Video aus (Teil-)Stream abspielen

[himitsu]

Mal was Billiges:

Delphi-Quellcode:

Type TStreamPart = Class(TStream)
  Private
    _Stream: TStream;
    _Offset, _Len: Int64;
  Protected
    Function  GetSize: Int64;                          Override;
    Procedure SetSize(NewSize: LongInt);     Overload; Override;
    Procedure SetSize(Const NewSize: Int64); Overload; Override;
  Public
    Constructor Create(Stream: TStream; Const Start, Length: Int64);
    Function Read(Var Buffer; Count: LongInt): LongInt;                       Override;
    Function Write(Const Buffer; Count: LongInt): LongInt;                    Override;
    Function Seek(Offset: LongInt; Origin: Word): LongInt;          Overload; Override;
    Function Seek(Const Offset: Int64; Origin: TSeekOrigin): Int64; Overload; Override;
  End;

Function TStreamPart.GetSize: Int64;
  Begin
    Result := Min(Max(_Stream.Size - _Offset, 0), _Len);
  End;

Procedure TStreamPart.SetSize(NewSize: LongInt);
  Begin
    SetSize(Int64(NewSize));
  End;

Procedure TStreamPart.SetSize(Const NewSize: Int64);
  Begin
    Raise Exception.Create('read only');
  End;

Constructor TStreamPart.Create(Stream: TStream; Const Start, Length: Int64);
  Begin
    _Stream := Stream;
    _Offset := Start;
    _Len    := Length;
  End;

Function TStreamPart.Read(Var Buffer; Count: LongInt): LongInt;
  Begin
    Result := _Stream.Read(Buffer, Min(Int64(Count), Size - Position));
  End;

Function TStreamPart.Write(Const Buffer; Count: LongInt): LongInt;
  Begin
    Result := _Stream.Write(Buffer, Min(Int64(Count), Size - Position));
  End;

Function TStreamPart.Seek(Offset: LongInt; Origin: Word): LongInt;
  Begin
    Result := _Stream.Seek(LongInt(Min(Max(Int64(Offset), 0) + _Offset, MaxInt)), Origin);
  End;

Function TStreamPart.Seek(Const Offset: Int64; Origin: TSeekOrigin): Int64;
  Begin
    Result := _Stream.Seek(Max(Offset, 0) + _Offset, Origin);
  End;

Delphi-Quellcode:

Var X: TStream;

X := TStreamPart.Create(MyFileStream, 1000, 10);

Und schon hat man einen neuen Stream, welcher einen Teil eines anderen Streams liefert.
In diesem Fall z.B. die Bytes 1000 bis 1009 von einem FileStream.
(falls ich mich jetzt nicht verdacht hab)