现在我的1080i 就是一个问题了，编码不稳定：
ARM Load: 12% Video fps: 28 fps Video bit rate: 822 kbps Sound bit rate: 0 kbps
Time: 00:00:09 Demo: Encode Display: 1080I 30Hz Video Codec: H.264 HP Resolution
: 1920x1080 Sound Codec: N/A Sampling Freq: N/A
ARM Load: 19% Video fps: 29 fps Video bit rate: 1497 kbps Sound bit rate: 0 kbps
Time: 00:00:10 Demo: Encode Display: 1080I 30Hz Video Codec: H.264 HP Resolutio
n: 1920x1080 Sound Codec: N/A Sampling Freq: N/A
ARM Load: 16% Video fps: 23 fps Video bit rate: 1457 kbps Sound bit rate: 0 kbps
Time: 00:00:12 Demo: Encode Display: 1080I 30Hz Video Codec: H.264 HP Resolutio
n: 1920x1080 Sound Codec: N/A Sampling Freq: N/A
ARM Load: 16% Video fps: 26 fps Video bit rate: 1326 kbps Sound bit rate: 0 kbps
Time: 00:00:13 Demo: Encode Display: 1080I 30Hz Video Codec: H.264 HP Resolutio
n: 1920x1080 Sound Codec: N/A Sampling Freq: N/A
fps 每秒都在变化，不知为什么？而 720p 的fps是固定在30