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notes by Adam Sullovey

web & mobile application developer
practicing in Toronto, ON

ffmpeg: concatenate image sequences and audio


assemble multiple image sequences and audio files into 1 video file


  • ffmpeg binary is sitting in my working folder and not in my PATH, so I reference it as ./ffmpeg instead of ffmpeg
  • ffmpeg version info is:

    fmpeg version N-82143-gbf14393-tessus Copyright (c) 2000-2016 the FFmpeg developers
    built with Apple LLVM version 8.0.0 (clang-800.0.38)
    configuration: --cc=/usr/bin/clang --prefix=/opt/ffmpeg --extra-version=tessus --enable-avisynth --enable-fontconfig --enable-gpl --enable-libass --enable-libbluray --enable-libfreetype --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopus --enable-libschroedinger --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libvidstab --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-libzmq --enable-version3 --disable-ffplay --disable-indev=qtkit --disable-indev=x11grab_xcb
    libavutil      55. 35.100 / 55. 35.100
    libavcodec     57. 65.100 / 57. 65.100
    libavformat    57. 57.100 / 57. 57.100
    libavdevice    57.  2.100 / 57.  2.100
    libavfilter     6. 66.100 /  6. 66.100
    libswscale      4.  3.100 /  4.  3.100
    libswresample   2.  4.100 /  2.  4.100
    libpostproc    54.  2.100 / 54.  2.100
    Hyper fast Audio and Video encoder
    usage: ffmpeg [options] [[infile options] -i infile]... {[outfile options] outfile}...
  • all my images in image sequences are the same dimensions and format

  • all my audio files are the same format

  • this page offers a small mp4 file to work with: http://techslides.com/sample-webm-ogg-and-mp4-video-files-for-html5

  • this is helpful https://trac.ffmpeg.org/wiki/Concatenate

Convert Video to Image Sequence:

I need images to work with, so make some!

  • images will go into the frames directory with names like frame_0001.png, frame_0002.png etc
/ffmpeg -i test7.mp4 frames/frame_%04d.png

Convert Image Sequence back to Video


  • -c:v libx264 sets the video codec
  • -crf 23 sets the quality
  • -pix_fmt yuv420p sets the pixel format to something QuickTime can read
  • -r 24 sets input and output framerates
    • input framerate is how fast the images and the sequence are meant to be played back
    • output framerate sets how much time between frames in the output video
    • fast input and slow output results in a slideshow or timelapse
    • slow input and fast output results in duplicate frames (I think)
  • -y to overwrite files without asking
/ffmpeg -r 30 -i frames/frame_%04d.png -c:v libx264 -pix_fmt yuv420p -crf 23 -r 30  -y video-from-frames.mp4

Convert Image Sequence to Video + add audio track


  • -i Bonobo - Kong.mp3 specifies another input stream
  • -c:a aac converts audio to AAC format
  • -shortest limits the length of the output video to the shortest audio or video stream (in this case, the video stream is shorter)
/ffmpeg -r 24 -i frames/frame_%04d.png -i "Bonobo - Kong.mp3" -c:v libx264 -c:a aac -pix_fmt yuv420p -crf 23 -r 24 -shortest -y video-from-frames.mp4

Concatenate multiple image sequences with 1 audio track

Put this into video-input-list.txt. The images in the image sequences must all be the same size and format

file './intro/frame_%04d.png'
file './frames/frame_%04d.png'
file './outro/frame_%04d.png'

then run the command:

  • -f concat tells ffmpeg to use the concat filter
  • -safe 0 has something to do with letting ffmpeg read relative paths in the text file
/ffmpeg -r 24 -f concat -safe 0 -i video-input-list.txt -i "Bonobo - Kong.mp3" -c:v libx264 -c:a aac -pix_fmt yuv420p -crf 23 -r 24 -shortest -y video-from-frames.mp4

Concatenate multiple images sequences and concatenate multiple audio tracks

Put this into audio-input-list.txt.

file 'big_trash_tv_hit.aif.mp3'
file 'recording.mp3'
file 'vocoded-note.aif.mp3'
file 'Bonobo - Kong.mp3'

then run the command:

  • remember to specify -f concat -safe 0 again before the second input source -i audio-input-list.txt
./ffmpeg -r 24 -f concat -safe 0 -i video-input-list.txt -f concat -safe 0 -i audio-input-list.txt -c:a aac -pix_fmt yuv420p -crf 23 -r 24 -shortest -y video-from-frames.mp4

This does what I am looking for!

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