Re: [whatwg] Why does CanvasRenderingContext2D.drawImage not draw a video's poster?
On Jul 21, 2012, at 1:20 PM, Silvia Pfeiffer silviapfeiff...@gmail.com wrote: I'm not opposed to the idea, but I'm failing to see the benefit. The advantage clearly is that if you have a canvas that is copying data out of the video, it includes the poster without having to write custom code for it. The poster is an integral part of the video (it's not distinguishable by the user whether it is a separate picture or a frame from the video), so I don't see why it should need custom handling. Canvas is a lot of low level custom code. As a polyfill, it seems that Canvas coders ought to consider checking for a poster attribute in their code path regardless of how this goes. Still, if there's going to be one, we're going to need an onposterloaded event. Why? onmetadataloaded provides a sufficiently stable stuation: either the poster img or video frame is then loaded (if @preload is not none) or it's black (if @poster is not set and @preload is none). Seems like a good place to spec this. +1. I'm not up to speed on the video spec, but if this behavior for poster is not in there, consider proposing it to the editor(s). -Charles
Re: [whatwg] Why does CanvasRenderingContext2D.drawImage not draw a video's poster?
On Thu, Jul 19, 2012 at 2:46 AM, Charles Pritchard ch...@jumis.com wrote: On 7/17/2012 11:06 PM, Silvia Pfeiffer wrote: On Wed, Jul 18, 2012 at 6:57 AM, Charles Pritchard ch...@jumis.com wrote: On Jul 17, 2012, at 9:04 PM, Mark Callow callow_m...@hicorp.co.jp wrote: On 18/07/2012 00:17, Silvia Pfeiffer wrote: I think this is simply an idea that hasn't been raised before. I like it. Though even then sometimes there may be nothing when there is no explicit poster and preload is set to none. The language gives me the impression that drawing nothing was a deliberate choice, in particular because later on it says: We don't have events based on poster, so we don't know whether or not it's been loaded. Poster is meant for the video implementation. We use other events to know if video is playing. So as a coder, I can just do an attribute check to see if poster exists, then load it into an image tag. It's a normal part of working with Canvas. We always follow onload events. IIUC, that still excludes the case where there is no @poster attribute set on video, @autoplay is set to none, and the browsers load the first frame as the poster. It would make sense in this case to hand that poster to the canvas. And it would make it easier if the explicitly set @poster attribute would be used, too, so you don't have to do that by hand. We need more data if we're going to try that, and I'm still rather timid on the idea though it would be nice if img would load the first frame of video (and .gif for that matter). We really don't know what the browser is going to show if it's not showing a poster. It could show an arbitrary frame, it could show some kind of frame with a blur or opacity change, it could add on various controls. This is all theoretical. In practice, all browsers show a black frame, since no other frame is actually available. I'm not opposed to the idea, but I'm failing to see the benefit. The advantage clearly is that if you have a canvas that is copying data out of the video, it includes the poster without having to write custom code for it. The poster is an integral part of the video (it's not distinguishable by the user whether it is a separate picture or a frame from the video), so I don't see why it should need custom handling. Still, if there's going to be one, we're going to need an onposterloaded event. Why? onmetadataloaded provides a sufficiently stable stuation: either the poster img or video frame is then loaded (if @preload is not none) or it's black (if @poster is not set and @preload is none). I don't follow the objections. Cheers, Silvia.
Re: [whatwg] Why does CanvasRenderingContext2D.drawImage not draw a video's poster?
On Wed, Jul 18, 2012 at 6:57 AM, Charles Pritchard ch...@jumis.com wrote: On Jul 17, 2012, at 9:04 PM, Mark Callow callow_m...@hicorp.co.jp wrote: On 18/07/2012 00:17, Silvia Pfeiffer wrote: I think this is simply an idea that hasn't been raised before. I like it. Though even then sometimes there may be nothing when there is no explicit poster and preload is set to none. The language gives me the impression that drawing nothing was a deliberate choice, in particular because later on it says: We don't have events based on poster, so we don't know whether or not it's been loaded. Poster is meant for the video implementation. We use other events to know if video is playing. So as a coder, I can just do an attribute check to see if poster exists, then load it into an image tag. It's a normal part of working with Canvas. We always follow onload events. IIUC, that still excludes the case where there is no @poster attribute set on video, @autoplay is set to none, and the browsers load the first frame as the poster. It would make sense in this case to hand that poster to the canvas. And it would make it easier if the explicitly set @poster attribute would be used, too, so you don't have to do that by hand. Silvia.
Re: [whatwg] Why does CanvasRenderingContext2D.drawImage not draw a video's poster?
On 7/17/2012 11:06 PM, Silvia Pfeiffer wrote: On Wed, Jul 18, 2012 at 6:57 AM, Charles Pritchard ch...@jumis.com wrote: On Jul 17, 2012, at 9:04 PM, Mark Callow callow_m...@hicorp.co.jp wrote: On 18/07/2012 00:17, Silvia Pfeiffer wrote: I think this is simply an idea that hasn't been raised before. I like it. Though even then sometimes there may be nothing when there is no explicit poster and preload is set to none. The language gives me the impression that drawing nothing was a deliberate choice, in particular because later on it says: We don't have events based on poster, so we don't know whether or not it's been loaded. Poster is meant for the video implementation. We use other events to know if video is playing. So as a coder, I can just do an attribute check to see if poster exists, then load it into an image tag. It's a normal part of working with Canvas. We always follow onload events. IIUC, that still excludes the case where there is no @poster attribute set on video, @autoplay is set to none, and the browsers load the first frame as the poster. It would make sense in this case to hand that poster to the canvas. And it would make it easier if the explicitly set @poster attribute would be used, too, so you don't have to do that by hand. We need more data if we're going to try that, and I'm still rather timid on the idea though it would be nice if img would load the first frame of video (and .gif for that matter). We really don't know what the browser is going to show if it's not showing a poster. It could show an arbitrary frame, it could show some kind of frame with a blur or opacity change, it could add on various controls. I'm not opposed to the idea, but I'm failing to see the benefit. Still, if there's going to be one, we're going to need an onposterloaded event.
Re: [whatwg] Why does CanvasRenderingContext2D.drawImage not draw a video's poster?
On 18/07/2012 13:57, Charles Pritchard wrote: We don't have events based on poster, so we don't know whether or not it's been loaded. On 19/07/2012 09:46, Charles Pritchard wrote: I'm not opposed to the idea, but I'm failing to see the benefit. Still, if there's going to be one, we're going to need an onposterloaded event. I don't understand these concerns. Step 4 of the algorithm to be run when the video element is created or the @poster attribute is set, changed or removed says: Fetch http://www.whatwg.org/specs/web-apps/current-work/multipage/fetching-resources.html#fetch the resulting absolute URL http://www.whatwg.org/specs/web-apps/current-work/multipage/urls.html#absolute-url, from the element's |Document http://www.whatwg.org/specs/web-apps/current-work/multipage/dom.html#document|'s origin http://www.whatwg.org/specs/web-apps/current-work/multipage/origin-0.html#origin. This must delay the load event http://www.whatwg.org/specs/web-apps/current-work/multipage/the-end.html#delay-the-load-event of the element's document. So once the documented is loaded, the poster, if there is one, will be available. Regards -Mark -- 注意：この電子メールには、株式会社エイチアイの機密情報が含まれている場合 が有ります。正式なメール受信者では無い場合はメール複製、 再配信または情 報の使用を固く禁じております。エラー、手違いでこのメールを受け取られまし たら削除を行い配信者にご連絡をお願いいたし ます。 NOTE: This electronic mail message may contain confidential and privileged information from HI Corporation. If you are not the intended recipient, any disclosure, photocopying, distribution or use of the contents of the received information is prohibited. If you have received this e-mail in error, please notify the sender immediately and permanently delete this message and all related copies.
Re: [whatwg] Why does CanvasRenderingContext2D.drawImage not draw a video's poster?
What do we do when the document has already loaded and we've added a new video element? Also, the concern was about elements that do not have a poster attribute defined: the section you mentioned would not be relevant. I'm all for inclusiveness: I need to meet obligations of programmatic availability. -Charles On Jul 18, 2012, at 9:14 PM, Mark Callow callow_m...@hicorp.co.jp wrote: On 18/07/2012 13:57, Charles Pritchard wrote: We don't have events based on poster, so we don't know whether or not it's been loaded. On 19/07/2012 09:46, Charles Pritchard wrote: I'm not opposed to the idea, but I'm failing to see the benefit. Still, if there's going to be one, we're going to need an onposterloaded event. I don't understand these concerns. Step 4 of the algorithm to be run when the video element is created or the @poster attribute is set, changed or removed says: Fetch http://www.whatwg.org/specs/web-apps/current-work/multipage/fetching-resources.html#fetch the resulting absolute URL http://www.whatwg.org/specs/web-apps/current-work/multipage/urls.html#absolute-url, from the element's |Document http://www.whatwg.org/specs/web-apps/current-work/multipage/dom.html#document|'s origin http://www.whatwg.org/specs/web-apps/current-work/multipage/origin-0.html#origin. This must delay the load event http://www.whatwg.org/specs/web-apps/current-work/multipage/the-end.html#delay-the-load-event of the element's document. So once the documented is loaded, the poster, if there is one, will be available. Regards -Mark -- 注意：この電子メールには、株式会社エイチアイの機密情報が含まれている場合 が有ります。正式なメール受信者では無い場合はメール複製、 再配信または情 報の使用を固く禁じております。エラー、手違いでこのメールを受け取られまし たら削除を行い配信者にご連絡をお願いいたし ます。 NOTE: This electronic mail message may contain confidential and privileged information from HI Corporation. If you are not the intended recipient, any disclosure, photocopying, distribution or use of the contents of the received information is prohibited. If you have received this e-mail in error, please notify the sender immediately and permanently delete this message and all related copies.
[whatwg] Why does CanvasRenderingContext2D.drawImage not draw a video's poster?
The spec. for CanvasRenderingContext2D.drawImage says draw nothing when a video element's readyState is HAVE_NOTHING or HAVE_METADATA. I was wondering why this was chosen vs. drawing the poster. A search in the list archive didn't turn up any discussion or explanation. Regards -Mark -- 注意：この電子メールには、株式会社エイチアイの機密情報が含まれている場合 が有ります。正式なメール受信者では無い場合はメール複製、 再配信または情 報の使用を固く禁じております。エラー、手違いでこのメールを受け取られまし たら削除を行い配信者にご連絡をお願いいたし ます。 NOTE: This electronic mail message may contain confidential and privileged information from HI Corporation. If you are not the intended recipient, any disclosure, photocopying, distribution or use of the contents of the received information is prohibited. If you have received this e-mail in error, please notify the sender immediately and permanently delete this message and all related copies.
Re: [whatwg] Why does CanvasRenderingContext2D.drawImage not draw a video's poster?
I think this is simply an idea that hasn't been raised before. I like it. Though even then sometimes there may be nothing when there is no explicit poster and preload is set to none. Regards, Silvia. On Tue, Jul 17, 2012 at 9:58 AM, Mark Callow callow_m...@hicorp.co.jp wrote: The spec. for CanvasRenderingContext2D.drawImage says draw nothing when a video element's readyState is HAVE_NOTHING or HAVE_METADATA. I was wondering why this was chosen vs. drawing the poster. A search in the list archive didn't turn up any discussion or explanation. Regards -Mark -- 注意：この電子メールには、株式会社エイチアイの機密情報が含まれている場合 が有ります。正式なメール受信者では無い場合はメール複製、 再配信または情 報の使用を固く禁じております。エラー、手違いでこのメールを受け取られまし たら削除を行い配信者にご連絡をお願いいたし ます。 NOTE: This electronic mail message may contain confidential and privileged information from HI Corporation. If you are not the intended recipient, any disclosure, photocopying, distribution or use of the contents of the received information is prohibited. If you have received this e-mail in error, please notify the sender immediately and permanently delete this message and all related copies.
Re: [whatwg] Why does CanvasRenderingContext2D.drawImage not draw a video's poster?
On Jul 17, 2012, at 9:04 PM, Mark Callow callow_m...@hicorp.co.jp wrote: On 18/07/2012 00:17, Silvia Pfeiffer wrote: I think this is simply an idea that hasn't been raised before. I like it. Though even then sometimes there may be nothing when there is no explicit poster and preload is set to none. The language gives me the impression that drawing nothing was a deliberate choice, in particular because later on it says: We don't have events based on poster, so we don't know whether or not it's been loaded. Poster is meant for the video implementation. We use other events to know if video is playing. So as a coder, I can just do an attribute check to see if poster exists, then load it into an image tag. It's a normal part of working with Canvas. We always follow onload events. -Charles
