Writing codecs in C ?
Posted 19 July 2008 - 10:35 PM
I'm totally new to sound and music programming (I don't even know whether I'm in the right section or not ! ) so, I'll try to make my question as clear as possible and I would be really grateful if anyone could help me.
I want to learn about how to write codecs in C to enable a media player to play .rm and .ram for example.
Where should I go to find info about this ? if there are any books on the topic, tutorials .. etc . because I googled a lot and couldn't find what I was looking for.
excuse me if this sounded totally dumb :). I really have no idea about that specific topic.
Posted 20 July 2008 - 10:04 AM
Now the A/V content is normally encoded and that's where a codec comes into play. There are probably a dozen different codecs that could be used in a RealMedia container, and most are likely protected intellectual property with hefty licensing fees.
Other than adding VoIP to an application using the speex codec and a quick and dirty implementation of Realtime Transport Protocol (RTP) many years ago, I don't have much experience in this realm. So, I don't know of any books/references to refer to you.
PS - I do remember discussing audio compression using convolution filters from my college signals and systems class though! :geek:
Edit: It may be easier to start with something very open with easily obtainable specifications like Ogg/Theora/Vorbis. In this case ogg is a container analogous to RM, theora is a video codec and vorbis is an audio codec. These are all open formats as opposed to proprietary RealNetworks IP.
Posted 21 July 2008 - 05:23 PM
Thanks for taking the time to reply but I'm not looking for how to play rm files, I actually want to learn how to de-/encode rm and convert it to other formats ( by writing my own converter, for the sake of learning).
Posted 21 July 2008 - 06:41 PM
As for actually writing a codec, I don't have any experience there so I unfortunately don't know where to point you. You could try downloading the source to some open-source codec, looking to see how it interfaces with Windows and then look up the appropriate keywords in the MSDN (hopefully, info about WMP codecs should be in there, someplace).
Posted 18 December 2008 - 04:43 PM
To be able to make a codec for that format, you must first reverse-engineer the format because you don't even know what the audio compression techniques employed, how is it stored in the file, etc because i think they have not declared there format.
Reverse engineering the format is the problem not writing the codec itself, it will be very tedious task you must know how the audio compressing works, they are using regular PCM or they uses something like vocoders, etc.
I did not see(Maybe there is, i don't know if there please tell me about it) any applications that convert that format into another format, unless they use a workaround of playing the rm file and recording the audio output and saving it in the other format.
Finally IMHO Real Alternative just uses realplayer original dlls to decode the audio so it is not really a codec.
Posted 20 December 2008 - 01:29 PM
Currently working on: the 3D engine for Tomb Raider.
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