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bayer2rgb: Add comment on bayer_orc_horiz_upsample

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Explain how the bayer_orc_horiz_upsample function works and
what it does with the pixels, as this may not be obvious.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/4686>
This commit is contained in:
Marek Vasut 2023-05-20 16:55:48 +02:00
parent 4efe11a705
commit 920851945f
1 changed files with 52 additions and 0 deletions
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52
subprojects/gst-plugins-bad/gst/bayer/gstbayer2rgb.c
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@ -358,6 +358,58 @@ gst_bayer2rgb_split_and_upsample_horiz (guint8 * dest0, guint8 * dest1,
int n = bayer2rgb->width;
int i;
/*
* Pre-process line of source data in 'src' into two neighboring
* lines of temporary data 'dest0' and 'dest1' as follows. Note
* that first two pixels of both 'dest0' and 'dest1' are special,
* and so are the last two pixels of both 'dest0' and 'dest1' .
*
* The gist of this transformation is this:
* - Assume the source data contain this BG bayer pattern on input
* data line 0 (this is the same as src[0, 1, 2, 3, 4, 5 ...]):
* src 0 : B0 G0 B1 G1 B2 G2
* - This gets transformed into two lines:
* line 0: B0 avg(B0, B1) B1 avg(B1, B2) B2 avg(B2, B3)...
* line 1: G0 G0 avg(G0, G1) G1 avg(G1, G2) G2...
* - Notice ^^ ^^ ^^^^^^^^^^^ ^^ ^^^^^^^^^^^
* These are interpolated BG pairs, one for each input bayer pixel.
*
* The immediatelly following call to this function operates on the next
* input data line 1 as follows:
* - Assume the source data contain this GR bayer pattern on line 1:
* src 0 : G0 R0 G1 R1 G2 R2
* - This gets transformed into two lines:
* line 2: G0 avg(G0, G1) G1 avg(G1, G2) G2 avg(G2, G3)...
* line 3: R0 R0 avg(R0, R1) R1 avg(R1, R2) R2...
* - Notice ^^ ^^ ^^^^^^^^^^^ ^^ ^^^^^^^^^^^
* These are interpolated GR pairs, one for each input bayer pixel.
*
* First two pixels are special, two more pixels as an example of the rest:
* || 0 | 1 || 2 | 3 ::
* ------||--------+----------------++----------------+----------------+:
* DEST0 || src[0] | avg(src[0, 2]) || src[2] | avg(src[2, 4]) ::
* ------||--------+----------------++----------------+----------------+:
* DEST1 || src[1] | src[1] || avg(src[1, 3]) | src[3] ::
* ------||--------+----------------++----------------+----------------+:
*
* Inner block of pixels:
* : | n | n+1 :
* :-------+--------------------+------------------:
* : DEST0 | src[n] | avg(src[n, n+2]) :
* :-------+--------------------+------------------:
* : DEST1 | avg(src[n-1, n+1]) | src[n+1] :
* :-------+--------------------+------------------:
*
* Last two pixels:
* w is EVEN w is ODD
* : | w-2 | w-1 || : | w-2 | w-1 ||
* :-------+----------+----------|| :-------+----------+----------||
* : DEST0 | src[w-2] | src[w-2] || : DEST0 | src[w-3] | src[w-1] ||
* :-------+----------+----------|| :-------+----------+----------||
* : DEST1 | src[w-3] | src[w-1] || : DEST1 | src[w-2] | src[w-2] ||
* :-------+----------+----------|| :-------+----------+----------||
*/
dest0[0] = src[0];
dest1[0] = src[1];
dest0[1] = (src[0] + src[2] + 1) >> 1;