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• ffmpeg creates empty mpd-file

  1er avril 2021, par Macster

  I'm trying to live stream a webm file using ffmpeg and Dash.js as a Player. Creating chunks with ffmpeg seems to work fine, but when want to create the manifest it says Could not find codec parameters for stream 0 (Video: vp9, none, 640x480): unspecified pixel format Consider increasing the value for the 'analyzeduration' and 'probesize' options and at the end Output file is empty, nothing was encoded (check -ss / -t / -frames parameters if used).

  


  Commands I use

  


  ffmpeg -re -r 25 -i Dash/strm.webm
 -map 0:v:0
 -pix_fmt yuv420p
 -c:v libvpx-vp9
 -s 640x480 -keyint_min 25 -g 25 
 -speed 6 -threads 8 -static-thresh 0 -max-intra-rate 300 
 -deadline realtime -lag-in-frames 0 -error-resilient 1
 -f webm_chunk 
 -header "Dash/glass_360.hdr"
 -chunk_start_index 1
 Dash\glass_360_%d.chk


  


  Manifest

  


  ffmpeg ^
 -f webm_dash_manifest -live 1
 -r 25
 -i Dash/glass_360.hdr
 -c copy
 -map 0
 -r 25
 -framerate 25
 -f webm_dash_manifest -live 1
 -adaptation_sets "id=0,streams=0"
 -chunk_start_index 1
 -chunk_duration_ms 1000
 -time_shift_buffer_depth 7200
 -minimum_update_period 7200
 Dash/glass_live_manifest.mpd


  


  Manifest Output

  


   libavutil      56. 49.100 / 56. 49.100
  libavcodec     58. 87.101 / 58. 87.101
  libavformat    58. 43.100 / 58. 43.100
  libavdevice    58.  9.103 / 58.  9.103
  libavfilter     7. 83.100 /  7. 83.100
  libswscale      5.  6.101 /  5.  6.101
  libswresample   3.  6.100 /  3.  6.100
  libpostproc    55.  6.100 / 55.  6.100
[webm_dash_manifest @ 0000015f19f2ea40] Could not find codec parameters for stream 0 (Video: vp9, none, 640x480): unspecified pixel format
Consider increasing the value for the 'analyzeduration' and 'probesize' options
Input #0, webm_dash_manifest, from 'Dash/glass_360.hdr':
  Metadata:
    ENCODER         : Lavf58.43.100
  Duration: N/A, bitrate: N/A
    Stream #0:0(eng): Video: vp9, none, 640x480, SAR 1:1 DAR 4:3, 1k tbr, 1k tbn, 1k tbc (default)
    Metadata:
      ALPHA_MODE      : 1
      ENCODER         : Lavc58.87.101 libvpx-vp9
      webm_dash_manifest_file_name: glass_360.hdr
      webm_dash_manifest_track_number: 1
Output #0, webm_dash_manifest, to 'stream_manifest.mpd':
  Metadata:
    encoder         : Lavf58.43.100
    Stream #0:0(eng): Video: vp9, none, 640x480 [SAR 1:1 DAR 4:3], q=2-31, 1k tbr, 1k tbn, 1k tbc (default)
    Metadata:
      ALPHA_MODE      : 1
      ENCODER         : Lavc58.87.101 libvpx-vp9
      webm_dash_manifest_file_name: glass_360.hdr
      webm_dash_manifest_track_number: 1
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
Press [q] to stop, [?] for help
frame=    0 fps=0.0 q=-1.0 Lsize=       1kB time=00:00:00.00 bitrate=N/A speed=   0x
video:0kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
Output file is empty, nothing was encoded (check -ss / -t / -frames parameters if used)


  


  glass_live_manifest.mpd

  


  &lt;?xml version="1.0" encoding="UTF-8"?>&#xA;&#xA;<period start="PT0S">&#xA;<adaptationset mimetype="video/webm" codecs="vp9" lang="eng" bitstreamswitching="true" subsegmentalignment="true" subsegmentstartswithsap="1">&#xA;<contentcomponent type="video"></contentcomponent>&#xA;<segmenttemplate timescale="1000" duration="1000" media="glass_$RepresentationID$_$Number$.chk" startnumber="1" initialization="glass_$RepresentationID$.hdr"></segmenttemplate>&#xA;<representation bandwidth="1000000" width="640" height="480" codecs="vp9" mimetype="video/webm" startswithsap="1"></representation>&#xA;</adaptationset>&#xA;</period>&#xA;&#xA;

  


  UPDATE

  


  I fixed the "warnings" by changing the comands like this :

  


  ffmpeg -re -r 25 -i Dash/strm.webm
-map 0:v:0
-pix_fmt yuv420p
-c:v libvpx
-s 640x480 -keyint_min 60 -g 60 -speed 6 -tile-columns 4 -frame-parallel 1 -threads 8 -static-thresh 0 -max-intra-rate 300 -deadline realtime -lag-in-frames 0 -error-resilient 1
-b:v 3000k
-f webm_chunk
-header "Dash/glass_360.hdr"
-chunk_start_index 1 Dash/glass_360_%d.chk
-map 0:a:0
-c:a libvorbis
-b:a 128k -ar 44100
-f webm_chunk
-audio_chunk_duration 2000
-header Dash/glass_171.hdr
-chunk_start_index 1 Dash/glass_171_%d.chk

ffmpeg
-f webm_dash_manifest -live 1
-i Dash/glass_360.hdr
-f webm_dash_manifest -live 1
-i Dash/glass_171.hdr
-c copy
-map 0 -map 1
-f webm_dash_manifest -live 1
-adaptation_sets "id=0,streams=0 id=1,streams=1"
-chunk_start_index 1
-chunk_duration_ms 2000
-time_shift_buffer_depth 7200
-minimum_update_period 7200 Dash/glass_video_manifest.mpd


  


  However, it's still not working.

  


• How to record from webcam using ffmpeg with precise time information of when it was taken ?

  27 février 2021, par Trac3rZ

  I need to record from my 2 webcams and output each frame recorded into images. An additional requirement is I need the time when the image is captured (it has to be precise up to around 10 milliseconds)

  


  Things I've tried :

  


  ffmpeg -y -f video4linux2 -r $frame_rate -i /dev/video0 -vframes 100 -strftime 1 cam0_"%H-%M-%S".png &
ffmpeg -y -f video4linux2 -r $frame_rate -i /dev/video1 -vframes 100 -strftime 1 cam1_"%H-%M-%S".png


  


  This is only good up to a second, so if 2 images are taken within 1 second, 1 is overwritten.

  


  for i in [1..100]
    ffmpeg -y -f video4linux2 -r $frame_rate -i /dev/video0 -vframes 1 -strftime 1 cam0_%5d.png
    date +%s%3N >> time.txt


  


  Then 2 scripts are run in parallel. The timing is now precise up to a millisecond but this degrades the performance a lot since ffmpeg has to be initialized again each time I call the script.

  


  I also tried this

  


  ffmpeg -f video4linux2 -pixel_format yuv420p -timestamps abs -copyts \
   -i /dev/video0 -vf setpts=PTS-STARTPTS -vsync 0 -vframes 10 \
   camera0-%5d.jpeg -c copy -vsync 0 -vframes 10 -f mkvtimestamp_v2 timings.txt


  


  And here's timings.txt

  


  1614427227518
1614427227718
1614427227818
1614427227918
1614427228018
1614427228118
1614427228218
1614427228318
1614427228418
1614427228518


  


  This is good up to 100ms.

  


  Is there any better way to do this ?

  


• how to make work opencv with FFMPEG driver

  14 janvier 2021, par user3313834

  I have a camera on my linuxbox it is working well :

  


  # $ ls -al /dev/video*
# crw-rw----+ 1 root video 81, 0 janv.  8 16:13 /dev/video0
# crw-rw----+ 1 root video 81, 1 janv.  8 16:13 /dev/video1
# $ groups
# adm cdrom sudo dip video plugdev lpadmin lxd sambashare docker libvirt


  


  From python with cv2 it work well with the default driver CAP_V4L2

  


  >>> from pathlib import Path
>>> import cv2
>>> print(cv2.VideoCapture(0, apiPreference=cv2.cv2.CAP_V4L2).isOpened())
True
>>>


  


  I would like to access it with the FFMPEG driver (no success) :

  


  >>> print(cv2.VideoCapture(0, apiPreference=cv2.CAP_FFMPEG).isOpened())
False
>>>


  


  From Python side the opencv look like to have the FFMPEG Driver :

  


    >>> cv2.__version__
  '4.4.0'
  >>> info = cv2.getBuildInformation()
  >>> video, parallel = info.index('Video'), info.index('Parallel')
  >>> print(info[video:parallel])
  Video I/O:
       DC1394:                      NO
       FFMPEG:                      YES
         avcodec:                   YES (58.109.100)
         avformat:                  YES (58.61.100)
         avutil:                    YES (56.60.100)
         swscale:                   YES (5.8.100)
         avresample:                NO
       GStreamer:                   NO
       v4l/v4l2:                    YES (linux/videodev2.h)
  >>>


  


  From Linux side look ok too :

  


  $ dpkg -l |grep -i opencv
ii  libopencv-core4.2:amd64                    4.2.0+dfsg-5                          amd64        computer vision core library
ii  libopencv-imgcodecs4.2:amd64               4.2.0+dfsg-5                          amd64        computer vision Image Codecs library
ii  libopencv-imgproc4.2:amd64                 4.2.0+dfsg-5                          amd64        computer vision Image Processing library
ii  libopencv-videoio4.2:amd64                 4.2.0+dfsg-5                          amd64        computer vision Video I/O library

$ dpkg -l |grep -i ffm
ii  ffmpeg                                     7:4.2.4-1ubuntu0.1                    amd64        Tools for transcoding, streaming and playing of multimedia files
ii  gstreamer1.0-libav:amd64                   1.16.2-2                              amd64        ffmpeg plugin for GStreamer
ii  libavcodec-extra:amd64                     7:4.2.4-1ubuntu0.1                    amd64        FFmpeg library with extra codecs (metapackage)
ii  libavcodec-extra58:amd64                   7:4.2.4-1ubuntu0.1                    amd64        FFmpeg library with additional de/encoders for audio/video codecs
ii  libavdevice58:amd64                        7:4.2.4-1ubuntu0.1                    amd64        FFmpeg library for handling input and output devices - runtime files
ii  libavfilter7:amd64                         7:4.2.4-1ubuntu0.1                    amd64        FFmpeg library containing media filters - runtime files
ii  libavformat58:amd64                        7:4.2.4-1ubuntu0.1                    amd64        FFmpeg library with (de)muxers for multimedia containers - runtime files
ii  libavresample4:amd64                       7:4.2.4-1ubuntu0.1                    amd64        FFmpeg compatibility library for resampling - runtime files
ii  libavutil56:amd64                          7:4.2.4-1ubuntu0.1                    amd64        FFmpeg library with functions for simplifying programming - runtime files
ii  libffmpegthumbnailer4v5                    2.1.1-0.2build2                       amd64        shared library for ffmpegthumbnailer
ii  libpostproc55:amd64                        7:4.2.4-1ubuntu0.1                    amd64        FFmpeg library for post processing - runtime files
ii  libswresample3:amd64                       7:4.2.4-1ubuntu0.1                    amd64        FFmpeg library for audio resampling, rematrixing etc. - runtime files
ii  libswscale5:amd64                          7:4.2.4-1ubuntu0.1                    amd64        FFmpeg library for image scaling and various conversions - runtime files
$