Encoding Video

There is no single optimal video encoding to be used for Videosync, since different codecs have different benefits and drawbacks, and the choice depends on your situation. See below for our recommendations.

Compatibility
  • Videosync uses AV Foundation for video playback. This means that all formats that can be played with Quicktime Player 10 can be played by Videosync. When opening a video with an older codec in Quicktime 10, it will automatically be converted to a format that is supported by Videosync.
  • The HAP codec is fully supported by Videosync.
Codecs and containers

Here is a list of pros and cons of video codecs most often used for live performances:

  • H264: this is currently the most used compression algorithm for consumers, it stores high-quality video in small files, so there is little strain on the hard drive when playing them. Decoding is accelerated by the graphics device. Since H264 uses a more complicated compression algorithm than earlier codecs like Photo/jpeg, it uses more GPU power. This means that theoretically, playing H264 allows less room for effects processing, which is also done on the GPU. However when playing back multiple large video files, not the GPU but the storage disk will very likely be the performance bottleneck, usually making H264 a better choice than Photo/jpeg.
  • Photo/jpeg: this uses an older and relatively simple compression algorithm, the biggest drawback being that it has more visible artefacts, in other words, files sizes with comparable quality are significantly larger in Photo/jpeg than in H264. Colors tend to be slightly more natural and vibrant than with H264. Photo/jpeg uses no time-based compression, so every frame is stored independently making it easy to skip through, meaning seek times will be shorter. This may be noticeable for example when triggering a clip multiple times repetitively.
  • HAP, a new codec developed by Vidvox, stores video with high quality in still relatively small files. HAP also has a minimal seek time and supports storing alpha. This is currently the most optimal codec for real-time video playback. The only drawback is that it is not natively supported by the OS, meaning for example that things like Quick Look (pressing space bar to get a preview in Finder) do not work with HAP and that support for the codec needs to be separately installed.
  • Prores 422 is the successor of Apple Intermediate Codec, meant for storing files during editing, not for real-time use. It optimizes quality over file size. We don’t use this codec for live performance because it puts quite a high strain on the storage drive.
  • Prores 4444, however, is the only modern codec supported natively by macOS that stores an alpha channel. Previously the Animation codec was the go-to option for this, with equally large file sizes. Whenever possible, we recommend using HAP Alpha for real-time video playback with an alpha channel for its smaller file size and thus smaller load on the storage drive.
  • Mpeg 1 to 4 were the consumer codecs of choice before H264. Currently, it offers no benefits over using H264.
  • DXV is a codec developed by Resolume. Like HAP, it is not natively supported by the operating system. Outside of use with Resolume software, it has no benefits over using HAP, which has better performance and quality versus file size.
Best practices when converting to another codec

When converting movies to a codec of choice, for the best results always start from the original file at the highest available resolution and only convert once, directly to the codec and resolution you need. It should never be necessary to convert a video twice; you will never gain quality when converting, you can only lose it.

It should never be necessary to add black bars around video files (letterboxing). Videosync takes care of properly fitting a video of any dimension to the output screen.

Containers

A video file can be saved in various ‘containers’, ways to store metadata of a file, distinguishable by the file extension, like .mov or .mp4.

The container of a video file is not related to the codec, it has no effect on the quality or playback speed of the video.

Mov (also called Quicktime Movie) is a Mac-only container while MP4 can be played by almost all Apple and Windows video applications. However Mov supports more codecs than MP4. .mp4 files can only contain H264 and Mpeg codecs, so to use Photo/jpeg, HAP or Prores codecs, you need a .mov file.

Videosync plays both Mov and MP4 files.



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