Recherche avancée

Sur d’autres sites (4947)

• FFMPEG - why zoompan causes stretching

  14 septembre 2020, par Sarmad S.

  I have two images as input, both are 1600x1066. I am vertically stacking them. Then I am drawing a box and vertically stacking that box under both of the image. Inside of the box I write text, then I output a video that is 1080x1920. Everything works well, until I use zoompan to zoom in on the images, I get weird behavior. basically all input images including the box stretchs (shrink) horizontally and no longer fit the entire height of the video which is 1920.

  


  The command (removed some drawtext commands from it) :

  


  -filter_complex 
"color=s=1600x1066:color=blue, drawtext=fontfile=font.otf: text='My Text':fontcolor=white: fontsize=30: x=50: y=50[box]; 
[0]scale=4000x4000,zoompan=z='min(zoom+0.0015,1.5)':x='iw/2-(iw/zoom/2)':y='ih/2-(ih/zoom/2)':d=125:s=1600x1066[z0];
[1]scale=4000x4000,zoompan=z='min(zoom+0.0015,1.5)':x='iw/2-(iw/zoom/2)':y='ih/2-(ih/zoom/2)':d=125:s=1600x1600[z1];
[z0][z1][box]vstack=inputs=3"


  


  How do I fix this ? I want to zoom in without stretching the images

  


  Before using zoompan this is how the video looks like (I want to keep it this way while zooming in the images) :


  


  After using zoompan this is how the video looks like :

  


  

  


• ffmpeg through python subprocess fails to find camera

  27 juillet 2021, par Ofer Sadan

  Weird problem here, i use this command to capture my webcam through ffmpeg (through cmd on windows) :

  



  ffmpeg -y -t 300 -rtbufsize 1024M -f dshow -i video="Lenovo EasyCamera" -c:v libx264 -preset veryslow -crf 25 Desktop.mkv


  



  and everything works fine. But when i try the very same command through python as a subprocess it fails. Here's the python code :

  



  from subprocess import Popen
cmd = ['ffmpeg', '-y', '-t', '300', '-rtbufsize', '1024M', '-f', 'dshow', '-i', 'video="Lenovo EasyCamera"', '-c:v', 'libx264', '-preset', 'veryslow', '-crf', '25', 'Desktop.mkv']
p = Popen(cmd)


  



  Outputs the following error and freezes :

  



  [dshow @ 00000000023a2cc0] Could not find video device with name ["Lenovo EasyCamera"] among source devices of type video.
video="Lenovo EasyCamera": I/O error


  



  Can anyone figure this out and tell me what i'm doing wrong ? Or is it some known bug in python or the subprocess module (using python 3.6.1, but not attached to the specific version if it will help me solve this problem) ?

  



  Thanks in advance !

  



  P.S. This question is a follow up to this one, if that's relevant : How to grab laptop webcam video with ffmpeg in windows

  


• Node.JS Live Streaming Audio with FFMPEG

  20 avril 2021, par nicnacnic

  I'm trying to create an Express server to live stream audio captured from another application (Discord in this case). I'm able to get a server up and running, but there are a couple issues that need to be solved. Here's my server code so far.

  


  const app = express();
app.get("/", function(req, res) {
    res.sendFile(__dirname + "/index.html");
});
app.get("/audio", function(req, res) {
    const stream = ffmpeg(audio).inputOptions(["-f", "s16le", "-ar", "48k", "-ac", "2"]).format('wav');
    res.writeHead(200, { "Content-Type": "audio/wav" });
    stream.pipe(res);
});
app.listen(8080)


  


  

  1. Silent sections of audio need to be added. When there's no activity on the input, there's no data written to the audio variable. This causes weird behavior, for example I can speak and the audio comes through a second later. Then, if I wait 10 seconds then speak again, the audio comes through 4-5 seconds later. I believe this is a problem with the way I'm using ffmpeg to transcode, but I have no idea how to fix it.

  


  2. Refreshing the client crashes the program. Every time I refresh the client I get an ffmpeg error. Error: Output stream closed. This error doesn't happen if I close it, only on reload.

  


  3. The audio is not synced between clients. Every time I open a new connection, the audio starts playing from the beginning instead of being synced with each other and playing the audio live.

  


  


  This is how it's supposed to work : it captures audio from my app in PCM, converts the audio to WAV with ffmpeg, and then streams the audio live to the clients. The audio needs to be synced with all the clients as best as possible to reduce delay. And I'm using fluent-ffmpeg instead of just regular ffmpeg for the transcoding.
Thanks !