMLVersion = 0x4286,
     EBMLReadVersion = 0x42F7,
     EBMLMaxIDLength = 0x42F2,
     EBMLMaxSizeLength = 0x42F3,
     DocType = 0x4282,
     DocTypeVersion = 0x4287,
     DocTypeReadVersion = 0x4285,
 //  CRC_32 = 0xBF,
     Void = 0xEC,
     SignatureSlot = 0x1B538667,
     SignatureAlgo = 0x7E8A,
     SignatureHash = 0x7E9A,
     SignaturePublicKey = 0x7EA5,
     Signature = 0x7EB5,
     SignatureElements = 0x7E5B,
     SignatureElementList = 0x7E7B,
     SignedElement = 0x6532,
     //segment
     Segment = 0x18538067,
     //Meta Seek Information
     SeekHead = 0x114D9B74,
     Seek = 0x4DBB,
     SeekID = 0x53AB,
     SeekPosition = 0x53AC,
     //Segment Information
     Info = 0x1549A966,
 //  SegmentUID = 0x73A4,
 //  SegmentFilename = 0x7384,
 //  PrevUID = 0x3CB923,
 //  PrevFilename = 0x3C83AB,
 //  NextUID = 0x3EB923,
 //  NextFilename = 0x3E83BB,
 //  SegmentFamily = 0x4444,
 //  ChapterTranslate = 0x6924,
 //  ChapterTranslateEditionUID = 0x69FC,
 //  ChapterTranslateCodec = 0x69BF,
 //  ChapterTranslateID = 0x69A5,
     TimecodeScale = 0x2AD7B1,
     Segment_Duration = 0x4489,
     DateUTC = 0x4461,
 //  Title = 0x7BA9,
     MuxingApp = 0x4D80,
     WritingApp = 0x5741,
     //Cluster
     Cluster = 0x1F43B675,
     Timecode = 0xE7,
 //  SilentTracks = 0x5854,
 //  SilentTrackNumber = 0x58D7,
 //  Position = 0xA7,
     PrevSize = 0xAB,
     BlockGroup = 0xA0,
     Block = 0xA1,
 //  BlockVirtual = 0xA2,
 //  BlockAdditions = 0x75A1,
 //  BlockMore = 0xA6,
 //  BlockAddID = 0xEE,
 //  BlockAdditional = 0xA5,
     BlockDuration = 0x9B,
 //  ReferencePriority = 0xFA,
     ReferenceBlock = 0xFB,
 //  ReferenceVirtual = 0xFD,
 //  CodecState = 0xA4,
 //  Slices = 0x8E,
 //  TimeSlice = 0xE8,
     LaceNumber = 0xCC,
 //  FrameNumber = 0xCD,
 //  BlockAdditionID = 0xCB,
 //  MkvDelay = 0xCE,
 //  Cluster_Duration = 0xCF,
     SimpleBlock = 0xA3,
 //  EncryptedBlock = 0xAF,
     //Track
     Tracks = 0x1654AE6B,
     TrackEntry = 0xAE,
     TrackNumber = 0xD7,
     TrackUID = 0x73C5,
     TrackType = 0x83,
     FlagEnabled = 0xB9,
     FlagDefault = 0x88,
     FlagForced = 0x55AA,
     FlagLacing = 0x9C,
 //  MinCache = 0x6DE7,
 //  MaxCache = 0x6DF8,
     DefaultDuration = 0x23E383,
 //  TrackTimecodeScale = 0x23314F,
 //  TrackOffset = 0x537F,
 //  MaxBlockAdditionID = 0x55EE,
     Name = 0x536E,
     Language = 0x22B59C,
     CodecID = 0x86,
     CodecPrivate = 0x63A2,
     CodecName = 0x258688,
 //  AttachmentLink = 0x7446,
 //  CodecSettings = 0x3A9697,
 //  CodecInfoURL = 0x3B4040,
 //  CodecDownloadURL = 0x26B240,
 //  CodecDecodeAll = 0xAA,
 //  TrackOverlay = 0x6FAB,
 //  TrackTranslate = 0x6624,
 //  TrackTranslateEditionUID = 0x66FC,
 //  TrackTranslateCodec = 0x66BF,
 //  TrackTranslateTrackID = 0x66A5,
     //video
     Video = 0xE0,
     FlagInterlaced = 0x9A,
 //  StereoMode = 0x53B8,
     PixelWidth = 0xB0,
     PixelHeight = 0xBA,
     PixelCropBottom = 0x54AA,
     PixelCropTop = 0x54BB,
     PixelCropLeft = 0x54CC,
     PixelCropRight = 0x54DD,
     DisplayWidth = 0x54B0,
     DisplayHeight = 0x54BA,
     DisplayUnit = 0x54B2,
     AspectRatioType = 0x54B3,
 //  ColourSpace = 0x2EB524,
 //  GammaValue = 0x2FB523,
     FrameRate = 0x2383E3,
     //end video
     //audio
     Audio = 0xE1,
     SamplingFrequency = 0xB5,
     OutputSamplingFrequency = 0x78B5,
     Channels = 0x9F,
 //  ChannelPositions = 0x7D7B,
     BitDepth = 0x6264,
     //end audio
     //content encoding
 //  ContentEncodings = 0x6d80,
 //  ContentEncoding = 0x6240,
 //  ContentEncodingOrder = 0x5031,
 //  ContentEncodingScope = 0x5032,
 //  ContentEncodingType = 0x5033,
 //  ContentCompression = 0x5034,
 //  ContentCompAlgo = 0x4254,
 //  ContentCompSettings = 0x4255,
 //  ContentEncryption = 0x5035,
 //  ContentEncAlgo = 0x47e1,
 //  ContentEncKeyID = 0x47e2,
 //  ContentSignature = 0x47e3,
 //  ContentSigKeyID = 0x47e4,
 //  ContentSigAlgo = 0x47e5,
 //  ContentSigHashAlgo = 0x47e6,
     //end content encoding
     //Cueing Data
     Cues = 0x1C53BB6B,
     CuePoint = 0xBB,
     CueTime = 0xB3,
     CueTrackPositions = 0xB7,
     CueTrack = 0xF7,
     CueClusterPosition = 0xF1,
     CueBlockNumber = 0x5378
 //  CueCodecState = 0xEA,
 //  CueReference = 0xDB,
 //  CueRefTime = 0x96,
 //  CueRefCluster = 0x97,
 //  CueRefNumber = 0x535F,
 //  CueRefCodecState = 0xEB,
     //Attachment
 //  Attachments = 0x1941A469,
 //  AttachedFile = 0x61A7,
 //  FileDescription = 0x467E,
 //  FileName = 0x466E,
 //  FileMimeType = 0x4660,
 //  FileData = 0x465C,
 //  FileUID = 0x46AE,
 //  FileReferral = 0x4675,
     //Chapters
 //  Chapters = 0x1043A770,
 //  EditionEntry = 0x45B9,
 //  EditionUID = 0x45BC,
 //  EditionFlagHidden = 0x45BD,
 //  EditionFlagDefault = 0x45DB,
 //  EditionFlagOrdered = 0x45DD,
 //  ChapterAtom = 0xB6,
 //  ChapterUID = 0x73C4,
 //  ChapterTimeStart = 0x91,
 //  ChapterTimeEnd = 0x92,
 //  ChapterFlagHidden = 0x98,
 //  ChapterFlagEnabled = 0x4598,
 //  ChapterSegmentUID = 0x6E67,
 //  ChapterSegmentEditionUID = 0x6EBC,
 //  ChapterPhysicalEquiv = 0x63C3,
 //  ChapterTrack = 0x8F,
 //  ChapterTrackNumber = 0x89,
 //  ChapterDisplay = 0x80,
 //  ChapString = 0x85,
 //  ChapLanguage = 0x437C,
 //  ChapCountry = 0x437E,
 //  ChapProcess = 0x6944,
 //  ChapProcessCodecID = 0x6955,
 //  ChapProcessPrivate = 0x450D,
 //  ChapProcessCommand = 0x6911,
 //  ChapProcessTime = 0x6922,
 //  ChapProcessData = 0x6933,
     //Tagging
 //  Tags = 0x1254C367,
 //  Tag = 0x7373,
 //  Targets = 0x63C0,
 //  TargetTypeValue = 0x68CA,
 //  TargetType = 0x63CA,
 //  Tagging_TrackUID = 0x63C5,
 //  Tagging_EditionUID = 0x63C9,
 //  Tagging_ChapterUID = 0x63C4,
 //  AttachmentUID = 0x63C6,
 //  SimpleTag = 0x67C8,
 //  TagName = 0x45A3,
 //  TagLanguage = 0x447A,
 //  TagDefault = 0x4484,
 //  TagString = 0x4487,
 //  TagBinary = 0x4485,
 };

class Ebml
{
public:
    typedef uint32_t EbmlClassId;

private:

    struct EbmlSubElement
    {
        uint64_t offset;
        EbmlClassId classId;
        EbmlSubElement(uint64_t offs, EbmlClassId cid) : offset(offs), classId(cid) {}
    };

    std::stack<EbmlSubElement> m_Elements;
    RTFILE m_File;

public:

    /* Creates EBML output file. */
    inline int create(const char *a_pszFilename)
    {
      return RTFileOpen(&m_File, a_pszFilename, RTFILE_O_CREATE | RTFILE_O_WRITE | RTFILE_O_DENY_NONE);
    }

    /* Returns file size. */
    inline uint64_t getFileSize()
    {
        return RTFileTell(m_File);
    }

    /* Get reference to file descriptor */
    inline const RTFILE &getFile()
    {
        return m_File;
    }

    /* Returns available space on storage. */
    inline uint64_t getAvailableSpace()
    {
        RTFOFF pcbFree;
        int rc = RTFileQueryFsSizes(m_File, NULL, &pcbFree, 0, 0);
        return (RT_SUCCESS(rc)? (uint64_t)pcbFree : UINT64_MAX);
    }

    /* Closes the file. */
    inline void close()
    {
        RTFileClose(m_File);
    }

    /* Starts an EBML sub-element. */
    inline Ebml &subStart(EbmlClassId classId)
    {
        writeClassId(classId);
        /* store the current file offset. */
        m_Elements.push(EbmlSubElement(RTFileTell(m_File), classId));
        /* Indicates that size of the element
         * is unkown (as according to EBML specs).
         */
        writeUnsignedInteger(UINT64_C(0x01FFFFFFFFFFFFFF));
        return *this;
    }

    /* Ends an EBML sub-element. */
    inline Ebml &subEnd(EbmlClassId classId)
    {
        /* Class ID on the top of the stack should match the class ID passed
         * to the function. Otherwise it may mean that we have a bug in the code.
         */
        if(m_Elements.empty() || m_Elements.top().classId != classId) throw VERR_INTERNAL_ERROR;

        uint64_t uPos = RTFileTell(m_File);
        uint64_t uSize = uPos - m_Elements.top().offset - 8;
        RTFileSeek(m_File, m_Elements.top().offset, RTFILE_SEEK_BEGIN, NULL);

        /* make sure that size will be serialized as uint64 */
        writeUnsignedInteger(uSize | UINT64_C(0x0100000000000000));
        RTFileSeek(m_File, uPos, RTFILE_SEEK_BEGIN, NULL);
        m_Elements.pop();
        return *this;
    }

    /* Serializes a null-terminated string. */
    inline Ebml &serializeString(EbmlClassId classId, const char *str)
    {
        writeClassId(classId);
        uint64_t size = strlen(str);
        writeSize(size);
        write(str, size);
        return *this;
    }

    /* Serializes an UNSIGNED integer
     * If size is zero then it will be detected automatically. */
    inline Ebml &serializeUnsignedInteger(EbmlClassId classId, uint64_t parm, size_t size = 0)
    {
        writeClassId(classId);
        if (!size) size = getSizeOfUInt(parm);
        writeSize(size);
        writeUnsignedInteger(parm, size);
        return *this;
    }

    /* Serializes a floating point value.
     * Only 8-bytes double precision values are supported
     * by this function.
     */
    inline Ebml &serializeFloat(EbmlClassId classId, double value)
    {
        writeClassId(classId);
        writeSize(sizeof(double));
        writeUnsignedInteger(*reinterpret_cast<uint64_t*>(&value));
        return *this;
    }

    /* Writes raw data to file. */
    inline void write(const void *data, size_t size)
    {
        int rc = RTFileWrite(m_File, data, size, NULL);
        if (!RT_SUCCESS(rc)) throw rc;
    }

    /* Writes an unsigned integer of variable of fixed size. */
    inline void writeUnsignedInteger(uint64_t value, size_t size = sizeof(uint64_t))
    {
        /* convert to big-endian */
        value = RT_H2BE_U64(value);
        write(reinterpret_cast<uint8_t*>(&value) + sizeof(value) - size, size);
    }

    /* Writes EBML class ID to file.
     * EBML ID already has a UTF8-like represenation
     * so getSizeOfUInt is used to determine
     * the number of its bytes.
     */
    inline void writeClassId(EbmlClassId parm)
    {
        writeUnsignedInteger(parm, getSizeOfUInt(parm));
    }

    /* Writes data size value. */
    inline void writeSize(uint64_t parm)
    {
        /* The following expression defines the size of the value that will be serialized
         * as an EBML UTF-8 like integer (with trailing bits represeting its size):
          1xxx xxxx                                                                              - value 0 to  2^7-2
          01xx xxxx  xxxx xxxx                                                                   - value 0 to 2^14-2
          001x xxxx  xxxx xxxx  xxxx xxxx                                                        - value 0 to 2^21-2
          0001 xxxx  xxxx xxxx  xxxx xxxx  xxxx xxxx                                             - value 0 to 2^28-2
          0000 1xxx  xxxx xxxx  xxxx xxxx  xxxx xxxx  xxxx xxxx                                  - value 0 to 2^35-2
          0000 01xx  xxxx xxxx  xxxx xxxx  xxxx xxxx  xxxx xxxx  xxxx xxxx                       - value 0 to 2^42-2
          0000 001x  xxxx xxxx  xxxx xxxx  xxxx xxxx  xxxx xxxx  xxxx xxxx  xxxx xxxx            - value 0 to 2^49-2
          0000 0001  xxxx xxxx  xxxx xxxx  xxxx xxxx  xxxx xxxx  xxxx xxxx  xxxx xxxx  xxxx xxxx - value 0 to 2^56-2
         */
        size_t size = 8 - ! (parm & (UINT64_MAX << 49)) - ! (parm & (UINT64_MAX << 42)) -
                          ! (parm & (UINT64_MAX << 35)) - ! (parm & (UINT64_MAX << 28)) -
                          ! (parm & (UINT64_MAX << 21)) - ! (parm & (UINT64_MAX << 14)) -
                          ! (parm & (UINT64_MAX << 7));
        /* One is subtracted in order to avoid loosing significant bit when size = 8. */
        uint64_t mask = RT_BIT_64(size * 8 - 1);
        writeUnsignedInteger((parm & (((mask << 1) - 1) >> size)) | (mask >> (size - 1)), size);
    }
    /* Size calculation for variable size UNSIGNED integer.
     * The function defines the size of the number by trimming
     * consequent trailing zero bytes starting from the most significant.
     * The following statement is always true:
     * 1 <= getSizeOfUInt(arg) <= 8.
     *
     * Every !(arg & (UINT64_MAX << X)) expression gives one
     * if an only if all the bits from X to 63 are set to zero.
     */
    static inline size_t getSizeOfUInt(uint64_t arg)
    {
        return 8 - ! (arg & (UINT64_MAX << 56)) - ! (arg & (UINT64_MAX << 48)) -
                   ! (arg & (UINT64_MAX << 40)) - ! (arg & (UINT64_MAX << 32)) -
                   ! (arg & (UINT64_MAX << 24)) - ! (arg & (UINT64_MAX << 16)) -
                   ! (arg & (UINT64_MAX << 8));
    }

private:
    void operator=(const Ebml &);

};

class WebMWriter_Impl
{

    struct CueEntry
    {
        uint32_t    time;
        uint64_t    loc;
        CueEntry(uint32_t t, uint64_t l) : time(t), loc(l) {}
    };

    bool            m_bDebug;
    int64_t         m_iLastPtsMs;
    int64_t         m_iInitialPtsMs;
    vpx_rational_t  m_Framerate;

    uint64_t        m_uPositionReference;
    uint64_t        m_uSeekInfoPos;
    uint64_t        m_uSegmentInfoPos;
    uint64_t        m_uTrackPos;
    uint64_t        m_uCuePos;
    uint64_t        m_uClusterPos;

    uint64_t        m_uTrackIdPos;

    uint64_t        m_uStartSegment;

    uint32_t        m_uClusterTimecode;
    bool            m_bClusterOpen;

    std::list<CueEntry> m_CueList;

    Ebml m_Ebml;

public:

    WebMWriter_Impl() :
        m_bDebug(false),
        m_iLastPtsMs(-1),
        m_iInitialPtsMs(-1),
        m_Framerate(),
        m_uPositionReference(0),
        m_uSeekInfoPos(0),
        m_uSegmentInfoPos(0),
        m_uTrackPos(0),
        m_uCuePos(0),
        m_uClusterPos(0),
        m_uTrackIdPos(0),
        m_uStartSegment(0),
        m_uClusterTimecode(0),
        m_bClusterOpen(false) {}

    void writeHeader(const vpx_codec_enc_cfg_t *a_pCfg,
                     const struct vpx_rational *a_pFps)
    {
        m_Ebml.subStart(EBML)
              .serializeUnsignedInteger(EBMLVersion, 1)
              .serializeUnsignedInteger(EBMLReadVersion, 1)
              .serializeUnsignedInteger(EBMLMaxIDLength, 4)
              .serializeUnsignedInteger(EBMLMaxSizeLength, 8)
              .serializeString(DocType, "webm")
              .serializeUnsignedInteger(DocTypeVersion, 2)
              .serializeUnsignedInteger(DocTypeReadVersion, 2)
              .subEnd(EBML);

        m_Ebml.subStart(Segment);

        m_uPositionReference = RTFileTell(m_Ebml.getFile());
        m_Framerate = *a_pFps;

        writeSeekInfo();

        m_uTrackPos = RTFileTell(m_Ebml.getFile());

        m_Ebml.subStart(Tracks)
              .subStart(TrackEntry)
              .serializeUnsignedInteger(TrackNumber, 1);

        m_uTrackIdPos = RTFileTell(m_Ebml.getFile());

        m_Ebml.serializeUnsignedInteger(TrackUID, 0, 4)
              .serializeUnsignedInteger(TrackType, 1)
              .serializeString(CodecID, "V_VP8")
              .subStart(Video)
              .serializeUnsignedInteger(PixelWidth, a_pCfg->g_w)
              .serializeUnsignedInteger(PixelHeight, a_pCfg->g_h)
              .serializeFloat(FrameRate, (double) a_pFps->num / a_pFps->den)
              .subEnd(Video)
              .subEnd(TrackEntry)
              .subEnd(Tracks);
    }

    void writeBlock(const vpx_codec_enc_cfg_t *a_pCfg,
                                const vpx_codec_cx_pkt_t *a_pPkt)
    {
        uint16_t uBlockTimecode = 0;
        int64_t  iPtsMs;
        bool     bStartCluster = false;

        /* Calculate the PTS of this frame in milliseconds */
        iPtsMs = a_pPkt->data.frame.pts * 1000
                 * (uint64_t) a_pCfg->g_timebase.num / a_pCfg->g_timebase.den;
        if (iPtsMs <= m_iLastPtsMs)
            iPtsMs = m_iLastPtsMs + 1;
        m_iLastPtsMs = iPtsMs;

        if (m_iInitialPtsMs < 0)
          m_iInitialPtsMs = m_iLastPtsMs;

        /* Calculate the relative time of this block */
        if (iPtsMs - m_uClusterTimecode > 65536)
            bStartCluster = 1;
        else
            uBlockTimecode = static_cast<uint16_t>(iPtsMs - m_uClusterTimecode);

        int fKeyframe = (a_pPkt->data.frame.flags & VPX_FRAME_IS_KEY);
        if (bStartCluster || fKeyframe)
        {
            if (m_bClusterOpen)
                m_Ebml.subEnd(Cluster);

            /* Open a new cluster */
            uBlockTimecode = 0;
            m_bClusterOpen = true;
            m_uClusterTimecode = (uint32_t)iPtsMs;
            m_uClusterPos = RTFileTell(m_Ebml.getFile());
            m_Ebml.subStart(Cluster)
                  .serializeUnsignedInteger(Timecode, m_uClusterTimecode);

            /* Save a cue point if this is a keyframe. */
            if (fKeyframe)
            {
                CueEntry cue(m_uClusterTimecode, m_uClusterPos);
                m_CueList.push_back(cue);
            }
        }

        /* Write a Simple Block */
        m_Ebml.writeClassId(SimpleBlock);
        m_Ebml.writeUnsignedInteger(0x10000000u | (4 + a_pPkt->data.frame.sz), 4);
        m_Ebml.writeSize(1);
        m_Ebml.writeUnsignedInteger(uBlockTimecode, 2);
        m_Ebml.writeUnsignedInteger((fKeyframe ? 0x80 : 0) | (a_pPkt->data.frame.flags & VPX_FRAME_IS_INVISIBLE ? 0x08 : 0), 1);
        m_Ebml.write(a_pPkt->data.frame.buf, a_pPkt->data.frame.sz);
    }

    void writeFooter(uint32_t a_u64Hash)
    {
        if (m_bClusterOpen)
            m_Ebml.subEnd(Cluster);

        m_uCuePos = RTFileTell(m_Ebml.getFile());
        m_Ebml.subStart(Cues);
        for (std::list<CueEntry>::iterator it = m_CueList.begin(); it != m_CueList.end(); ++it)
        {
          m_Ebml.subStart(CuePoint)
                .serializeUnsignedInteger(CueTime, it->time)
                .subStart(CueTrackPositions)
                .serializeUnsignedInteger(CueTrack, 1)
                .serializeUnsignedInteger(CueClusterPosition, it->loc - m_uPositionReference, 8)
                .subEnd(CueTrackPositions)
                .subEnd(CuePoint);
        }

        m_Ebml.subEnd(Cues)
              .subEnd(Segment);

        writeSeekInfo();

        int rc = RTFileSeek(m_Ebml.getFile(), m_uTrackIdPos, RTFILE_SEEK_BEGIN, NULL);
        if (!RT_SUCCESS(rc)) throw rc;

        m_Ebml.serializeUnsignedInteger(TrackUID, (m_bDebug ? 0xDEADBEEF : a_u64Hash), 4);

        rc = RTFileSeek(m_Ebml.getFile(), 0, RTFILE_SEEK_END, NULL);
        if (!RT_SUCCESS(rc)) throw rc;
    }

    friend class WebMWriter;

private:

    void writeSeekInfo()
    {
        uint64_t uPos = RTFileTell(m_Ebml.getFile());
        if (m_uSeekInfoPos)
            RTFileSeek(m_Ebml.getFile(), m_uSeekInfoPos, RTFILE_SEEK_BEGIN, NULL);
        else
            m_uSeekInfoPos = uPos;

        m_Ebml.subStart(SeekHead)

              .subStart(Seek)
              .serializeUnsignedInteger(SeekID, Tracks)
              .serializeUnsignedInteger(SeekPosition, m_uTrackPos - m_uPositionReference, 8)
              .subEnd(Seek)

              .subStart(Seek)
              .serializeUnsignedInteger(SeekID, Cues)
              .serializeUnsignedInteger(SeekPosition, m_uCuePos - m_uPositionReference, 8)
              .subEnd(Seek)

              .subStart(Seek)
              .serializeUnsignedInteger(SeekID, Info)
              .serializeUnsignedInteger(SeekPosition, m_uSegmentInfoPos - m_uPositionReference, 8)
              .subEnd(Seek)

              .subEnd(SeekHead);

        int64_t iFrameTime = (int64_t)1000 * m_Framerate.den / m_Framerate.num;
        m_uSegmentInfoPos = RTFileTell(m_Ebml.getFile());

        char szVersion[64];
        RTStrPrintf(szVersion, sizeof(szVersion), "vpxenc%s",
                    m_bDebug ? "" : vpx_codec_version_str());

        m_Ebml.subStart(Info)
              .serializeUnsignedInteger(TimecodeScale, 1000000)
              .serializeFloat(Segment_Duration, m_iLastPtsMs + iFrameTime - m_iInitialPtsMs)
              .serializeString(MuxingApp, szVersion)
              .serializeString(WritingApp, szVersion)
              .subEnd(Info);
    }
};

WebMWriter::WebMWriter() : m_Impl(new WebMWriter_Impl()) {}

WebMWriter::~WebMWriter()
{
    delete m_Impl;
}

int WebMWriter::create(const char *a_pszFilename)
{
    return m_Impl->m_Ebml.create(a_pszFilename);
}

void WebMWriter::close()
{
    m_Impl->m_Ebml.close();
}

int WebMWriter::writeHeader(const vpx_codec_enc_cfg_t *a_pCfg, const vpx_rational *a_pFps)
{
    try
    {
        m_Impl->writeHeader(a_pCfg, a_pFps);
    }
    catch(int rc)
    {
        return rc;
    }
    return VINF_SUCCESS;
}

int WebMWriter::writeBlock(const vpx_codec_enc_cfg_t *a_pCfg, const vpx_codec_cx_pkt_t *a_pPkt)
{
    try
    {
        m_Impl->writeBlock(a_pCfg, a_pPkt);
    }
    catch(int rc)
    {
        return rc;
    }
    return VINF_SUCCESS;
}

int WebMWriter::writeFooter(uint32_t a_u64Hash)
{
    try
    {
        m_Impl->writeFooter(a_u64Hash);
    }
    catch(int rc)
    {
        return rc;
    }
    return VINF_SUCCESS;
}

uint64_t WebMWriter::getFileSize()
{
    return m_Impl->m_Ebml.getFileSize();
}

uint64_t WebMWriter::getAvailableSpace()
{
    return m_Impl->m_Ebml.getAvailableSpace();
}