Stream properties

[bertelschmitt]

My application involves the continuous monitoring of the following properties, while the capture is running:

CAP_PROP_POS_FRAMES
CAP_PROP_POS_MSEC
CAP_PROP_MONOCHROME
CAP_PROP_FRAME_HEIGHT
CAP_PROP_FRAME_WIDTH
CAP_PROP_FRAME_COUNT
CAP_PROP_FOURCC
CAP_PROP_BUFFERSIZE
CAP_PROP_FPS

Is there a way if ffmpegcv to get these parameters on a continuous basis? With ffmpeg, most can be retrieved with ffprobe, but that takes time, and I need to monitor the properties while the capture is running.

[chenxinfeng4]

In a video file (or stream), it is commonly assumed that parameters such as "FPS (frames per second), resolution, and FOURCC" remain constant throughout. This consistency facilitates subsequent frame-by-frame reading, which is also the rule followed by tools like FFmpeg and ffmpegcv-stream.

Vid = ffmpegcv.VideoCaptureStreamRT("rtsp://192.168.xxx.xxx/xxxx")
print(Vid.width, Vid.height, Vid.fps)    # These values are constant.

I suspect that what you are trying to say is that the your video stream dynamic changine, contains non-constant video metadata, or that there may be disconnections. In such cases, ffmpegcv-stream indeed lacks effective methods for handling variable metadata.

[bertelschmitt]

Sadly, in real life streamed video, especially from on-line and from IP cameras, can have changing parameters. FPS often changes, especially when the camera changes to night mode. Same for color, black&white. If multiple cameras are employed, there often is time drift, which requires monitoring etc. A codec can change, and so forth. With OpenCV, this can be monitored in real time.

[bertelschmitt]

Sadly, in real life streamed video, especially from on-line and from IP cameras, can have changing parameters. FPS often changes, especially when the camera changes to night mode. Same for color, black&white. There can be short disruptions, errors in the encoding. If multiple cameras are employed, there often is time drift, which requires monitoring etc. A codec can change, and so forth. With OpenCV, this can be monitored in real time.

[chenxinfeng4]

I now understand the situation you described, and it indeed closely resembles real-world application scenarios. Cameras may disconnect, experience time drift, or undergo changes in resolution and frame rate. It has to be acknowledged that this is an extremely challenging scenario. Currently, the FFmpeg command-line tool (including ffmpegcv, which is based on it) is not capable of handling such situations; they can only operate effectively in simpler scenarios.

[chenxinfeng4]

Currently, ffmpegcv is unable to meet your needs for dynamic video stream reading, and it is technically very challenging to provide assistance in this regard. The ffmpegcv is primarily used in my laboratory scenarios. Your feedback from practical application scenarios has broadened my understanding.

[bertelschmitt]

Looking over the source, it turns out that some of these parameters, namely height, width, fps, are exposed as class properties. Count and duration come back as None on my RTSP stream, but that could be fixed. FPS is reported as double the correct FPS, as in 16fps for an 8 fps video. ffprobe on the same stream is reporting the correct 8 fps.