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• Piping output of youtube-dl to a script using ffmpeg looks ok using echo but returns an error when executing

  29 mai 2020, par I0_ol

  I am trying to use youtube-dl to get the urls of some videos and then pipe the resulting urls into the input of my script. So in my terminal I do

  



  youtube-dl --ignore-config -iga ~/Desktop/youtube/videolist.txt | myscript.sh


  



  In my script I define things as

  



  command='ffmpeg'        
inputArgs='-i'              
outputArgs='-c:v libx264 -preset ultrafast -qp 0'       
directory="${HOME}/Desktop/Videos/"
output="video${count}"      
extension='mp4'         


  



  I test it with echo to make sure everything appears in the correct order.

  



  echo "${command}" "${inputArgs}" "${input}" "${outputArgs}" \
"${directory}""${output}${count}"."${extension}"


  



  And the output from that looks correct. But when I try to run the same thing without the preceding echo command, i.e.,

  



  "${command}" "${inputArgs}" "${input}" "${outputArgs}" \
"${directory}""${output}${count}"."${extension}"


  



  I get an error message that says

  



  


  At least one output file must be specified.

  


  



  So it seems pretty obvious to me that I'm doing something wrong when attempting to execute it.

  



  I have tried :

  



  

  • quoting the entire line as a whole

  


  • quoting different sections together

  


  • using the exec command in front of everything

  


  



  No matter what I do, an error occurs at some point in the process. I know it's something simple I'm doing wrong. Would someone please enlighten me as to what that might be ?

  



  I feel very strongly that the . shouldn't just be in the middle of everything like that, but I really don't know.

  



  Again, everything looks as it should when I run echo before the string of shell parameters.

  



  If more of the script I'm using is needed to understand what I'm talking about, that is not a problem.

  


• avformat/matroskaenc : Avoid unnecessary seek

  2 mai 2020, par Andreas Rheinhardt

  avformat/matroskaenc : Avoid unnecessary seek
  The Matroska muxer has a pair of functions designed to write master
  
  elements whose exact length is not known in advance : start_ebml_master()
  
  and end_ebml_master(). The first one of these would write the EBML ID of
  
  the master element that is about to be started, reserve some bytes for
  
  the length field and record the current position as well as how many
  
  bytes were used for the length field. When writing the master's contents
  
  is finished, end_ebml_master() gets the current position (at the end of
  
  the master element), seeks to the length field using the recorded
  
  position, writes the length field and seeks back to the end of the
  
  master element so that one can continue writing other elements.
  But if one wants to modify the content of the master element itself,
  
  then the seek back is superfluous. This is the scenario that presents
  
  itself when writing the trailer : One wants to update several elements
  
  contained in the Segment master element (this is the main/root master
  
  element of a Matroska file) that were already written when writing the
  
  header. The current approach is to seek to the beginning of the file
  
  to update the elements, then seek to the end, call end_ebml_master()
  
  which immediately seeks to the beginning to write the length and seeks
  
  back. The seek to the end (which has only been performed because
  
  end_ebml_master() uses the initial position to determine the length
  
  of the master element) and the seek back are of course superfluous.
  This commit avoids these seeks by no longer using start/end_ebml_master()
  
  to write the segment's length field. Instead, it is now written
  
  manually. The new approach is : Seek to the beginning to write the length
  
  field, then update the elements (in the order they appear in the file)
  
  and seek back to the end.
  This reduces the ordinary amount of seeks of the Matroska muxer to two
  
  (ordinary excludes scenarios where one has big Chapters or Attachments
  
  or where one writes the Cues at the front).
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/matroskaenc.c

• '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 !