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Re: [MSE] Issue on seeking from the end time position

From: Aaron Colwell <acolwell@google.com>
Date: Tue, 3 Sep 2013 08:23:03 -0700
Message-ID: <CAA0c1bBjAmG0tqqHR2A8Nr8KVmz29TndHzRhTKqFs_vzPA_W=Q@mail.gmail.com>
To: "Igarashi, Tatsuya" <Tatsuya.Igarashi@jp.sony.com>
Cc: "public-html-media@w3.org" <public-html-media@w3.org>
Hi,

This sounds like a bug in the MSE implementation. I'm assuming you are
seeing this in Chrome, so please file a bug at http://crbug.com/ . Please
include the version of Chrome, a simple page that reproduces the problem,
and assign the Cr-Internals-Media-Source label to the bug.

Further discussion of this particular issue should probably not happen on
this list. The seeking behavior should not be effected by where the seek
was initiated from. The steps in the spec outline what the proper behavior
should be, if Chrome isn't following the spec in this case, then we'll fix
the implementation. Thanks for bringing the issue to my attention.

Aaron


On Sun, Sep 1, 2013 at 10:30 PM, Igarashi, Tatsuya <
Tatsuya.Igarashi@jp.sony.com> wrote:

> Thanks, Aaron.****
>
> ** **
>
> The problem which I observed on seeking from the end time position is as
> follows;****
>
> ** **
>
> **1.     **On seek event,  the web application invokes appendBuffer() to
> add the data at the new position.****
>
> **2.     **The prepare append algorithm described 3.5.4 runs. At step 3,
> the sub-steps reopen the source Buffer because the readyState of the
> mediaSource is “ended” by the endOfStream(null).****
>
> **3.     **The event of “sourceopen” is fired  and it seems to clear the
> currentTime state of the media element object and it cannot resume the seek
> algorithm as normal seeking.****
>
> ** **
>
> I tried to resolve this issue by storing the currentTime on seek event and
> the web application resumes the seeking by itself.  But I think that it is
> better if the normal seeking steps described in 2.3.4 can run even in the
> case of the endOfStream(null) is invoked. So, I wonder that seeking from
> the end time position should change the currentState from “ended” to “open”.
> ****
>
> ** **
>
> You said that the transition from “ended” to “open” should only happen if
> the application appends more data. Does the transition described in the
> step 3 of the prepare append algorithm ?  Does the transition assume this
> case of seeking from the end time position ?****
>
> ** **
>
> Thank you.****
>
> ** **
>
> -***---***---***---***---***---***---***---***---***--***---***---***-****
>
> Tatsuya Igarashi (Tatsuya.Igarashi@jp.sony.com)****
>
> Information Technology Development Div, R&D Platform****
>
> Sony Corporation****
>
> ** **
>
> ** **
>
> ** **
>
> *From:* Aaron Colwell [mailto:acolwell@google.com]
> *Sent:* Friday, August 30, 2013 11:41 PM
>
> *To:* Igarashi, Tatsuya
> *Cc:* public-html-media@w3.org
> *Subject:* Re: [MSE] Issue on seeking from the end time position****
>
> ** **
>
> I'm not sure I understand the problem you are having. The
> MediaSource.readyState being "ended" should not effect seekability. You
> should be able to seek whether the readyState is "open" or "ended". Why do
> you think there needs to be a transition from "ended" to "open"? I think
> this transition should only happen if the application appends more data,
> which is what the current spec says should happen. ****
>
> ** **
>
> Please provide more details so I can better understand the issue you are
> having.****
>
> ** **
>
> Aaron****
>
> ** **
>
> On Fri, Aug 30, 2013 at 2:33 AM, Igarashi, Tatsuya <
> Tatsuya.Igarashi@jp.sony.com> wrote:****
>
> Hi,****
>
>  ****
>
> I have a problem in the case of seeking from the end time position, i.e.
> video.currentTime== video.duration. The following NOTE of EndOfStream()
> descibles a very useful idea for the MPEG DASH and I use the
> endOfStream(null) when all media segments are appended to the source
> buffer. However this way does not allow to use the existing source buffer
> as the seek algorithm since the ready state becomes from “open” to “ended”
> by the endOFStream(null).  I wonder that seeking from the end time position
> should automatically change the readyState of the sourceBuffer from “ended”
> to “open” if endOFStream() is called without an error. ****
>
>  ****
>
> *NOTE*****
>
> *This allows the duration to properly reflect the end of the appended
> media segments. For example, if the duration was explicitly set to 10
> seconds and only media segments for 0 to 5 seconds were appended before
> endOfStream() was called, then the duration will get updated to 5 seconds*
> .****
>
>  ****
>
> Thank you.****
>
>  ****
>
> -***---***---***---***---***---***---***---***---***--***---***---***-****
>
> Tatsuya Igarashi (Tatsuya.Igarashi@jp.sony.com)****
>
> Information Technology Development Div, R&D Platform****
>
> Sony Corporation****
>
>  ****
>
> ** **
>
Received on Tuesday, 3 September 2013 15:23:31 UTC

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