[FFmpeg-devel] [PATCH 7/9] avcodec/mdct_template: use lrint instead of floor hack

[Ganesh Ajjanagadde]

On Thu, Dec 10, 2015 at 8:54 AM, Ganesh Ajjanagadde
<gajjanagadde at gmail.com> wrote:
> On Sun, Dec 6, 2015 at 8:20 AM, Ganesh Ajjanagadde
> <gajjanagadde at gmail.com> wrote:
>> On Tue, Dec 1, 2015 at 7:27 PM, Ganesh Ajjanagadde
>> <gajjanagadde at gmail.com> wrote:
>>> Signed-off-by: Ganesh Ajjanagadde <gajjanagadde at gmail.com>
>>> ---
>>>  libavcodec/mdct_template.c | 5 +++--
>>>  1 file changed, 3 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/libavcodec/mdct_template.c b/libavcodec/mdct_template.c
>>> index e7e5f62..ecdeb54 100644
>>> --- a/libavcodec/mdct_template.c
>>> +++ b/libavcodec/mdct_template.c
>>> @@ -23,6 +23,7 @@
>>>  #include <string.h>
>>>  #include "libavutil/common.h"
>>>  #include "libavutil/mathematics.h"
>>> +#include "libavutil/libm.h"
>>>  #include "fft.h"
>>>  #include "fft-internal.h"
>>>
>>> @@ -82,8 +83,8 @@ av_cold int ff_mdct_init(FFTContext *s, int nbits, int inverse, double scale)
>>>      for(i=0;i<n4;i++) {
>>>          alpha = 2 * M_PI * (i + theta) / n;
>>>  #if FFT_FIXED_32
>>> -        s->tcos[i*tstep] = (FFTSample)floor(-cos(alpha) * 2147483648.0 + 0.5);
>>> -        s->tsin[i*tstep] = (FFTSample)floor(-sin(alpha) * 2147483648.0 + 0.5);
>>> +        s->tcos[i*tstep] = lrint(-cos(alpha) * 2147483648.0);
>>> +        s->tsin[i*tstep] = lrint(-sin(alpha) * 2147483648.0);
>>>  #else
>>>          s->tcos[i*tstep] = FIX15(-cos(alpha) * scale);
>>>          s->tsin[i*tstep] = FIX15(-sin(alpha) * scale);
>>> --
>>> 2.6.2
>>>
>>
>> Ping for this one, it is relatively important among the lrint patches
>> as this is frequently used and table may be large, making speed
>> benefit somewhat useful.
>> I have noted the header alphabetical include order mistake above.
>
> This is going in soon, as it actually fixes a bug since cos, sin can
> be positive in the relevant ranges here. Last call.
> Note: I think there might be undefined behavior here (before and after
> the patch) since cos(alpha) can be -1 (or very close it) here. That is
> a separate issue that I will examine some time.

pushed