UserAgent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/62.0.3202.62 Safari/537.36

Example URL:
https://yt-dash-mse-test.commondatastorage.googleapis.com/unit-tests/2018.html?test_type=conformance-test&command=run&tests=31

Steps to reproduce the problem:
With https://bugs.chromium.org/p/chromium/issues/detail?id=776704 fixed it should be easy to reproduce going with this reproduction scenario.

-----

1. Host attached test case on any web server (it's stripped down version of 2018's QUAL MSE-conformance, mainly test `31. DurationAfterAppendOpusAudio`)
2. Run in Chrome/Chromium link: http://localhost/path/to/attached/qual/test/2018.html?test_type=conformance-test&command=run&tests=31
3. Observe printed logs
3.1. There are some extra logs added which will print fired events (they start with `###`)
4. Note that `durationchange` event will come after `updateend` and not between `updatestart` and `update` events.

Version with plan QUAL 2018 (MSE-conformance test) using built-in DevTools:

1. Run: https://yt-dash-mse-test.commondatastorage.googleapis.com/unit-tests/2018.html?test_type=conformance-test&command=run&tests=31
2. Open DevTools -> Sources tab
3. Open file from unit-tests/js/tests/2018/conformanceTest-$ver$.js
4. Find `createDurationAfterAppendTest()` function
5. Add some extra logs in there on `media` variable for `durationchange` event on HTMLMediaElement and `updatestart`, `update` and `updateend` events on SourceBuffer object.
6. Note that `durationchange` event will come after `updateend` and not between `updatestart` and `update` events.

What is the expected behavior?
According to MSE specification (https://www.w3.org/TR/media-source/) when `appendBuffer()` is called on SourceBuffer object (https://www.w3.org/TR/media-source/#dom-sourcebuffer-appendbuffer), we should do:

  ...
  4. Queue a task to fire a simple event named updatestart at this SourceBuffer object.
  5. Asynchronously run the buffer append algorithm.

Now if we inspect buffer append algorithm (https://www.w3.org/TR/media-source/#sourcebuffer-buffer-append), we will note that the order of steps is as follows:

  1. Run the segment parser loop algorithm.
  ...
  4. Queue a task to fire a simple event named update at this SourceBuffer object.
  5. Queue a task to fire a simple event named updateend at this SourceBuffer object.

If we inspect "segment parser loop algorithm" (https://www.w3.org/TR/media-source/#sourcebuffer-segment-parser-loop) we can find that it might lead to duration change algorithm (either when parsing initialization segment or media segment exceeds current duration) and that algorithm (https://www.w3.org/TR/media-source/#duration-change-algorithm) invokes HTMLMediaElement duration change algorithm (https://www.w3.org/TR/html51/semantics-embedded-content.html#durationChange) which forces browser to fire `durationchange` event.

As we can see, that `durationchange` event SHOULD be sent BEFORE firing `update` and `updateend` events.

What went wrong?
In Chrome/Chromium, `durationchange` event can came AFTER firing `update` and `updateend` events. This is due to the fact, that code in 

  `SourceBuffer::AppendBufferAsyncPart()` 

(https://cs.chromium.org/chromium/src/third_party/WebKit/Source/modules/mediasource/SourceBuffer.cpp?sq=package:chromium&l=1219) invokes 

  `WebSourceBufferImpl::Append()`

(https://cs.chromium.org/chromium/src/media/blink/websourcebuffer_impl.cc?sq=package:chromium&l=132) for last chunk of data and then immediately schedules events `update` and `updateend`. The problem is that this code assumes that `Append()` call on `WebSourceBuffer` there is synchronous, but in fact this is not true! This append will lead right through:

  `ChunkDemuxer::AppendData()`
(https://cs.chromium.org/chromium/src/media/filters/chunk_demuxer.cc?sq=package:chromium&l=859)

(right here it will go through some classes, but if it will parse initialization segment and find duration, or it will parse media segment which exceeds current duration, then this will be called:)

  `ChunkDemuxer::UpdateDuration()`
(https://cs.chromium.org/chromium/src/media/filters/chunk_demuxer.cc?sq=package:chromium&l=1313)

and this will go through

  ` PipelineImpl::RendererWrapper::SetDuration()`
(https://cs.chromium.org/chromium/src/media/base/pipeline_impl.cc?sq=package:chromium&l=503)

which post-tasks work regarding setting duration.
Due to that fact, Chromium will first issue `update` and `updateend` events (on the same task) and only when that posted task will execute, only then `durationchange` event will be called.

Did this work before? N/A 

Is it a problem with Flash or HTML5? HTML5

Does this work in other browsers? N/A

Chrome version: 62.0.3202.62  Channel: stable
OS Version: 
Flash Version: 

Contents of chrome://gpu: 
Note: To properly save this page, select the "Webpage, Complete" option in the Save File dialog.
Graphics Feature Status
Canvas: Software only, hardware acceleration unavailable
CheckerImaging: Disabled
Flash: Software only, hardware acceleration unavailable
Flash Stage3D: Software only, hardware acceleration unavailable
Flash Stage3D Baseline profile: Software only, hardware acceleration unavailable
Compositing: Software only, hardware acceleration unavailable
Multiple Raster Threads: Enabled
Native GpuMemoryBuffers: Software only. Hardware acceleration disabled
Rasterization: Software only, hardware acceleration unavailable
Video Decode: Software only, hardware acceleration unavailable
Video Encode: Software only, hardware acceleration unavailable
WebGL: Hardware accelerated but at reduced performance
WebGL2: Unavailable
Problems Detected
ATI/AMD cards with older drivers in Linux are crash-prone: 71381, 76428, 73910, 101225, 136240, 357314
Disabled Features: flash_stage3d, gpu_compositing, panel_fitting, flash3d, gpu_rasterization, accelerated_2d_canvas, accelerated_video_decode, webgl2, accelerated_webgl, flash_stage3d_baseline, accelerated_video_encode
Accelerated video decode is unavailable on Linux: 137247
Disabled Features: accelerated_video_decode
Accelerated video encode is unavailable on Linux
Disabled Features: accelerated_video_encode
Native GpuMemoryBuffers have been disabled, either via about:flags or command line.
Disabled Features: native_gpu_memory_buffers
Checker-imaging has been disabled via finch trial or the command line.
Disabled Features: checker_imaging
Version Information
Data exported	10/20/2017, 1:56:55 PM
Chrome version	Chrome/62.0.3202.62
Operating system	Linux 4.10.0-37-generic
Software rendering list version	13.12
Driver bug list version	10.30
ANGLE commit id	e8ef2bc4bd01
2D graphics backend	Skia/62 e74b41c6c84638d5a9ee6d254a715bcd9e17c603-
Command Line	/usr/bin/google-chrome-stable --enable-blink-features=MediaSourceNewAbortAndDuration --flag-switches-begin --flag-switches-end
Driver Information
Initialization time	0
In-process GPU	true
Passthrough Command Decoder	false
Supports overlays	false
Sandboxed	false
GPU0	VENDOR = 0x1002, DEVICE= 0x6610
Optimus	false
Optimus	false
AMD switchable	false
Driver vendor	Google Inc.
Driver version	3.3.0.2
Driver date	2017/04/07
Pixel shader version	3.0
Vertex shader version	3.0
Max. MSAA samples	4
Machine model name	
Machine model version	
GL_VENDOR	Google Inc.
GL_RENDERER	Google SwiftShader
GL_VERSION	OpenGL ES 2.0 SwiftShader
GL_EXTENSIONS	
Disabled Extensions	
Window system binding vendor	
Window system binding version	
Window system binding extensions	
Window manager	Compiz
XDG_CURRENT_DESKTOP	Unity
GDMSESSION	ubuntu
Compositing manager	Yes
Direct rendering	Yes
Reset notification strategy	0x0000
GPU process crash count	0
System visual ID	0
RGBA visual ID	0
Compositor Information
Tile Update Mode	One-copy
Partial Raster	Enabled
GpuMemoryBuffers Status
ATC	Software only
ATCIA	Software only
DXT1	Software only
DXT5	Software only
ETC1	Software only
R_8	Software only
R_16	Software only
RG_88	Software only
BGR_565	Software only
RGBA_4444	Software only
RGBX_8888	Software only
RGBA_8888	Software only
BGRX_8888	Software only
BGRA_8888	Software only
RGBA_F16	Software only
YVU_420	Software only
YUV_420_BIPLANAR	Software only
UYVY_422	Software only

- Much easier to reproduce when https://bugs.chromium.org/p/chromium/issues/detail?id=776704 will be finished. 
- Breaks conformance with MSE specification.
 

Deleted: minified_qual_2018_mse.zip 1.2 MB

minified_qual_2018_mse.zip 1.2 MB Download