[FFmpeg-devel] [PATCH] atrac decoder

[Benjamin Larsson]

Michael Niedermayer wrote:
> On Tue, Jun 09, 2009 at 11:00:38AM +0200, Benjamin Larsson wrote:
>   
>> Michael Niedermayer wrote:
>>     
> [...]
>   
>>>   
>>>       
>>>> +
>>>> +    ff_imdct_calc(mdct_context,out,spec);
>>>>     
>>>>         
>>> cant imdct_half be used?
>>>   
>>>       
>> If you/someone explain what imdct_half does. I need the complete output 
>> from the imdct per my understanding.
>>     
>
> the complete output is the half output twice
> see ff_imdct_calc_c()
>
>   

Ok, now I get it. The actual transform has symmetries but the complete 
output isn't calculated at the time. So that job is passed on to 
vector_fmul_window which does what the last part of imdct_calc did 
before. But this change needs a complete mdct window so I won't be able 
to remove the multiplication by 0 and 1. It should cut the size of the 
windows in half though. Is that good enough ?

MvH
Benjamin Larsson