As part of my #StillStanding project I need to handle a lot of video files on a daily basis. Today, I wanted to check the duration and pixel dimensions of a bunch of files in different folders. As always, I turned to FFmpeg, or more specifically FFprobe, for help. However, figuring out all the details of how to get out the right information is tricky. So I decided to ask ChatGPT for help.

There is always a need to add fade-in and fade-out to audio tracks. Here is a way of doing it for a bunch of video files. It may come in handy with the audio normalization script I have shown previously. That script is based on continuously normalizing the audio, which may result in some noise in the beginning and end (because there is little/no sound in those parts, hence they are normalized more).

After exploring some visualizations of kayaking, I was eager to see how a similar approach could work for walking. On a trip to the Norwegian mountains, specifically at Haugastøl, situated halfway between Oslo and Bergen, I strapped a GoPro Hero Black 10 on my chest and walked up and down a nearby hill called Storevarden. The walk was approximately 25 minutes up and down, and a fast-forward version of the video can be seen here:

Last year, I wrote about video-based motion analysis of kayaking. Those videos were recorded with a GoPro Hero 8 and I tested some of the video visualization methods of the Musical Gestures Toolbox for Python. This summer I am testing out some 360 cameras for my upcoming AMBIENT project. I thought I should take one of these, a GoPro Max, out for some kayaking in the Oslo fjord. Here are some impressions of the trip (and recording).

Today, I recorded Sound Action 194 - Rolling Dice as part of my year-long sound action project. The idea has been to do as little processing as possible to the recordings. That is because I want to capture sounds and actions as naturally as possible. The recorded files will also serve as source material for both scientific and artistic explorations later. For that reason, I only trim the recordings non-destructively using FFmpeg.

In my ever-growing collection of FFmpeg-related blog posts, I will today show how to add subtitles to videos. These tricks are based on the need to create a captioned version of a video I made to introduce the Workshop on NIME Archiving for the 2022 edition of the International Conference on New Interfaces for Musical Expression (NIME). This is the video I discuss in this blog post: Note that YouTube supports turning on and off the subtitles (CC button).

I have been doing several long recordings with GoPro cameras recently. The cameras automatically split the recordings into 4GB files, which leaves me with a myriad of files to work with. I have therefore made a script to help with the pre-processing of the files. This is somewhat similar to the script I made to convert MXF files to MP4, but with better handling of the temp file for storing information about the files to merge:

I am recording a lot of short videos these days for my sound actions project. Sometimes the recordings end up being rotated, which is based on the orientation sensor (probably the gyroscope) of my mobile phone. This rotation is not part of the recorded video data, it is just information written into the header of the MPEG file. That also means that it is possible to change the rotation without recoding the file.

This week we started up our new online course, Motion Capture: The Art of Studying Human Activity, and we are also rerunning Music Moves: Why Does Music Make You Move? for the seventh time. Most of the material for these courses is premade, but we record a new wrap-up video at the end of each week. This makes it possible to answer questions that have been posed during the week and add some new and relevant material.

I often want to create motion videos, that is, videos that only show what changed between frames. Such videos are nice to look at, and so-called “frame differencing” is also the start point for many computer vision algorithms. We have made several tools for creating motion videos (and more) at the University of Oslo: the standalone VideoAnalysis app (Win/Mac) and the different versions of the Musical Gestures Toolbox. These are all great tools, but sometimes it would be nice also to create motion videos in the terminal using FFmpeg.

I have previously written about how it is possible to “flatten” a Ricoh Theta+ recording using FFmpeg. Now, I have spent some time exploring how to process some recordings from a Garmin VIRB camera. Some hours of recordings The starting point was a bunch of recordings from our recent MusicLab Copenhagen featuring the amazing Danish String Quartet. A team of RITMO researchers went to Copenhagen and captured the quartet in both rehearsal and performance.

Typical video files, such as MP4 files with H.264 compression, are usually small in size and with high visual quality. Such files are suitable for visual inspection but do not work well for video analysis. In most cases, computer vision software prefers to work with raw data or other compression formats. The Musical Gestures Toolbox for Matlab works best with these file types: Video: use .jpg (Motion.jpg) as the compression format.

Here is another FFmpeg-related blog post, this time to explain how to rotate a video using the command-line tool FFmpeg. There are two ways of doing this, and I will explain both in the following. Rotation in metadata The best first try could be to make the rotation by only modifying the metadata in the file. This does not work for all file types, but should work for some (including .

I have previously written about how to trim video files with FFmpeg. It is also easy to crop a video file. Here is a short how-to guide for myself and others. Cropping is not the same as trimming This may be basic, but I often see the concepts of cropping and trimming used interchangeably. So, to clarify, trimming a video file means making it shorter by removing frames in the beginning and/or end.

Sometimes, there is a need to convert an audio file into a blank video file with an audio track. This can be useful if you are on a system that does not have a dedicated audio player but a video player (yes, rare, but I work with odd technologies…). Here is a quick recipe FFmpeg to the rescue When it comes to converting from one media format to another, I always turn to FFmpeg.

We are organizing the Rhythm Production and Perception Workshop at RITMO next week. As mentioned in another blog post, we have asked presenters to send us pre-recorded videos. They are all available on the workshop page. During the workshop, we will play sets of videos in sequence. When doing a test run today, we discovered that the sound levels differed wildly between files. There is clearly the need for normalizing the sound levels to create a good listener experience.

We are organizing the Rhythm Production and Perception Workshop 2021 at RITMO a week from now. Like many other conferences these days, this one will also be run online. Presentations have been pre-recorded (10 minutes each) and we also have short poster blitz videos (1 minute each). Pre-recorded videos People have sent us their videos in advance, but they all have different first “slides”. So, to create some consistency among the videos, we decided to make an introduction slide for each of them.

When working with various types of video analysis, I often end up with video files without audio. So I need to add the audio track by copying either from the source video file or from a separate audio file. There are many ways of doing this. Many people would probably reach for a video editor, but the problem is that you would most likely end up recompressing both the audio and video file.

In my ever-growing collection of smart FFmpeg tricks, here is a way of converting from one container format to another. Here I will convert from a QuickTime (.mov) file to a standard MPEG-4 (.mp4), but the recipe should work between other formats too. If you came here to just see the solution, here you go: ffmpeg -i infile.mov -acodec copy -vcodec copy outfile.mp4 In the following I will explain everything in a little more detail.

I take a lot of timelapse shots with a GoPro camera. Usually, I do this with the camera’s photo setting instead of the video setting. That is because I find it easier to delete unwanted pictures from the series that way. It also simplifies selecting individual photos when I want that. But then I need a way to create a timelapse video from the photos easily. Here is an FFmpeg one-liner that does the job:

FFmpeg is a fantastic resource for doing all sorts of video manipulations from the terminal. However, it has a lot of features, and it is not always easy to understand what they all mean. I was interested in understanding more about how the tblend function works. This is a function that blends successive frames in 30 different ways. To get a visual understanding of how the different operations work, I decided to try them all out on the same video file.

Continuing my explorations of FFmpeg for video visualization, today I came across this very nice blog post on creating “pixel array” images of videos. Here the idea is to reduce every single frame into only one pixel, and to plot this next to each other on a line. Of course, I wanted to try this out myself. I find that creating motiongrams or videograms is a good way to visualize the content of videos.

{width=“300”} This is a note to self, and could potentially also be useful to others in need of converting “old-school” MPEG-2 files into more modern MPEG-4 files using FFmpeg. In the fourMs lab we have a bunch of Canon XF105 video cameras that record .MXF files with MPEG-2 compression. This is not a very useful format for other things we are doing, so I often have to recompress them to something else.

I am continuing my explorations of the great terminal-based video tool FFmpeg. Now I wanted to see if I could “flatten” a 360-degree video recorded with a Ricoh Theta camera. These cameras contain two fisheye lenses, capturing two 180-degree videos next to each other. This results in video files like the one I show a screenshot of below. These files are not very useful to watch or work with, so we need to somehow “flatten” them into a more meaningful video file.

In some recent posts I have explored the creation of motiongrams and average images, multi-exposure displays, and image masks. In this blog post I will explore different ways of generating keyframe displays using the very handy command line tool FFmpeg. As in the previous posts, I will use a contemporary dance video from the AIST Dance Video Database as an example: The first attempt is to create a 3x3 grid image by just sampling frames from the original image.

As part of my exploration in creating multi-exposure keyframe image displays with FFmpeg and ImageMagick, I tried out a number of things that did not help solve the initial problem but still could be interesting for other things. Most interesting was the automagic creation of image masks from a video file. I will use a contemporary dance video from the AIST Dance Video Database as an example: The first step is to extract keyframes from the video file using this one-liner ffmpeg command:

While I was testing visualization of some videos from the AIST database earlier today, I wanted to also create some “keyframe image displays”. This can be seen as a way of doing multi-exposure photography, and should be quite straightforward to do. Still it took me quite some time to figure out exactly how to implement it. It may be that I was searching for the wrong things, but in case anyone else is looking for the same, here is a quick write up.

We have a bunch of Canon XF105 at RITMO, a camera that records MXF files. This is not a particularly useful file format (unless for further processing). Since many of our recordings are just for documentation purposes, we often see the need to convert to MP4. Here I present two solutions for converting MXF files to MP4, both as individual files and a combined file from a folder. These are shell scripts based on the handy FFmpeg.

This is a note to self, and hopefully others, about how to easily and quickly trim videos without recompressing the file. I often have long video recordings that I want to split or trim. Splitting and trimming are temporal transformations and should not be confused with the spatial transformation cropping. Cropping a video means cutting out parts of the image, and I have another blog post on cropping video files using FFmpeg.