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• How to pipe frames in stdout using FFMPEG and Golang

  6 avril 2020, par Sven.DG

  I am fairly new to Golang, my goal is to build a script in Golang that :

  



  

  1. Transcodes the video input .MOV file into frames, using FFMPEG

  


  2. Some downstream process that does something with the emitted frames.

  


  



  Currently I have the following code as a first attempt :

  



  package main

import (
    "fmt"
    "os/exec"
    "strconv"
    "io"
)

const (
    frameX      = 240
    frameY      = 135
    frameSize   = frameX * frameY * 3
)

func main() {
    ffmpeg := exec.Command("ffmpeg", "-i", "project/data/sample.mov", "-vf",  "fps=fps=1/2", "-s", strconv.Itoa(frameX)+"x"+strconv.Itoa(frameY), "-f", "rawvideo", "pipe:1") //nolint
    ffmpegOut, _ := ffmpeg.StdoutPipe()

    if err := ffmpeg.Start(); err != nil {
        panic(err)
    }

    reader(ffmpegOut)
    fmt.Println("Completed. YAY")
}

func reader(ffmpegOut io.Reader) {
    buf := make([]byte, frameSize)
    fmt.Println("Looping..")
    counter := 0
    for {
        if _, err := io.ReadFull(ffmpegOut, buf); err != nil {
            // fmt.Println(err)
        }
        if buf[0] != 0 {
            fmt.Println("Got a frame!!")
            counter++
            fmt.Println(counter)
        }
    }
    fmt.Println("total amount of frames", counter)
}


  



  This is mainly based on this example : https://github.com/pion/example-webrtc-applications/blob/master/gocv-receive/main.go

  



  However, when running this code, it appears that I'm getting an endless amount of data in my downstream reader. I would expect that the counter equals the amount of frames but that is clearly not the case looking at the rate at which the counter increases, so obviously I am doing something wrong. Can anybody point me in the right direction ?

  



  I used the sample .mov file with 1280 x 720 resolution here : https://file-examples.com/index.php/sample-video-files/sample-mov-files-download/.
The video is about 31 seconds so I would expect to see 15 frames downstream in the reader.

  



  Cheers !

  


• How to pipe rawvideo to v4l2loopback using ffmpeg ?

  3 août 2020, par sepehr78

  I am trying to process a video by OpenCV in Python and then send each frame to a virtual camera (i.e., v4l2loopback). I have seen questions asked where OpenCV output is piped to ffmpeg and saved into a file, and other questions where a video file is piped to v4l2 using ffmpeg, but no question where these two are combined. I can do either of the above two things on their own, but not combined.

  



  My Python code uses a subprocess to pipe each frame to ffmpeg. The ffmpeg command for piping the output of OpenCV to an .mp4 file is

  



  ffmpeg -y -f rawvideo -vcodec rawvideo -s 1280x720 -pix_fmt bgr24 -i - -vcodec libx264 -crf 0 -preset fast output.mp4


  



  This works and I have tested it.

  



  The ffmpeg command to pipe a video file to the v4l2 virtual camera is

  



  ffmpeg -re -i input.mp4 -map 0:v -f v4l2 /dev/video0


  



  This also works and I have tested it.

  



  I tried combining the above two commands and came up with

  



  ffmpeg -y -f rawvideo -vcodec rawvideo -s 1280x720 -pix_fmt bgr24 -i - -vcodec libx264 -crf 0 -preset fast -map 0:v -f v4l2 /dev/video0


  



  but I get the following error

  



  


  [NULL @ 0x55a12fcc60] Unable to find a suitable output format for ''
 : Invalid argument

  


  



  I would be glad if anyone could help me figure this out.

  



  Thanks.

  


• How to add BGM when pipe opencv images to ffmpeg - python

  23 mars 2020, par karobben

  Basically, I know how to stream by Pipe opencv to ffmpeg using python.
  But my problem is I can’t add an audio file (BGM) for it. Does anyone know how to make it with python ?

  my python code is :

  import cv2 as cv
  
  import subprocess as sp
  
  
  
  # ffmpeg command
  
  
  
  command = ['ffmpeg',
  
          #'-re', '-stream_loop', '-1', 
  
          #'-i', '/home/pi/scrpt/Blive/StarBucks_BGN.mp3',
  
          '-y',
  
          '-f', 'rawvideo',
  
          '-vcodec','rawvideo',
  
          '-pix_fmt', 'bgr24',
  
          '-s', "{}x{}".format(width, height),
  
          '-r', str(fps),
  
          '-i', '-',
  
          '-c:v', 'libx264',
  
          '-pix_fmt', 'yuv420p',
  
          '-preset', 'ultrafast',
  
          '-f', 'flv',
  
          rtmpUrl]

  I know that I can achieve this by :

  sudo raspivid -o - -t 0 -w 1280 -h 720 -fps 24 -b 1000000 | 
  
                  ffmpeg  -re -stream_loop -1 -i  "/home/pi/scrpt/Blive/StarBucks_BGN.mp3" \
  
          -f h264 -i - -vcodec copy -r 30 -acodec aac -b:a 100k -preset ultrafast \
  
          -tune zerolatency -f flv "rtmp://"

  So, I tried to add -re -stream_loop -1 -i  "/home/pi/scrpt/Blive/StarBucks_BGN.mp3" into the python pipe, but it crashed with :

  [libx264 @ 0x1952aa0] using cpu capabilities: ARMv6 NEON
  
  [libx264 @ 0x1952aa0] profile Constrained Baseline, level 3.1
  
  [libx264 @ 0x1952aa0] 264 - core 148 r2748 97eaef2 - H.264/MPEG-4 AVC codec - Copyleft 2003-2016 - http://www.videolan.org/x264.html - options: cabac=0 ref=1 deblock=0:0:0 analyse=0:0 me=dia subme=0 psy=1 psy_rd=1.00:0.00 mixed_ref=0 me_range=16 chroma_me=1 trellis=0 8x8dct=0 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=0 threads=6 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=0 weightp=0 keyint=250 keyint_min=25 scenecut=0 intra_refresh=0 rc=crf mbtree=0 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=0
  
  [flv @ 0x1951d00] FLV does not support sample rate 48000, choose from (44100, 22050, 11025)
  
  [flv @ 0x1951d00] Audio codec mp3 not compatible with flv
  
  Could not write header for output file #0 (incorrect codec parameters ?): Function not implementedStream mapping:
  
    Stream #1:0 -> #0:0 (rawvideo (native) -> h264 (libx264))
  
    Stream #0:0 -> #0:1 (mp3 (native) -> mp3 (libmp3lame))
  
      Last message repeated 1 times
  
  Traceback (most recent call last):
  
    File "With_BG.py", line 57, in <module>
  
      p.stdin.write(BG.tostring())
  
  BrokenPipeError: [Errno 32] Broken pipe
  
  </module>