[whatwg] HTML5 video: frame accuracy / SMPTE

Eric Carlson eric.carlson at apple.com
Tue Jan 11 13:29:33 PST 2011

On Jan 11, 2011, at 12:54 PM, Rob Coenen wrote:

> Eric, not sure if I understand what you mean. Are you referring to digitally encoded files where frame #1 has a different duration than frame #2?
  Exactly, every frame can have an arbitrary duration so "frame rate" may have no meaning. Even in the case of video captured from film, the original frame rate is often not stored in the digital file so there is no way to programmatically determine the original frame rate.


> On Tue, Jan 11, 2011 at 6:10 PM, Eric Carlson <eric.carlson at apple.com> wrote:
> On Jan 11, 2011, at 9:54 AM, Rob Coenen wrote:
> > just a follow up question in relation to SMPTE / frame accurate playback: As
> > far as I can tell there is nothing specified in the HTML5 specs that will
> > allow us to determine the actual frame rate (FPS) of a movie? In order to do
> > proper time-code calculations it's essential to know both the video.duration
> > and video.fps - and all I can find in the specs is video.duration, nothing
> > in video.fps
> >
>  What does "frames per second" mean for a digitally encoded video file, where frames can have arbitrary duration?
> eric

More information about the whatwg mailing list