I have vast experience in debugging and trouble shooting performance as well as memory related issues for different types of applications. I have worked with gstreamer, ffmpeg, directshow, custom players, screen records, video conferencing applications and have in-dept knowledge of video streaming and deep understanding of all the moving parts :).
The most common solution is to use tools to profile the code, however if that's not possible then custom approaches may be used, e.g. narrow down code area by looking at the rate at which memory is growing or the operations that trigger the memory leak, adding a tracking mechanism for memory allocation etc.