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• 'arecord' works but FFMPEG 'cannot open audio device'

  16 mai 2020, par kwithnail

  On my Linux-based QNAP NAS, I can successfully record my Loopback audio device using :

  



  # arecord -D default:CARD=Loopback test.wav


  



  However, FFMPEG cannot use this same audio device. It returns :

  



      [alsa @ 0x5a45880] cannot open audio device hw:default:CARD=Loopback (No such file or directory)
hw:default:CARD=Loopback: Input/output error


  



  I've also tried any number of hw: options in FFMPEG. For what it's worth, the arecord -l command returns :

  



  **** List of CAPTURE Hardware Devices ****
card 0: PCH [HDA Intel PCH], device 0: ALC262 Analog [ALC262 Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: Loopback [Loopback], device 0: Loopback PCM [Loopback PCM]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: Loopback [Loopback], device 1: Loopback PCM [Loopback PCM]
  Subdevices: 1/1
  Subdevice #0: subdevice #0


  



  arecord -L returns :

  



  [~] # arecord -L
null
    Discard all samples (playback) or generate zero samples (capture)
sysdefault:CARD=PCH
    HDA Intel PCH, ALC262 Analog
    Default Audio Device
front:CARD=PCH,DEV=0
    HDA Intel PCH, ALC262 Analog
    Front speakers
sysdefault:CARD=Loopback
    Loopback, Loopback PCM
    Default Audio Device
front:CARD=Loopback,DEV=0
    Loopback, Loopback PCM
    Front speakers
surround21:CARD=Loopback,DEV=0
    Loopback, Loopback PCM
    2.1 Surround output to Front and Subwoofer speakers
surround40:CARD=Loopback,DEV=0
    Loopback, Loopback PCM
    4.0 Surround output to Front and Rear speakers
surround41:CARD=Loopback,DEV=0
    Loopback, Loopback PCM
    4.1 Surround output to Front, Rear and Subwoofer speakers
surround50:CARD=Loopback,DEV=0
    Loopback, Loopback PCM
    5.0 Surround output to Front, Center and Rear speakers
surround51:CARD=Loopback,DEV=0
    Loopback, Loopback PCM
    5.1 Surround output to Front, Center, Rear and Subwoofer speakers
surround71:CARD=Loopback,DEV=0
    Loopback, Loopback PCM
    7.1 Surround output to Front, Center, Side, Rear and Woofer speakers


  



  FFMPEG command and response is :

  



  [~] # /share/CACHEDEV1_DATA/.qpkg/ffmpeg/ffmpeg -f alsa -i hw:default:CARD=Loopback test.mp3
ffmpeg version 4.2.1-static https://johnvansickle.com/ffmpeg/  Copyright (c) 2000-2019 the FFmpeg developers
  built with gcc 6.3.0 (Debian 6.3.0-18+deb9u1) 20170516
  configuration: --enable-gpl --enable-version3 --enable-static --disable-debug --disable-ffplay --disable-indev=sndio --disable-outdev=sndio --cc=gcc-6 --enable-fontconfig --enable-frei0r --enable-gnutls --enable-gmp --enable-libgme --enable-gray --enable-libaom --enable-libfribidi --enable-libass --enable-libvmaf --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librubberband --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libvorbis --enable-libopus --enable-libtheora --enable-libvidstab --enable-libvo-amrwbenc --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libdav1d --enable-libxvid --enable-libzvbi --enable-libzimg
  libavutil      56. 31.100 / 56. 31.100
  libavcodec     58. 54.100 / 58. 54.100
  libavformat    58. 29.100 / 58. 29.100
  libavdevice    58.  8.100 / 58.  8.100
  libavfilter     7. 57.100 /  7. 57.100
  libswscale      5.  5.100 /  5.  5.100
  libswresample   3.  5.100 /  3.  5.100
  libpostproc    55.  5.100 / 55.  5.100
ALSA lib ../../../src/pcm/pcm.c:2564:(snd_pcm_open_noupdate) Unknown PCM hw:default:CARD=Loopback
[alsa @ 0x5f64800] cannot open audio device hw:default:CARD=Loopback (No such file or directory)
hw:default:CARD=Loopback: Input/output error


  



  FFMPEG -sources alsa gives :

  



  [~] # /share/CACHEDEV1_DATA/.qpkg/ffmpeg/ffmpeg -sources alsa
ffmpeg version 4.2.1-static https://johnvansickle.com/ffmpeg/  Copyright (c) 2000-2019 the FFmpeg developers
  built with gcc 6.3.0 (Debian 6.3.0-18+deb9u1) 20170516
  configuration: --enable-gpl --enable-version3 --enable-static --disable-debug --disable-ffplay --disable-indev=sndio --disable-outdev=sndio --cc=gcc-6 --enable-fontconfig --enable-frei0r --enable-gnutls --enable-gmp --enable-libgme --enable-gray --enable-libaom --enable-libfribidi --enable-libass --enable-libvmaf --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librubberband --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libvorbis --enable-libopus --enable-libtheora --enable-libvidstab --enable-libvo-amrwbenc --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libdav1d --enable-libxvid --enable-libzvbi --enable-libzimg
  libavutil      56. 31.100 / 56. 31.100
  libavcodec     58. 54.100 / 58. 54.100
  libavformat    58. 29.100 / 58. 29.100
  libavdevice    58.  8.100 / 58.  8.100
  libavfilter     7. 57.100 /  7. 57.100
  libswscale      5.  5.100 /  5.  5.100
  libswresample   3.  5.100 /  3.  5.100
  libpostproc    55.  5.100 / 55.  5.100
Auto-detected sources for alsa:
ALSA lib ../../../src/control/control.c:1375:(snd_ctl_open_noupdate) Invalid CTL hw:0
Cannot list sources.


  



  Can anyone shed some light on why this is impossible in FFMPEG and suggest what I'm doing wrong here ? FFMPEG includes the ALSA module, and is version 4.2.1. Thanks !

  


• avformat/webm_chunk : Open AVIOContext before initializing sub-muxer

  17 mai 2020, par Andreas Rheinhardt

  avformat/webm_chunk : Open AVIOContext before initializing sub-muxer
  The description of AVOutputFormat.init contains the statement that "this
  
  method must not write output". Due to this, the webm_chunk muxer defers
  
  opening the AVIOContext for the child muxer until avformat_write_header(),
  
  i.e. there is no AVIOContext when the sub-muxer's avformat_init_output()
  
  is called. But this violates the documentation of said function which
  
  requires the AVFormatContext to have an already opened AVIOContext.
  
  This commit fixes this.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/webm_chunk.c

• Vidgear write Video not open

  25 août 2020, par MrTuyen

  Source code

  



  Command : (https://drive.google.com/file/d/14YGKIhftAidQVvR_nMWY3oIhcWFzLERE/view?usp=sharing)

  



  No errors occurred. I have been trying to figure out how to write videos with Vidgear. I am working with windows and webcam.

  



  Error : "Output.mp4" Opened is a black color. (https://drive.google.com/file/d/11x-q_w59gdaAECtRIqi0MNGIOZ-Vuati/view?usp=sharing)

  



  # import required libraries
from vidgear.gears import CamGear
from vidgear.gears import WriteGear
import cv2

# Open live video stream on webcam at first index(i.e. 0) device
stream = CamGear(source=0).start()

# retrieve framerate from CamGear Stream and pass it as `-input_framerate` parameter
output_params = {"-input_framerate":stream.framerate}

# Define writer with defined parameters and suitable output filename for e.g. `Output.mp4`
writer = WriteGear(output_filename = 'Output.mp4', **output_params)

# loop over
while True:

    # read frames from stream
    frame = stream.read()

    # check for frame if None-type
    if frame is None:
        break


    # {do something with the frame here}


    # write frame to writer
    writer.write(frame)

    # Show output window
    cv2.imshow("Output Frame", frame)

    # check for 'q' key if pressed
    key = cv2.waitKey(1) & 0xFF
    if key == ord("q"):
        break

# close output window
cv2.destroyAllWindows()

# safely close video stream
stream.stop()

# safely close writer
writer.close()