ObscuraCam
Obscuring Videos
The process of obscuring videos demands quite a lot from your phone. You may find that the process works better with newer devices with more powerful processing power, especially for longer videos.
To obscure videos start ObscuraCam in the normal way and click on Obscure Video.
Automatically obscuring videos
You will then be asked to find a video file on your Android device. If you have your videos in various locations you will get a choice.
After selecting your video. You will be asked if you want ObscuraCam to try to automatically detect faces in the video.
Try it by selecting Yes.
You will see the ObscuraCam app trying to recognise the faces in the video.
If this process is successful we should click on the Save button to start the process of saving our obscured video.
If this automatic process does not detect all the faces that we want to obscure or if we want to make other changes we can do this manually. It is possible add regions to be tagged, change their size and also move them.
Manually adding and altering video regions to obscure
To manually add video regions to obscure, start by selecting the first area you want to obscure. If the area is too small or too big you can resize it in the same way as with a still image.
Now touch on the the play icon on the video play bar at the bottom of the screen.
As the video plays, touch and hold the selected area. As the face moves around on the screen, follow it by moving the selected area.
You will see a green trail start to emerge which maps the movement of the selected area.
As you are tracking you can select the Pause button to resize or move your selected area accurately.
Press Play again to resume the process.
When you have finished tracking the face you can touch the selected area again and select Set Out Point.
This process creates a Trail a series of Keyframes which map the location and size of the selected area (tag) to be blurred.
If you make a mistake it is possible to Remove Keyframes. Or if you make a big mistake you can remove the whole trail to start again.
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As you play the video you will see a circle moving to the right showing the progress along the timeline at the bottom of the screen.
You can touch and drag this circle backwards or forwards to review the video and check if the areas are obscured correctly.
If there is more than one face or area that you want to obscured then you can repeat the process above. When you are happy with the areas to be obscured you can touch the Save icon on your options.
You should see a progress bar letting you know the progress of the outputting of your obscured video.
When this is complete, you can use a video player to review the video you have created before you upload it or share it in other ways.
It is possible to click on the Share icon to list the different apps on your phone that can help you do this. 
Video output options
Selecting the more actions bar allows you to change video Preferences. 
These preferences affect the video output settings.
If we look at the defaults for a device after installing ObscuraCam, there are as follows.
Output Framerate: 15 fps
Output Bitrate: 300 kbps
Custom Video Width: 480px
Custom Video Height: 320px
Output Format: 3gp
Output Video Codec: libx264
Output Audio Codec: copy
These default settings are very suitable for sharing a video file quickly as the file size will be relatively small. However, with these settings you may lose a fair amount of quality. Many android devices record video at high quality. As such, there is a trade off between how quickly you can upload your clip and its quality.
If you wanted to change the settings to keep some of this quality but still reduce the file size you may choose some settings like the following.
Output Framerate: 30 fps
Output Bitrate: 900 kbps
Custom Video Width: 640px
Custom Video Height: 360px
Output Format: mp4
Output Video Codec: libx264
Output Audio Codec: copy
Other tools for obscuring video
Blurring using YouTube
YouTube blurring is a feature that has been introduced to the video sharing service relatively recently. Here is a short guide on the process.
When signed in, click the arrow next to the Upload button at the top of any YouTube page. Select Video Manager then select the Edit button for the video you want to blur. Next select Enhancements and select Face Blurring.
When this is done, make sure to preview the video. Often not all faces will be blurred. You need to check this carefully. If you are happy with the result then, click Save rather than Save As this will delete the original video from YouTube's servers.
This subject is covered in more details on the blog of Witness.
http://blog.witness.org/2012/07/visual-anonymity-and-youtubes-new-blurring-tool/