When I encode every channel video using h264 through m3 video, how can I encode video frame using jpeg and store them on a8 in jpg format.

My program encode every channel video using h264 through m3 video, at the same time I also need encode video frame of a special channel  using JPEG and store them on a8 in jpg format. Now I get video data from dsp and encode video frame using jpeg through a8, but I find this way will lead to other task run error, maybe the effect is too low to using a8 encode. I know dsp can  be used to encde, I don't know whether a good way is existed in DVRRDK_4.0 or not. I'm looking forward  to your answer, thanks.