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• How can I record an audio from USB audio device using C++ with ffmpeg on Linux ?

  9 mai 2018, par Hunter Haimin Zhang

  How can I record an audio from USB audio device using C++ with ffmpeg on Linux ?
  I have the following code. But I have no idea how to set the parameter of ’url’ in the function of avformat_open_input.
  Could assistance be provided by anybody ? Much appreciated.

     27     av_register_all();
  
     28     avdevice_register_all();
  
     29
  
     30     //pAudioInputFmt =av_find_input_format("dshow");
  
     31     pAudioInputFmt =av_find_input_format("alsa");
  
     32     //assert(pAudioInputFmt != NULL);
  
     33     if (!(pAudioInputFmt != NULL))
  
     34     {
  
     35         printf("Error %s %d\n", __FILE__, __LINE__);
  
     36         char ch = cin.get();
  
     37         cout << "ch = "<< ch << endl;
  
     38         return (-1);
  
     39     }
  
     40
  
     41     // I have no idear how to set the second parameter on Linux.
  
     42     if (!(avformat_open_input(&pFmtCtx, "=Device)", pAudioInputFmt,NULL) == 0))
  
     43     {
  
     44         printf("Error %s %d\n", __FILE__, __LINE__);
  
     45         system("pause");
  
     46         return (-1);
  
     47     }

• How to record desktop while on x2go session via a command line tool ?

  4 décembre 2017, par haragei

  the Goal :
  I am trying to record a specific X display on a remote server with a command line tool.

  the Problem :
  The output file contains a pure black video stream for the whole duration of the recording.

  My Approach :
  I am connecting to a remote server via x2go. The Server runs Ubuntu 16.04.2 with Xfce Desktop Environment. The Display I try to record is :50 (which gets created when I connect to the x2go server). I can control the remote server totally fine through x2go.

  My commands for recording via ffmpeg (or avconv/recordmydesktop, which use ffmpeg underneath) all look more or less the same and are like this :
  ffmpeg -f x11grab -r 25 -s 1854x1176 -i :50.0 -c:v libx264 screencast.mkv

  Sample output :

  user@machine:~/$ ffmpeg -f x11grab -r 25 -s 1854x1176 -i :50.0+0,0 -c:v libx264 -vb 4000k -an screencast.mkv
  
  ffmpeg version N-86766-g264f6c6 Copyright (c) 2000-2017 the FFmpeg developers
  
    built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.4) 20160609
  
    configuration: --prefix=/home/user/ffmpeg_build --pkg-config-flags=--static --extra-cflags=-I/home/user/ffmpeg_build/include --extra-ldflags=-L/home/user/ffmpeg_build/lib --bindir=/home/user/bin --enable-gpl --enable-libass --enable-libfdk-aac --enable-libfreetype --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-nonfree
  
    libavutil      55. 67.100 / 55. 67.100
  
    libavcodec     57.100.104 / 57.100.104
  
    libavformat    57. 75.100 / 57. 75.100
  
    libavdevice    57.  7.100 / 57.  7.100
  
    libavfilter     6. 95.100 /  6. 95.100
  
    libswscale      4.  7.101 /  4.  7.101
  
    libswresample   2.  8.100 /  2.  8.100
  
    libpostproc    54.  6.100 / 54.  6.100
  
  [x11grab @ 0x1fd9b40] XFixes not available, cannot draw the mouse.
  
  [x11grab @ 0x1fd9b40] Stream #0: not enough frames to estimate rate; consider increasing probesize
  
  Input #0, x11grab, from ':50.0+0,0':
  
    Duration: N/A, start: 1500041497.684675, bitrate: N/A
  
      Stream #0:0: Video: rawvideo (BGR[0] / 0x524742), bgr0, 1854x1176, 25 fps, 1000k tbr, 1000k tbn, 1000k tbc
  
  File 'screencast.mkv' already exists. Overwrite ? [y/N] y
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (rawvideo (native) -> h264 (libx264))
  
  Press [q] to stop, [?] for help
  
  [libx264 @ 0x1fe3040] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX
  
  [libx264 @ 0x1fe3040] profile High 4:4:4 Predictive, level 4.2, 4:4:4 8-bit
  
  [libx264 @ 0x1fe3040] 264 - core 148 r2643 5c65704 - H.264/MPEG-4 AVC codec - Copyleft 2003-2015 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=4 threads=12 lookahead_threads=2 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=abr mbtree=1 bitrate=4000 ratetol=1.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
  
  Output #0, matroska, to 'screencast.mkv':
  
    Metadata:
  
      encoder         : Lavf57.75.100
  
      Stream #0:0: Video: h264 (libx264) (H264 / 0x34363248), yuv444p, 1854x1176, q=-1--1, 4000 kb/s, 25 fps, 1k tbn, 25 tbc
  
      Metadata:
  
        encoder         : Lavc57.100.104 libx264
  
      Side data:
  
        cpb: bitrate max/min/avg: 0/0/4000000 buffer size: 0 vbv_delay: -1
  
  [swscaler @ 0x1fe94e0] Warning: data is not aligned! This can lead to a speedloss
  
  frame=  179 fps= 36 q=-1.0 Lsize=      16kB time=00:00:07.04 bitrate=  18.8kbits/s speed=1.43x    
  
  video:14kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 12.869934%
  
  [libx264 @ 0x1fe3040] frame I:1     Avg QP: 6.00  size:   518
  
  [libx264 @ 0x1fe3040] frame P:45    Avg QP: 0.44  size:    81
  
  [libx264 @ 0x1fe3040] frame B:133   Avg QP: 0.94  size:    73
  
  [libx264 @ 0x1fe3040] consecutive B-frames:  0.6%  1.1%  0.0% 98.3%
  
  [libx264 @ 0x1fe3040] mb I  I16..4:  0.0% 100.0%  0.0%
  
  [libx264 @ 0x1fe3040] mb P  I16..4:  0.0%  0.0%  0.0%  P16..4:  0.0%  0.0%  0.0%  0.0%  0.0%    skip:100.0%
  
  [libx264 @ 0x1fe3040] mb B  I16..4:  0.0%  0.0%  0.0%  B16..8:  0.0%  0.0%  0.0%  direct: 0.0%  skip:100.0%
  
  [libx264 @ 0x1fe3040] final ratefactor: -23.85
  
  [libx264 @ 0x1fe3040] 8x8 transform intra:100.0%
  
  [libx264 @ 0x1fe3040] coded y,u,v intra: 0.0% 0.0% 0.0% inter: 0.0% 0.0% 0.0%
  
  [libx264 @ 0x1fe3040] i16 v,h,dc,p:  0%  0% 100%  0%
  
  [libx264 @ 0x1fe3040] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu:  0%  0% 100%  0%  0%  0%  0%  0%  0%
  
  [libx264 @ 0x1fe3040] Weighted P-Frames: Y:0.0% UV:0.0%
  
  [libx264 @ 0x1fe3040] kb/s:15.56

  Using : Ubuntu 16.04.2 LTS

  I have successfully accomplished to capture the display :50 with "simplescreenrecorder", but that tool has no command line interface. It uses ffmpeg also, so it somehow should be possible to caputure the display but I can´t get it to work properly.

• Ble with record video

  24 juillet 2017, par Vitaly

  I’m working on rpi3.
  When I try to run the command :

  sudo ffmpeg -f video4linux2 -i /dev/video0 -video_size 640x480 -r 25 output.avi

  to record a video using ffmpeg.

  In this time,I try to connect with Bluetooth.

  The BT cannot connect.

  the exception I get is :
  A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.

  top result :

  1156 root 20 0 299860 197172 137736 S 80.6 20.9 40:21.35 ffmpeg

  80.6 % cpu and 20.9 % mem.

  all the other processes take less than 1%.

  Did you encounter with this ?
  Do you have a clue what can be done ?

  Thanks