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• Raw extraction of frames from a movie

  29 septembre 2016, par vkubicki

  I would like to extract images from a grayscale mj2 movie. Each pixel is encoded using 16 bits. Since this is a technical movie, I need to extract the value at each pixel without processing, as those values linearly map to a physical quantity (a heatmap from an infrared camera). I am using Scala, and I do not find any suitable solution for a direct extraction (either in Scala or in Java, but I am a beginner). Therefore I intend to use ffmpeg to extract individual frames on the disk, then load them as BufferedImage in Scala and process them.

  Is this a good approach ? Which format should I use to avoid any transformation in the data ? I want each extracted frame to ba as "raw" as possible ? Is it possible to directly output a csv containing the aforementionned values ?

• For modifying MPEG-2 Part 4 video, which is the easiest library/approach can I use ?

  17 décembre 2015, par liamzebedee

  I’m trying to implement a video watermarking system which modifies a subset of individual pixels (i.e. the RGB values at sets of x,y). The base use case would be modifying an MP4, which consists of modifying the contained MPEG-2 Part 4 Video stream.

  I’ve done some research, and have found that it isn’t as simple as just modifying the raw frames, as the ubiquitous P-frames and B-frames rely on compressing the output by only storing the differences between frames.

  I’m relatively technology-agnostic, I just want to find a solution. Which library/framework should I use (seems like ffmpeg for now) and which approach do I take ?

• Decode h264 video bytes into JPEG frames in memory with ffmpeg

  5 février 2024, par John Karkas

  I'm using python and ffmpeg (4.4.2) to generate a h264 video stream from images produced continuously from a process. I am aiming to send this stream over websocket connection and decode it to individual image frames at the receiving end, and emulate a stream by continuously pushing frames to an <img style='max-width: 300px; max-height: 300px' /> tag in my HTML.

  


  However, I cannot read images at the receiving end, after trying combinations of rawvideo input format, image2pipe format, re-encoding the incoming stream with mjpeg and png, etc. So I would be happy to know what the standard way of doing something like this would be.

  


  At the source, I'm piping frames from a while loop into ffmpeg to assemble a h264 encoded video. My command is :

  


          command = [
            'ffmpeg',
            '-f', 'rawvideo',
            '-pix_fmt', 'rgb24',
            '-s', f'{shape[1]}x{shape[0]}',
            '-re',
            '-i', 'pipe:',
            '-vcodec', 'h264',
            '-f', 'rawvideo',
            # '-vsync', 'vfr',
            '-hide_banner',
            '-loglevel', 'error',
            'pipe:'
        ]


  


  At the receiving end of the websocket connection, I can store the images in storage by including :

  


          command = [
            'ffmpeg',
            '-i', '-',  # Read from stdin
            '-c:v', 'mjpeg',
            '-f', 'image2',
            '-hide_banner',
            '-loglevel', 'error',
            f'encoded/img_%d_encoded.jpg'
        ]


  


  in my ffmpeg command.

  


  But, I want to instead extract each individual frame coming in the pipe and load in my application, without saving them in storage. So basically, I want whatever is happening at by the 'encoded/img_%d_encoded.jpg' line in ffmpeg, but allowing me to access each frame in the stdout subprocess pipe of an ffmpeg pipeline at the receiving end, running in its own thread.

  


  

  • What would be the most appropriate ffmpeg command to fulfil a use case like the above ? And how could it be tuned to be faster or have more quality ?

  


  • Would I be able to read from the stdout buffer with process.stdout.read(2560x1440x3) for each frame ?

  


  


  If you feel strongly about referring me to a more update version of ffmpeg, please do so.

  


  PS : It is understandable this may not be the optimal way to create a stream. Nevertheless, I do not find there should be much complexity in this and the latency should be low. I could instead communicate JPEG images via the websocket and view them in my <img style='max-width: 300px; max-height: 300px' /> tag, but I want to save on bandwidth and relay some computational effort at the receiving end.