[FFmpeg-devel] [PATCH] Make h264idct.c compilation optional

Panagiotis Issaris takis.issaris
Mon May 21 17:49:21 CEST 2007

Hash: SHA1


Loren Merritt wrote:
> On Mon, 14 May 2007, Aurelien Jacobs wrote:
>> Panagiotis Issaris wrote:
>>> The attached patch tries to make the h264idct.c compilation optional.
>>> Not meant for direct inclusion, as I am not sure about the correctness...
>>> In dsputil_init() currently [1], for lowres decoding, when idct_algo's
>>> other than FF_IDCT_INT or FF_IDCT_AUTO are selected, h264 related
>>> functions (ff_h264_lowres_idct_put|add_c) are being used. Are these two
>>> functions in fact more generic then their name implies (in fact just
>>> misnamed), and should they be relocated to some other common file?
>>> Or are they really H.264 specific functions? ... but in that case it
>>> seems weird that selecting f.e. FF_IDCT_VP3 or FF_IDCT_SIMPLEMMX would
>>> result in using these H.264 specific functions.
>> Patch seems ok, but I also would like to hear first what's the purpose
>> of ff_h264_lowres_idct_put/add_c (is it h264 only or more general ?).
> ff_h264_lowres_idct* are not used in h264. They're so named because 
> they apply h264's idct algo to other codecs, when whe user requests 
> non-standards-compliant speedups. They're not the default because they're 
> even less precise than the other lowres idct.

I see; thanks for the explanation.

So, I could:
* Move both functions to dsputil.c as they are only used there.
* Keep them in h264idct.c, but disable their usage when H.264 decoder
support is not compiled in. This shouldn't break anything as in that
case ff_jref_idct4_put() would be used instead for lowres==1.

Any opinions?

With friendly regards,

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