Phonon and filters

[THRESHE]

Hi everybody

In the application I'm writing I need to link filters in a chain to output video stream. One of the filters is a codec that decrypts an XOR-ed file. I need to link these filters on two systems (Windows and Mac OS X).

So the question is are there any methods to explicitly link these filters with Phonon ?
If there aren't phonon methods to do it are there any DirectShow and QuickTime methods to do so?

[wysota]

So first you have a xor encrypted file, which should after decryption be subject to regular video decoding?

Phonon::MediaSource takes QIODevice pointer as its argument, so you can create a QIODevice that will do the decryption on the fly. I did it once for RC4 and it's very simple. There is an article on QQ that deals with the subject.

[THRESHE]

Thanks for your reply Wysota.

But the problem is that if DirectShow links filters one can write a codec that will just link on the top of my codec and dump all decrypted data to a file. My codec is a DRM codec so the aim is to protect data (though personally I think that DRM is stupid it's my job )

[wysota]

Where in the stream does the codec reside?

[THRESHE]

AsyncReader->My filter->Haali Media Splitter ( splits stream to audio and video)->something...->render

[wysota]

So where does the actual frame decoding go?

[THRESHE]

What do you mean ?

[wysota]

Where are the video and audio streams decoded into single images and audio chunks? Before or after your DRM thing?

[THRESHE]

They are decoded after my DRM filter. My filter is a low level one and it can only read raw data from asyncreader end decode them into same raw data but unencrypted.

[wysota]

So how does that make my solution from post #2 invalid? If someone has access to decrypted frames before sending them to the video decoder, using a crafted codec will allow one to intercept the video stream anyway...

[THRESHE]

Yes but if I link filters manually it won't be possible