Short intro to project butter
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Project Butter aims to improve smoothness (UX) in Android through techniques like VSync, triple buffering, and the Choreographer. VSync synchronizes rendering to a display's refresh rate. Triple buffering uses three buffers to minimize tearing. The Choreographer coordinates animations, input and drawing, and notifies of VSync signals, allowing apps to optimize for smoothness. However, it only works within an app rather than system-wide.
Short intro to project butter
- 1. Short Intro for Project Butter Yoshi@8/5/2015 (Photo by Malcolm Dunbar/Picture Post/Getty Images)
- 2. Project Butter is…? • Butter, smoothness, for better UX • Started at Android 4.1 (2012, API Level 16) • Three main parts – VSync – Triple Buffering – Touch Responsiveness (Choreographer)
- 3. Pseudocode of VSync-Style Program No VSync Style VSync Style
- 4. VSync is … (In Android) • A periodical interrupt – To call your callback function • Two possible implementations 1.Hardware timer 2.Software simulation • A high priority thread which wakes up every 16.7ms
- 5. With and Without VSync No VSync With VSync
- 6. VSyncThread Either HW or SW implementation
- 7. “Triple” Buffers? • It doesn’t mean to buffer something in many contexts – Not a verb, but a noun – It’s more like # of buffers it uses • It can be proved that only 3 buffers are required at most – So you will never see 4+ buffer in game settings of a game
- 8. Triple Buffer Double buffer (A,B) Triple Buffer (A,B,C)
- 9. Intro to Choreographer • Choreographer (from Android Doc) – Coordinates the timing of animations, input and drawing – The choreographer receives timing pulses (such as vertical synchronization) from the display subsystem • Schedules work to occur as part of rendering the next display frame Image: http://jordanmleczko.weebly.com/my-future.html
- 10. Using Choreographer to Detect FPS and Frame Dropping https://github.com/yoshijava/Choreographer
- 11. Issue of Choreographer Choreographer is designed to bind with a specific looper (of an app) But we need a system-wide frame-dropping and FPS notifier
- 12. Choreographer VSyncThread (HW or SW) VSync signals looper looper looper looper Choreographer Choreographer Choreographer
- 13. Looper.myLooper(); Static method; Thread-Local Storage (TLS) Choreographer has no public constructor, only static getInstance() Static method; Thread-Local Storage (TLS)
- 14. Using Choreographer in any Activity How about extending ChoreographerTest?
- 15. With callback, we can get # of dropped frames and estimate FPS manually
- 16. Summary • Project Butter is not a new thing – VSync and triple buffer are an old thing in desktop – However, introduced to Android in 2012 • Choreographer is “per app” design – Every app developer can optimize their apps by getting notified when VSync signal comes – Note that it is not system-wide (?)