Check the mp4 at the beginning and end

YUViewLib/src/filesource/FileSourceFFmpegFile.cpp

@@ -237,27 +237,44 @@ ByteVector FileSourceFFmpegFile::getLhvCData()
 
  // This is a bit of a hack. The problem is that FFmpeg can currently not extract this for us.
  // Maybe this will be added in the future. So the only option we have here is to manually extract
- // the lhvC data from the mp4 file.
- std::ifstream input(this->fileName.toStdString(), std::ios::binary);
- const auto rawFileData = functions::readData(input, 1024);
- if (rawFileData.empty())
- return {};
+ // the lhvC data from the mp4 file. In mp4, the boxes can be at the beginning or at the end of the
+ // file.
+ enum class SearchPosition
+ {
+ Beginning,
+ End
+ };
 
- const std::string searchString = "lhvC";
- const auto lhvcPos =
- std::search(rawFileData.begin(), rawFileData.end(), searchString.begin(), searchString.end());
- if (lhvcPos == rawFileData.end())
- return {};
+ std::ifstream inputFile(this->fileName.toStdString(), std::ios::binary);
+ for (const auto searchPosition : {SearchPosition::Beginning, SearchPosition::End})
+ {
+ constexpr auto NR_SEARCH_BYTES = 5120;
 
- if (std::distance(rawFileData.begin(), lhvcPos) < 4)
- return {};
+  if (searchPosition == SearchPosition::End)
+  inputFile.seekg(-NR_SEARCH_BYTES, std::ios_base::end);
 
- const auto boxSize = getBoxSize(lhvcPos - 4);
- if (boxSize == 0 || boxSize > std::distance(lhvcPos, rawFileData.end()))
- return {};
+ const auto rawFileData = functions::readData(inputFile, NR_SEARCH_BYTES);
+ if (rawFileData.empty())
+ continue;
+
+ const std::string searchString = "lhvC";
+ auto lhvcPos = std::search(
+ rawFileData.begin(), rawFileData.end(), searchString.begin(), searchString.end());
+ if (lhvcPos == rawFileData.end())
+ continue;
+
+ if (std::distance(rawFileData.begin(), lhvcPos) < 4)
+ continue;
+
+ const auto boxSize = getBoxSize(lhvcPos - 4);
+ if (boxSize == 0 || boxSize > std::distance(lhvcPos, rawFileData.end()))
+ continue;
+
+ // We just return the payload without the box size or the "lhvC" tag
+ return ByteVector(lhvcPos + 4, lhvcPos + boxSize - 4);
+ }
 
- // We just return the payload without the box size or the "lhvC" tag
- return ByteVector(lhvcPos + 4, lhvcPos + boxSize - 4);
+ return {};
 }
 
 QList<QByteArray> FileSourceFFmpegFile::getParameterSets()