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• Opencv Java VideoCapture image corruption, possibly frame rate driven

  30 septembre 2019, par A. Scientist

  I’m having difficulty with OpenCV java cleanly capturing an image from a video stream from a video capture card. So far none of the other advice around here has helped me (I’ve spent a whole day looking through it). Each time it returns a corrupt or blank image so I suspect frame rate issues, although I am able to use ffmpeg to capture an image of it cleanly (for project reasons I strongly prefer to this in Java). Both ffmpeg and opencv report they are capturing at 30 fps and using the YUYV format through v4l2.
  My code :

  Mat frame = new Mat();
  
  VideoCapture camera = new VideoCapture(0);
  
  int fcc = VideoWriter.fourcc('Y', 'U', 'Y', 'V');
  
  System.out.println(camera.get(Videoio.CAP_PROP_FPS)+
  
  " "+camera.get(Videoio.CAP_PROP_FOURCC)+" "+fcc);
  
  wait_for(10000);//wrapper for TimeUnit.MILLISECONDS.sleep()
  
  while (!camera.isOpened()){//this part never runs
  
      wait_for(50);
  
      if(c++>500){
  
          break;
  
      }
  
  }
  
  while (true) {
  
          if (camera.read(frame)) {
  
              if(Core.sumElems(nframe).val[0]>Math.pow(10, 4)){
  
                  Imgcodecs.imwrite("/home/anon/testimg.jpg", frame);
  
                  break;
  
              }
  
          }
  
   }

  

• discord.py music bot slowing down for longer audio queries

  1er janvier 2023, par Bobluge

  So I'm trying to make a music bot with discord.py. Shown below is a minimum working example of the bot with the problematic functions :

  


  import os

import discord
from discord.ext import commands
from discord import player as p

import yt_dlp as youtube_dl

intents = discord.Intents.default()
intents.members = True

bot = commands.Bot(command_prefix=';')

class Music(commands.Cog):
    def __init__(self, bot):
        self.bot = bot
        self.yt-dlp_opts = {
            'format': 'bestaudio/best',
            'outtmpl': '%(extractor)s-%(id)s-%(title)s.%(ext)s',
            'restrictfilenames': True,
            'noplaylist': True,
            'playlistend': 1,
            'nocheckcertificate': True,
            'ignoreerrors': False,
            'logtostderr': False,
            'quiet': True,
            'no_warnings': True,
            'default_search': 'auto',
            'source_address': '0.0.0.0', # bind to ipv4 since ipv6 addresses cause issues sometimes
        }
        self.ffmpeg_opts = {
            'options': '-vn',
            # Source: https://stackoverflow.com/questions/66070749/
            "before_options": "-reconnect 1 -reconnect_streamed 1 -reconnect_delay_max 5",
        }
        self.cur_stream = None
        self.cur_link = None

    @commands.command(aliases=["p"])
    async def play(self, ctx, url):
        yt-dlp = youtube_dl.YoutubeDL(self.ytdl_opts)
        data = yt-dlp.extract_info(url, download=False)
        filename = data['url']  # So far only works with links
        print(filename)
        audio = p.FFmpegPCMAudio(filename, **self.ffmpeg_opts)
        self.cur_stream = audio
        self.cur_link = filename

        # You must be connected to a voice channel first
        await ctx.author.voice.channel.connect()
        ctx.voice_client.play(audio)
        await ctx.send(f"now playing")

    @commands.command(aliases=["ff"])
    async def seek(self, ctx):
        """
        Fast forwards 10 seconds
        """
        ctx.voice_client.pause()
        for _ in range(500):
            self.cur_stream.read()  # 500*20ms of audio = 10000ms = 10s
        ctx.voice_client.resume()

        await ctx.send(f"fast forwarded 10 seconds")

    @commands.command(aliases=["j"])
    async def jump(self, ctx, time):
        """
        Jumps to a time in the song, input in the format of HH:MM:SS
        """
        ctx.voice_client.stop()
        temp_ffempg = {
            'options': '-vn',
            # Keyframe skipping when passed as an input option (fast)
            "before_options": f"-ss {time} -reconnect 1 -reconnect_streamed 1 -reconnect_delay_max 5",
        }
        new_audio = p.FFmpegPCMAudio(self.cur_link, **temp_ffempg)
        self.cur_stream = new_audio
        ctx.voice_client.play(new_audio)
        await ctx.send(f"skipped to {time}")


bot.add_cog(Music(bot))
bot.run(os.environ["BOT_TOKEN"])


  


  My requirements.txt file :

  


  discord.py[voice]==1.7.3
yt-dlp==2021.9.2


  


  To play a song in Discord the following format is used :

  


  ;p 


  


  Where is any link that yt-dlp supports. Under normal circumstances, the ;p command is used with songs that are relatively short, to which seek() and jump() work extremely quickly to do what they are supposed to do. For example if I execute these sequence of commands in Discord :

  


  ;p https://www.youtube.com/watch?v=n8X9_MgEdCg  <- 4 min song


  


  And when the bot starts playing, spam the following :

  


  ;ff
;ff
;ff
;ff
;ff


  


  The bot is able to almost instantly seek five 10-second increments of the song. Additionally, I can jump to the three minute mark very quickly with :

  


  ;j 00:03:00


  


  From some experimentation, the seek() and jump() functions seem to work quickly for songs that are under 10 minutes. If I try the exact same sequence of commands but with a 15 minute song like https://www.youtube.com/watch?v=Ks9Ck5LfGWE or longer https://www.youtube.com/watch?v=VThrx5MRJXA (10 hours classical music), there is an evident slowdown when running the ;ff command. However, when I include a few seconds of delay between firings of the ;ff command, the seeking is just as fast as previously mentioned. I'm not exactly sure what is going on with yt-dlp/FFmpeg behind the scenes when streaming, but I speculate that there is some sort of internal buffer, and songs that pass a certain length threshold are processed differently.

  


  For longer songs, the seek() command takes longer to get to the desired position, which makes sense since this site specifies that -ss used as an input option loops through keyframes (as there must be more keyframes in longer songs). However, if the following commands are run in Discord :

  


  ;p https://www.youtube.com/watch?v=VThrx5MRJXA  <- 10 hour classical music
;j 09:00:00                                     <- jump to 9 hour mark
;j 00:03:00                                     <- jump to 3 minute mark


  


  The first seek command takes around 5 to 10 seconds to perform a successful seek, which isn't bad, but it could be better. The second seek command takes around the same time as the first command, which doesn't make sense to me, because I thought less keyframes were skipped in order to reach the 3 minute mark.

  


  So I'm wondering what's going on, and how to potentially solve the following :

  


  

  • What is actually going on with the seek() command ? My implementation of seek() uses discord.py's discord.player.FFmpegPCMAudio.read() method, which apparently runs slower if the song's length is longer ? Why ?

  


  • Why does input seeking for long YouTube videos take almost the same time no matter where I seek to ?

  


  • How the yt-dlp and FFmpeg commands work behind the scenes to stream a video from YouTube (or any other website that YTDL supports). Does yt-dlp and FFmpeg behave differently for audio streams above a certain length threshold ?

  


  • Potential ways to speed up seek() and jump() for long songs. I recall some well-known discord music bots were able to do this very quickly.

  


  


• Receiving RTP stream - AudioStream, AudioGroup

  21 février 2020, par totten

  I would like to listen an RTP audio stream, however the voice has little gaps in it - not continues. What may be the solution ? Am I missing something on Receiver(android) side or Streamer(ffmpeg) side ?

  I’m using ffmpeg to stream RTP audio,

  ffmpeg -f lavfi -i aevalsrc="sin(400*2*PI*t)" -ar 8000 -vcodec pcm_u8 -f rtp rtp://192.168.0.15:41954 (port changes.)

  And here is my related android code :

  AudioStream audioStream;
  
  AudioGroup audioGroup;
  
  @Override
  
  public void onStart() {
  
      super.onStart();
  
      StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitNetwork().build();
  
      StrictMode.setThreadPolicy(policy);
  
      AudioManager audio = (AudioManager)getSystemService(AUDIO_SERVICE);
  
      audio.setMode(AudioManager.MODE_IN_COMMUNICATION);
  
      audioGroup = new AudioGroup();
  
      audioGroup.setMode(AudioGroup.MODE_ECHO_SUPPRESSION);
  
      InetAddress inetAddress;
  
      try {
  
          inetAddress = InetAddress.getByName("192.168.0.15");
  
          audioStream = new AudioStream(inetAddress);
  
          audioStream.setCodec(AudioCodec.PCMU);
  
          audioStream.setMode(RtpStream.MODE_NORMAL);
  
          InetAddress inetAddressRemote = InetAddress.getByName("192.168.0.14");
  
          audioStream.associate(inetAddressRemote, 6000);
  
          ((TextView)findViewById(R.id.tv_port)).setText("Port : " + String.valueOf(audioStream.getLocalPort()));
  
          audioStream.join(audioGroup);
  
      }
  
      catch ( UnknownHostException e ) {
  
          e.printStackTrace();
  
      }
  
      catch ( SocketException e ) {
  
          e.printStackTrace();
  
      }
  
  }