Not all file formats support multi channel audio, or work with it equally well. We found it easiest to work with raw wave files (for great support with Audacity, e.g.) or AAC.

MP4 videos contain a flag that tells the player when it can start, called the moov atom. When this flag is set at the end of a file, some players will wait until the entire video is downloaded before they start playing. To speed up this process, always look for a checkbox called ‘fast start’ or ‘web optimized’ or ‘streaming enabled’ and enable it when exporting a video.

Extract a still frame

The following uses ffmpeg to compress a video that is optimally compressed for size while keeping an ok quality, and ensures compatibility across 99.99% of the Android and iOS devices.

Usually very straightforward, ffmpeg picks the output format using the file extension. Wave to mp3, 5 seconds only, 128kb/s, is:

FFMPEG is a great tool for doing anything programmatically with audio or video files, but the default installation contains only open standards, and is therefore utterly incapable of converting AAC files and other common standards. Time to build it ourselves!

To combine a series of images (PNG or JPEG) into a video, use the following. There is a more standard way to select the images by numbering them in a specific way, but the following makes it easier to work with wildcards without having to rename the images.