/// <summary>
/// Reads the chapter information from the specified file.
/// </summary>
/// <param name="fileHandle">The handle to the file from which to read the chapter information.</param>
/// <returns>A new instance of a <see cref="ChapterList"/> object containing the information
/// about the chapters for the file.</returns>
internal static ChapterList ReadFromFile(IntPtr fileHandle)
{
ChapterList list = new ChapterList();
IntPtr chapterListPointer = IntPtr.Zero;
int chapterCount = 0;
NativeMethods.MP4ChapterType chapterType = NativeMethods.MP4GetChapters(fileHandle, ref chapterListPointer, ref chapterCount, NativeMethods.MP4ChapterType.Qt);
if (chapterType != NativeMethods.MP4ChapterType.None && chapterCount != 0)
{
IntPtr currentChapterPointer = chapterListPointer;
for (int i = 0; i < chapterCount; i++)
{
NativeMethods.MP4Chapter currentChapter = currentChapterPointer.ReadStructure <NativeMethods.MP4Chapter>();
TimeSpan duration = TimeSpan.FromMilliseconds(currentChapter.duration);
string title = Encoding.UTF8.GetString(currentChapter.title);
if ((currentChapter.title[0] == 0xFE && currentChapter.title[1] == 0xFF) ||
(currentChapter.title[0] == 0xFF && currentChapter.title[1] == 0xFE))
{
title = Encoding.Unicode.GetString(currentChapter.title);
}
title = title.Substring(0, title.IndexOf('\0'));
list.AddInternal(new Chapter()
{
Duration = duration, Title = title
});
currentChapterPointer = IntPtr.Add(currentChapterPointer, Marshal.SizeOf(currentChapter));
}
}
else
{
int timeScale = NativeMethods.MP4GetTimeScale(fileHandle);
long duration = NativeMethods.MP4GetDuration(fileHandle);
list.AddInternal(new Chapter()
{
Duration = TimeSpan.FromSeconds(duration / timeScale), Title = "Chapter 1"
});
}
if (chapterListPointer != IntPtr.Zero)
{
NativeMethods.MP4Free(chapterListPointer);
}
return(list);
}
/// <summary>
/// Writes the chapter information to the file.
/// </summary>
/// <param name="fileHandle">The handle to the file to which to write the chapter information.</param>
internal void WriteToFile(IntPtr fileHandle)
{
// Only write to the file if there have been changes since the chapters were read.
// Note that a happy side effect of this is that if there were no chapters specified
// in the file at read time, and no manipulation was done before write, we will not
// write chapters into the file, even though our internal representation will contain
// a single chapter with the full duration of the file, and the title of "Chapter 1".
if (this.IsDirty)
{
// Find the first video track, so that we make sure the total duration
// of the chapters we add does not exceed the length of the file.
int referenceTrackId = -1;
for (short i = 0; i < NativeMethods.MP4GetNumberOfTracks(fileHandle, null, 0); i++)
{
int currentTrackId = NativeMethods.MP4FindTrackId(fileHandle, i, null, 0);
string trackType = NativeMethods.MP4GetTrackType(fileHandle, currentTrackId);
if (trackType == NativeMethods.MP4VideoTrackType)
{
referenceTrackId = currentTrackId;
break;
}
}
// If we don't have a video track, then we have an audio file, which has
// only one track, and we can use it to find the duration.
referenceTrackId = referenceTrackId <= 0 ? 1 : referenceTrackId;
long referenceTrackDuration = NativeMethods.MP4ConvertFromTrackDuration(fileHandle, referenceTrackId, NativeMethods.MP4GetTrackDuration(fileHandle, referenceTrackId), NativeMethods.MP4TimeScale.Milliseconds);
long runningTotal = 0;
List <NativeMethods.MP4Chapter> nativeChapters = new List <NativeMethods.MP4Chapter>();
foreach (Chapter chapter in this.chapters)
{
NativeMethods.MP4Chapter nativeChapter = new NativeMethods.MP4Chapter();
// Set the title
nativeChapter.title = new byte[1024];
byte[] titleByteArray = Encoding.UTF8.GetBytes(chapter.Title);
Array.Copy(titleByteArray, nativeChapter.title, titleByteArray.Length);
// Set the duration, making sure that we only use durations up to
// the length of the reference track.
long chapterLength = (long)chapter.Duration.TotalMilliseconds;
if (runningTotal + chapterLength > referenceTrackDuration)
{
nativeChapter.duration = referenceTrackDuration - runningTotal;
}
else
{
nativeChapter.duration = chapterLength;
}
runningTotal += chapterLength;
nativeChapters.Add(nativeChapter);
if (runningTotal > referenceTrackDuration)
{
break;
}
}
NativeMethods.MP4Chapter[] chapterArray = nativeChapters.ToArray();
NativeMethods.MP4SetChapters(fileHandle, chapterArray, chapterArray.Length, NativeMethods.MP4ChapterType.Qt);
}
}
