[FFmpeg-cvslog] r24213 - trunk/libavcodec/dca.c

[Alex Converse]

2010/7/12 M?ns Rullg?rd <mans at mansr.com>:
> "Ronald S. Bultje" <rsbultje at gmail.com> writes:
>
>> Hi,
>>
>> 2010/7/12 M?ns Rullg?rd <mans at mansr.com>:
>>> Vitor Sessak <vitor1001 at gmail.com> writes:
>>>> On 07/12/2010 02:32 PM, benoit wrote:
>>>>> Author: benoit
>>>>> Date: Mon Jul 12 14:32:24 2010
>>>>> New Revision: 24213
>>>>>
>>>>> Log:
>>>>> Use math constant instead of hardcoded rounded value for sqrt(0.5).
>>>>> Patch by Christophe.Gisquet (gmail)
>>>>>
>>>>> Modified:
>>>>> ? ? trunk/libavcodec/dca.c
>>>>>
>>>>> Modified: trunk/libavcodec/dca.c
>>>>> ==============================================================================
>>>>> --- trunk/libavcodec/dca.c ? Mon Jul 12 12:17:20 2010 ? ? ? ?(r24212)
>>>>> +++ trunk/libavcodec/dca.c ? Mon Jul 12 14:32:24 2010 ? ? ? ?(r24213)
>>>>> @@ -1403,8 +1403,8 @@ static int dca_decode_frame(AVCodecConte
>>>>> ? ? ? ? ? ? ? float* rt_chan ? = s->samples + s->channel_order_tab[s->xch_base_channel - 1] * 256;
>>>>> ? ? ? ? ? ? ? int j;
>>>>> ? ? ? ? ? ? ? for(j = 0; j< ?256; ++j) {
>>>>> - ? ? ? ? ? ? ? ?lt_chan[j] -= (back_chan[j] - s->add_bias) * 0.707107f;
>>>>> - ? ? ? ? ? ? ? ?rt_chan[j] -= (back_chan[j] - s->add_bias) * 0.707107f;
>>>>> + ? ? ? ? ? ? ? ?lt_chan[j] -= (back_chan[j] - s->add_bias) * M_SQRT1_2;
>>>>> + ? ? ? ? ? ? ? ?rt_chan[j] -= (back_chan[j] - s->add_bias) * M_SQRT1_2;
>>>>
>>>> Won't this patch make it use double-precision floating point math when
>>>> not needed?
>>>
>>> Time for f-versions of those constants?
>>
>> They're defines, just add a "f" behind it when using it, e.g. M_SQRT1_2 f.
>
> That doesn't work. ?It has to be a single token.
>

A (float) cast should fold it to a float constant at compile time.