Digital video comes in many formats and files can be very large particularly for high-quality video. For video to play well online, it needs to start playing whilst it continues to download. This streaming playback can only be done with specially prepared video files. To do this, like YouTube and Vimeo, Good Grants transcodes video files. Following is an explanation of the end-to-end process and some of the considerations that you should be aware of.
Video formats, compression, codecs and transcoding
Video files come in a number of different file types, nearly always compressed to reduce file size (uncompressed video is enormous and only ever used in high-end production environments). So irrespective of file type, chances are it is compressed, or encoded. For video to play back it is decompressed, or decoded. The processes of compression and decompression are done by a codec (coder-decoder). There are many different codecs in common use. For video software such as a video player to handle a video, it needs to support the codec used by the video file.
To play streaming video smoothly in modern web browsers, there are limited file types and codecs this can be done with. So, to support upload of source video in the widest possible range of source formats, and still be able to play the video easily for judging, we transcode uploaded videos— transcoding is the process of re-encoding video into a different format with a different codec. Good Grants stores the original source video, but embeds a different, transcoded version of the video for playback in the browser.
Whilst it's almost certain that any source video that an entrant may upload is already compressed, files can still be very large. At high resolution and high quality, movie length video content can easily run to several gigagytes (GB). The Good Grants platform itself has no technical / theoretical limit to supported file size, however in practice the user's upload bandwidth will be the main limiting factor on successful upload. Uploads of 5GB have been tested on high-speed internet connections and work fine. On an average broadband connection, a 5GB upload could take several hours however. The longer it takes to upload a video, the more likely there could be an interruption to network connectivity, and difficulties completing an upload.
Video file type is indicated by the video file name extension. Good Grants supports the following types:
Note that amongst these file types many different codecs may be used, and cannot be so easily identified. Good Grants uses an Amazon Web Service to transcode video files. The transcoder supports most codecs in common use. Some specialised codecs may not be supported— a user may be able to successfully upload a video of an accepted file type, only for the transcoder to fail because of an unsupported codec. Should this happen, the user is given a message to explain the video cannot be transcoded. The user needs to prepare their video with a different, supported codec and re-upload the file.
Supported input video codecs
For a video to be transcoded on Good Grants, all of its codecs need to be supported by Amazon Web Services. Please find the latest and complete list of supported codecs here.