#Ffmpeg python dashcam how to#
Use pass_fds option of subprocess.Popen to create the second " stdout." See this link for an example of how to passing additional pipe via pass_fds.
#Ffmpeg python dashcam windows#
(I'm a Windows guy for the most part so take this with a grain of salt) The difficult part is how to pipe 2 different streams. Choose an appropriate audio format, and specify any other needed arguments. We can process the audio by creating a separate stream. But we can - it's as simple as shown at the top of the documentation: ffmpeg.input(.).video.output(.). We don't need to select the video from the input stream in order to filter it out. Notice that at no point here did we attempt to separate audio and video - this is because a rawvideo codec, as the name implies, won't output any audio data. Pretty straightforward: we iteratively read that amount of data, check for the end of the stream, and then create the frame with standard Numpy stuff. Which is exactly what we see later in the example: while True:
That will be the width of the video, times the height, times three (for RGB components at 1 byte each). We don't want to read data in arbitrary "packet" sizes for this we want to read exactly as much data as is needed for one frame. Having created such an input stream, we can read from its stdout and create Numpy arrays from each piece of data.
And, yes, you would specify this as -pix_fmt at the command line. There are a bunch of pre-defined values for this which you can see with ffmpeg -pix_fmts. The pix_fmt keyword parameter means what it sounds like: 24 bits per pixel, representing red, green and blue components. (This is what we would pass as a -f option at the command line.) 'rawvideo' means exactly what it sounds like, and is suitable for reading the data into a Numpy array. The key difference is that we specify a format that we know how to handle. The documentation's example does not pipe_stderr, but that shouldn't matter since we do not plan to read from the stderr either way. The documentation's example uses 'pipe:' to specify writing to stdout this should be the same as '-'. The next step is to specify how the stream outputs (i.e., what kind of data we will get out when we read from the stdout of the process. (Just like we could use either for a -i argument for the command-line ffmpeg program.) It does not matter whether we use a file or a URL for our input source - ffmpeg.input figures that out for us, and at that point we just have an ffmpeg.Stream either way. Let's compare that to the one in the example partway down the documentation, titled "Process video frame-by-frame using numpy:" (I reformatted it a little to match): process1 = ( There is a lot there, but you can learn it a piece at a time according to your actual needs. It's useful to understand the FFMpeg program itself, in particular the command-line arguments it takes. It's worth understanding off the top that these are bindings for FFMpeg, which is doing all the work. ).run_async(pipe_stdout=True, pipe_stderr=True)Įssentially I need a numpy array of video and separate audio for each package. I know how to get sound from this packet object, but I don’t understand how to get a video frame from the packet object? I would like to present the video stream as a picture by picture and a separate sound for audio and video processing in the program. To do this, I run it like this on my rasbery pi: ffmpeg -f alsa -thread_queue_size 1024 -channels 1 -i hw:2,0 -thread_queue_size 1024 -s 1920x1080 -i /dev/video0 -listen 1 -f matroska -vcodec libx264 -preset veryfast -tune zerolatency From the server side, I connect to the stream like this. I want to get separate video and separate audio objects from ffmpeg stream (python)
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