[FFmpeg-devel] [PATCH] avfilter/vf_zscale: fix output color_range discrepancy

[Pavel Koshevoy]

On Fri, Sep 17, 2021 at 12:45 AM Paul B Mahol <onemda at gmail.com> wrote:

> I doubt this is correct, something is fishy here.
>

The issue is that you are assigning a value of type zimg_color_family_e to
a variable of type AVColorRange.

typedef enum zimg_pixel_range_e {
ZIMG_RANGE_INTERNAL = -1, /**< Not part of the API. */
ZIMG_RANGE_LIMITED  = 0,  /**< Studio (TV) legal range, 16-235 in 8 bits. */
ZIMG_RANGE_FULL     = 1   /**< Full (PC) dynamic range, 0-255 in 8 bits. */
} zimg_pixel_range_e;

enum AVColorRange {
    AVCOL_RANGE_UNSPECIFIED = 0,
    AVCOL_RANGE_MPEG        = 1,
    AVCOL_RANGE_JPEG        = 2,
    AVCOL_RANGE_NB               ///< Not part of ABI
};

As you can see, (int)ZIMG_RANGE_FULL is not the same as
(int)AVCOL_RANGE_JPEG.
And you've apparently had run into this once before, 6 years ago:

$ git annotate libavfilter/vf_zscale.c | grep 'color_range' | grep out
b5cf307d        (Paul B Mahol   2016-09-02 16:03:58 +0200       580)
|| s->out_range != out->color_range
416e35e5        (Paul B Mahol   2015-09-21 15:34:15 +0200       620)
     out->color_range = (int)s->dst_format.pixel_range + 1;
416e35e5        (Paul B Mahol   2015-09-21 15:34:15 +0200       640)
 s->out_range      = out->color_range;
416e35e5        (Paul B Mahol   2015-09-21 15:34:15 +0200       679)
 out->color_range = (int)s->dst_format.pixel_range;


I hope this clears your doubt.

Thank you,
    Pavel.



>
> On Fri, Sep 17, 2021 at 4:17 AM Pavel Koshevoy <pkoshevoy at gmail.com>
> wrote:
>
>> This filter chain was supposed to convert from narrow range
>> to full range yuv444p, but didn't:
>>
>> buffer=width=1280:height=720:pix_fmt=yuv444p:frame_rate=25/1:\
>> time_base=1/25:sar=1/1,zscale=min=709:rin=limited:pin=709:\
>> tin=709:t=linear,format=gbrpf32le,zscale=tin=linear:p=709:m=709:\
>> r=full:t=709,format=pix_fmts=yuv444p,buffersink
>> ---
>>  libavfilter/vf_zscale.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/libavfilter/vf_zscale.c b/libavfilter/vf_zscale.c
>> index dfea00f9eb..06a025e6e6 100644
>> --- a/libavfilter/vf_zscale.c
>> +++ b/libavfilter/vf_zscale.c
>> @@ -676,7 +676,7 @@ static int filter_frame(AVFilterLink *link, AVFrame
>> *in)
>>          out->color_primaries = (int)s->dst_format.color_primaries;
>>
>>      if (s->range != -1)
>> -        out->color_range = (int)s->dst_format.pixel_range;
>> +        out->color_range = (int)s->dst_format.pixel_range + 1;
>>
>>      if (s->trc != -1)
>>          out->color_trc = (int)s->dst_format.transfer_characteristics;
>> --
>> 2.26.2
>>
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>