waveform80
commented
10 years ago Hi Luke,
Yup - to address your first attempt: when you set the resolution of the camera, that's the resolution the camera will attempt to run at (or more precisely, that will influence the resolution the camera will run at; the first section in Camera Hardware has the gory details). The resize parameter does literally that: applies a resizer in the image/video processing pipeline.
When you set the camera to 320x240 (and I'm guessing 30fps), the camera will switch to 1296x972 resolution and down-scale to 320x240. Recording with resize=2592x1944 will stick a resizer in the pipeline just before the H.264 encoder which will blow that 320x240 output up to 2592x1944.
Conversely when you set the camera to 2592x1944 (and presumably 15fps), the camera will switch to the full 2592x1944 mode. It's impossible to record H.264 directly at this resolution (not enough GPU oomph for the encoder as I understand it), but you can throw a resizer in there, as you have done, to down-scale the full frames to 320x240 before the encoder has to deal with it, and that allows the recording to work.
Now, at this point you should be able to simultaneously capture an image using the video port without dropping any frames, albeit at a slightly lower quality than using the still port (and indeed this seems to work happily for me in 1.5 and 1.6), but with the full resolution of the camera (in this case 2592x1944).
If you want to capture with the still port while recording, things are a tad more complicated. Capturing JPEGs on the still port requires opaque encoding. Still port encoding can only be changed by disabling and re-enabling the camera so obviously it can't be done while recording. To work around this, one might attempt to force a still-port JPEG capture prior to recording to ensure the still port's encoding is set correctly. However, this won't work because start_recording forces still-port encoding to I420 prior to recording video. This reason this was introduced (way back in #59) was another limitation: the resizer doesn't work with opaque encoding. In order to ensure the widest variety of formats (unencoded ones in this case) and options were available for captures from the still port while recording, the start_recording method sets the still port to I420 encoding prior to starting the recording.
So ... if you want to capture images from the still port while recording they have to be unencoded (YUV, RGB, etc.) images:
import picamera
with picamera.PiCamera() as camera:
camera.resolution = camera.MAX_RESOLUTION
camera.framerate = 15
camera.start_recording('video.h264', resize=(320, 240))
camera.wait_recording(10)
camera.capture('foo.data', 'yuv')
camera.wait_recording(10)
camera.stop_recording()However, you can always capture JPEGs from the video port while recording:
import picamera
with picamera.PiCamera() as camera:
camera.resolution = camera.MAX_RESOLUTION
camera.framerate = 15
camera.start_recording('video.h264', resize=(320, 240))
camera.wait_recording(10)
camera.capture('foo.jpg', use_video_port=True)
camera.wait_recording(10)
camera.stop_recording()
guardrex
bennettrogers
weijian19391
Hello Dave,
The Encoders section and recipes don't quite match what I'm trying to accomplish. I want to snap high quality images at high resolution with the still port while capturing lower resolution video from the video port. I don't care about dropped frames if a mode change is needed as long as the video capture isn't killed. I've tried to accomplish this by doing the following:
Set the camera resolution to 320x240 Start video capture Snap image with resize=2592x1944 using video_port=False
Problem: Judging by the poor quality of the image taken, the use of resize seems to be resizing a capture at the camera resolution of 320x240 to 2592x1944 ... not actually taking the still image at 2592x1944.
If I flip this and hit it the other way ...
Set the camera resolution to 2592x1944 Start video capture with resize=320x240 Snap image using video_port = False
Problems: (1) Many dropped frames in the video (even when I'm not calling for a
.capture()image), (2) When I attempt to snap the image, it throws an exception: "Recording is currently running."So far, it seems that the only way to do something like this (along the lines of my first attempt) would be to capture video at high resolution (>=1292x730) so that the resize with
.capture()will not result in a great loss of image quality. Is that the only way to pull this off?