Ffmpeg Back

1. Install

1.1 Configure

Ubuntu 14.04 LTS
  • ./configure --extra-version=tessus --enable-avisynth --enable-fontconfig --enable-gpl --enable-libass --enable-libfreetype --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libx264 --enable-version3
Ubuntu 12.04

  • ./configure --extra-version=tessus --enable-avisynth --enable-fontconfig --enable-gpl --enable-libass --enable-libfreetype --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libx264 --enable-version3 --enable-pic --enable-shared

  • Note: --enable-libbluray will cause problems when building opencv

  • Note: if you found that the libraries have not been installed, you can use apt-get install to install the related libraries. (always you can use tab key to find the dev edition to install)
  • Note: libsoxr cannot be installed by apt-get in Ubuntu 12.04, so you should download three package and install them by ordered
    1. libsoxr0
    2. libsoxr-lsr0
    3. libsoxr-dev
  • Note: in Ubuntu 12.04, you should recompile libx264 and ffmpeg with --enable-pic and --enable-shared.(Be sure that you have completely uninstall ffmpeg before recompile libx264, more details in step 7 and 8).
  • Remember to type make distclean before you configure again.
  • Problem: ffmpeg: error while loading shared libraries: libavdevice.so.55: cannot open shared object file: No such file or directory.
  • Solution:
# vim /etc/ld.so.conf and add this line
/usr/local/ffmpeg/lib

# then type ldconfig to load config

1.2 Make

  • make

1.3 Make Install

  • make install

2. Command of generating codes

2.1 Concat

2.1.1 Convert .mp4 to .ts

ffmpeg -y -i input.mp4 -vcodec copy -acodec copy -vbsf h264_mp4toannexb output.ts

2.1.2 Concat two videos

ffmpeg -y -i "concat:input1.ts|input2.ts" -acodec copy -vcodec copy -absf aac_adtstoasc output.mp4

2.1.3 Concat sounds with a .txt file

ffmpeg -y -f concat -i input.txt -c copy output.wav

2.1.4 Problem
  • Problem: Different resolution ratio(分辨率) of two videos will result in distortion(失真) of images and sounds.
  • Solution: Change the resolution ratio of two videos.
    • ffmpeg -y -i input.mp4 -s 1280x720 -ar 44100 -strict -2 output.mp4

2.2 Synthesis(合成)

2.2.1 Sampling sounds to 44100Hz

ffmpeg -y -i input.mp4 -ar 44100 -strict -2 output.mp4

2.2.2 Synthesize the video with sounds

ffmpeg -y -i input.mp4 -i input.wav -filter_complex amix=inputs=2:duration=first:dropout_transition=2 -ar 44100 -strict -2 output.mp4

2.2.3 Problem
  • Problem: Sampling will result in distortion of images when not enable libx264.
  • Solution: Configure the ffmpeg again, and enable libx264.
2.2.4 Combine audio and video

ffmpeg -y -i audio.mp3 -i input.mp4 -c:v copy -absf aac_adtstoasc -b 192k output.mp4

3. Usage

3.1 crop a video

ffmpeg -i input.mp4 -filter:v "crop=w:h:x:y" -pix_fmt yuv420p output.mp4

  • w: width
  • h: height
  • x, y: crop from the start point (x, y)

3.2 cut a video

ffmpeg -ss [start] -i intput.mp4 -t [duration] -c:v copy -c:a copy output.mp4

  • -ss: to specify the start time (Notice that the position of -ss will cause problem of durations of the video)
  • -t: to specify the duration
  • -c:v copy and -c:a copy: to copy the video and audio stream without any re-encoding actions.

3.3 change frame rate

  • firstly, what you should do is to export all the frames of the videos with it's origin rate:

ffmpeg -r "[origin-rate]" -i input.mp4 "frame/f_%1d.png"

  • the next step to do is to generate a new video with all the frames:

ffmpeg -r "[new-rate]" -i "frame/f_%1d.png" -start_number 1 -vcodec "libx264" -crf "0" -pix_fmt yuv420p output.mp4

  • Notice: without -pix_fmt yuv420p, the video codec is not supported for iOS, Safari, and so on.

3.4 extract a specific frame

ffmpeg -ss [time] -i input.mp4 -vframes 1 output.jpg

3.5 admix two audio, and put one audio in the specifc time

i. create a blank video of the longest time:

ffmpeg -f lavfi -i anullsrc=r=44100:cl=mono -t <seconds> -q:a 9 -acodec libmp3lame <blank audio>

ii. add the clip audio(the shorter one) to the blank audio in a specific time.

ffmpeg -i <blank audio> -i <shorter audio file> -filter_complex "aevalsrc=0:d= <time> [s1];[s1][1:a]concat=n=2:v=0:a=1[aout]" -c:v copy -map [aout] <reserved file>

iii. combine with the origin audio file:

ffmpeg -i <resreved file> -i <original longer audio file> -filter_complex "amix=inputs=2:duration=longest:dropout_transition=2, volume=2" <output audio file>

3.6 sample audio stream with slow down filter

ffmpeg -i input.mp4 -vn -ar 44100 -ac 2 -ab 192k -f mp3 -filter:a "atempo=0.5" sample.mp3

  • atempo: it's used to slow down/speed up an audio file, which should be between 0.5~2.

3.7 get video bitrate

ffprobe -v error -select_streams v:0 -show_entries stream=bit_rate -of default=noprint_wrappers=1:nokey=1 input.mp4

3.8 convert a video into a gif format picture

generate a palette with output width 320 pixels:

ffmpeg -i input.mp4 -vf fps=10,scale=320:-1:flags=lanczos,palettegen palette.png

output a gif with the palette:

ffmpeg -i input.mp4 -i palette.png -filter_complex "fps=10,scale=320:-1:flags=lanczos[x];[x][1:v]paletteuse" output.gif

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