Calculating Parameter Values
| Microsoft DirectShow 9.0 |
Calculating Parameter Values
Potentially, an input buffer could be very large. Ideally, when the DMO processes the buffer, the parameters will exactly follow their curves throughout the entire batch of data. However, a DMO has some leeway in how it calculates those values.
- The most accurate approach is to calculate the exact value for every atomic unit of data; for example, each audio sample. This approach is the most computationally expensive.
- Another approach is to slice the data into smaller units of some fixed size, such as 100 samples. This approach creates a "stair-stepping" effect. For some parameters, that might be acceptable. In audio effects, it might create audible artifacts.
- A compromise is to use the previous technique, but within each batch, perform a linear interpolation of the parameter value for each sample.
These issues are especially important for audio processing. One second of audio might contain 48,000 audio samples per channel, which is a lot of calculations to perform, yet the ear is sensitive to artifacts such as aliasing.
See Also