I've got a MediaRecorder recording video, and I'm very confused by the effect of setCaptureRate().
Specifically, I prepare my MediaRecorder as follows:
mMediaRecorder = new MediaRecorder();
mCamera.stopPreview();
mCamera.unlock();
mMediaRecorder.setCamera(mCamera);
mMediaRecorder.setVideoSource(MediaRecorder.VideoSource.CAMERA);
mMediaRecorder.setProfile(CamcorderProfile.QUALITY_TIME_LAPSE_480P);
mMediaRecorder.setCaptureRate(30f);
mMediaRecorder.setOrientationHint(270);
mMediaRecorder.setOutputFile(...);
mMediaRecorder.setPreviewDisplay(...);
mMediaRecorder.prepare();
I record for five seconds (with a CountDownTimer, but that's irrelevant), and this is the file that gets generated:
$ ffmpeg -i ~/CaptureRate30fps.mp4
...
Seems stream 0 codec frame rate differs from container frame rate: 180000.00 (180000/1) -> 30.00 (30/1)
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/home/mspitz/CaptureRate30fps.mp4':
Metadata:
major_brand : isom
minor_version : 0
compatible_brands: isom3gp4
creation_time : 2013-06-04 00:52:00
Duration: 00:00:02.59, start: 0.000000, bitrate: 5238 kb/s
Stream #0.0(eng): Video: h264 (Baseline), yuv420p, 720x480, 5235 kb/s, PAR 65536:65536 DAR 3:2, 30 fps, 30 tbr, 90k tbn, 180k tbc
Metadata:
creation_time : 2013-06-04 00:52:00
Note that the Duration is just about 3 seconds. The video also plays much faster, as if it were 5 seconds of video crammed into 3.
Now, if I record by preparing my mediaRecorder exactly as above, but subtracting the setCaptureRate(30f) line, I get a file like this:
$ ffmpeg -i ~/NoSetCaptureRate.mp4
...
Seems stream 0 codec frame rate differs from container frame rate: 180000.00 (180000/1) -> 90000.00 (180000/2)
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/home/mspitz/NoSetCaptureRate.mp4':
Metadata:
major_brand : isom
minor_version : 0
compatible_brands: isom3gp4
creation_time : 2013-06-04 00:50:41
Duration: 00:00:04.87, start: 0.000000, bitrate: 2803 kb/s
Stream #0.0(eng): Video: h264 (Baseline), yuv420p, 720x480, 2801 kb/s, PAR 65536:65536 DAR 3:2, 16.01 fps, 90k tbr, 90k tbn, 180k tbc
Metadata:
creation_time : 2013-06-04 00:50:41
Note that the Duration is as expected, about 5 seconds. The video also plays at a normal speed.
I'm using setCaptureRate(30f) because 30 frames per second is the value of my CamcorderProfile's videoFrameRate. On my Galaxy Nexus S2 (4.2.1), omitting setCaptureRate() is fine, but when I tested on a Galaxy Nexus S3 (4.1.1), omitting setCaptureRate() results in the ever-helpful "start failed -22" error when I called mMediaRecorder.start()
.
So, what am I missing? I thought that the capture rate and the video frame rate were independent, but it's clear that they're not. Is there a way to determine programmatically what I need to set the capture rate at in order to determine that my video plays back at 1x speed?