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• Why X.Org's X Server has stopped working on Google Colab ?

  20 février 2021, par Rahul

  I am Using X server for the virtual screen on Google Colab and capturing that screen with ffmpeg to record it and live stream it to twitch. (for the reinforcement learning project)

  


  


  The above process was completely working till my last use of my Colab notebook (on mid-January 2021), but now (on 19th February 2021) I am using the same notebook and the streaming code has stopped working.

  


  


  I am adding config and log file data below. (I have never seen these files before because it was working, now it's not so I don't have any idea what wrong)

  


  The config file stored at /etc/X11/xorg.conf have the following data :

  


  # nvidia-xconfig: X configuration file generated by nvidia-xconfig
# nvidia-xconfig:  version 418.67

Section "ServerLayout"
    Identifier     "Layout0"
    Screen      0  "Screen0"
    InputDevice    "Keyboard0" "CoreKeyboard"
    InputDevice    "Mouse0" "CorePointer"
EndSection

Section "Files"
EndSection

Section "InputDevice"
    # generated from default
    Identifier     "Mouse0"
    Driver         "mouse"
    Option         "Protocol" "auto"
    Option         "Device" "/dev/mouse"
    Option         "Emulate3Buttons" "no"
    Option         "ZAxisMapping" "4 5"
EndSection

Section "InputDevice"
    # generated from default
    Identifier     "Keyboard0"
    Driver         "kbd"
EndSection

Section "Monitor"
    Identifier     "Monitor0"
    VendorName     "Unknown"
    ModelName      "Unknown"
    HorizSync       28.0 - 33.0
    VertRefresh     43.0 - 72.0
    Option         "DPMS"
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "Tesla T4"
    BusID          "PCI:0:4:0"
    MatchSeat      "seat-1"
EndSection

Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    Option         "AllowEmptyInitialConfiguration" "True"
    SubSection     "Display"
        Virtual     1920 1080
        Depth       24
    EndSubSection
EndSection


  


  The log file stored at /var/log/Xorg.0.log have the following data :

  


  [   464.605] 
X.Org X Server 1.19.6
Release Date: 2017-12-20
[   464.605] X Protocol Version 11, Revision 0
[   464.605] Build Operating System: Linux 4.15.0-124-generic x86_64 Ubuntu
[   464.605] Current Operating System: Linux 9d3fe3949671 4.19.112+ #1 SMP Thu Jul 23 08:00:38 PDT 2020 x86_64
[   464.605] Kernel command line: BOOT_IMAGE=/syslinux/vmlinuz.A init=/usr/lib/systemd/systemd boot=local rootwait ro noresume noswap loglevel=7 noinitrd console=ttyS0 security=apparmor virtio_net.napi_tx=1 systemd.unified_cgroup_hierarchy=false systemd.legacy_systemd_cgroup_controller=false csm.disabled=1 dm_verity.error_behavior=3 dm_verity.max_bios=-1 dm_verity.dev_wait=1 i915.modeset=1 cros_efi loadpin.enabled=0 root=/dev/dm-0 "dm=1 vroot none ro 1,0 4077568 verity payload=PARTUUID=555BDB75-CBD7-CD4A-B24E-29B13D7AC0DF hashtree=PARTUUID=555BDB75-CBD7-CD4A-B24E-29B13D7AC0DF hashstart=4077568 alg=sha256 root_hexdigest=42104d547ac104fb7061529e78f53e4f3e8c3d3cbb040dc6e0f84aad68491347 salt=9dc7f3acc4e2ce65be16356e960c2b21b51a917fa31d2e891fd295490c991e41" mitigations=off
[   464.605] Build Date: 30 November 2020  08:01:56PM
[   464.605] xorg-server 2:1.19.6-1ubuntu4.8 (For technical support please see http://www.ubuntu.com/support) 
[   464.605] Current version of pixman: 0.34.0
[   464.605]    Before reporting problems, check http://wiki.x.org
    to make sure that you have the latest version.
[   464.605] Markers: (--) probed, (**) from config file, (==) default setting,
    (++) from command line, (!!) notice, (II) informational,
    (WW) warning, (EE) error, (NI) not implemented, (??) unknown.
[   464.605] (==) Log file: "/var/log/Xorg.0.log", Time: Sat Feb 20 03:10:44 2021
[   464.606] (==) Using config file: "/etc/X11/xorg.conf"
[   464.606] (==) Using system config directory "/usr/share/X11/xorg.conf.d"
[   464.607] (==) ServerLayout "Layout0"
[   464.607] (**) |-->Screen "Screen0" (0)
[   464.607] (**) |   |-->Monitor "Monitor0"
[   464.607] (**) |   |-->Device "Device0"
[   464.607] (**) |-->Input Device "Keyboard0"
[   464.607] (**) |-->Input Device "Mouse0"
[   464.607] (==) Automatically adding devices
[   464.607] (==) Automatically enabling devices
[   464.607] (==) Automatically adding GPU devices
[   464.607] (==) Automatically binding GPU devices
[   464.607] (==) Max clients allowed: 256, resource mask: 0x1fffff
[   464.607] (WW) The directory "/usr/share/fonts/X11/cyrillic" does not exist.
[   464.607]    Entry deleted from font path.
[   464.607] (WW) The directory "/usr/share/fonts/X11/100dpi/" does not exist.
[   464.607]    Entry deleted from font path.
[   464.607] (WW) The directory "/usr/share/fonts/X11/75dpi/" does not exist.
[   464.607]    Entry deleted from font path.
[   464.607] (WW) The directory "/usr/share/fonts/X11/Type1" does not exist.
[   464.607]    Entry deleted from font path.
[   464.607] (WW) The directory "/usr/share/fonts/X11/100dpi" does not exist.
[   464.607]    Entry deleted from font path.
[   464.607] (WW) The directory "/usr/share/fonts/X11/75dpi" does not exist.
[   464.607]    Entry deleted from font path.
[   464.607] (==) FontPath set to:
    /usr/share/fonts/X11/misc,
    built-ins
[   464.607] (==) ModulePath set to "/usr/lib/xorg/modules"
[   464.607] (WW) Hotplugging is on, devices using drivers 'kbd', 'mouse' or 'vmmouse' will be disabled.
[   464.607] (WW) Disabling Keyboard0
[   464.607] (WW) Disabling Mouse0
[   464.607] (II) Loader magic: 0x556eb77b8020
[   464.607] (II) Module ABI versions:
[   464.607]    X.Org ANSI C Emulation: 0.4
[   464.607]    X.Org Video Driver: 23.0
[   464.607]    X.Org XInput driver : 24.1
[   464.607]    X.Org Server Extension : 10.0
[   464.607] (EE) dbus-core: error connecting to system bus: org.freedesktop.DBus.Error.FileNotFound (Failed to connect to socket /var/run/dbus/system_bus_socket: No such file or directory)
[   464.609] (--) PCI: (0:0:4:0) 10de:1eb8:10de:12a2 rev 161, Mem @ 0xc0000000/16777216, 0x380000000/268435456, 0x390000000/33554432
[   464.609] (II) no primary bus or device found
[   464.609] (II) LoadModule: "glx"
[   464.609] (II) Loading /usr/lib/xorg/modules/extensions/libglx.so
[   464.610] (II) Module glx: vendor="X.Org Foundation"
[   464.610]    compiled for 1.19.6, module version = 1.0.0
[   464.610]    ABI class: X.Org Server Extension, version 10.0
[   464.610] (II) LoadModule: "nvidia"
[   464.610] (II) Loading /usr/lib/xorg/modules/drivers/nvidia_drv.so
[   464.610] (II) Module nvidia: vendor="NVIDIA Corporation"
[   464.610]    compiled for 4.0.2, module version = 1.0.0
[   464.610]    Module class: X.Org Video Driver
[   464.610] (II) NVIDIA dlloader X Driver  418.67  Sat Apr  6 02:51:17 CDT 2019
[   464.610] (II) NVIDIA Unified Driver for all Supported NVIDIA GPUs
[   464.610] xf86EnableIOPorts: failed to set IOPL for I/O (Operation not permitted)
[   464.610] (II) Loading sub module "fb"
[   464.610] (II) LoadModule: "fb"
[   464.611] (II) Loading /usr/lib/xorg/modules/libfb.so
[   464.611] (II) Module fb: vendor="X.Org Foundation"
[   464.611]    compiled for 1.19.6, module version = 1.0.0
[   464.611]    ABI class: X.Org ANSI C Emulation, version 0.4
[   464.611] (II) Loading sub module "wfb"
[   464.611] (II) LoadModule: "wfb"
[   464.611] (II) Loading /usr/lib/xorg/modules/libwfb.so
[   464.611] (II) Module wfb: vendor="X.Org Foundation"
[   464.611]    compiled for 1.19.6, module version = 1.0.0
[   464.611]    ABI class: X.Org ANSI C Emulation, version 0.4
[   464.611] (II) Loading sub module "ramdac"
[   464.611] (II) LoadModule: "ramdac"
[   464.611] (II) Module "ramdac" already built-in
[   464.637] (EE) NVIDIA: Failed to initialize the NVIDIA kernel module. Please see the
[   464.637] (EE) NVIDIA:     system's kernel log for additional error messages and
[   464.637] (EE) NVIDIA:     consult the NVIDIA README for details.
[   464.662] (EE) NVIDIA: Failed to initialize the NVIDIA kernel module. Please see the
[   464.662] (EE) NVIDIA:     system's kernel log for additional error messages and
[   464.662] (EE) NVIDIA:     consult the NVIDIA README for details.
[   464.662] (EE) No devices detected.
[   464.662] (==) Matched modesetting as autoconfigured driver 0
[   464.662] (==) Matched fbdev as autoconfigured driver 1
[   464.662] (==) Matched vesa as autoconfigured driver 2
[   464.662] (==) Assigned the driver to the xf86ConfigLayout
[   464.662] (II) LoadModule: "modesetting"
[   464.662] (II) Loading /usr/lib/xorg/modules/drivers/modesetting_drv.so
[   464.663] (II) Module modesetting: vendor="X.Org Foundation"
[   464.663]    compiled for 1.19.6, module version = 1.19.6
[   464.663]    Module class: X.Org Video Driver
[   464.663]    ABI class: X.Org Video Driver, version 23.0
[   464.663] (II) LoadModule: "fbdev"
[   464.663] (II) Loading /usr/lib/xorg/modules/drivers/fbdev_drv.so
[   464.663] (II) Module fbdev: vendor="X.Org Foundation"
[   464.663]    compiled for 1.19.3, module version = 0.4.4
[   464.663]    Module class: X.Org Video Driver
[   464.663]    ABI class: X.Org Video Driver, version 23.0
[   464.663] (II) LoadModule: "vesa"
[   464.663] (II) Loading /usr/lib/xorg/modules/drivers/vesa_drv.so
[   464.663] (II) Module vesa: vendor="X.Org Foundation"
[   464.663]    compiled for 1.19.3, module version = 2.3.4
[   464.663]    Module class: X.Org Video Driver
[   464.663]    ABI class: X.Org Video Driver, version 23.0
[   464.663] (II) NVIDIA dlloader X Driver  418.67  Sat Apr  6 02:51:17 CDT 2019
[   464.663] (II) NVIDIA Unified Driver for all Supported NVIDIA GPUs
[   464.663] (II) modesetting: Driver for Modesetting Kernel Drivers: kms
[   464.663] (II) FBDEV: driver for framebuffer: fbdev
[   464.663] (II) VESA: driver for VESA chipsets: vesa
[   464.663] xf86EnableIOPorts: failed to set IOPL for I/O (Operation not permitted)
[   464.663] (EE) open /dev/dri/card0: No such file or directory
[   464.663] (WW) Falling back to old probe method for modesetting
[   464.663] (EE) open /dev/dri/card0: No such file or directory
[   464.663] (WW) Falling back to old probe method for fbdev
[   464.663] (II) Loading sub module "fbdevhw"
[   464.663] (II) LoadModule: "fbdevhw"
[   464.663] (II) Loading /usr/lib/xorg/modules/libfbdevhw.so
[   464.663] (II) Module fbdevhw: vendor="X.Org Foundation"
[   464.663]    compiled for 1.19.6, module version = 0.0.2
[   464.663]    ABI class: X.Org Video Driver, version 23.0
[   464.664] (EE) open /dev/fb0: No such file or directory
[   464.664] (WW) Falling back to old probe method for vesa
[   464.664] (WW) VGA arbiter: cannot open kernel arbiter, no multi-card support
[   464.664] (EE) Screen 0 deleted because of no matching config section.
[   464.664] (II) UnloadModule: "modesetting"
[   464.664] (EE) Device(s) detected, but none match those in the config file.
[   464.664] (EE) 
Fatal server error:
[   464.664] (EE) no screens found(EE) 
[   464.664] (EE) 
Please consult the The X.Org Foundation support 
     at http://wiki.x.org
 for help. 
[   464.664] (EE) Please also check the log file at "/var/log/Xorg.0.log" for additional information.
[   464.664] (EE) 
[   464.664] (EE) Server terminated with error (1). Closing log file.



  


  I am using this github repo to setup the video-streamer

  


  If anyone wants the colab notebook for the example then I will add it over here.

  


  For this problem I am really not sure where to file an issue for this so that's why I am writing this here.

  


• When I use Fluent-Ffmpeg to access Ffmpeg, there are two different threads but I dont want it

  25 mars 2019, par Ahmet Hakan Billur

  I try to broadcast with rtsp live stream from IP camera on web app that is improved with node.js-jsmpeg([a link]https://www.npmjs.com/package/fluent-ffmpeg !), web socket, html5(canvas).Everything ok that live streaming works but missing frame and high CPU usaged by streaming on web app and I try to reduce so I can intervene ffmpeg with fluent-ffmpeg but when I monitor CPU usaged I can see there 2 different threads following as and look at screenshot of CPU ;
  

  ffmpeg -rtsp_trasport tcp -i rtsp ://10.6.0.225 -f mpeg1video - is worked by jsmpeg and canvas/html5
  index.html

      
  
  
  
      
  
      
  
      
  
      
  
  
  
      <div><canvas width="640" height="360"></canvas></div>
  
      div><canvas width="640" height="360"></canvas>  
  
      <code class="echappe-js">&lt;script type=&quot;text/javascript&quot; src='http://stackoverflow.com/feeds/tag/jsLib/jsmpeg.js'&gt;&lt;/script&gt;
      
  &lt;script type=&quot;text/javascript&quot; src='http://stackoverflow.com/feeds/tag/jsLib/ffmpegUtil.js'&gt;&lt;/script&gt;
  &lt;script type=&quot;text/javascript&quot;&gt;<br />
  
        var canvas = document.getElementById('videoCanvas');<br />
  
        var ws = new WebSocket(&quot;ws://10.6.0.206:9999&quot;)<br />
  
        var player = new jsmpeg(ws, {canvas:canvas, autoplay:true,audio:false,loop: true});<br />
  
      &lt;/script&gt;
  

  other one /usr/bin/ffmpeg -i rtsp ://10.6.0.225 -y out.ts is work by following piece of code in app.js

  Stream = require('node-rtsp-stream');
  
  stream = new Stream({
  
      name: 'name',
  
      streamUrl: 'rtsp://10.6.0.225',
  
      wsPort: 9999
  
  });
  
  
  
  var ffmpeg = require('fluent-ffmpeg');
  
  var proc = new ffmpeg();
  
  
  
  proc
  
  .addInput('rtsp://10.6.0.225')
  
  .on('start', function(ffmpegCommand) {
  
      /// log something maybe
  
      console.log('start-->'+ffmpegCommand)
  
  })
  
  .on('progress', function(data) {
  
      /// do stuff with progress data if you want
  
      console.log('progress-->'+data)
  
  })
  
  .on('end', function() {
  
      /// encoding is complete, so callback or move on at this point
  
      console.log('end-->')
  
  })
  
  .on('error', function(error) {
  
      /// error handling
  
      console.log('error-->'+error)
  
  
  
  })
  
  .output('out.ts')
  
  .run();

  and then I don’t want to get two different ffmpeg command threads in there.
  Does anyone have an idea ?
  Thanks in advice.

• Inside WebM Technology : The VP8 Alternate Reference Frame

  15 juin 2010, par noreply@blogger.com (John Luther) — inside webm, vp8

  Since the WebM project was open-sourced just a week ago, we’ve seen blog posts and articles about its capabilities. As an open project, we welcome technical scrutiny and contributions that improve the codec. We know from our extensive testing that VP8 can match or exceed other leading codecs, but to get the best results, it helps to understand more about how the codec works. In this first of a series of blog posts, I’ll explain some of the fundamental techniques in VP8, along with examples and metrics.

  The alternative reference frame is one of the most exciting quality innovations in VP8. Let’s delve into how VP8 uses these frames to improve prediction and thereby overall video quality.

  Alternate Reference Frames in VP8

  VP8 uses three types of reference frames for inter prediction : the last frame, a "golden" frame (one frame worth of decompressed data from the arbitrarily distant past) and an alternate reference frame. Overall, this design has a much smaller memory footprint on both encoders and decoders than designs with many more reference frames. In video compression, it is very rare for more than three reference frames to provide significant quality benefit, but the undesirable increase in memory footprint from the extra frames is substantial.

  Unlike other types of reference frames used in video compression, which are displayed to the user by the decoder, the VP8 alternate reference frame is decoded normally but is never shown to the user. It is used solely as a reference to improve inter prediction for other coded frames. Because alternate reference frames are not displayed, VP8 encoders can use them to transmit any data that are helpful to compression. For example, a VP8 encoder can construct one alternate reference frame from multiple source frames, or it can create an alternate reference frame using different macroblocks from hundreds of different video frames.

  The current VP8 implementation enables two different types of usage for the alternate reference frame : noise-reduced prediction and past/future directional prediction.

  Noise-Reduced Prediction

  The alternate reference frame is transmitted and decoded similar to other frames, hence its usage does not add extra computation in decoding. The VP8 encoder however is free to use more sophisticated processing to create them in off-line encoding. One application of the alternate reference frame is for noise-reduced prediction. In this application, the VP8 encoder uses multiple input source frames to construct one reference frame through temporal or spatial noise filtering. This "noise-free" alternate reference frame is then used to improve prediction for encoding subsequent frames.

  You can make use of this feature by setting ARNR parameters in VP8 encoding, where ARNR stands for "Alternate Reference Noise Reduction." A sample two-pass encoding setting with the parameters :

  --arnr-maxframes=5 --arnr-strength=3

  enables the encoder to use "5" consecutive input source frames to produce one alternate reference frame using a filtering strength of "3". Here is an example showing the quality benefit of using this experimental "ARNR" feature on the standard test clip "Hall Monitor." (Each line on the graph represents the quality of an encoded stream on a given clip at multiple datarates. The higher points on the Y axis (PSNR) indicates the stream with the better quality.)

  
  

  The only difference between the two curves in the graph is that VP8_ARNR was produced by encodings with ARNR parameters and VP8_NO_ARNR was not. As we can see from the graph, noise reduced prediction is very helpful to compression quality when encoding noisy sources. We’ve just started to explore this idea but have already seen strong improvements on noisy input clips similar to this "Hall Monitor." We feel there’s a lot more we can do in this area.

  Improving Prediction without B Frames

  The lack of B frames in VP8 has sparked some discussion about its ability to achieve competitive compression efficiency. VP8 encoders, however, can make intelligent use of the golden reference and the alternate reference frames to compensate for this. The VP8 encoder can choose to transmit an alternate reference frame similar to a "future" frame, and encoding of subsequent frames can make use of information from the past (last frame and golden frame) and from the future (alternate reference frame). Effectively, this helps the encoder to achieve results similar to bidirectional (B frame) prediction without requiring frame reordering in the decoder. Running in two-pass encoding mode, compression can be improved in the VP8 encoder by using encoding parameters that enable lagged encoding and automatic placement of alternate reference frames :

  --auto-alt-ref=1 --lag-in-frames=16

  Used this way, the VP8 encoder can achieve improved prediction and compression efficiency without increasing the decoder’s complexity :

  
  

  In the video compression community, "Mobile and calendar" is known as a clip that benefits significantly from the usage of B frames. The graph above illustrates that the use of alternate reference frame benefits VP8 significantly without using B frames.

  Keep an eye on this blog for more posts about VP8 encoding. You can find more information on above encoding parameters or other detailed instructions to use with our VP8 encoders on our site, or join our discussion list.

  Yaowu Xu, Ph.D. is a codec engineer at Google.