Encoding Quality and Compression
Motif provides a variety of ways to record images. These different codecs will have different affects on your video quality. The best codec for your needs, needs to be determined through experimentation.
Note
All codecs shipped with Motif are high quality, producing videos better than the quality of blue-ray. It is quite possible you will be unable to notice the difference between the original video and the compressed one. The available codecs are specific to your Motif system.
| Class | Name of Codec | Description | Size of a Sample Image with 1920x1200pix |
|---|---|---|---|
| lossless | raw | Raw images are saved, no information loss. | 2.3 MB |
| ll | Visually lossless compressed to h264, extremely high quality. | 1.3 MB | |
| lossy | hq | Very high quality. (h264) | 0.8 - 0.1 MB |
| mq | High quality, similar to blue ray (h264). | 0.05 - 0.01 MB | |
| lq | Good quality. | 0.005 MB |
Note
Codecs with "gray" in their name are optimized and only for the use with grayscale cameras.
How Much Data to Expect
Motif supports a variety of cameras and camera interfaces. The camera interface describes the maximal data rate a camera can send to a Motif recording unit.
The most common interfaces are GigE and USB3, with USB3 providing a higher bandwidth. This means that a USB3 camera can operate with an up to 3.2 times higher frame rate than a GigE camera with the same camera resolution.
USB3 Camera - Data Rate
A Motif USB3 camera operating at its full frame rate and resolution (e.g. 1936x1216pix at 161fps or 2048x2048pix at 90fps) will use the full USB3 bandwidth and send about 356MB of raw data to the Motif recording unit each second.
For most USB3 cameras the full bandwidth is reached if operated at the specified maximal frame rate and resolution.
The estimated video size saved for a USB3 camera at ifs full bandwidth for some example codec configurations are as follows:
| Class | Name of Codec | Data/Sec [MB] | Data/Min [GB] | Data/Hour [TB] | Data/Day [TB] | Data/Week [TB] |
|---|---|---|---|---|---|---|
| lossless | raw | 379 | 22 | 1.36 | 32.7 | 229 |
| ll | 214 | 13 | 0.77 | 18.5 | 129 | |
| lossy | hq | 16 - 131 | 0.99 - 8 | 0.06 - 0.47 | 1.4 - 11 | 10 - 80 |
| mq | 1.6 - 8.2 | 0.1 - 0.5 | 0.006 - 0.03 | 0.14 - 0.7 | 1 - 5 | |
| lq | 0.8 - 8 | 0.05 - 0.5 | 0.003 - 0.03 | 0.07 - 0.7 | 0.5 - 5 |
Effect of Image Modality on Compression
The image modality, or scene composition, has a significant effect on:
- the maximal possible recording frame rate of a Motif recording system
- the factor of compression
Focus and Gradients
Images which are sharp, in focus, and not blurry compress much better and will result in less storage being required than images that are out of focus or feature brightness or color gradients. Gradients are very hard to compress resulting in larger video/image files and an higher utilization of the system. They often occurr if an arena is not illuminated evenly (spot light causing a brightness gradient) or if strong and large shades are introduced.
Image Noise
Temporal image noise is a random variation of brightness or color pixel information and results in less compression, therefore larger files. This is often caused by increasing the Gain of the camera, a high camera temperature caused by not enough cooling and a very short exposure time.
Cameras with larger pixels (larger pixel size) usually have less noise.
The exposure time set for the camera has a crucial role to play with regards to noise. As very short exposure will result in "fixed pattern noise" while a very long exposure will result in "random noise".
Motion
Scenes with high motion components such as panning the camera or if there are many objects in motion in the view of the camera result in larger resulting files.
Complexity
The complexity of an image increases with more differences and finer structures it has. Large, simple and homogeneous areas of the same color and brightness are most efficient to compress (e.g. white or black background).