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• Decode h264 video

  27 juillet 2020, par john bowring

  I am looking for a way to decode h264 (or indeed any video format) using c#. The ultimate goal is to be able to decode the images and very strictly control the playback in real time. The project I am working on is a non-linear video art piece where the HD footage is required to loop and edit itself on the fly, playing back certain frame ranges and then jumping to the next randomly selected frame range seamlessly.

  



  I have created an app which reads image files (jpegs) in from the disk and plays them on screen in order, I have total control over which frame is loaded and when it is displayed but at full HD res it takes slightly longer than I want to load the images from hard drive (which are about 500k each), I am thinking that using a compressed video format would be smaller and therefore faster to read and decode into a particular frame however I cannot find any readily available way to do this.

  



  Are there any libraries which can do this ? i.e. extract an arbitrary frame from a video file and serve it to my app in less time than it takes to show the frame (running at 25fps), I have looked into the vlc libraries and wrappers for ffmpeg but I don't know which would be better or if there would be another even better option. Also I don't know which codec would be the best choice as some are key frame based making arbitrary frame extraction probably very difficult.

  



  Any advice welcome, thanks

  


• How to save the stream URL chunks as a video in NodeJs

  2 octobre 2020, par Harsh Lodhi

  I'm trying to download a piece of video from the below URL using axios.

  


  https://r5---sn-gwpa-civy.googlevideo.com/videoplayback?...&range=32104-500230


  


  I'm using below code to fetch the above URL and for save the chunk to the mp4 file.

  


  axios({
        url: MY_URL`,
        method: 'GET',
        responseType: 'stream'
    }).then(function (response) {
        let buffArray = []
        response.data.on('data', (chunk) => {
            buffArray .push(chunk)
        })

        response.data.on('end', (chunk) => {
            let buff = Buffer.concat(buffArray)
            fs.writeFile('output.mp4', buff, (dt) => {
                console.log("File created");
            })
        })
    })


  


  above code is working fine and I'm able to save the video but the video is not able to play.
when I set the range in URL from &range=32104-500230 to &range=0-500230 then video is working properly. Please try to help that how can I save a video from small chunk of video stream instead of saving full video.

  


• ffmpeg-python multiple outputs at different resolutions

  3 janvier 2021, par Darius Mandres

  I am using ffmpeg-python to convert .mp4 files to HLS streamable formats. Currently I can get it to work at full resolution using this piece of code

  


  video = ffmpeg.input(file_path)
output = ffmpeg.output(
  video,
  filename=f"{base_path}{uuid}.m3u8",
  format="hls",
  start_number=0,
  hls_time=10,
  hls_list_size=0
)

output.run()


  


  If the original video is 1920x1080 the resulting .ts files will be of the same resolution. What do I have to do to get multiple resolutions ? Say 360p 480p, 720p ?

  


  And how does ffmpeg handle a resolution when the original is smaller ? Say I try to convert a 480p video to a resolution of 720p ?