[FFmpeg-devel] [PATCH 1/2] lavu: add a gamma field to AVMasteringDisplayMetadata

[Hendrik Leppkes]

On Wed, Sep 20, 2017 at 4:34 PM, Rostislav Pehlivanov
<atomnuker at gmail.com> wrote:
> On 20 September 2017 at 12:55, Vittorio Giovara <vittorio.giovara at gmail.com>
> wrote:
>
>> diff --git a/libavutil/mastering_display_metadata.h
>> b/libavutil/mastering_display_metadata.h
>> index 847b0b62c6..3de58bf468 100644
>> --- a/libavutil/mastering_display_metadata.h
>> +++ b/libavutil/mastering_display_metadata.h
>> @@ -66,6 +66,16 @@ typedef struct AVMasteringDisplayMetadata {
>>       */
>>      int has_luminance;
>>
>> +    /**
>> +     * The power-law response exponent needed to compensate for
>> nonlinearity.
>> +     */
>> +    AVRational gamma;
>> +
>> +    /**
>> +     * Flag indicating whether the gamma has been set.
>> +     */
>> +    int has_gamma;
>> +
>>  } AVMasteringDisplayMetadata;
>>
>>
>> In my opinion we should not add new fields to structures that map 1:1 to
>> something defined elsewhere (with the exception of booleans).
>> I think this should be a separate side data and type, ie AVGammaResponse,
>> that can of course reside in the same header.
>> --
>> Vittorio
>> _______________________________________________
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>> ffmpeg-devel at ffmpeg.org
>> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>>
>
> Why? I don't see anything special about the struct. And this value fits in
> exactly to what the struct is all about.

I basically agree with Vittorio, the struct basically represents the
HDR metadata as specified for SMPTE ST 2086 (and as signaled as such
in HEVC and various container formats). Jumbling other values in which
are not part of that standard doesn't seem ideal.

- Hendrik