[whatwg] HTML5 video: frame accuracy / SMPTE
eric.carlson at apple.com
Mon Jan 10 06:54:24 PST 2011
On Jan 9, 2011, at 11:14 AM, Rob Coenen wrote:
> I have written a simple test using a H264 video with burned-in timecode (every frame is visually marked with the actual SMPTE timecode)
> Webkit is unable to seek to the correct timecode using 'currentTime', it's always a whole bunch of frames off from the requested position. I reckon it simply seeks to the nearest keyframe?
WebKit's HTMLMediaElement implementation uses different media engines on different platforms (eg. QuickTime, QTKit, GStreamer, etc). Each media engine has somewhat different playback characteristics so it is impossible to say what you are experiencing without more information. Please file a bug report at https://bugs.webkit.org/ with your test page and video file, and someone will look into it.
> On Fri, Jan 7, 2011 at 5:02 PM, Eric Carlson <eric.carlson at apple.com> wrote:
> On Jan 7, 2011, at 8:22 AM, Rob Coenen wrote:
> > are there any plans on adding frame accuracy and/or SMPTE support to HTML5
> > video?
> > As far as I know it's currently impossible to play HTML5 video
> > frame-by-frame, or seek to a SMPTE compliant (frame accurate) time-code.
> > The nearest seek seems to be precise to roughly 1-second (or nearest
> > keyframe perhaps, can't tell).
> > Flash seems to be the only solution that I'm aware of that can access video
> > on a frame-by-frame basis (even though you the Flash Media Server to make it
> > work).
> > Seeking to a SMPTE time-code is completely impossible with any solution I
> > have looked at.
> > Very interested to learn what the community POV is, and why it isn't already
> > implemented.
> 'currentTime' is a double so you should be able to seek more accurately than one second - modulo the timescale of the video file and how the UA supports seeking to inter-frame times.
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