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• Streaming the output of a subprocess to 2 or more clients

  11 juillet 2023, par Chris

  I have a basic example here

  


  import subprocess
from flask import (
    Flask,
    Response,
)
app = Flask(__name__)

stream = None

@app.route("/play", methods=["GET"])
def channel():
    def createStream():
        global stream
        print("create stream")
        stream = subprocess.Popen(
                ffmpegcmd,
                stdin=subprocess.DEVNULL,
                stdout=subprocess.PIPE,
                stderr=subprocess.DEVNULL,
            )

    def streamData():
        print("stream data")
        try:
            while True:
                chunk = stream.stdout.read(1024)
                if len(chunk) == 0:
                    break
                yield chunk
        except:
            pass


    if not stream:
        link = "https://cph-p2p-msl.akamaized.net/hls/live/2000341/test/master.m3u8"

        ffmpegcmd = [
            "ffmpeg",
            "-re",
            "-i",
            link,
            "-map",
            "0",
            "-codec",
            "copy",
            "-f",
            "mpegts",
            "pipe:"
        ]

        createStream()

        return Response(streamData(), mimetype="application/octet-stream")

    else:

        return Response(streamData(), mimetype="application/octet-stream")

if __name__ == "__main__":
    app.run(host="0.0.0.0", port=8001, debug=True)


  


  If 2 or more clients try to stream at the same time, all streams freeze. Closing all streams and re-requesting /play picks up the existing sp and it plays ok.

  


  Does anyone understand what is happening and why it doesn't work ?
Is this a bug or limitation of subprocesses ?

  


• Concat a spliced video around altered frames at a certain point

  3 août 2021, par Jesse Hix

  All the commands used were ffmpeg or ffprobe based and on a Linux OS.

  


  To start I have extracted a certain range of frames from a video and altered them for what I am doing. The frames are somewhat identical to the original frames before extraction and if there is any audio it gets extracted before frame removal.

  


  I would like to take the altered frames and concat or insert the frames at the same frame/time as they were originally. I was thinking the easiest way would be to split the original video from start to before the first altered frame and then from last altered frame to the end, with the altered frames between the two videos. The only issue is that I removed the frames I wanted to alter using command $(ffmpeg -i INPUT -vf select="between(n\,'$x'\,'$y'\)" -vsync 0 frames/frames%d.png)which is based on frames but the concat command uses timecodes.

  


  Question : Is there a way to concat using frames and if not is there an easy way to find timecodes based on frames ?

  


• cross compiling OpenCV with ffmpeg support for arm target fails

  1er juin 2013, par user2361999

  I am trying to cross compile OpenCV with ffmpeg support for mini2440(arm based). The following are the steps i followed.

  1. Cross compiled ffmpeg 0.5.1 and successfully created the libraries following this guide.(http://luupkceit.blogspot.in/2011/07/motion-webcam-on-mini2440-this-is.html)

     ./configure --prefix=/usr --libdir=/lib --datadir=/usr/share --enable-shared --enable-cross-compile --arch=arm --cc=arm-linux-gcc --host-ldflags="-L/rootfs/lib" --host-cflags="-I/rootfs/usr/include"

     make

     make install DESTDIR=/install/ffmpeg

  2. I downloaded openCV 2.0.0 and ran the the following configure command.

     ./configure --prefix=$TGT_DIR --host=arm-linux CPPFLAGS=-I/install/ffmpeg/usr/include LDFLAGS=-L/install/ffmpeg/lib --with-python=no --with-ffmpeg=yes --without-quicktime --with-imageio=no --with-gtk=no --with-carbon=no --with-unicap=no --with-gthread=no

  My ffmpeg libraries are at /install/ffmpeg/lib and my include files are at /install/ffmpeg/usr/include

  The above configure step finishes running and produces the following log :

  file(http://pastebin.com/nAV0zyPW).
  ffmpeg support does NOT get turned on.

  Please let me know how i can turn on ffmpeg support for OpenCV for arm target.

  Any help is greatly appreciated.

  Thanks,
  Anvesh