Hi,
Using BT709 I see a difference between the “normal” and extended range. BT709 in normal range is closer to the original images and could be a first but not perfect solution.
Using BT601 I see no difference between the normal and extended range. I did some research on how they should differ and also looked at the YUV files: Regardless of the specified range, the color transformation is performed using extended range. Is there another way to force normal range for BT601?
Command to create YUV files:
gst-launch-1.0 multifilesrc location=ramp228/image_ramp_%d.png start-index=1 stop-index=1000 caps="image/png, framerate=25/1, format=GRAY8" ! pngdec ! queue ! videoconvert ! video/x-raw,format=I420,colorimetry="1:4:0:0" ! multifilesink location=YUV/dump_%05d.YUV
Command to create compressed video:
gst-launch-1.0 multifilesrc location=ramp228_3/image_ramp_%d.png start-index=1 stop-index=1000 caps="image/png, framerate=25/1, format=GRAY8" ! pngdec ! queue ! videoconvert ! video/x-raw,format=I420,colorimetry="1:4:0:0" ! x265enc ! h265parse ! qtmux ! filesink location=ramp228.mp4
My result:
| colormetry | np.min(img) | np.max(img) | img[1, 1] |
|---|---|---|---|
| original | 25 | 248 | [228 228 228] |
| 1;3;0;0 | 6 | 255 | [244 247 244] |
| 2;3;0;0 | 17 | 247 | [224 226 225] |
| 1;4;0;0 | 8 | 255 | [245 245 245] |
| 2;4;0;0 | 8 | 255 | [245 245 245] |
legend: colormetry=range:matrix:transfers:primaries
range: 1 → RANGE_0_255, 2 → RANGE_16_235
matrix: 3 → MATRIX_BT709, 4 → MATRIX_BT601
transfer: 0 → TRANSFER_UNKNOWN
primaries: 0 → PRIMARIES_UNKNOWN