Grafika

Grafika is an open-source (Apache 2 license) collection of Android graphics and media hacks. It serves as a practical companion to the Android System-Level Graphics Architecture documentation.

Key Characteristics:

• Target API: Developed for API 18 (Android 4.3), with sporadic support for older versions.
• Implementation: All code is written in Java; the NDK is not used.
• Focus Areas: The project emphasizes thread safety (especially regarding GL/EGL and thread-local storage) and minimizing garbage collection (GC) pauses to prevent jank.
• Stability: It is a work-in-progress, not a polished or stable library, and is not intended to demonstrate the 'proper' way to implement features.

The RecordFBOActivity simultaneously draws to the display and a video encoder using OpenGL ES and Framebuffer Objects (FBOs) to avoid redundant rendering.

Technical Details:

• Rendering Trigger: Uses Choreographer to update every vsync. If the system falls behind, frames are skipped (indicated by an on-screen drop counter and border flash).
• Encoder Rate: The encoder is fed every-other frame, resulting in ~30fps output on typical devices.
• Output Format: Produces a video-only MP4 file named fbo-gl-recording.mp4.
• Aspect Ratio: Recording is letter- or pillar-boxed to match the display aspect ratio.
• Implementation: Located in app/src/main/java/com/android/grafika/RecordFBOActivity.java.

The ContinuousCaptureActivity implements a circular buffer to store video, allowing you to save a segment when the 'capture' button is pressed.

Technical Specifications:

• Buffer Configuration: Hard-wired to capture approximately 7 seconds of video from the camera at 6MB/sec (targeting 15fps 720p). The buffer size is roughly 5MB.
• Output Format: Produces a video-only MP4 file named constant-capture.mp4.
• Resolution: Video is always 1280x720. If the camera input does not match this, the aspect ratio may be incorrect.
• Implementation: Located in app/src/main/java/com/android/grafika/ContinuousCaptureActivity.java.

The ScreenRecordActivity records the device screen to a movie using the MediaProjectionManager API.

Requirement: This requires API level 23 (Marshmallow) or greater. Implementation: Located in app/src/main/java/com/android/grafika/ScreenRecordActivity.java.

The PlayMovieActivity plays the video track from an MP4 file using a TextureView for output.

Usage Details:

• File Access: It only accesses files located in /data/data/com.android.grafika/files/. This directory also contains two automatically generated videos: gen-eight-rects.mp4 and gen-slides.mp4.
• Playback Options: By default, video plays once at the recorded rate. You can enable looping or force playback at a fixed 60 FPS via checkboxes.
• Implementation: Located in app/src/main/java/com/android/grafika/PlayMovieActivity.java.

The ScheduledSwapActivity exercises a SurfaceFlinger feature that allows submitting buffers to be displayed at a specific time.

Requirements and Usage:

• API Requirement: Requires API 19 (Android 4.4 KitKat) for full functionality.
• Configuration: Users can configure frame delivery timing (e.g., a 3-2 pattern for 24fps) and how far in advance frames are scheduled. Selecting "ASAP" disables scheduling.
• Debugging: Use systrace with the following tags to observe effects: sched gfx view --app=com.android.grafika.
• Implementation: Located in app/src/main/java/com/android/grafika/ScheduledSwapActivity.java.

The DoubleDecodeActivity decodes two video streams side-by-side, outputting to a pair of TextureViews.

Key Behaviors:

• Rotation Handling: When the screen rotates, the activity retains the SurfaceTexture and re-attaches it to the new TextureView to avoid expensive codec reconfiguration.
• Resource Management: Decoders stop when the activity is exited to free hardware codec resources.
• Layout: Provides distinct layouts for portrait and landscape modes, scaling videos to fit.
• Implementation: Located in app/src/main/java/com/android/grafika/DoubleDecodeActivity.java.

The CameraCaptureActivity attempts to record 720p video from the front-facing camera while simultaneously displaying the preview.

Usage Details:

• Recording: Use the record button to toggle recording. Note that if you exit and return to the activity, recording restarts, creating a gap in the timeline.
• Filters: You can select filters to apply to the preview; however, these filters are not applied to the actual recording.
• Output Format: Produces a video-only MP4 file named camera-test.mp4. The recorded video is scaled to 640x480, which may result in a squished aspect ratio.
• Implementation: Located in app/src/main/java/com/android/grafika/CameraCaptureActivity.java.