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/*
* Copyright (C) 2005-2021 Team Kodi
* This file is part of Kodi - https://kodi.tv
*
* SPDX-License-Identifier: GPL-2.0-or-later
* See LICENSES/README.md for more information.
*/
#include "WebVTTISOHandler.h"
#include "cores/VideoPlayer/Interface/TimingConstants.h"
#include "utils/CharArrayParser.h"
#include "utils/CharsetConverter.h"
#include "utils/StreamUtils.h"
#include "utils/StringUtils.h"
#include "utils/log.h"
#include <cstring>
#include <stdint.h>
// WebVTT in MP4 encapsulated subtitles (ISO/IEC 14496-30:2014)
// This format type that differ from the text WebVTT, it makes use
// of ISO BMFF byte stream where the data are enclosed in boxes (first 4 byte
// specify the size and next 4 byte specify the type).
// Start/Stop times info are not included, the start time is the current pts
// provided from the decoder, the stop time is defined from the pts of the next
// packages (depends from the box type).
namespace
{
constexpr int defaultSubDuration = 20 * static_cast<int>(DVD_TIME_BASE);
// VTTEmptyCueBox
constexpr uint32_t ISO_BOX_TYPE_VTTE = StreamUtils::MakeFourCC('v', 't', 't', 'e');
// VTTCueBox
constexpr uint32_t ISO_BOX_TYPE_VTTC = StreamUtils::MakeFourCC('v', 't', 't', 'c');
// VTTContinuationCueBox
constexpr uint32_t ISO_BOX_TYPE_VTTX = StreamUtils::MakeFourCC('v', 't', 't', 'x');
// CueIDBox
constexpr uint32_t ISO_BOX_TYPE_IDEN = StreamUtils::MakeFourCC('i', 'd', 'e', 'n');
// CueSettingsBox
constexpr uint32_t ISO_BOX_TYPE_STTG = StreamUtils::MakeFourCC('s', 't', 't', 'g');
// CuePayloadBox
constexpr uint32_t ISO_BOX_TYPE_PAYL = StreamUtils::MakeFourCC('p', 'a', 'y', 'l');
} // unnamed namespace
void CWebVTTISOHandler::DecodeStream(const char* buffer,
int bufferSize,
double pts,
std::vector<subtitleData>* subList,
double& prevSubStopTime)
{
CCharArrayParser sampleData;
sampleData.Reset(buffer, bufferSize);
// A sample data package can contain:
// - One VTTE
// or
// - One or more VTTC and/or VTTX (where all share the same start/stop times)
while (sampleData.CharsLeft() > 0)
{
if (sampleData.CharsLeft() < MP4_BOX_HEADER_SIZE)
{
CLog::Log(LOGWARNING, "{} - Incomplete box header found", __FUNCTION__);
break;
}
uint32_t boxSize = sampleData.ReadNextUnsignedInt();
uint32_t boxType = sampleData.ReadNextUnsignedInt();
if (boxType == ISO_BOX_TYPE_VTTE)
{
// VTTE is used to set the stop time value to previously subtitles
prevSubStopTime = pts;
sampleData.SkipChars(boxSize - MP4_BOX_HEADER_SIZE);
}
else if (boxType == ISO_BOX_TYPE_VTTC)
{
// VTTC can be used to set the stop time value to previously subtitles
prevSubStopTime = pts;
m_subtitleData = subtitleData();
m_subtitleData.startTime = pts;
m_subtitleData.stopTime = pts + defaultSubDuration;
if (ParseVTTCueBox(sampleData, boxSize - MP4_BOX_HEADER_SIZE, subList))
subList->emplace_back(m_subtitleData);
}
else if (boxType == ISO_BOX_TYPE_VTTX)
{
// VTTX could be used to set the stop time value to previously subtitles
prevSubStopTime = pts;
m_subtitleData = subtitleData();
m_subtitleData.startTime = pts;
m_subtitleData.stopTime = pts + defaultSubDuration;
if (ParseVTTCueBox(sampleData, boxSize - MP4_BOX_HEADER_SIZE, subList))
subList->emplace_back(m_subtitleData);
}
else
{
// Skip unsupported box types
sampleData.SkipChars(boxSize - MP4_BOX_HEADER_SIZE);
}
}
}
bool CWebVTTISOHandler::ParseVTTCueBox(CCharArrayParser& sampleData,
int remainingCueBoxChars,
std::vector<subtitleData>* subList)
{
std::string cueId;
std::string cueSettings;
std::string subtitleText;
// No order is imposed between box types,
// so we have to process the data after retrieving them.
while (remainingCueBoxChars > 0)
{
if (remainingCueBoxChars < MP4_BOX_HEADER_SIZE)
{
CLog::Log(LOGWARNING, "{} - Incomplete VTT Cue box header found", __FUNCTION__);
return false;
}
uint32_t boxSize = sampleData.ReadNextUnsignedInt();
uint32_t boxType = sampleData.ReadNextUnsignedInt();
int payloadLength = boxSize - MP4_BOX_HEADER_SIZE;
remainingCueBoxChars -= MP4_BOX_HEADER_SIZE;
remainingCueBoxChars -= payloadLength;
std::string payload = sampleData.ReadNextString(payloadLength);
if (boxType == ISO_BOX_TYPE_IDEN) // Optional
{
cueId = payload;
}
else if (boxType == ISO_BOX_TYPE_STTG) // Optional
{
cueSettings = payload;
}
else if (boxType == ISO_BOX_TYPE_PAYL)
{
subtitleText = payload;
}
}
m_subtitleData.cueSettings.id = cueId;
GetCueSettings(cueSettings);
CalculateTextPosition(subtitleText);
ConvertSubtitle(subtitleText);
m_subtitleData.text = subtitleText;
return true;
}
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