[vlc-devel] Encrypting x264 data...

[Peter Tap]

Hi Kaarlo,

Thank you once again for your help. Now vlc model has started to become clear. A module would typically add "Open" and "Close" static methods within vlc_module_begin() and vlc_module_end() pair. In the "Open" method itself, the module can specify additional functions such as Mux, AddStream, DelStream, etc. Wish there was some documentation on this.

There is one thing that is still confusing. As I now plan to encrypt the whole file, I guess I have no choice but to implement my own container. Glancing through the source files, it appears containers implement "demux" mechanism and not "mux". Hence they are all under "demux" directory. Your suggestion is that I need to look into "mux" directory. I am guessing muxing comes "after" decoding. I may not get a chance to decrypt before decoding happens. Am I missing something?

Appreciate your help.

Regards,
Peter



________________________________
From: Kaarlo Räihä <kaarlo.raiha at gmail.com>
To: Mailing list for VLC media player developers <vlc-devel at videolan.org>
Sent: Monday, August 22, 2011 10:18 PM
Subject: Re: [vlc-devel] Encrypting x264 data...


2011/8/23 Peter Tap <ptrtap at yahoo.com>

Kaarlo,
>
>
>Thank you very much for your help. I looked at "demux" directory and mp4 as well as mkv examples. However, the use of API is not clear. I would imagine the APIs should be:
>1. Can you handle "xyz" extension?

If you mean file extensions, they are generally a bad way to detect stuff, but if you are only planning limited distribution it is OK.
 
2. Give me the type of streams (audio, video, etc.) along with the format type (AAC, x264, etc.)
>3. Give me the next x bytes from nth stream.
>
>
>On the developer corner, I couldn't find any documentation on how to write a muxer. Other than vlc_open and vlc_close, what other methods need to be implemented?

You can reuse some existing muxer/demux and just encode/decode before/after file writing/reading. You have to implement mux, control etc. parts, if you want to create completely new muxer see http://git.videolan.org/?p=vlc.git;a=blob;f=modules/mux/avi.c and lines 164-168
 

>
>Appreciate your help.
>
>
>Regards,
>Peter
>
>
>
>________________________________
>From: Kaarlo Räihä <kaarlo.raiha at gmail.com>
>
>To: Mailing list for VLC media player developers <vlc-devel at videolan.org>
>Sent: Sunday, August 21, 2011 11:26 PM
>
>Subject: Re: [vlc-devel] Encrypting x264 data...
>
>
>
>2011/8/22 Peter Tap <ptrtap at yahoo.com>
>
>Folks,
>>
>>
>>For the project I am working on, I need to create a new container format, encrypt x264 data and store it. This file can only be played through vlc and I need to provide on-the-fly decryption.
>>
>>
>>
>>
>>I have downloaded and built vlc code. I have also gone through various documentation pages. However, I am still confused on where to start. I would appreciate it if someone can help me with the following questions:
>>
>>
>>1. How to write a new container module?
>
>
>If you are only interested about VLC, you have to create new demux and mux modules. 
> 
>2. I need to use x264 module internally. I need to integrate with it such that each block that x264 decodes needs to be decrypted first and passed on to x264 decoder. I am wondering what would be a good way to achieve this?
>>3. Although I have built vlc source and vlc seems to run correctly, I am a bit confused about where the source files for each module really is. For example, when I look under contrib/src/x264, I don't see any .h or .c files. I need to debug and step through x264 code. How can I achieve this? Note that during the initial ".configure" step, I did specify enable-debug as a flag.
>>
>>
>>Also, may be there is a simpler way of what I am trying to achieve. Perhaps I can just hook into x264 decoding mechanism. Is this possible? 
>
>
>Do encryption stuff on muxer level. There really isn't any point to change x264 and H.264 decoders. With muxer level encryption you can also protect the audio tracks and subtitles.  
> 
>
>>
>>Thank you in advance for your help.
>>
>>
>>Regards,
>>Peter
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