Android Camera Filter using JavaCV

Hi I'm Newbie, I found a custom android camera app which using JavaCV(https://github.com/sourab-sharma/TouchToRecord). I want add filter string command into RecorderThread.java class in this app. I added string command with colorchannelmixer param into FFmpegFrameFilter string command as:

1. String cropVideo = "crop=w=" + Config.CAMERA_CONSTANTS.OUTPUT_WIDTH + ":h=" + Config.CAMERA_CONSTANTS.OUTPUT_HEIGHT + ":x=" + 0 + ":y=" + 0;
2. String rotateVideoFrontCam = "transpose=cclock,hflip,colorchannelmixer=.393:.769:.189:0:.349:.686:.168:0:.272:.534:.131," + cropVideo;
3. String rotateVideoBackCam = "transpose=clock,colorchannelmixer=.393:.769:.189:0:.349:.686:.168:0:.272:.534:.131," + cropVideo; String cropVideoFrontCam = "hflip,colorchannelmixer=.393:.769:.189:0:.349:.686:.168:0:.272:.534:.131," + cropVideo;
4. filterRotateVideoFrontCam = new FFmpegFrameFilter(rotateVideoFrontCam, previewWidth, previewHeight);
5. filterRotateVideoFrontCam.setPixelFormat(avutil.AV_PIX_FMT_NV21);

But, I do not understand colorchannelmixer params and FFmpeg homepage have 2 example:

1. Convert source to grayscale: colorchannelmixer=.3:.4:.3:0:.3:.4:.3:0:.3:.4:.3
2. Simulate sepia tones: colorchannelmixer=.393:.769:.189:0:.349:.686:.168:0:.272:.534:.131

I have 2 question:

• How exactly to add params to colorchannelmixer params and change them?
• Have other solution for resolv this problem?

Thank so much!