[maemo-developers] Help with YV12->YUV420 converter

[From: Charles 'Buck' Krasic]

Simon Pickering wrote:

> Hi Buck,
>
>> I have not looked at your code, so forgive me if I say something 
>> obvious.
>>
>> The one thing that bit me was the fact that the DSP/toolchain did not
>> handle access to data objects larger than 64k, due to 16 bit
>> restrictions on the DSP.  My understanding is that later toolchains
>> removed those limitations (although I do not know if they ever became
>> freely available).   I wrote very ugly workarounds to handle cases
>> where pointer values crossed 16bit boundaries.  I worked, but overall
>> my code was horribly slow.  If this is news to you, I can provide more
>> details.
>
>
> I'd be interested to see what you did.
>
> When I first started looking at accessing large regions of shared  
> memory I may have run up against that 64k limit (I certainly had some  
> weird errors). I was advised to never attempt to access memory as an  
> array (i.e. ptr[n]) but to always use pointer arithmetic directly  
> (i.e. *(ptr + n)) and it seems to have worked thus far.
>
> Cheers for the advice,
>
>
> Simon
>
Hi Simon,

You can find the code I wrote here:

   http://qstream.org/viewvc/trunk/qvid/src/video_out/maemo_dsp_yuv/

A whole bunch of DSP related documents and things I collected are here:

  http://qstream.org/~krasic/770/dsp/

-- Buck