[FFmpeg-devel] [PATCH] lavu: Adding hybrid-log gamma enum value and transfer function.
Neil Birkbeck
neil.birkbeck at gmail.com
Wed Jun 1 06:02:44 CEST 2016
Any other thoughts on we should move forward with the _ARIB_STD name
or to use something like HYBRID_LOG_GAMMA?
On Thu, Apr 21, 2016 at 5:04 PM, Neil Birkbeck <neil.birkbeck at gmail.com> wrote:
> Thanks Hendrik.
>
> For now, I've updated the patch with a better comment and commit
> message, and will change name to the more intuitive _HLG or
> (_HYBRID_LOG_GAMMA) if you feel this is better. Seems that the more
> recent enums use a standard as the name for the enum (e.g.,
> SMPTEST2084 is often referred to as Perceptual Quantizer or PQ).
>
>
>
> On Thu, Apr 21, 2016 at 2:03 PM, Hendrik Leppkes <h.leppkes at gmail.com> wrote:
>> On Thu, Apr 21, 2016 at 10:57 PM, Neil Birkbeck <neil.birkbeck at gmail.com> wrote:
>>> The standard:
>>> http://www.arib.or.jp/english/html/overview/doc/2-STD-B67v1_0.pdf
>>>
>>> The choice of enum value of 18 is consistent with HEVC:
>>> http://phenix.it-sudparis.eu/jct/doc_end_user/current_document.php?id=10481
>>>
>>> and also with latest proposal for color trc in mkv:
>>> https://mailarchive.ietf.org/arch/search/?email_list=cellar&gbt=1&q=Colour+Format+proposal
>>>
>>> Signed-off-by: Neil Birkbeck <neil.birkbeck at gmail.com>
>>> ---
>>> libavutil/color_utils.c | 16 ++++++++++++++++
>>> libavutil/pixdesc.c | 2 +-
>>> libavutil/pixfmt.h | 1 +
>>> tests/ref/fate/color_utils | 19 +++++++++++++++++++
>>> 4 files changed, 37 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/libavutil/color_utils.c b/libavutil/color_utils.c
>>> index 6dba46a..87e5f5e 100644
>>> --- a/libavutil/color_utils.c
>>> +++ b/libavutil/color_utils.c
>>> @@ -155,6 +155,18 @@ static double avpriv_trc_smpte_st428_1(double Lc)
>>> : pow(48.0 * Lc / 52.37, 1.0 / 2.6);
>>> }
>>>
>>> +
>>> +static double avpriv_trc_arib_std_b67(double Lc) {
>>> + // The function uses the definition from HEVC, which assumes that the peak
>>> + // white is input level = 1. (this is equivalent to scaling E = Lc * 12 and
>>> + // using the definition from the arib standard)
>>> + const double a = 0.17883277;
>>> + const double b = 0.28466892;
>>> + const double c = 0.55991073;
>>> + return (0.0 > Lc) ? 0.0 :
>>> + (Lc <= 1.0 / 12.0 ? sqrt(3.0 * Lc) : a * log(12.0 * Lc - b) + c);
>>> +}
>>> +
>>> avpriv_trc_function avpriv_get_trc_function_from_trc(enum AVColorTransferCharacteristic trc)
>>> {
>>> avpriv_trc_function func = NULL;
>>> @@ -209,6 +221,10 @@ avpriv_trc_function avpriv_get_trc_function_from_trc(enum AVColorTransferCharact
>>> func = avpriv_trc_smpte_st428_1;
>>> break;
>>>
>>> + case AVCOL_TRC_ARIB_STD_B67:
>>> + func = avpriv_trc_arib_std_b67;
>>> + break;
>>> +
>>> case AVCOL_TRC_RESERVED0:
>>> case AVCOL_TRC_UNSPECIFIED:
>>> case AVCOL_TRC_RESERVED:
>>> diff --git a/libavutil/pixdesc.c b/libavutil/pixdesc.c
>>> index 8a9475c..995244b 100644
>>> --- a/libavutil/pixdesc.c
>>> +++ b/libavutil/pixdesc.c
>>> @@ -2080,6 +2080,7 @@ static const char *color_transfer_names[AVCOL_TRC_NB] = {
>>> "bt470bg", "smpte170m", "smpte240m", "linear", "log100",
>>> "log316", "iec61966-2-4", "bt1361e", "iec61966-2-1",
>>> "bt2020-10", "bt2020-20", "smpte2084", "smpte428-1",
>>> + "arib-std-b67"
>>> };
>>>
>>> static const char *color_space_names[AVCOL_SPC_NB] = {
>>> @@ -2560,4 +2561,3 @@ int main(void){
>>> }
>>>
>>> #endif
>>> -
>>> diff --git a/libavutil/pixfmt.h b/libavutil/pixfmt.h
>>> index 546eb44..16bd5bc 100644
>>> --- a/libavutil/pixfmt.h
>>> +++ b/libavutil/pixfmt.h
>>> @@ -420,6 +420,7 @@ enum AVColorTransferCharacteristic {
>>> AVCOL_TRC_BT2020_12 = 15, ///< ITU-R BT2020 for 12 bit system
>>> AVCOL_TRC_SMPTEST2084 = 16, ///< SMPTE ST 2084 for 10, 12, 14 and 16 bit systems
>>> AVCOL_TRC_SMPTEST428_1 = 17, ///< SMPTE ST 428-1
>>> + AVCOL_TRC_ARIB_STD_B67 = 18, ///< Hybrid log-gamma
>>
>> I find it odd that the name is seemingly unrelated to the comment, the
>> comment should probably elaborate more.
>> The commit message could probably also benefit from using the same name.
>>
>>> AVCOL_TRC_NB, ///< Not part of ABI
>>> };
>>>
>>> diff --git a/tests/ref/fate/color_utils b/tests/ref/fate/color_utils
>>> index 6e80ebd..10f8055 100644
>>> --- a/tests/ref/fate/color_utils
>>> +++ b/tests/ref/fate/color_utils
>>> @@ -283,3 +283,22 @@ AVColorTransferCharacteristic=17 calling func(15123.456700) expected=39.174525
>>> AVColorTransferCharacteristic=17 calling func(19845.889230) expected=43.490646
>>> AVColorTransferCharacteristic=17 calling func(98678.423100) expected=80.593559
>>> AVColorTransferCharacteristic=17 calling func(99999.899998) expected=81.006971
>>> +AVColorTransferCharacteristic=18 calling func(-0.100000) expected=0.000000
>>> +AVColorTransferCharacteristic=18 calling func(-0.018054) expected=0.000000
>>> +AVColorTransferCharacteristic=18 calling func(-0.010000) expected=0.000000
>>> +AVColorTransferCharacteristic=18 calling func(-0.004490) expected=0.000000
>>> +AVColorTransferCharacteristic=18 calling func(0.000000) expected=0.000000
>>> +AVColorTransferCharacteristic=18 calling func(0.003162) expected=0.097400
>>> +AVColorTransferCharacteristic=18 calling func(0.005000) expected=0.122474
>>> +AVColorTransferCharacteristic=18 calling func(0.009000) expected=0.164317
>>> +AVColorTransferCharacteristic=18 calling func(0.015000) expected=0.212132
>>> +AVColorTransferCharacteristic=18 calling func(0.100000) expected=0.544089
>>> +AVColorTransferCharacteristic=18 calling func(1.000000) expected=1.000000
>>> +AVColorTransferCharacteristic=18 calling func(52.370000) expected=1.712092
>>> +AVColorTransferCharacteristic=18 calling func(125.098765) expected=1.867862
>>> +AVColorTransferCharacteristic=18 calling func(1999.111230) expected=2.363502
>>> +AVColorTransferCharacteristic=18 calling func(6945.443000) expected=2.586219
>>> +AVColorTransferCharacteristic=18 calling func(15123.456700) expected=2.725380
>>> +AVColorTransferCharacteristic=18 calling func(19845.889230) expected=2.773978
>>> +AVColorTransferCharacteristic=18 calling func(98678.423100) expected=3.060803
>>> +AVColorTransferCharacteristic=18 calling func(99999.899998) expected=3.063182
>>> --
>>> 2.8.0.rc3.226.g39d4020
>>>
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