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• Reduce RTMP buffer while decoding using ffmpeg

  15 janvier 2019, par Alberto Padilla

  I’m setting up a new server using nginx and nginx-rtmp-module. I installed a DeckLink Duo2 card to output SDI signals comming from the RTMP stream.

  Everything works really great using this simple nginx.conf configuration :

  rtmp {
  
      server {
  
              listen 1935;
  
              chunk_size 4096;
  
  
  
              wait_video on;
  
              wait_key on;
  
  
  
              sync 10ms;
  
  
  
              application live {
  
                  live on;
  
                  record off;
  
  
  
                  exec_push /home/myuser/bin/ffmpeg -i rtmp://127.0.0.1/live/mystreamname -f decklink -format_code pal -pix_fmt uyvy422 'DeckLink Duo (1)';
  
              }  
  
     }
  
  }

  My goal is to achieve the absolute minimum delay between the received stream and the SDI output.

  I can achieve 3 seconds "waving hand" delay using the configuration that I mentioned. However, using ffplay I observe 1.5s delay using the -fflags nobuffer option.

  As ffplay cannot output to a decklink device, I want ffmpeg to reduce the buffer to the minimum, but I can’t find the way to do it. All the -rtmp_buffer or -fflag nobuffer or any other options have no impact on the delay.

  The stream is being received in the same machine ffmpeg is running, that is why it makes sense to reduce the ffmpeg buffering to the minimum if I want to achieve low delay.

  Any tips ?

• Using ffmpeg to print onto video clip actual time and duration from original clip

  24 mai 2023, par Kes

  I am using arch linux and bash and ffmpeg, all are up to date and the latest versions.

  


  I am clipping a video that is 30 seconds long and wish to clip from 5 secs to 10 seconds to a new file, from the original.

  


  In the bottom right hand corner of the clip I wish to show timestamps from the original video as follows

  


  

  • in the 5th second "00:00:05/ 00:00:30"

  


  • in the 6th second "00:00:06/ 00:00:30"
    
etc

  


  • in the 10th second "00:00:10/ 00:00:30"

  


  


  This is an apparentley simple question(?) but the syntax of the command is not at all obvious and I am hoping an expert may shed some light on this.

  


  All I have so far for the drawtext part, which does not do what I want as it only counts the elapsed time from t=0 of the clip, whereas I want it to show the timestamp and total duration of the original clip

  


  drawtext I started with

  


  "drawtext=text='%{pts\:gmtime\:0\:%M\\\\\:%S}':fontsize=24:fontcolor=black:x=(w-text_w-10):y=(h-text_h-10)"


  


  ffmpeg line with drawtext I have started with

  


  ffmpeg -ss 00:00:05 -i  "$in_file" -filter_complex "drawtext=fontfile=font.ttf:text='sample text':x=10:y=10:fontsize=12:fontcolor=white:box=1:boxcolor=black@0.5:boxborderw=5,drawtext=text='%{duration\:hms}':fontsize=12:fontcolor=black:x=(w-text_w-10):y=(h-text_h-10)" -t 5 -c:a copy -c:v libx264 out_file.mp4


  


• Ffmpeg returning error code 1 in AWS Lamda function

  14 avril 2018, par Tometoyou

  I’m running a lambda function which takes an mp4 video, and adds a watermark of a png image over the top of it in the bottom right hand corner (with a 10px margin). It then outputs that image to a temporary location. It keeps failing with Error code 1, but that isn’t very helpful. I’m using a binary version of ffmpeg that is specified in the main directory of the code. I know that ffmpeg is set up correctly due to using it in another lambda function in this way, which works. But adding an overlay fails. Here is the relevant part of my code :

  function addWatermark(next) {
  
      var ffmpeg = child_process.spawn("ffmpeg", [
  
        "-i", target, // url to stream from
  
        "-i", watermarkPath,
  
        "-filter_complex" ,"overlay=x=W-w-10:y=H-h-10:format=rgb,format=yuv420p",
  
        "-c:a", "copy",
  
        "pipe:1"
  
      ]);
  
      ffmpeg.on("error", function(err) {
  
        console.log(err);
  
      })
  
      ffmpeg.on("close", function(code) {
  
        if (code != 0 ) {
  
          console.log("child process exited with code " + code); // Always exits here.
  
        } else {
  
          console.log("Processing finished !");
  
        }
  
        tmpFile.end(); 
  
        next(code);
  
      });
  
      tmpFile.on("error", function(err) {
  
        console.log("stream err: ", err);
  
      });
  
      ffmpeg.on("end", function() {
  
        tmpFile.end();  
  
      })
  
      ffmpeg.stdout.pipe(tmpFile)
  
      .on("error", function(err){
  
        console.log("error while writing: ",err);
  
      });
  
  }

  Can anyone spot what may be wrong ?

  UPDATE

  I’ve managed to print out some more logs, I’m getting the error :

  [NULL @ 0x42923e0] Unable to find a suitable output format for 'pipe:1'