How to Read Meta-Tags of a MP4-File?

Question

In Windows 11 you can modify Meta-Tags of MP4-Files. Are there libraries for .net core 8 web api available which are able to modify these? Is there a posibility to do that over API-Calls?

I already get to know to the library taglib but this one seems not cover alle my needs, I also can't read out the Subtitle.

Accepted Answer

With Win32 API/Intefaces, it is done with IPropertyStore

Test reading/writing Subtitle on a random .mp4 :

{
    string sFileName = @"E:\Phone265.mp4";
    IPropertyStore pPropertyStore = null;
    Guid PropertyStoreGuid = typeof(IPropertyStore).GUID;
    HRESULT hr = SHGetPropertyStoreFromParsingName(sFileName, IntPtr.Zero, GETPROPERTYSTOREFLAGS.GPS_READWRITE, ref PropertyStoreGuid, out pPropertyStore);
    if (hr == HRESULT.S_OK)
    {
        var pv = new PROPVARIANT();
        hr = pPropertyStore.GetValue(PKEY_Title, out pv);
        if (hr == HRESULT.S_OK)
        {
            string sTitle = Marshal.PtrToStringUni(pv.pwszVal);
            Console.WriteLine("Original Title : {0}", sTitle);
        }
        hr = pPropertyStore.GetValue(PKEY_Media_SubTitle, out pv);
        if (hr == HRESULT.S_OK)
        {
            string sSubTitle = Marshal.PtrToStringUni(pv.pwszVal);
            Console.WriteLine("Original SubTitle : {0}", sSubTitle);
        }

        string sNewSubTitle = "New SubTitle";
        PROPVARIANT pvNewSubTitle = new PROPVARIANT();
        pvNewSubTitle.varType = (ushort)VARENUM.VT_LPWSTR;
        pvNewSubTitle.pwszVal = Marshal.StringToHGlobalUni(sNewSubTitle);
        hr = pPropertyStore.SetValue(PKEY_Media_SubTitle, pvNewSubTitle);
        if (hr == HRESULT.S_OK)
            hr = pPropertyStore.Commit();

        if (hr == HRESULT.S_OK)
        {
            hr = pPropertyStore.GetValue(PKEY_Media_SubTitle, out pv);
            string sSubTitle = Marshal.PtrToStringUni(pv.pwszVal);
            Console.WriteLine("New SubTitle : {0}", sSubTitle);
        }

        Marshal.ReleaseComObject(pPropertyStore);
    }
}

With declarations :

public enum HRESULT : int
{
    S_OK = 0,
    S_FALSE = 1,
    E_NOINTERFACE = unchecked((int)0x80004002),
    E_NOTIMPL = unchecked((int)0x80004001),
    E_FAIL = unchecked((int)0x80004005),
    E_UNEXPECTED = unchecked((int)0x8000FFFFL)
}

[DllImport("Shell32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
public static extern HRESULT SHGetPropertyStoreFromParsingName(string pszPath, IntPtr pbc, GETPROPERTYSTOREFLAGS flags, ref Guid iid, [MarshalAs(UnmanagedType.Interface)] out IPropertyStore propertyStore);

public enum GETPROPERTYSTOREFLAGS
{
    GPS_DEFAULT = 0,
    GPS_HANDLERPROPERTIESONLY = 0x1,
    GPS_READWRITE = 0x2,
    GPS_TEMPORARY = 0x4,
    GPS_FASTPROPERTIESONLY = 0x8,
    GPS_OPENSLOWITEM = 0x10,
    GPS_DELAYCREATION = 0x20,
    GPS_BESTEFFORT = 0x40,
    GPS_NO_OPLOCK = 0x80,
    GPS_PREFERQUERYPROPERTIES = 0x100,
    GPS_EXTRINSICPROPERTIES = 0x200,
    GPS_EXTRINSICPROPERTIESONLY = 0x400,
    GPS_VOLATILEPROPERTIES = 0x800,
    GPS_VOLATILEPROPERTIESONLY = 0x1000,
    GPS_MASK_VALID = 0x1FFF
}

[ComImport, Guid("886D8EEB-8CF2-4446-8D02-CDBA1DBDCF99"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
public interface IPropertyStore
{
    HRESULT GetCount([Out] out uint propertyCount);
    HRESULT GetAt([In] uint propertyIndex, [Out, MarshalAs(UnmanagedType.Struct)] out PROPERTYKEY key);
    HRESULT GetValue([In, MarshalAs(UnmanagedType.Struct)] ref PROPERTYKEY key, [Out, MarshalAs(UnmanagedType.Struct)] out PROPVARIANT pv);
    HRESULT SetValue([In, MarshalAs(UnmanagedType.Struct)] ref PROPERTYKEY key, [In, MarshalAs(UnmanagedType.Struct)] ref PROPVARIANT pv);
    HRESULT Commit();
}

[StructLayout(LayoutKind.Sequential, Pack = 4)]
public struct PROPERTYKEY
{
    private readonly Guid _fmtid;
    private readonly uint _pid;

    public PROPERTYKEY(Guid fmtid, uint pid)
    {
        _fmtid = fmtid;
        _pid = pid;
    }
}

public static readonly PROPERTYKEY PKEY_Title = new PROPERTYKEY(new Guid("F29F85E0-4FF9-1068-AB91-08002B27B3D9"), 2);
public static readonly PROPERTYKEY PKEY_Keywords = new PROPERTYKEY(new Guid("F29F85E0-4FF9-1068-AB91-08002B27B3D9"), 5);
public static readonly PROPERTYKEY PKEY_Media_SubTitle = new PROPERTYKEY(new Guid("56A3372E-CE9C-11D2-9F0E-006097C686F6"), 38);

[StructLayout(LayoutKind.Sequential, Pack = 0)]
public struct PROPARRAY
{
    public UInt32 cElems;
    public IntPtr pElems;
}

[StructLayout(LayoutKind.Explicit, Pack = 1)]
public struct PROPVARIANT
{
    [FieldOffset(0)]
    public ushort varType;
    [FieldOffset(2)]
    public ushort wReserved1;
    [FieldOffset(4)]
    public ushort wReserved2;
    [FieldOffset(6)]
    public ushort wReserved3;

    [FieldOffset(8)]
    public byte bVal;
    [FieldOffset(8)]
    public sbyte cVal;
    [FieldOffset(8)]
    public ushort uiVal;
    [FieldOffset(8)]
    public short iVal;
    [FieldOffset(8)]
    public UInt32 uintVal;
    [FieldOffset(8)]
    public Int32 intVal;
    [FieldOffset(8)]
    public UInt64 ulVal;
    [FieldOffset(8)]
    public Int64 lVal;
    [FieldOffset(8)]
    public float fltVal;
    [FieldOffset(8)]
    public double dblVal;
    [FieldOffset(8)]
    public short boolVal;
    [FieldOffset(8)]
    public IntPtr pclsidVal; // GUID ID pointer  
    [FieldOffset(8)]
    public IntPtr pszVal; // Ansi string pointer  
    [FieldOffset(8)]
    public IntPtr pwszVal; // Unicode string pointer  
    [FieldOffset(8)]
    public IntPtr punkVal; // punkVal (interface pointer)  
    [FieldOffset(8)]
    public PROPARRAY ca;
    [FieldOffset(8)]
    public System.Runtime.InteropServices.ComTypes.FILETIME filetime;
}

public enum VARENUM
{
    VT_EMPTY = 0,
    VT_NULL = 1,
    VT_I2 = 2,
    VT_I4 = 3,
    VT_R4 = 4,
    VT_R8 = 5,
    VT_CY = 6,
    VT_DATE = 7,
    VT_BSTR = 8,
    VT_DISPATCH = 9,
    VT_ERROR = 10,
    VT_BOOL = 11,
    VT_VARIANT = 12,
    VT_UNKNOWN = 13,
    VT_DECIMAL = 14,
    VT_I1 = 16,
    VT_UI1 = 17,
    VT_UI2 = 18,
    VT_UI4 = 19,
    VT_I8 = 20,
    VT_UI8 = 21,
    VT_INT = 22,
    VT_UINT = 23,
    VT_VOID = 24,
    VT_HRESULT = 25,
    VT_PTR = 26,
    VT_SAFEARRAY = 27,
    VT_CARRAY = 28,
    VT_USERDEFINED = 29,
    VT_LPSTR = 30,
    VT_LPWSTR = 31,
    VT_RECORD = 36,
    VT_INT_PTR = 37,
    VT_UINT_PTR = 38,
    VT_FILETIME = 64,
    VT_BLOB = 65,
    VT_STREAM = 66,
    VT_STORAGE = 67,
    VT_STREAMED_OBJECT = 68,
    VT_STORED_OBJECT = 69,
    VT_BLOB_OBJECT = 70,
    VT_CF = 71,
    VT_CLSID = 72,
    VT_VERSIONED_STREAM = 73,
    VT_BSTR_BLOB = 0xfff,
    VT_VECTOR = 0x1000,
    VT_ARRAY = 0x2000,
    VT_BYREF = 0x4000,
    VT_RESERVED = 0x8000,
    VT_ILLEGAL = 0xffff,
    VT_ILLEGALMASKED = 0xfff,
    VT_TYPEMASK = 0xfff
};

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How to Read Meta-Tags of a MP4-File?

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