WebMElement.c

// 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 "EbmlBufferWriter.h"
#include "EbmlIDs.h"
#include "WebMElement.h"
#include <stdio.h>

#define kVorbisPrivateMaxSize  4000

void writeHeader(EbmlGlobal *glob) {
  EbmlLoc start;
  Ebml_StartSubElement(glob, &start, EBML);
  Ebml_SerializeUnsigned(glob, EBMLVersion, 1);
  Ebml_SerializeUnsigned(glob, EBMLReadVersion, 1); // EBML Read Version
  Ebml_SerializeUnsigned(glob, EBMLMaxIDLength, 4); // EBML Max ID Length
  Ebml_SerializeUnsigned(glob, EBMLMaxSizeLength, 8); // EBML Max Size Length
  Ebml_SerializeString(glob, DocType, "webm"); // Doc Type
  Ebml_SerializeUnsigned(glob, DocTypeVersion, 2); // Doc Type Version
  Ebml_SerializeUnsigned(glob, DocTypeReadVersion, 2); // Doc Type Read Version
  Ebml_EndSubElement(glob, &start);
}

void writeSimpleBlock(EbmlGlobal *glob, unsigned char trackNumber, short timeCode,
                      int isKeyframe, unsigned char lacingFlag, int discardable,
                      unsigned char *data, unsigned long dataLength) {
  Ebml_WriteID(glob, SimpleBlock);
  unsigned long blockLength = 4 + dataLength;
  blockLength |= 0x10000000; // TODO check length < 0x0FFFFFFFF
  Ebml_Serialize(glob, &blockLength, sizeof(blockLength), 4);
  trackNumber |= 0x80;  // TODO check track nubmer < 128
  Ebml_Write(glob, &trackNumber, 1);
  // Ebml_WriteSigned16(glob, timeCode,2); //this is 3 bytes
  Ebml_Serialize(glob, &timeCode, sizeof(timeCode), 2);
  unsigned char flags = 0x00 | (isKeyframe ? 0x80 : 0x00) | (lacingFlag << 1) | discardable;
  Ebml_Write(glob, &flags, 1);
  Ebml_Write(glob, data, dataLength);
}

static UInt64 generateTrackID(unsigned int trackNumber) {
  UInt64 t = time(NULL) * trackNumber;
  UInt64 r = rand();
  r = r << 32;
  r +=  rand();
  UInt64 rval = t ^ r;
  return rval;
}

void writeVideoTrack(EbmlGlobal *glob, unsigned int trackNumber, int flagLacing,
                     char *codecId, unsigned int pixelWidth, unsigned int pixelHeight,
                     double frameRate) {
  EbmlLoc start;
  Ebml_StartSubElement(glob, &start, TrackEntry);
  Ebml_SerializeUnsigned(glob, TrackNumber, trackNumber);
  UInt64 trackID = generateTrackID(trackNumber);
  Ebml_SerializeUnsigned(glob, TrackUID, trackID);
  Ebml_SerializeString(glob, CodecName, "VP8");  // TODO shouldn't be fixed

  Ebml_SerializeUnsigned(glob, TrackType, 1); // video is always 1
  Ebml_SerializeString(glob, CodecID, codecId);
  {
    EbmlLoc videoStart;
    Ebml_StartSubElement(glob, &videoStart, Video);
    Ebml_SerializeUnsigned(glob, PixelWidth, pixelWidth);