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<div style="FONT: 10pt arial">--------- Original Message --------<br /> Da: "Maik Merten" <maikmerten@googlemail.com><br /> To: "WHATWG Proposals" <whatwg@lists.whatwg.org><br /> Oggetto: Re: [whatwg] media elements: Relative seeking<br /> Data: 24/11/08 08:45<br /></div>
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<p><span style="font-family: Courier New; font-size: x-small;"><br /> <br />> Eric Carlson schrieb:<br /> >> QuickTime has used this method this since it started supporting VBR <br /> >> mp3 in 2000, and in practice it works quite well. I am sure that there <br /> >> are degenerate cases where the initial estimate is way off, but <br /> >> generally it is accurate enough that it isn't a problem. An initial <br /> >> estimate is more likely to be wrong for a very long file, but each pixel <br /> >> represents a larger amount of time in the time slider with a long <br /> >> duration so changes less noticeable.<br /> ><br /> > Well, I do believe this works fine for audio (which usually hasn't a <br /> > wildly fluctuating bitrate if you e.g. average over a second or two), <br /> > I'm mostly concerned about video. An example for an outrageously off <br /> > estimate would be the trailer for "Generic space-pirate movie".
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><br /> > The first few seconds would be mostly a static green/red/yellow/whatever <br /> > screen ("This pirate movie has been rated ARRRRRR!") - this part would <br /> > be coded with like 100 kbit/s or less. The next few scenes (this is a <br /> > trailer, after all) would mostly show exploding ships, genetically <br /> > engineered mutant parrots attacking space-adventurers and a few cuts <br /> > into random love scenes - so this part can be multi-megabit/s. After <br /> > this the bitrate would dramatically decrease again as the last few <br /> > seconds will just show "Summer 2010".</span><span style="font-family: Courier New; font-size: x-small;"> ></span></p>
<p><span style="font-family: Courier New; font-size: x-small;"><br />> Does QuickTime also handle such content gracefully (e.g. display a <br /> > position slider that doesn't jump around wildly)? Am I overestimating <br /> > the problem?<br /> <br />> Maik</span></p>
<p>The slider should just indicate a relative position (i.e. a percentage) between 0 and the (currently known) duration of the content, which may be estimated with a variable average time, perhaps retarded at the beginning, and varied according to the bitrate variation with some euristic, to make the computation more accurate (or maybe a few consecutive evaluation, at fixed and rapid intervals, could be averaged to get a better value, before updating anything), so no "crazy horse jumping" should happen. Silvia Pfeiffer has proposed a 'length' attribute to indicate the overall duration in the markup, and I think its value could help to improve accuracy, even when wrong.</p><br><p><font face=Verdana,Arial size=2>----<br>
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