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• ffmpeg itsoffset doesnt apply offset to mp4

  26 juillet 2019, par brux

  The following command mixes an mp4 and an mp3 together, keeping the audio from the mp4.

  ffmpeg -i video.mp4 -i audio.mp3 -map 0:v -c:v copy -filter_complex '[0:a][1:a]amix[aout]' -map '[aout]' -shortest out.mp4

  The command works as expected.

  Now I want to offset the mp4 file (both the audio and video stream of the mp4) so that there is a delay of 500ms at the start of the mp4, here is my command :

  ffmpeg -itsoffset 00:00:00.500 -i video.mp4 -i audio.mp3 -map 0:v -c:v copy -filter_complex '[0:a][1:a]amix[aout]' -map '[aout]' -shortest out.mp4

  This doesnt work as expected, the output doesnt have the expected delay of 500ms at the start of the mp4 streams. It appears the output is just the same as the first command I ran.

  The version of ffmpeg I am using is :

  ffmpeg version n4.0-39-gda39990

  Here are the files I’m using :

  video.mp4

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/storage/emulated/0/video.mp4':
  
        Metadata:
  
          major_brand     : mp42
  
          minor_version   : 0
  
          compatible_brands: isommp42
  
          creation_time   : 2019-07-26T03:28:49.000000Z
  
          com.android.version: 8.0.0
  
        Duration: 00:00:07.64, start: 0.000000, bitrate: 20534 kb/s
  
          Stream #0:0(eng): Video: h264 (avc1 / 0x31637661), yuvj420p(pc, smpte170m), 1920x1080, 20966 kb/s, SAR 1:1 DAR 16:9, 29.70 fps, 29.75 tbr, 90k tbn, 180k tbc (default)
  
          Metadata:
  
            rotate          : 270
  
            creation_time   : 2019-07-26T03:28:49.000000Z
  
            handler_name    : VideoHandle
  
          Side data:
  
            displaymatrix: rotation of 90.00 degrees
  
          Stream #0:1(eng): Audio: aac (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 96 kb/s (default)
  
          Metadata:
  
            creation_time   : 2019-07-26T03:28:49.000000Z
  
            handler_name    : SoundHandle

  audio.mp3

  Input #0, mp3, from '/storage/emulated/0/audio.mp3':
  
        Metadata:
  
          album           : Sunflower (Spider-Man: Into the Spider-Verse) - Single
  
          composer        : Louis Bell, Carter Lang, Austin Richard Post, Billy Walsh & Khalif Malik Ibin Shaman Brown
  
          genre           : Hip-Hop/Rap
  
          copyright       : This Compilation ℗ 2018 Republic Records, a division of UMG Recordings, Inc.
  
          title           : Sunflower (Spider-Man: Into the Spider-Verse)
  
          artist          : Post Malone & Swae Lee
  
          album_artist    : Post Malone & Swae Lee
  
          track           : 01/01
  
          TYER            : 2018-10-18T07:00:00Z
  
        Duration: 00:02:38.07, start: 0.000000, bitrate: 325 kb/s
  
          Stream #0:0: Audio: mp3, 44100 Hz, stereo, fltp, 320 kb/s
  
          Stream #0:1: Video: mjpeg, yuvj444p(pc, bt470bg/unknown/unknown), 1400x1400 [SAR 300:300 DAR 1:1], 90k tbr, 90k tbn, 90k tbc
  
          Metadata:
  
            comment         : Cover (front)

• ffmpeg - How to convert massive amounts of files in parallel ?

  15 juillet 2019, par Forivin

  I need to convert about 1.5TiB or audio files which are in either flac or wav format. They need to be converted into mp3 files, keeping important meta data and the cover art etc. and the bitrate needs to be 320k.

  This alone is easy :

  ffmpeg -i "$flacFile" -ab 320k -map_metadata 0 -id3v2_version 3 -vsync 2 "$mp3File" < /dev/null

  But the problem is making it faster. The command from above only uses 12.5% of the CPU. I’d much rather use like 80%. So I played around with the threads flag, but it doesn’t make it faster or slower :

  ffmpeg -i "$flacFile" -ab 320k -map_metadata 0 -id3v2_version 3 -vsync 2 -threads 4 "$mp3File" < /dev/null

  But it only utilizes my CPU by 13%. I think it only uses one thread. My CPU has 8 physical cores btw (+ hyperthreading).

  So my idea now is to somehow have multiple instances of ffmpeg running at the same time, but I have no clue how to do that properly.

  This is my current script to take all flac/wav files from one directory (recursively) and convert them to mp3 files in a new directory with the exact same structure :

  #!/bin/bash
  
  
  
  SOURCE_DIR="/home/fedora/audiodata_flac"
  
  TARGET_DIR="/home/fedora/audiodata_mp3"
  
  
  
  echo "FLAC/WAV files will be read from '$SOURCE_DIR' and MP3 files will be written to '$TARGET_DIR'!"
  
  read -p "Are you sure? (y/N)" -n 1 -r
  
  echo    # (optional) move to a new line
  
  if [[ $REPLY =~ ^[Yy]$ ]] ; then # Continue if user enters "y"
  
  
  
      # Find all flac/wav files in the given SOURCE_DIR and iterate over them:
  
      find "${SOURCE_DIR}" -type f \( -iname "*.flac" -or -iname "*.wav" \) -print0 | while IFS= read -r -d '' flacFile; do
  
          if [[ "$(basename "${flacFile}")" != ._* ]] ; then # Skip files starting with "._"
  
              tmpVar="${flacFile%.*}.mp3"
  
              mp3File="${tmpVar/$SOURCE_DIR/$TARGET_DIR}"
  
              mp3FilePath=$(dirname "${mp3File}")
  
              mkdir -p "${mp3FilePath}"
  
              if [ ! -f "$mp3File" ]; then # If the mp3 file doesn't exist already
  
                  echo "Input: $flacFile"
  
                  echo "Output: $mp3File"
  
                  ffmpeg -i "$flacFile" -ab 320k -map_metadata 0 -id3v2_version 3 -vsync 2 "$mp3File" < /dev/null
  
              fi
  
          fi
  
      done
  
  fi

  I mean I guess I could append an & to the ffmpeg command, but that would cause throusands of ffmpeg instances to run at the same time, which is too much.

• ffplay playback h264 encoded camera preview blur

  11 juillet 2019, par doufu

  I use the ffplay tool provided by ffmpeg to play an h264 encoded camera. When the camera is still, the interface will be very clear, but when I cover the camera for a while to remove the occlusion or move the camera quickly, the interface will be blurred, resulting in a mosaic-like picture, but the interface will become clear after a few seconds.
  Why is this happening ?
  Am I missing some options to run ffplay ?
  PS：Using AMCap will not have the above problem.
  The command opening my camera I used :

  ffplay.exe -f dshow -i video="camera name"

  Preview screencast video is uploaded to youtube

  The following is the printout information of ffplay：