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• ffmpeg : Audio input device not recognized

  8 février 2020, par shrimpwidget

  What is needed for my ffmpeg command to recognize my audio input device ?

  The following reference has not helped resolve my problem : enter link description here

  I want to record me talking (to my Windows laptop) while my screen activity is captured. While I have succeeded in capturing what’s on the screen (by removing all mention of audio from my command), I have been unable to capture audio, as the device I mention is not recognized by ffmpeg. (I routinely use the default laptop for audio input to Audacity...surely there’s some way to use it in this ffmpeg command, too.)

  My audio devices :

  ffmpeg -list_devices true -f dshow -i dummy
  
  
  
      [dshow @ 000000000044a940] DirectShow audio devices
  
      [dshow @ 000000000044a940]  "Microphone Array (IDT High Defi"
  
      [dshow @ 000000000044a940]     Alternative name "@device_cm_{33D9A762-90C8-11D0-BD43-00A0C911CE86}\Microphone Array (IDT High Defi"
  
      [dshow @ 000000000044a940]  "Dock Mic (IDT High Definition A"
  
      [dshow @ 000000000044a940]     Alternative name "@device_cm_{33D9A762-90C8-11D0-BD43-00A0C911CE86}\Dock Mic (IDT High Definition A"
  
      [dshow @ 000000000044a940]  "Jack Mic (IDT High Definition A"
  
      [dshow @ 000000000044a940]     Alternative name "@device_cm_{33D9A762-90C8-11D0-BD43-00A0C911CE86}\Jack Mic (IDT High Definition A"
  
      [dshow @ 000000000044a940]  "Rec. Playback (IDT High Definit"
  
      [dshow @ 000000000044a940]     Alternative name "@device_cm_{33D9A762-90C8-11D0-BD43-00A0C911CE86}\Rec. Playback (IDT High Definit"

  The full name is found via regedit : Microphone Array (IDT High Definition Audio CODEC)

  Why isn’t the audio input device found ?

  ffmpeg -y -f gdigrab -i desktop -framerate 10 -f dshow -i audio="Microphone Array (IDT High Definition Audio CODEC)" -vcodec libx264 "C:\jed\ffmpeg\_mydata\clip.mp4"
  
  
  
      [gdigrab @ 0000000000498540] Capturing whole desktop as 1366x768x32 at (0,0)
  
      [gdigrab @ 0000000000498540] Stream #0: not enough frames to estimate rate; consider increasing probesize
  
      Input #0, gdigrab, from 'desktop':
  
        Duration: N/A, start: 1575576239.093815, bitrate: 1006131 kb/s
  
          Stream #0:0: Video: bmp, bgra, 1366x768, 1006131 kb/s, 29.97 fps, 1000k tbr, 1000k tbn, 1000k tbc
  
      [dshow @ 000000000049a5e0] Could not find audio only device with name [Microphone Array (IDT High Definition Audio CODEC)] among source devices of type audio.
  
      [dshow @ 000000000049a5e0] Searching for audio device within video devices for Microphone Array (IDT High Definition Audio CODEC)
  
      [dshow @ 000000000049a5e0] Could not find audio only device with name [Microphone Array (IDT High Definition Audio CODEC)] among source devices of type video.
  
      audio=Microphone Array (IDT High Definition Audio CODEC): I/O error

• How to map frame extracted with ffmpeg and subtitle of a video ? (frame accuracy problem)

  14 novembre 2019, par Abitbol

  would like to generate text files for frames extracted with ffmpeg, containing subtitle of the frame if any, on a video for which I have burn the subtitles using ffmpeg also.

  I use a python script with pysrt to open the subrip file and generate the text files.
  What I am doing is that each frames is named with the frame number by ffmpeg, then and since they are extracted at a constant rate, I can easily retrieve the time position of the frame using the formula t1 = fnum/fps, where fnum is the number of the frame retrieved with the filename, and fps is the frequency passed to ffmpeg for the frame extraction.

  Even though I am using the same subtitle file to retrieve the text positions in the timeline, that the one that has been used in the video, I still get accuracy errors. Most I have some text files missing or some that shouldn’t be present.

  Because time is not really continuous when talking about frames, I have tried recalibrating t using the fps of the video wih the hardcoded subtitles, let’s call that fps vfps for video fps (I have ensured that the video fps is the same before and after subtitle burning). I get the formula : t2 = int(t1*vfps)/vfps.
  It still is not 100% accurate.

  For example, my video is at 30fps (vfps=30) and I extracted frames at 4fps (fps=4).
  The extracted frame 166 (fnum=166) shows no subtitle. In the subrip file, the previous subtitle ends at t_prev=41.330 and the next subtitle begins at t_next=41.400, which means that t_sub should satisfy : t_prev < t_sub and t_sub < t_next, but I can’t make this happen.

  Formulas I have tried :

  t1 = fnum/fps  # 41.5 > t_next
  
  t2 = int(fnum*vfps/fps)/vfps  # 41.5 > t_next
  
  # is it because of a indexing problem? No:
  
  t3 = (fnum-1)/fps  # 41.25 < t_prev
  
  t4 = int((fnum-1)*vfps/fps)/vfps  # 41.23333333 < t_prev
  
  t5 = int(fnum*vfps/fps - 1)/vfps  # 41.466666 > t_next
  
  t6 = int((fnum-1)*vfps/fps + 1)/vfps  # 41.26666 < t_prev

  Command used :

  # burning subtitles
  
  # (previously)
  
  # ffmpeg -r 25 -i nosub.mp4 -vf subtitles=sub.srt withsub.mp4
  
  # now:
  
  ffmpeg -i nosub.mp4 -vf subtitles=sub.srt withsub.mp4
  
  # frames extraction
  
  ffmpeg -i withsub.mp4 -vf fps=4 extracted/%05.bmp -hide_banner

  Why does this happen and how can I solve this ?

  One thing I have noticed is that if I extract frames of the original video and the subtitle ones, do a difference of the frames, the result is not only the subtitles, there are variations in the background (that shouldn’t happen). If I do the same experience using the same video two times, the difference is null, which means that the frame extraction is consistant.

  Code for the difference :

  ffmpeg -i withsub.mp4 -vf fps=4 extracted/%05.bmp -hide_banner
  
  ffmpeg -i no_sub.mp4 -vf fps=4 extracted_no_sub/%05.bmp -hide_banner
  
  for img in no_sub/*.bmp; do
  
      convert extracted/${img##*/} $img -compose minus -composite diff/${img##*/}
  
  done

  Thanks.

• What are the licence free codecs for FFMPEG ?

  8 avril 2024, par FunkyPizza

  So I've recently started implementing ffmpeg in an application that I do intend to distribute commercially. And I've had an hard time getting my head around the whole licensing process.

  



  The most commonly answered question I've seen seems to be about x264 which requires a paid licence from x264.org in order to use it commercially (right ?). I started to look into mpeg4 instead but that too seemed to be locked behind some patent licensing fee (https://www.mpegla.com/programs/mpeg-4-visual/license-agreement/).

  



  I guess my question is the following, what video encoders compatible with FFMPEG are fully free to use ?

  



  Yes I barely know what I'm talking about, but I feel like I'm missing the elephant in the room here...