I just hate looking at my old footage and seeing the image dodge from side to side. You see this in professional video too. Its not just because it's distracting but it can be frustrating to fix.
Now, if you have an out of the box drone from DJI or 3DR, you may need to look for anwers with them, but if you are using DIY and OpenTx, I can help. There are 2 causes of this problem and both need to be addressed. The first is yaw tuning and that's my next blog . The second is pilot input and that can be fixed with the Tx config.
OpenTx and other transmitters allow you to add custom curves to your output mixes. If you are human then you can't hold anything totally still. The input of yaw by the pilot isn't noticeable until you record and play aerial video. Its common to edit out the wiggly bits but this problem doesn't have to be at all.
The yaw input is nearly always the cause. Long straight lines of flight look much better if the video doesn't twitching side to side. Often the solution used is a 3D gimbal but its not really the root of the problem. You should be able to hold the throttle/yaw or altitude/yaw stick, while doing a straight run and get zero deviations. That is "keep a perfectly straight heading".
Solution, you need is a dead zone in the center of the yaw curve, whilst still keeping control. Below is a custom curve I use to achieve this. While is looks exponential it isn't. It's a compromise between a straight line and expo. You really don't notice the difference while flying just afterwards when you view the recorded video.
You can use only this or switch it off when it's not required. Below is a channel mix that I use for one of my imaging-UAVs.
I us the input mix to implement the curve and the output to implement the switch (on-off).
It always amazed me how much yaw crept into my video. Now I usually get a pleasant surprise. I hope you do too.
I hope this is helpful, there will be a post on yaw tuning in a few days.