To optimize a media playback application and reduce memory usage, it is essential to approach the task with care. Here are some steps to consider:

1. **Efficient Media Loading and Playback**: Use ExoPlayer, a highly optimized media player library for Android, which provides better memory management than the standard media API.
2. **Bitmap Management**: Implement efficient image loading libraries such as Glide or Picasso, and downsample images to reduce memory consumption.
3. **Caching Strategies**: Employ in-memory caching for frequently accessed media data to minimize the need for repeated loading from storage.
4. **Efficient Data Structures**: Choose SparseArray over HashMap for integer keys, as this can help save memory.
5. **Context and Large Data Objects**: Avoid memory leaks by carefully managing context and large data objects, using weak references when appropriate.
6. **Garbage Collection**: While encouraging garbage collection is beneficial, refrain from making frequent calls to `System.gc()`, as this can adversely affect performance.
7. **Lifecycle Management**: Properly manage lifecycle events by releasing and reinitializing resources as needed during activity and fragment transitions.
8. **Leak Detection**: Utilize tools like LeakCanary to identify and resolve memory leaks.

By following these strategies, you can effectively reduce memory usage while ensuring smooth and efficient media playback.