I've found some useful info at linuxtv.org.
I need to setup my camera to bnw (grayscale) and here is the option:
but i can not find this options at documentationV4L2_CID_COLOR_KILLER boolean Enable the color killer (i. e. force a black & white image in case of a weak video signal).
V4L2_CID_COLORFX enum Selects a color effect. The following values are defined:
V4L2_COLORFX_NONE Color effect is disabled.
V4L2_COLORFX_ANTIQUE An aging (old photo) effect.
V4L2_COLORFX_ART_FREEZE Frost color effect.
V4L2_COLORFX_AQUA Water color, cool tone.
V4L2_COLORFX_BW Black and white.
V4L2_COLORFX_EMBOSS Emboss, the highlights and shadows replace light/dark boundaries and low contrast areas are set to a gray background.
V4L2_COLORFX_GRASS_GREEN Grass green.
V4L2_COLORFX_NEGATIVE Negative.
V4L2_COLORFX_SEPIA Sepia tone.
V4L2_COLORFX_SKETCH Sketch.
V4L2_COLORFX_SKIN_WHITEN Skin whiten.
V4L2_COLORFX_SKY_BLUE Sky blue.
V4L2_COLORFX_SOLARIZATION Solarization, the image is partially reversed in tone, only color values above or below a certain threshold are inverted.
V4L2_COLORFX_SILHOUETTE Silhouette (outline).
V4L2_COLORFX_VIVID Vivid colors.
V4L2_COLORFX_SET_CBCR The Cb and Cr chroma components are replaced by fixed coefficients determined by V4L2_CID_COLORFX_CBCR control.
Will it ever be implemented?
Best regards!