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[whatwg] HTML5 video: frame accuracy / SMPTE

From: Rob Coenen <coenen.rob@gmail.com>
Date: Tue, 11 Jan 2011 17:54:52 +0000
Message-ID: <AANLkTikhgrX95PC8OUR1F3+_5sU9V5Smbr=2FZJ1EfJD@mail.gmail.com>
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

-Rob


On Mon, Jan 10, 2011 at 9:32 PM, Kevin Marks <kevinmarks at gmail.com> wrote:

> If you really want to test timecode, you need to get into SMPTE drop-frame
> timecode too (possibly the single most annoying standards decision of. all
> time was choosing 30000/1001 as the framerate of NTSC video)
>
> Eric, can you make BipBop movie for this? - Like the ones used in this
> demo:
>
>
> http://developer.apple.com/library/mac/#documentation/NetworkingInternet/Conceptual/StreamingMediaGuide/UsingHTTPLiveStreaming/UsingHTTPLiveStreaming.html
>
> http://devimages.apple.com/iphone/samples/bipbopgear3.html
>
>
> On Mon, Jan 10, 2011 at 11:18 AM, Rob Coenen <coenen.rob at gmail.com> wrote:
>
>> Thanks for the update.
>> I have been testing with WebKit nightly / 75294 on MacOSX 10.6.6 / 13"
>> Macbook Pro, Core Duo.
>>
>> Here's a test movie that I created a while back. Nevermind the video
>> quality- the burned-in timecodes are 100% correct, I have verified this by
>> exploring each single frame by hand.
>>
>>
>> http://www.massive-interactive.nl/html5_video/transcoded_03_30_TC_sec_ReviewTest.mp4
>>
>> Please let me know once you guys have downloaded the file, I like to
>> remove
>> it from my el-cheapo hosting account ASAP.
>>
>> thanks,
>>
>> Rob
>>
>>
>> On Mon, Jan 10, 2011 at 2:54 PM, Eric Carlson <eric.carlson at apple.com
>> >wrote:
>>
>> >
>> > 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.
>> >
>> > eric
>> >
>> >
>>
>
>
Received on Tuesday, 11 January 2011 09:54:52 UTC

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