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• ffmpeg - compositing a video within a video in the centre

  1er mars 2017, par kieran

  I’m looking to composite a video with ffmpeg that places the video in the centre no matter what the composited video’s aspect ratio/size.

  The "background" video will always be 16:9 and 1920x1080px. I won’t know the aspect ratio or size of the overlay video as it will be user uploaded and could be any size/ratio.

  Here’s an example of what I’m trying to achieve :

  This is the background image :

  

  Now I want to overlay a video over the top :

  

  This should also work :

  Essentially no matter what the dimensions I want to ensure it’s always resized to fit within 1920x1080 and in addition ensure it’s always centred.

  Finally, if the uploaded video is also 16:9 it should simply overlay the entire video :
  

• Express - FFMPEG : Serve transcoded video instead of static video file

  30 septembre 2020, par No stupid questions

  I am creating a website to host videos downloaded on my computer online. However, many of these videos are not in a web friendly format (like .mkv or .flv). It is not an option to convert these files on the disk and then serve them as static files, converting needs to be done live by the server. I want to transcode these videos with ffmpeg to a web friendly format like webm.

  


  So far, I have been able to somewhat successfully transcode a video and serve it :

  


  import express from 'express';
import cors from 'cors';
import ffmpeg from 'fluent-ffmpeg';

const app = express();

app.use(cors());
app.use(express.json());

app.use('/static/videos', globalPasswordMiddleware, (req, res) => {
    res.contentType('webm');
    const videoPath = path.join('C:/videos', decodeURIComponent(req.path));
    ffmpeg(videoPath)
        .format('webm')
        .on('end', function () {
            console.log('file has been converted succesfully');
        })
        .on('error', function (err) {
            console.log('an error happened: ' + err.message);
        })
        .pipe(res, { end: true });
});


  


  However, I am still encountering three different issues :

  


  Firstly, while this code seems to work for transcoding something like a flash video into webm, there are still a number of videos I cannot get to play. For example, a number of videos that play in Chrome will still not play in Firefox or a number of videos that play on my PC won't on my ancient iPad. Are there more arguments I need to be passing to ffmpeg to transcode the video in a way that it will work on a greater number or devices/browsers ?

  


  Second, there is no ability to seek on the video or see how much time remains. When viewing a transcoded video it behaves more like a livestream than if I were serving it as a static file. How can I fix this ?

  


  And finally third, the transcoding is massively slow. Running in production mode, video playback has to buffer for a few seconds every five or so seconds. I am aware transcoding video is an intense process but I believe given my computer's hardware (i9 9900K) and how much faster it is at transcoding videos on Plex that I should be able to transcode videos faster than this.

  


• FFMPEG - Add (white, color-less, analog) grain to the video without desaturating video itself

  2 décembre 2018, par dd_code

  I am working on old videos where I am basically converting them to HVEC and sharpening, so i.e. my command can look like this

  .\ffmpeg.exe -i F:\file.mkv -vf unsharp=3:3:1.5 -c:v hevc_nvenc -qp 27 -a:c copy file_new.mkv

  inherent problem with this is, of course that with reducing bitrate and sharpening every now and then I can notice some nasty artifacts around the edges and on at plain-color objects.

  I noticed with some older, many times remastered movies/series that they have quite a lot of grain in the video, so I was thinking - what if I add grain and help it to mask the compression and sharpening artifacts ?

  After bit of searching I got to
  https://ffmpeg.org/ffmpeg-filters.html#noise
  and now I am using this command

  .\ffmpeg.exe -i F:\file.mkv -vf unsharp=3:3:1.5,noise=alls=14:allf=t+u -c:v hevc_nvenc -qp 30 -a:c copy file_new.mkv

  however this has one big problem, it is merely a digital RGB noise, is there a way to make it desaturated, analog-ish ? I tried adding h=s=0, however this is applying 0 saturation to the video track as a whole. Is there an effect which would achieve this or is there a way that I can reduce the saturation only of the very effect which then gets to "overlay" the video track, so the track would not be touched ?