[FFmpeg-devel] [PATCH] mpegaudio float default

Michael Niedermayer michaelni
Wed May 19 02:12:04 CEST 2010

On Tue, May 18, 2010 at 10:18:46PM +0200, Benjamin Larsson wrote:
> On 18/05/10 20:51, Michael Niedermayer wrote:
>> On Mon, May 17, 2010 at 11:47:08AM -0400, Ronald S. Bultje wrote:
>>> Hi,
>>> On Mon, May 17, 2010 at 11:18 AM, Michael Niedermayer<michaelni at gmx.at>  
>>> wrote:
>>>> On Thu, May 13, 2010 at 06:23:46PM -0400, Ronald S. Bultje wrote:
>>>>> Hi,
>>>>> On Thu, May 13, 2010 at 6:12 PM, Michael Niedermayer<michaelni at gmx.at>  
>>>>> wrote:
>>>>>> On Thu, May 13, 2010 at 10:56:36PM +0100, M?ns Rullg?rd wrote:
>>>>>>> Michael Niedermayer<michaelni at gmx.at>  writes:
>>>>>>> 3x slower on Cortex-A8.  We need to discuss betters way to choose
>>>>>>> implementation.  Ideally we should have something that extends well 
>>>>>>> to
>>>>>>> other codecs too.  There are fixed-point versions of at least wma
>>>>>>> floating about, and IMO we should be working towards merging them.
>>>>>> someone is working on fixp wma ? :)
>>>>> Rockbox (?) already has a fxp wma1/2 decoder, based on the FFmpeg one
>>>>> from several years ago, that they'd like to backport into our tree if
>>>>> we're interested.
>>>> ive been pointed to
>>>> http://www.mail-archive.com/rockbox-dev at cool.haxx.se/msg07388.html
>>>> http://www.mail-archive.com/rockbox-dev at cool.haxx.se/msg07413.html
>>>> This thread does not sound like the rockbox devels seriously intent to
>>>> integrate fixed point support back into the ffmpeg codecs.
>>>> But iam not on their ML so its easy for me to misinterrpret this.
>>> I think you're right, and re-reading my original reply I was too
>>> positive. Just alone looking at their reference to tremor, I don't
>>> think they have any idea of how to do this in a good way (= code
>>> sharing between fixp/float impls where possible, etc.), they simply
>>> want to plumb a new codec in our tree called "wmafixed", which decodes
>>> streams that are syntactically similar to wma1/2 but which shares 0%
>>> code with any of the rest of the FFmpeg tree.
>>> I don't think that's useful.
>> so back to my original question
>> do we have someone who wants to work on adding fixp support to out wma 
>> decoder?
>> mans? ben?
>> if no i might (emphasis is "might") eventually try to do it myself,
>> but mans would be the more ideal person to do this because he is actually
>> interrested in it and has fpu-less hardware.
>> Its not particularely hard work, just converting one function at a time to
>> fixp and verifying that it still works. One just has to try to maximize
>> precission while preventing overflows and redusing rescaling steps
> The thing is that rockbox has good mdct code. We should try to get that 
> merged first. After that step is done we can merge the cook patch that was 
> posted years ago. But currently I don't have time to do it, I'll talk to 
> some Rockbox guys tomorrow though and see if they can do it.

ok, please keep us/me updated on this, id like to see wma-fixp in lavc
before everyone had to waste their time figuring out how to use thr rockbox
code directly


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Those who are too smart to engage in politics are punished by being
governed by those who are dumber. -- Plato 
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