The document discusses video rotation correction in a video player. It describes how the video recorder records orientation information and how the player can use this to properly display the video based on its original orientation. It involves: 1) The video recorder setting the orientation hint and encoding it in the composition matrix in the video file. 2) The player extracting the composition matrix from the file to determine the original orientation. 3) The player then rotating the video frames accordingly before display to match the original orientation.

1. Video rotation correction Author : Fred Hsu Date : 2011/08/31

7. MediaRecorder setOrientationHint flow Java MediaRecorder Jni android_media_MediaRecorder Framework MediaRecorder IPC Framework IMediaRecorder Framework MediaRecorderClient Framework StagefrightRecorder Store rotation degrees MPEG4Writer Convert to Composition matrix

11. Second stage : trace video player rotation parameter(2) StagefrightPlayer 3gp file header composition matrix libstagefrighthw Convert to degrees Create renderer with degrees Display with rotation ISurface Part of stagefright system Surface system Overlay Video Device Overlay system

12. Q & A