...
If a rendition/quality of an asset is requested but has not been generated yet, it is always automatically generated. This is feature referred to as on-demand transcoding. This feature and makes it possible to ensure that renditions/qualities are only generated when needed. Thus, storage space is not wasted on saving renditions/qualities that are never used.
The transcode system also supports pre-generating renditions/qualities before they are requested. This is e.g. useful for thumbnails and previews, which are always needed. However, it can e.g. also be used to automatically start time-consuming transcodes of large videos that are likely to be requested.
Renditions/qualities can be pre-generated in two ways:
On upload and replace: This can be configured with the “Immediately generated for” parameter when defining a format, as described above. Note that if a new format is defined with this setting, existing assets in the system must be republished to pre-generate renditions/qualities of the format for these assets.
Triggered from an automation: The automation step “Generate asset renditions” can be used to pre-generate renditions/qualities based on more complex conditions. For instance, an automation can be set up to pre-generate renditions/qualities for videos with a certain size or when an asset is published to a specific channel folder.
No matter if a rendition/quality is requested on-demand or pre-generated, it is never generated if it is already available. If the definition of a format changes, the corresponding renditions/qualities are automatically re-generated when they are requested again.