I'm still struggling with serious frame losses and inconsistent framerates. First I was using the RPi Cam Web Interface to record videos. I then discovered my issues, and I tried then raspivid. Problems got a bit better, but the still remained. The problems are:
What I did to "measure" (a) the dropped frames and (b) to detect inconsistent framerates was (a) to run a 2 minute timer in the video and (b) to walk around.
I did a lot of videos yet, 4 Examples:
RPi Cam Web Interface
Video mode: 1920x1080, 25fps, 17Mbit/s
Video 1: Video of timer on smartphone 2 min on times takes in the clip 1:49 --> Difference of 11s
Video 2: Video of me walking around and a timer 2 min on timer <--> 1:38 in clip --> Difference 22s; serious accelerations and deccelerations in the walking movements --> means that the framerate is inconsistent
Video mode: 1920x1080, 25fps, default bitrate
Video 3: Video of me walking around and a timer 2 min on timer <--> 1:44 in clip --> Difference 16s; accelerations and deccelerations in the walking movements
Video mode: 1920x1080, 25fps, 10Mbit/s
Video 4: Video of me walking around and a timer 2 min on timer <--> 1:47 in clip --> Difference 13s; accelerations and deccelerations in the walking movements
I'm using an Sandisk Extreme Plus, my benchmarks give me 16 MB/s write speed. I have created an XFS-partition, and the RPi Cam Web Interface is recording to that partition. But as you can see it doesn't help. I will try recording to the xfs partition with raspivid.
I'm a bit discouraged... Am I just expecting to much of the camera module? I have tried a lot of things (new better sd card, xfs partition) but the issue doesn't seem to get much better ( the best I get is a loss of frames of 10%....)
EDIT: youtube-link to video: http://youtu.be/2OhT4if5YP4