ios - GPUImage: synchronization of 2 branch chains -

i working on image stitching app, takes input camera, estimates image transformation , warped input image estimated transformation. shown in following figure, image camera input 2 branch of chains. however, processing of image warping dependent on result of transformation estimation. question how can make branch 1 wait results of branch 2?

if make image warping filter subclass of gpuimagetwoinputfilter, synchronization taken care of you.

target gpuimagevideocamera instance feature matching / transformation estimation filter , image warping filter, target feature matching / transformation estimation filter image warping filter. cause video input come in via first input image , results of feature matching , transformation estimation filter in second image. gpuimagetwoinputfilter subclasses process , output frame once input frames have been provided both inputs.

this should give synchronization want, , pretty straightforward set up.