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video-converter: Fix for broken gamma remap with high bitdepth YUV output

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Scale down the matrix before calculating RGB -> YUV matrix
otherwise offset values will be wrong

Fixing pipeline
videotestsrc ! video/x-raw,format=ARGB ! videoconvert gamma-mode=remap ! \
  video/x-raw,format=P010_10LE,colorimetry="bt2020"

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/1432>
This commit is contained in:
Seungha Yang 2021-12-10 20:09:42 +09:00 committed by GStreamer Marge Bot
parent 49eba42e08
commit fe870b706d
1 changed files with 22 additions and 2 deletions
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24
subprojects/gst-plugins-base/gst-libs/gst/video/video-converter.c
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@ -1974,13 +1974,33 @@ chain_convert_to_YUV (GstVideoConverter * convert, GstLineCache * prev,
if (idx == 0 && !convert->pack_rgb) {
color_matrix_set_identity (&convert->to_YUV_matrix);
compute_matrix_to_YUV (convert, &convert->to_YUV_matrix, FALSE);
/* matrix is in 0..255 range, scale to pack bits */
/* When gamma remap is enabled, we do
* 1) converts to ARGB64 linear RGB
* - if input is 8bits, convert to ARGB and scaled to 16bits with gamma
* decoding at once
* - otherwise converted ARGB64 and gamma decoded
* 2) scale/convert etc,
* 3) and gamma encode
*
* So source data to the do_convert_to_YUV_lines() method is always
* ARGB64
*
* Then, if output unpack format is 8bits, setup_gamma_encode() will scale
* ARGB64 down to ARGB as a part of gamma encoding, otherwise it's still
* ARGB64
*
* Finally this to_YUV_matrix is applied. Since compute_matrix_to_YUV()
* expects [0, 1.0] range RGB as an input, scale down identity matrix
* to expected scale here, otherwise offset of the matrix would be
* very wrong
*/
GST_DEBUG ("chain YUV convert");
scale = 1 << convert->pack_bits;
color_matrix_scale_components (&convert->to_YUV_matrix,
1 / (float) scale, 1 / (float) scale, 1 / (float) scale);
compute_matrix_to_YUV (convert, &convert->to_YUV_matrix, FALSE);
prepare_matrix (convert, &convert->to_YUV_matrix);
}
convert->current_format = convert->pack_format;