[Openchrome-users] New to the list

[Derek Adams]

Xavier Bachelot wrote:
> Derek Adams wrote:
>> Coleman Kane wrote:
>>> On Wed, 2008-06-04 at 08:14 -0700, Derek Adams wrote:
>>>  
>>>> Hello, I'm new to this list and I'm interested in development of 
>>>> the CX700M2 xvmc support.
>>>> I was wondering if people could clue me in with a little more 
>>>> detail than the site contains.
>>>>
>>>> 1. Is anyone working on CX700M2 xvmc support?
>>>> 2. Is anything preventing that development beyond a lack of workforce?
>>>>
> Lack of documentation.
>
>>>> I'd like to contribute to the effort of implementing xvmc on this 
>>>> chipset.
>>>> Thanks!
>>>>
>>>> -Derek
>>>>     
>>> I am attempting to do the same. I've been talking to the rep that runs
>>> http://linux.via.com, however the news looks grim. It seems that VIA
>>> won't release the XvMC docs for the newer hardware because they are
>>> worried about getting sued by the MPEG LA cartel. I've not been able to
>>> get much traction on convincing them to release it myself. VIA did 
>>> admit
>>> that Intel seems to be violating this "agreement" by releasing the same
>>> information for their IGP chipsets.
>>>
>>> If anyone knows has any ideas on pushing this, I'd like to hear. It
>>> would be really valuable for me to just get the docs, then we could
>>> write this part ourselves.
>>>
>>>   
>>
>> Has anyone made any attempt at reverse engineering the hardware?
>
> The current XvMC code was done thru RE.
>
>> Perhaps some of the registers are similar to previous chipsets that 
>> we have existing xvmc code for?
>
> Perhaps. The current hardware decoder engine is known as Unified Video 
> Decoder and has a lot of added capacities than the original engine 
> found on the Unichrome and Unichrome Pro.
>
>> Does VIA release source of their Linux driver?
>
> Only some part of the sources and the hardware decoder is just a 
> binary blob.
>
>> Do they have a driver that support xvmc on the CX700M2?
>>
> Yes, they do. They also have some patches to xine and mplayer to allow 
> them to take advantage of their binary blob.
>
>> Sorry for so many questions!
>>
> No worries. Feel free to ask if you have more.
>
> Regards,
> Xavier
>
>
Thanks very much for the info. I'll try to see what I can get out of 
inspecting the binaries and the mplayer patches. I potentially have 
access to a PCI bus analyzer which I have used in the past to do some 
reverse engineering. Hopefully, the secrets of that binary blob won't be 
secret for long!

*evil laugh*

A general question about MPEG decoders  though:
Do they usually work as a standalone function in the video chipset? If I 
send units of encoded data to them, do I get decoded units back that I 
have to piece together myself? Or does the decoded info get sent down 
some internal pipeline and is only then seen on the screen?

(sorry, I'm a newbie when it comes to video hardware and X)

-Derek