Integrating Auto Play Video Into Homepage
To answer your first question, providing user controls to pause, stop, or hide the movement (i.e. video) would be in conformance with WCAG. This is defined in the WCAG 2.0 Level A success criterion 2.2.2: Pause, Stop, Hide: if information presented in parallel with other content starts moving automatically and moves for more than five seconds, controls must be provided for a user to pause, stop, or hide the movement (unless essential to the activity, but that does not seem to be the case in this instance). One motivating factor behind this rule is that moving content can be distracting for some people. Additionally, if the video being played has an audio component to it and/or relays important information, proper transcripts and audio descriptions will need to be provided.
For the second part of your question around total video length there are no current WCAG guidelines around these parameters. An important aspect to think about when choosing the video length is how will it affect your page load speeds and will there be any detriments to user experience on other parts of the site.
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