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RE: Video MSE issue as of March 01 2017 - seamless switch to new media

From: Paul Cotton <Paul.Cotton@microsoft.com>
Date: Thu, 20 Apr 2017 13:34:57 +0000
To: "'public-html-media@w3.org'" <public-html-media@w3.org>
CC: Unreal Streaming Technologies <contact@umediaserver.net>, "Jerry Smith (WPT)" <jdsmith@microsoft.com>, Mark Watson <watsonm@netflix.com>, "wolenetz@google.com" <wolenetz@google.com>, "plh@w3.org" <plh@w3.org>, "fd@w3.org" <fd@w3.org>
Message-ID: <CY4PR03MB27287408DF1478EC8CB09450EA1B0@CY4PR03MB2728.namprd03.prod.outlook.com>
The UMedia team has requested that this MSE problem report be withdrawn with the following rationale:

It appears to be that our server software did not package fragmented .mp4 correctly at the time of switching to a different content.

Now that we have fixed our software, all MSE players switch seamlessly to new content.

The only issue remains, and looks like it is by design: if you first had audio+video stream and then you are switching to video-only stream (corresponding init segment will only have video) - that causes an immediate error in the SourceBuffer. Same about the opposite scenario:

your initial init segment (and mime-type string) had video-only, and while that stream is playing, you are switching to audio+video - same thing will happen - SourceBuffer sets an error.

Note that this scenario is supported by Flash player - it can switch from audio+video to video-only.


HME WG Chair

-----Original Message-----
From: Paul Cotton [mailto:Paul.Cotton@microsoft.com]
Sent: Friday, March 3, 2017 10:07 AM
To: 'public-html-media@w3.org' <public-html-media@w3.org>
Cc: Unreal Streaming Technologies <contact@umediaserver.net>; Jerry Smith (WPT) <jdsmith@microsoft.com>; Mark Watson <watsonm@netflix.com>; wolenetz@google.com; plh@w3.org; fd@w3.org
Subject: RE: Video MSE issue as of March 01 2017 - seamless switch to new media

With permission I am posting this to the public-html-media@w3.org<mailto:public-html-media@w3.org> email archive.


HME WG Chair

-----Original Message-----

From: Unreal Streaming Technologies [mailto:contact@umediaserver.net]

Sent: Friday, March 3, 2017 12:40 AM

To: Jerry Smith (WPT) <jdsmith@microsoft.com<mailto:jdsmith@microsoft.com>>; Mark Watson <watsonm@netflix.com<mailto:watsonm@netflix.com>>; wolenetz@google.com<mailto:wolenetz@google.com>; plh@w3.org<mailto:plh@w3.org>; fd@w3.org<mailto:fd@w3.org>; Paul Cotton <Paul.Cotton@microsoft.com<mailto:Paul.Cotton@microsoft.com>>

Subject: Video MSE issue as of March 01 2017 - seamless switch to new media


Big Pardon for intrusion; could anyone shed some light, please, on a cross-browser MSE issue?

It is about a  seamless switch to another media in the middle of a live stream. According to MSE spec, browsers should provide seamless switch to another media after new BMFF video/mp4 initialization segment. It does not work well in any browser! You can do it with Flash player, but not with MSE.

Context: Unreal Media Server sends very short (30-500 ms length) BMFF video/mp4 segments via WebSockets. That allows to achieve very low latency (0.2 - 1 sec) and works well in Chrome; a little worse in Edge and IE (higher latency). This article  in streamingmedia.com describes our approach:


Unreal Media Server also supports live playlists so you can switch the same live stream to a different content. In that case a new initialization segment is sent to a browser; but it only works well with video-only streams; if audio exists then it stops playing or plays badly. Of course we could completely re-initialize the sourcebuffer and the player, but that is not a seamless switch at all!

On the demo page


you can see a link to HTML5 player stream; that stream plays fine. But the link to live playlist with timeshift, if attempted with HTML5 player, would produce this issue.

Unreal Media Server:


Thank you!

UMedia team
Received on Thursday, 20 April 2017 13:35:43 UTC

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