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• when webm extracts aac, the duration is inconsistent

  25 juillet 2019, par Black-Hole

  When I try to extract aac from webm, there will be inconsistencies in duration. aac is ten minutes less. Different webm videos, the gap is not the same.

  webm video is generated by chrome extension chrome.tabCapture.capture

  code :

  chrome.tabCapture.capture({
  
    video: true,
  
    audio: true,
  
    videoConstraints: {
  
      mandatory: {
  
        minWidth: 1920,
  
        minHeight: 1080,
  
        maxWidth: 1920,
  
        maxHeight: 1080,
  
        maxFrameRate: 30,
  
        minFrameRate: 30,
  
      }
  
    }
  
  })

  The above code will return a stream, I will use JS’s MediaRecorder method to process this stream, and finally save it as a webm file.

  code :

  new MediaRecorder(stream, {
  
    audioBitsPerSecond: 128000,
  
    videoBitsPerSecond: 2500000,
  
    mimeType: 'video/webm;codecs=vp9'
  
  })

  If you don’t know the meaning of the above code, it doesn’t matter, I will explain the main information :

  1. width : 1920
  2. height : 1080
  3. FPS : 30
  4. audioBits : 128000
  5. videoBits : 2500000
  6. mimeType : video/webm;codecs=vp9

  I tried a lot of methods, like the following :

  # 1
  
  ffmpeg -i ./source.webm -y -fflags +genpts -max_muxing_queue_size 99999 -r 15 -crf 30 -filter:v crop=750:560:0:0 ./x.mp4
  
  ffmpeg -i ./x.mp4 -y -vn -acodec libfdk_aac -b:a 200k ./x.aac
  
  
  
  # 2
  
  ffmpeg -i ./source.webm -y -vn -acodec libfdk_aac -b:a 200k ./x.aac
  
  
  
  # 3
  
  ffmpeg -i ./source.webm -y -vn -acodec libfdk_aac -b:a 200k -map 0 ./x.aac
  
  
  
  # 4
  
  ffmpeg -i ./source.webm -y -max_muxing_queue_size 99999 -r 15 -crf 30 -filter:v crop=750:560:0:0 ./x.mp4
  
  ffmpeg -i ./source.webm -y -vn -acodec aac -b:a 200k ./x.aac
  
  
  
  # etc.

  But without exception, all failed. I have been plagued by this problem for 4 days.

  webm file download url : https://drive.google.com/file/d/1m4fC1hU-tXFPOZayrYCs-yteSTxw_TaW/view?usp=sharing

• Rotated video with ffmpeg doesn't play in flowplayer in IE9

  17 octobre 2013, par yoshi

  I have a script that rotates videos 90 degrees and then the videos are displayed on a web page using flowplayer (HTML5 version, not Flash). After the video is rotated once it does not play in IE9 but plays without any other problems in Chrome and Firefox.
  The error message is : Video file not found.

  I've looked in IE9's developer tools console, in the network tab and the browser streams the whole video.

  The following is the ffmpeg command I use to rotate and convert the video :

  ffmpeg -i input.mov -y -r 30 -b 4M -vf 'transpose=1,scale=800:trunc(ow/a/2)*2' -ar 48000 -vcodec libx264 -profile baseline -preset slow -level 2.2 output.mp4

  This is the input file which I used : https://dl.dropboxusercontent.com/u/37994/local%20capture.mov

  This is the output video : https://dl.dropboxusercontent.com/u/37994/local%20capture%20rotated.mp4

  The input video from above is a screen capture made using QuickTime on Mac OS.

  This also happened for this video : http://mirrorblender.top-ix.org/peach/bigbuckbunny_movies/big_buck_bunny_480p_h264.mov
  And also this one : https://dl.dropboxusercontent.com/u/37994/clipcanvas_14348_offline.mp4

  This didn't happen for the sample .mov from here : http://support.apple.com/kb/ht1425

  If I run the command twice, meaning I rotate the video 90 degrees and then I rotate the output using the same command once more, the problem disappears, but I need to be able to rotate only 90 degrees.

  This problem doesn't happen if I put IE9 in IE7 or IE8 compatibility mode.

  I was thinking that maybe the problem was how the server serves the video but there's no problem with other videos.

  I looked at the metadata with ffmpeg but didn't see anything significant.

  I already have AddType video/mp4 .mp4 in .htaccess.

  I can't seem to pin down what's causing this problem.

  Edit :

  Request in IE9
  

  Response in IE9
  

• Concatination of images and videos in FFMpeg [closed]

  29 octobre 2023, par Juliano David Hilario

  I've been trying to concat pieces of videos with mix of images in FFMpeg and I can not achieve desired results. I'm trying to create a mock interview project for a friend, she answers the questions from a script. The question should be flashed in the screen before the footage of her answering is shown. The videos are encoded in H.265, with frame rate of 30fps, (via mediainfo) and when I try to concat the videos and images using the concat demuxer, it shows this message in rapid succession and only output the first image in the given duration in the output file : (meaning it failed when concating the video, I assume this is due to the fact that demuxed images doesn't have audio streams.)

  


  [png @ 0x55b4a4cb3540] Invalid PNG signature 0x3DB0201D430.
Error while decoding stream #0:0: Invalid data found when processing input


  


  the command I've used :

  


  ffmpeg -hide_banner -y -f concat -safe 0 -i concat.con -r 30 -c:v libx265 -c:a aac -pix_fmt yuv420p out.mp4


  


  the slice of concat.con file :

  


  file slides/1.png
duration 6
file parts/1.mp4
file slides/2.png
duration 8
file parts/2.mp4
file slides/3.png
duration 9
file parts/3.mp4
. . .
duration 12
file parts/9.mp4
file slides/10.png
duration 9
file parts/10.mp4



  


  Since, I need to get this done if possible today, I tried this route of turning the images into videos by this command :

  


  #!/bin/sh

ffmpeg -f lavfi -i anullsrc=channel_layout=stereo:sample_rate=44100 -loop 1 -i "${1}.png" -c:v libx265 -r 30 -c:a aac -t "$2" -pix_fmt yuv420p "${1}_slide.mp4"


  


  This does create the desired result of a static video without sound but still has an audio channel (which is a pre-requisite for the concat demuxer), but when I concat it with the same command above with videos, the videos' audio desyncs and advances, now the video delays with the audio, which is not obviously feasable for the project. I suspect it has to do with frames and PTS, as MPV (a media player) logs when the duration of the video enters the video that has been concatinated that the PTS is invalid, and says :

  


  Invalid audio PTS: 6.037188 -> 6.553832

Audio/Video desynchronisation detected! Possible reasons include too slow
hardware, temporary CPU spikes, broken drivers, and broken files. Audio
position will not match to the video (see A-V status field).


  


  Tried turning the pictures into an image, and was expecting it to atleast sync with the audio