Posts Tagged ‘ffmpeg’

Silence please

Tuesday, April 19th, 2016

As all music copyright holders will tell you, adding music you like (but do not own) to family video clips is copyright infringement. As such, you should remove the audio track entirely to avoid getting into a lawsuit… or worse, getting your video removed from Youtube :)

The command below is will list all streams that exist in your video file.

$ ffmpeg -i yourfile.mp4

ffmpeg version N-60592-gfd982f2 Copyright (c) 2000-2014 the FFmpeg developers
  built on Feb 13 2014 22:05:50 with gcc 4.8.2 (GCC)
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libcaca --enable-libfreetype --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libx264 --enable-libxavs --enable-libxvid --enable-zlib
  libavutil      52. 63.101 / 52. 63.101
  libavcodec     55. 52.101 / 55. 52.101
  libavformat    55. 32.101 / 55. 32.101
  libavdevice    55.  9.100 / 55.  9.100
  libavfilter     4.  1.102 /  4.  1.102
  libswscale      2.  5.101 /  2.  5.101
  libswresample   0. 17.104 /  0. 17.104
  libpostproc    52.  3.100 / 52.  3.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'yourfile.mp4':
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: mp42mp41
    creation_time   : 2015-12-22 23:09:46
  Duration: 00:05:27.04, start: 0.000000, bitrate: 5836 kb/s
    Stream #0:0(eng): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv), 1280x720 [SAR 1:1 DAR 16:9], 5579 kb/s, 29.97 fps, 29.97 tbr, 30k tbn, 59.94 tbc (default)
      creation_time   : 2015-12-22 23:09:46
      handler_name    : Alias Data Handler
    Stream #0:1(eng): Audio: aac (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 253 kb/s (default)
      creation_time   : 2015-12-22 23:09:46
      handler_name    : Alias Data Handler

As you can see in the example above, my file contains two streams: the video stream (h264) as 0:0 and a single audio stream as 0:1

To get rid of the audio stream with ffmpeg, I simply needed to ask ffmpeg nicely to copy the file, keeping the 0:0 video stream, ignoring the audio stream and leaving the codecs alone (i.e., not trying to reencode anything):

ffmpeg -i yourfile.mp4 -map 0:0 -acodec copy -vcodec copy yourfile-silent.mp4

If you have multiple video streams or if you want to keep some audio streams, then just adapt the mappings accordingly.

Simple time-lapse using ffmpeg

Sunday, January 25th, 2015

In my previous post, I’ve described the little tool I’ve put together to help me out trigger my DSLR remotely & how I’ve used it to create basic time-lapse videos.

The video quality of my first attempts were pretty.. miserable. Soo I HAD TO try and find a better approach. Here’s where I am at right now and the next steps on my list to further improve the result quality.

Yesterday, I’ve taken two image sequences: one of my garden (again :p) and another one inside our living room. I’ve used a delay of 10 seconds for both but (somewhat) different settings for the shots.

I didn’t prepare much before taking these image sequences; my goal was only to have some raw material to use as input and to run some experiments with the tools currently at my disposal.

For the garden sequence, I’ve used a small — though not small enough — aperture (8) and a short exposition time (1/125s).

For the living room sequence, I’ve used a smaller aperture (f 11) and a longer exposition time.

Again, my goal wasn’t to have great images as input so don’t mention the images quality ;-)

I’ve gathered 384 shots for the first sequence and  165 for the second (time ran out ^^).

Here are the final videos. As you can see below, those videos are already of MUCH better quality than my first attempts.

First sequence:

Second sequence (fast):

Second sequence (medium):

Second sequence (slow):

Without further ado, let me describe how I went from the RAW input files (DNG) to the resulting video.

First, I had to convert my raw files to a file format that ffmpeg can work with. I’ve used XnConvert, but for CLI lovers, ImageMagick can probably do that too.

Next, I needed to rename all files to follow a very simple naming convention (you’ll see later why that’s useful). Here’s a simple one-liner to do that easily:

find . -name '*.png' | awk 'BEGIN{ a=0 }{ printf "mv %s %04d.png\n", $0, a++ }' | bash

What this command does is that it takes all .png files in the current (or sub) folder(s) and renames them, ensuring that they all contain 4 digits. For example ‘IMGP_20150124001.png’ will become ‘0001.png’ and ‘IMGP_20150124002.png’ will become ‘0002.png’.

The last step (yep, already) is to actually create the video. In the example below, I create the video and directly add a soundtrack to it:

ffmpeg -v info -y -f image2 -r 24 -i ./in/%4d.png -t 00:00:16 -i soundtrack.mp3 -c:a copy
\ -shortest -threads 8 -s:v 1920x1080 -vcodec libx264 -preset veryslow -qp 0 -map 0:0 -map 1:0 ./movie2.mkv

Here’s a breakdown of the command arguments. All arguments in italic are those I didn’t use in the example above but that can come in handy depending on what your goal is:

  • -v info
    • output information messages (default)
    • you can switch that to verbose, debug, … if you need to troubleshoot things
  • -y
    • overwrite existing files without asking
  • -r 24
    • fixed input frames per seconds to 24 (FPS)
      • note that 30fps or more is nicer for the human eye, but I didn’t have enough images to sustain that
    • with this, ffmpeg generates timestamps assuming constant fps
    • notice that the ‘-r’ argument is placed BEFORE the -i (inputs)! This is mandatory, otherwise it’ll specify the output framerate rather than the input, which is not what you want
  • -f image2
    • the input files format; in this case images
  • -i …
    • specifies the input files
    • you can now see why I’ve renamed the input files first; here I used a number mask ‘%4d’ which will match all our correctly named input files
    • notice that the images are loaded from a “in” sub-folder; I used that idiom to separate the input and the output
  • -i soundtrack.mp3
    • in this example, I add another input, which is an audio file that will be added to the video
  • -c:a copy
    • instructs ffmpeg to copy the input audio file without re-encoding it
    • I can do this since the video container that I’ve chosen — mkv — can hold the mp3 file as is
  • -shortest
    • stop when the shortest input is finished (i.e., stop when we run out of images or when the audio input file is finished
  • threads 8
    • self-explanatory :)
  • -qscale:a 0
  • -s:v 1920×1080
    • output video (:v) resolution, in this case full hd
  • -vcodec libx264
    • output video encoding: x.264
    • (since we all love x.264, right??!)
  • -t 00:00:16
    • duration of the video (hh:mm:ss)
    • I had 384 input images that I wanted to display at 24 fps thus 384/24 = 15.x seconds
    • since I specified the ‘-shortest’ option, I don’t care if the total duration is a bit too long
  • -b:v 2M (or more :p)
    • video (:v) bitrate. Useful if you must limit the file size
    • in my case I didn’t care about the output file size given the low number of input material
  • -preset veryslow
    • since I didn’t care about output file size, I went for the highest quality possible
    • x.264 lossless
  • -qp 0
  • -map 0:0 -map 1:0
    • map the video and audio tracks (only one -map argument is needed if there is no input audio!)
  • -loop 1
    • you can use this option if you want to loop your images (i.e., when the encoder has gone through all input images, it starts over with the first image)
    • this can be useful if you want to loop until something else is done (e.g., until the end of the audio input track if you remove the ‘-shortest’ argument)
  • ./blabla.mkv
    • self explanatory

Note that the order of the arguments DOES matter!

ffmpeg is a very versatile & powerful command line utility, so this barely scratches the surface of what it can do (and I’m by no means a specialist). If you want to know more, check out the official docs.

There you have it! Quite simple heh :)

In the example above, I’ve directly added the audio track using ffmpeg, but I don’t recommend this. You’ll be much better off adding the audio track afterwards; ideally using a video editing software such as Pinnacle Studio, Adobe Premiere, Adobe After Effects and the like ;-)

With these, you’ll be able to make nice transitions, precisely mix & match the audio and video, etc.

So to conclude, this is a much better approach for generating time-lapse videos than what I did at first.. but I realize that this is still very amateurish.

I want to further improve the output video quality (not only encoding-wise), but to do so, I’ll need to:

  • capture more input pictures so that I can make longer videos at a higher frame rate (ideally I’d like to try and generate 60fps videos)
  • think a bit more about the relation between:
    • the total number of frames
    • the delay between each frame
    • the obturation speed
    • the aperture
  • post-process the input frames at least a bit to even out the exposure, etc
    • this should really boost the resulting video quality
  • post-process the video once generated
    • add the audio and sync it correctly
    • add effects such as fade-in, fade-out, ease-in, ease-out
    • add an introduction
    • add a watermark
    • add credits ;-)
  • improve my gear (see my previous post for my ideas about that)
  • give LRTimeLapse a try as it looks like a great software solution with (partly) automated workflows for creating time-lapse videos
    • it seems to be able to work directly with the RAW input files (DNG in my case)
    • it seems to be very well integrated with Lightroom, which is already part of my photographic toolkit
    • finally, it creates the output video file using ffmpeg which is, as you’ve seen above, perfectly fine ;-)

And last but not least, I’ll need to choose something AWESOME to take pictures of ;-)