On Fri, Nov 13, 2015 at 9:33 AM, Hendrik Leppkes <h.lepp...@gmail.com> wrote:
> On Fri, Nov 13, 2015 at 3:23 PM, Ganesh Ajjanagadde
> <gajjanaga...@gmail.com> wrote:
>> The rationale for this function is reflected in the documentation for
>> it, and is copied here:
>>
>> Clip a double value into the long long amin-amax range.
>> This function is needed because conversion of floating point to integers when
>> it does not fit in the integer's representation does not necessarily saturate
>> correctly (usually converted to a cvttsd2si on x86) which saturates numbers
>>> INT64_MAX to INT64_MIN. The standard marks such conversions as undefined
>> behavior, allowing this sort of mathematically bogus conversions. This
>> provides
>> a safe alternative that is slower obviously but assures safety and better
>> mathematical behavior.
>> API:
>> @param a value to clip
>> @param amin minimum value of the clip range
>> @param amax maximum value of the clip range
>> @return clipped value
>>
>> Note that a priori if one can guarantee from the calling side that the
>> double is in range, it is safe to simply do an explicit/implicit cast,
>> and that will be far faster. However, otherwise this function should be
>> used.
>>
>> avutil minor version is bumped.
>>
>> Reviewed-by: Ronald S. Bultje <rsbul...@gmail.com>
>> Signed-off-by: Ganesh Ajjanagadde <gajjanaga...@gmail.com>
>> ---
>> libavutil/common.h | 34 ++++++++++++++++++++++++++++++++++
>> libavutil/version.h | 4 ++--
>> 2 files changed, 36 insertions(+), 2 deletions(-)
>>
>> diff --git a/libavutil/common.h b/libavutil/common.h
>> index 6f0f582..54e5109 100644
>> --- a/libavutil/common.h
>> +++ b/libavutil/common.h
>> @@ -298,6 +298,37 @@ static av_always_inline av_const double
>> av_clipd_c(double a, double amin, double
>> else return a;
>> }
>>
>> +/**
>> + * Clip and convert a double value into the long long amin-amax range.
>> + * This function is needed because conversion of floating point to integers
>> when
>> + * it does not fit in the integer's representation does not necessarily
>> saturate
>> + * correctly (usually converted to a cvttsd2si on x86) which saturates
>> numbers
>> + * > INT64_MAX to INT64_MIN. The standard marks such conversions as
>> undefined
>> + * behavior, allowing this sort of mathematically bogus conversions. This
>> provides
>> + * a safe alternative that is slower obviously but assures safety and better
>> + * mathematical behavior.
>> + * @param a value to clip
>> + * @param amin minimum value of the clip range
>> + * @param amax maximum value of the clip range
>> + * @return clipped value
>> + */
>> +static av_always_inline av_const int64_t av_rint64_clip_c(double a, int64_t
>> amin, int64_t amax)
>> +{
>> +#if defined(HAVE_AV_CONFIG_H) && defined(ASSERT_LEVEL) && ASSERT_LEVEL >= 2
>> + if (amin > amax) abort();
>> +#endif
>> + // INT64_MAX+1,INT64_MIN are exactly representable as IEEE doubles
>> + if (a >= 9223372036854775807.0)
>> + return FFMIN( 9223372036854775807, amax);
>
> How could amax ever be > INT64_MAX? The variable could not represent that.
>
>> + if (a <= -9223372036854775808.0)
>> + return FFMAX(-9223372036854775807-1, amin);
>
> Similar here.
Can be simplified to return amax and amin, thanks.
>
> If I'm missing some reason why this could be possible, these should
> still be using the INT64_MIN/MAX constants however, and the build
> problem fixed at the source.
> libutvideo are C++ files, they probably neglected to set a define to
> unlock these constants.
This usage should be entirely avoided with the above. I prefer keeping
the double constants as is.
>
>> + if (a < amin)
>> + return amin;
>> + if (a > amax)
>> + return amax;
>> + return llrint(a);
>> +}
>> +
>> /** Compute ceil(log2(x)).
>> * @param x value used to compute ceil(log2(x))
>> * @return computed ceiling of log2(x)
>> @@ -511,6 +542,9 @@ static av_always_inline av_const int
>> av_popcount64_c(uint64_t x)
>> #ifndef av_clipd
>> # define av_clipd av_clipd_c
>> #endif
>> +#ifndef av_rint64_clip
>> +# define av_rint64_clip av_rint64_clip_c
>> +#endif
>> #ifndef av_popcount
>> # define av_popcount av_popcount_c
>> #endif
>> diff --git a/libavutil/version.h b/libavutil/version.h
>> index 909f9a6..ea10ff0 100644
>> --- a/libavutil/version.h
>> +++ b/libavutil/version.h
>> @@ -56,8 +56,8 @@
>> */
>>
>> #define LIBAVUTIL_VERSION_MAJOR 55
>> -#define LIBAVUTIL_VERSION_MINOR 5
>> -#define LIBAVUTIL_VERSION_MICRO 100
>> +#define LIBAVUTIL_VERSION_MINOR 6
>> +#define LIBAVUTIL_VERSION_MICRO 0
>>
>> #define LIBAVUTIL_VERSION_INT AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \
>> LIBAVUTIL_VERSION_MINOR, \
>> --
>> 2.6.2
>>
>> _______________________________________________
>> ffmpeg-devel mailing list
>> ffmpeg-devel@ffmpeg.org
>> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel@ffmpeg.org
> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
_______________________________________________
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
