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• Python ffmpeg subprocess never exits on Linux, works on Windows

  24 mai 2021, par Chris

  I wonder if someone can help explain what is happening ?

  


  I run 2 subprocesses, 1 for ffprobe and 1 for ffmpeg.

  


  popen = subprocess.Popen(ffprobecmd, stderr=subprocess.PIPE, shell=True)


  


  And

  


  popen = subprocess.Popen(ffmpegcmd, shell=True, stdout=subprocess.PIPE)


  


  On both Windows and Linux the ffprobe command fires, finishes and gets removed from taskmanager/htop. But only on Windows does the same happen to ffmpeg. On Linux the command remains in htop...

  


  

  


  Can anyone explain what is going on, if it matters and how I can stop it from happening please ?

  


  EDIT : Here are the commands...

  


  ffprobecmd = 'ffprobe' + \
' -user_agent "' + request.headers['User-Agent'] + '"' + \
' -headers "Referer: ' + request.headers['Referer'] + '"' + \
' -timeout "5000000"' + \
' -v error -select_streams v -show_entries stream=height -of default=nw=1:nk=1' + \
' -i "' + request.url + '"'


  


  and

  


  ffmpegcmd = 'ffmpeg' + \
' -re' + \
' -user_agent "' + r.headers['User-Agent'] + '"' + \
' -headers "Referer: ' + r.headers['Referer'] + '"' + \
' -timeout "10"' + \
' -i "' + r.url + '"' + \
' -c copy' + \
' -f mpegts' + \
' pipe:'


  


  EDIT : Here is a example that behaves as described...

  


  import flask
from flask import Response
import subprocess

app = flask.Flask(__name__)

@app.route('/', methods=['GET'])
def go():
    def stream(ffmpegcmd):
        popen = subprocess.Popen(ffmpegcmd, stdout=subprocess.PIPE, shell=True)
        try:
            for stdout_line in iter(popen.stdout.readline, ""):
                yield stdout_line
        except GeneratorExit:
            raise

    url = "https://bitdash-a.akamaihd.net/content/MI201109210084_1/m3u8s/f08e80da-bf1d-4e3d-8899-f0f6155f6efa.m3u8"

    ffmpegcmd = 'ffmpeg' + \
                ' -re' + \
                ' -timeout "10"' + \
                ' -i "' + url + '"' + \
                ' -c copy' + \
                ' -f mpegts' + \
                ' pipe:'
    return Response(stream(ffmpegcmd))

if __name__ == '__main__':
    app.run(host= '0.0.0.0', port=5000)


  


• Low latency video player on android

  20 mai 2021, par Louis Blenner

  I'd like to be able to stream the video from my webcam to an Android app with a latency below 500ms, on my local network.

  


  To capture and send the video over the network, I use ffmpeg.

  


  ffmpeg -f v4l2 -i /dev/video0 -preset ultrafast -tune zerolatency -vcodec libx264 -an -vf format=yuv420p -f mpegts  udp://192.168.1.155:5000


  


  This command takes the webcam as an input, convert it and send it to a device using the mpegts protocol.
  
This is not a requirement, if another technique could work, I could change the way I send the video.

  


  I am able to read the video on another PC from the local network with a latency below 500 ms, using commands like

  


  gst-launch-1.0 -v udpsrc port=5000 ! video/mpegts ! tsdemux ! h264parse ! avdec_h264 ! fpsdisplaysink sync=false


  


  or

  


  mpv udp://0.0.0.0:5000 --no-cache --untimed --no-demuxer-thread --video-sync=audio --vd-lavc-threads=1 


  


  So it is possible to have this range of latency.
  
I'd like to have the same thing on Android.

  


  Here are my tries to do that.

  


  Exoplayer

  


  After looking at the different players available on Android studio, it seems like Exoplayer is the go-to choice.
  
I tried different options indicated in the live-streaming documentation, but I always end up with a stream taking seconds to start and with a latency of seconds.
  
I tried to add a Button to seek to the default position of the windows, but it results in a loading of several seconds.

  


  DefaultExtractorsFactory extractorsFactory =
                new DefaultExtractorsFactory()
                        .setTsExtractorFlags(DefaultTsPayloadReaderFactory.FLAG_IGNORE_AAC_STREAM);

        player = new SimpleExoPlayer.Builder(this)
                .setMediaSourceFactory(
                        new DefaultMediaSourceFactory(this, extractorsFactory))
                .setLoadControl(new DefaultLoadControl.Builder()
                        .setBufferDurationsMs(DefaultLoadControl.DEFAULT_MIN_BUFFER_MS, DefaultLoadControl.DEFAULT_MAX_BUFFER_MS, 200, 200)
                        .build())
                .build();
        MyPlayerView playerView = findViewById(R.id.player_view);
        // Bind the player to the view.
        playerView.setPlayer(player);
        // Build the media item.
        MediaItem mediaItem = new MediaItem.Builder()
                .setUri(Uri.parse("udp://0.0.0.0:5000"))
                .setLiveMaxOffsetMs(500)
                .setLiveTargetOffsetMs(0)
                .setLiveMinOffsetMs(0)
                .build();
        // Set the media item to be played.
        player.setMediaItem(mediaItem);
        // Prepare the player.
        player.setPlayWhenReady(true);
        player.prepare();
        //player.seekToDefaultPosition();


  


  This issue is about the same issue and the conclusion was that Exoplayer was not fit for this use case.

  


  


  I'll be honest, ultra low-latency like this isn't ExoPlayer's main use-case

  


  


  Vlc

  


  Another try was to use the Vlc library.
  
But I was unable to have the same low latency stream as with the two previous players with Vlc.
  
I tried changing the preferences of Vlc to stream as fast as possible as described here

  


  Input/Codecs -> x264 preset: ultrafast - zerolatency
Input/Codecs -> Access Module: UDP input
Input/Codecs -> Clock Jitter: 500
Audio: disable audio


  


  I also tried reducing the different buffers.
  
However, I still have a latency of more than 1 seconds with that.

  


  Gstreamer

  


  Another try was to create a react-native project to use the different players available here.
  
One player that seemed promising was react-native-gstreamer because it uses gstreamer which is able to stream with low latency (gst-launch command).
  
But the library is now outdated.

  


  Question

  


  There were other tries, but none were successful.
  
Is there a problem with one of my approaches ?
  
And if not, Is there a player on Android (that I missed) which is able to achieve low latency stream like gstream or mpv on linux ?

  


• Python subprocess. Linux vs Windows

  23 mai 2021, par Chris

  I wonder if someone can help explain what is happening ?

  


  I run 2 subprocesses, 1 for ffprobe and 1 for ffmpeg.

  


  popen = subprocess.Popen(ffprobecmd, stderr=subprocess.PIPE, shell=True)


  


  And

  


  popen = subprocess.Popen(ffmpegcmd, shell=True, stdout=subprocess.PIPE)


  


  On both Windows and Linux the ffprobe command fires, finishes and gets removed from taskmanager/htop. But only on Windows does the same happen to ffmpeg. On Linux the command remains in htop...

  


  

  


  Can anyone explain what is going on, if it matters and how I can stop it from happening please ?

  


  EDIT : Here are the commands...

  


  ffprobecmd = 'ffprobe' + \
' -user_agent "' + request.headers['User-Agent'] + '"' + \
' -headers "Referer: ' + request.headers['Referer'] + '"' + \
' -timeout "5000000"' + \
' -v error -select_streams v -show_entries stream=height -of default=nw=1:nk=1' + \
' -i "' + request.url + '"'


  


  and

  


  ffmpegcmd = 'ffmpeg' + \
' -re' + \
' -user_agent "' + r.headers['User-Agent'] + '"' + \
' -headers "Referer: ' + r.headers['Referer'] + '"' + \
' -timeout "10"' + \
' -i "' + r.url + '"' + \
' -c copy' + \
' -f mpegts' + \
' pipe:'


  


  EDIT : Here is a example that behaves as described...

  


  import flask
from flask import Response
import subprocess

app = flask.Flask(__name__)

@app.route('/', methods=['GET'])
def go():
    def stream(ffmpegcmd):
        popen = subprocess.Popen(ffmpegcmd, stdout=subprocess.PIPE, shell=True)
        try:
            for stdout_line in iter(popen.stdout.readline, ""):
                yield stdout_line
        except GeneratorExit:
            raise

    url = "https://bitdash-a.akamaihd.net/content/MI201109210084_1/m3u8s/f08e80da-bf1d-4e3d-8899-f0f6155f6efa.m3u8"

    ffmpegcmd = 'ffmpeg' + \
                ' -re' + \
                ' -timeout "10"' + \
                ' -i "' + url + '"' + \
                ' -c copy' + \
                ' -f mpegts' + \
                ' pipe:'
    return Response(stream(ffmpegcmd))

if __name__ == '__main__':
    app.run(host= '0.0.0.0', port=5000)