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• ffmpeg stream chrome kiosk mode ubuntu 16.04 server

  15 février 2021, par Raul

  I have a weird out-of-sync issue while using ffmpeg to stream to youtube live a chrome browser from an ub untu 16.04 server.

  



  Issue : output video streamed to youtube has audio/video out of sync, sometimes with as much as 3s

  



  Current flow :

  



  1) start pulseaudio - we using something like this to start it :

  



  pulseaudio --start -vvv --disallow-exit --log-target=syslog --high-priority --exit-idle-time=-1 --daemonize


  



  2) start Xvfb

  



  Xvfb :0 -ac -screen 0 1920x1080x24


  



  3) start chrome linux in kiosk mode

  



  google-chrome --kiosk --disable-gpu --incognito --no-first-run --disable-java --disable-plugins --disable-translate --disk-cache-size=$((1024 * 1024)) --disk-cache-dir=/tmp/chrome/ --user-data-dir=/tmp/chrome/ --force-device-scale-factor=1 --window-size=1920,1080 --window-position=0,0 LOCATION_URL


  



  4) start ffmpeg

  



  ffmpeg -y \
  -thread_queue_size 8192 -rtbufsize 250M -f x11grab -video_size 1920x1080 -framerate 24 -i :0 \
  -thread_queue_size 8192 -channel_layout stereo -f alsa -i pulse \
  -c:v libx264 -pix_fmt yuv420p -c:v libx264 -g 48 -crf 24 -filter:v fps=24 -preset ultrafast -tune zerolatency \
  -c:a aac -strict -2 -channel_layout stereo -ab 96k -ac 2 -flags +global_header \
  -f flv YOUTUBE_LIVE_STREAMING_RTMP


  



  Note : this is running on an amazon ec2 instance, meaning there is no soundcard, so alsa and pulseaudio are creating a dummy audio card. However, the latency does not come from there. Logs :

  



  Nov 25 06:14:22 ip-172-31-29-8 pulseaudio[26602]: [pulseaudio] protocol-native.c: Adjust latency mode enabled, configuring sink latency to half of overall latency.
Nov 25 06:14:22 ip-172-31-29-8 pulseaudio[26602]: [pulseaudio] protocol-native.c: Requested latency=23.22 ms, Received latency=23.22 ms
Nov 25 06:14:22 ip-172-31-29-8 pulseaudio[26602]: [pulseaudio] protocol-native.c: Final latency 69.66 ms = 23.22 ms + 2*11.61 ms + 23.22 ms


  



  At this point, here's what we observed :

  



  


  1. if we start ffmpeg exactly after issuing the command to start chrome, we see the DTS errors from ffmpeg. Audio is out of sync with the video and has delay of 3-5seconds AHEAD. We also noticed the out of sync remains the same for the full duration of the stream

  


  2. if we start ffmpeg after around 10seconds, audio and video are almost in sync. We then manually added a -itsoffset -0.125 to the ffmpeg command and everything is perfect.

  


  



  Questions :

  



  

  1. Why would ffmpeg have so much lag if it's started right after chrome ?

  


  2. Is starting the ffmpeg after 10s or X seconds the expected behavior ? That is, is this because the system needs to wait for audio/video signals to be "ready" or something ?

  


  3. Is there a way to 100% calculate or know when Chrome is fully ready and start ffmpeg ? We found sometimes it takes 5s, sometimes 10. Depends on the URL we load.

  


  4. Besides the DTS error that ffmpeg throws, is there any other way to know if audio/video is out-of-sync ? as sometimes we have a delay of between 0.5 to 1s, but ffmpeg does not report anything. And a restart is required to "re-balance" the audio/video inputs and get them back in sync.

  


  5. Can pulseaudio be the problem in this scenario ?

  


  



  Thank you

  



  UPDATE Dec 20

  



  We were able to do some tricks to force chrome to start the audio on page load, and that will force connect to pulseaudio. Doing that, plus adding a 3s delay for ffmpeg to start, there is no more delay when ffmpeg starts.
However, our app is a webRTC app, and we have a STRANGER thing happening : if we start the page with no webcam/audio, once the webcam/audio is enabled, ffmpeg (while showing no errors) has a delay of 2s or so. While keep talking, in about max 30s, that delay is GONE.

  



  So the new questions are :

  



  

  1. Besides the DTS error that ffmpeg throws, is there any other way to know if audio/video is out-of-sync ? as sometimes we have a delay of between 0.5 to 1s, but ffmpeg does not report anything.

  


  2. What could cause the initial audio/video out of sync issue and then catching up ?

  


  


• ffmpeg stream chrome kiosk mode ubuntu 16.04 server

  21 décembre 2016, par Raul

  I have a weird out-of-sync issue while using ffmpeg to stream to youtube live a chrome browser from an ub untu 16.04 server.

  Issue : output video streamed to youtube has audio/video out of sync, sometimes with as much as 3s

  Current flow :

  1) start pulseaudio - we using something like this to start it :

  pulseaudio --start -vvv --disallow-exit --log-target=syslog --high-priority --exit-idle-time=-1 --daemonize

  2) start Xvfb

  Xvfb :0 -ac -screen 0 1920x1080x24

  3) start chrome linux in kiosk mode

  google-chrome --kiosk --disable-gpu --incognito --no-first-run --disable-java --disable-plugins --disable-translate --disk-cache-size=$((1024 * 1024)) --disk-cache-dir=/tmp/chrome/ --user-data-dir=/tmp/chrome/ --force-device-scale-factor=1 --window-size=1920,1080 --window-position=0,0 LOCATION_URL

  4) start ffmpeg

  ffmpeg -y \
  
    -thread_queue_size 8192 -rtbufsize 250M -f x11grab -video_size 1920x1080 -framerate 24 -i :0 \
  
    -thread_queue_size 8192 -channel_layout stereo -f alsa -i pulse \
  
    -c:v libx264 -pix_fmt yuv420p -c:v libx264 -g 48 -crf 24 -filter:v fps=24 -preset ultrafast -tune zerolatency \
  
    -c:a aac -strict -2 -channel_layout stereo -ab 96k -ac 2 -flags +global_header \
  
    -f flv YOUTUBE_LIVE_STREAMING_RTMP

  Note : this is running on an amazon ec2 instance, meaning there is no soundcard, so alsa and pulseaudio are creating a dummy audio card. However, the latency does not come from there. Logs :

  Nov 25 06:14:22 ip-172-31-29-8 pulseaudio[26602]: [pulseaudio] protocol-native.c: Adjust latency mode enabled, configuring sink latency to half of overall latency.
  
  Nov 25 06:14:22 ip-172-31-29-8 pulseaudio[26602]: [pulseaudio] protocol-native.c: Requested latency=23.22 ms, Received latency=23.22 ms
  
  Nov 25 06:14:22 ip-172-31-29-8 pulseaudio[26602]: [pulseaudio] protocol-native.c: Final latency 69.66 ms = 23.22 ms + 2*11.61 ms + 23.22 ms

  At this point, here’s what we observed :

  1. if we start ffmpeg exactly after issuing the command to start chrome, we see the DTS errors from ffmpeg. Audio is out of sync with the video and has delay of 3-5seconds AHEAD. We also noticed the out of sync remains the same for the full duration of the stream

  2. if we start ffmpeg after around 10seconds, audio and video are almost in sync. We then manually added a -itsoffset -0.125 to the ffmpeg command and everything is perfect.

  Questions :

  1. Why would ffmpeg have so much lag if it’s started right after chrome ?
  2. Is starting the ffmpeg after 10s or X seconds the expected behavior ? That is, is this because the system needs to wait for audio/video signals to be "ready" or something ?
  3. Is there a way to 100% calculate or know when Chrome is fully ready and start ffmpeg ? We found sometimes it takes 5s, sometimes 10. Depends on the URL we load.
  4. Besides the DTS error that ffmpeg throws, is there any other way to know if audio/video is out-of-sync ? as sometimes we have a delay of between 0.5 to 1s, but ffmpeg does not report anything. And a restart is required to "re-balance" the audio/video inputs and get them back in sync.
  5. Can pulseaudio be the problem in this scenario ?

  Thank you

  UPDATE Dec 20

  We were able to do some tricks to force chrome to start the audio on page load, and that will force connect to pulseaudio. Doing that, plus adding a 3s delay for ffmpeg to start, there is no more delay when ffmpeg starts.
  However, our app is a webRTC app, and we have a STRANGER thing happening : if we start the page with no webcam/audio, once the webcam/audio is enabled, ffmpeg (while showing no errors) has a delay of 2s or so. While keep talking, in about max 30s, that delay is GONE.

  So the new questions are :

  1. Besides the DTS error that ffmpeg throws, is there any other way to know if audio/video is out-of-sync ? as sometimes we have a delay of between 0.5 to 1s, but ffmpeg does not report anything.
  2. What could cause the initial audio/video out of sync issue and then catching up ?

• How to record video from old webcam using ffmpeg on Linux ?

  5 février 2015, par Moomin

  After couple of hours I finally accepted my absolute lack of knowledge and decided to post this question here.
  I’m trying to record video from an old external USB webcam (Media-Tech MT400 -> 0c45:6029) with ffmpeg but without much success.

  First thing I’ve tried was to run to try something that works for the built-in webcam) :

  ffmpeg -f v4l2 -i /dev/video1 test.avi

  But that returned a following error :

  Cannot find a proper format for codec 'none' (id 0), pixel format 'none' (id -1)

  Here is what I get from v4l2-ctl -d /dev/video1/ --all --list-formats-ext

  Driver Info (not using libv4l2):
  
          Driver name   : sonixb
  
          Card type     : USB camera
  
          Bus info      : usb-0000:04:00.0-1
  
          Driver version: 3.10.17
  
          Capabilities  : 0x85000001
  
                  Video Capture
  
                  Read/Write
  
                  Streaming
  
                  Device Capabilities
  
          Device Caps   : 0x05000001
  
                  Video Capture
  
                  Read/Write
  
                  Streaming
  
  Priority: 2
  
  Video input : 0 (sonixb: ok)
  
  Format Video Capture:
  
          Width/Height  : 352/288
  
          Pixel Format  : 'S910'
  
          Field         : None
  
          Bytes per Line: 352
  
          Size Image    : 126720
  
          Colorspace    : SRGB
  
  Streaming Parameters Video Capture:
  
          Frames per second: invalid (0/0)
  
          Read buffers     : 2
  
  
  
  
  
  
  
  ioctl: VIDIOC_ENUM_FMT
  
      Index       : 0
  
      Type        : Video Capture
  
      Pixel Format: 'S910'
  
      Name        : S910
  
              Size: Discrete 160x120
  
              Size: Discrete 176x144
  
              Size: Discrete 320x240
  
              Size: Discrete 352x288
  
  
  
      Index       : 1
  
      Type        : Video Capture
  
      Pixel Format: 'BA81'
  
      Name        : BA81
  
              Size: Discrete 160x120
  
              Size: Discrete 176x144

  Unfortunately that was not of much help to me, but I tried capturing webcam output with VLC and recording it which.... WORKED !

  I tried ffmpeg -i vlc-record[...].avi on VLC recording which returned following information :

  Input #0, avi, from 'vlc-record-2015-02-05-05h22m52s-v4l2____dev_video1-.avi':
  
    Duration: 00:00:01.58, start: 0.000000, bitrate: 26937 kb/s
  
      Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 352x288, 27671 kb/s, 22.10 tbr, 22.10 tbn, 22.10 tbc

  I thought that was enough information (rawvideo and yuv420p) led to run ffmpeg with following arguments (I have found yuv4 using ffmpeg -formats)

  ffmpeg -f rawvideo -vcodec yuv4 -i /dev/video1 test.avi

  The result was only slightly better than one that I saw after my first attempt :

  [IMGUTILS @ 0x7fff497d3920] Picture size 0x0 is invalid
  
  [rawvideo @ 0x9c4720] Could not find codec parameters for stream 0 (Video: yuv4, yuv420p, -4 kb/s): unspecified size
  
  Consider increasing the value for the 'analyzeduration' and 'probesize' options
  
  /dev/video1: could not find codec parameters

  Again after some searching and several tries I added ’-video_size cif` option and.... it WORKED !!!!

  Well, not really...

  Input #0, rawvideo, from '/dev/video1':
  
    Duration: N/A, start: 0.000000, bitrate: 30412 kb/s
  
      Stream #0:0: Video: yuv4, yuv420p, 352x288, 30412 kb/s, 25 tbr, 25 tbn, 25 tbc
  
  Output #0, avi, to 'test.avi':
  
    Metadata:
  
      ISFT            : Lavf55.19.104
  
      Stream #0:0: Video: mpeg4 (FMP4 / 0x34504D46), yuv420p, 352x288, q=2-31, 200 kb/s, 25 tbn, 25 tbc
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (yuv4 -> mpeg4)
  
  Press [q] to stop, [?] for help
  
  frame=   13 fps=6.3 q=24.8 Lsize=    1064kB time=00:00:00.52 bitrate=16759.3kbits/s    
  
  video:1058kB audio:0kB subtitle:0 global headers:0kB muxing overhead 0.554114%

  LED on webcam turned on as during capturing video with VLC but all that was recorded was TV-like noise.

  So here I am after 7 hours - still without work solution - asking for your help.

  Thanks in advance.