w3c/media-source

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Media Source Extensions

Stars: 286
Forks: 55
Open beginner issues: 0
Indexed issues: 114

Dominant language: HTML
License: No license data
Last GitHub push: Aug 7, 2026
Latest indexed: Sep 20, 2026
Contributing guide: Contributing guide
Code of conduct: Code of conduct
Beginner labels: No beginner labels indexed
PR merge metrics: No merged PRs in 30d

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114 open issues indexed

Should HTMLMediaElement's buffered ranges be based on the active track buffers? Open

Difficulty 5/5 Over a week Newbie friendliness 32/100

w3c/media-source#379 · 2 comments · Opened Aug 31, 2026
Detaching from a media element doesn’t abort the buffer append algorithm — so an append queued beforehand still runs, against a reset media element Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

w3c/media-source#378 · Opened Aug 3, 2026
Empty edit (`elst media_time = -1`) handling under MSE diverges across engines and from non-MSE playback Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

w3c/media-source#377 · 7 comments · Opened Jul 23, 2026
Coded Frame Processing is unspecified when incoming coded frame's presentation timestamp coincides with an existing frame's Open

w3c/media-source#375 · 1 comment · 1 assignee · Opened May 13, 2026
Coded Frame Processing does not remove "SAP Type 2" decode-shadowed orphans (closes #187) Open

w3c/media-source#374 · 1 comment · 1 assignee · Opened May 13, 2026
Interop issues when an append overlaps currentTime Open

Difficulty 5/5 Over a week Newbie friendliness 25/100

w3c/media-source#373 · Opened May 12, 2026
Support MediaSource in SharedWorker Open

Difficulty 5/5 Over a week Newbie friendliness 25/100

w3c/media-source#371 · 2 comments · Opened Jan 18, 2026
BufferedChangeEvent members should be nullable Open

Difficulty 2/5 1-3 hours Newbie friendliness 45/100

w3c/media-source#370 · 4 comments · Opened Jan 10, 2026
Model `seekable` range for a MediaSource with finite duration Open

TPAC2025

Difficulty 5/5 Over a week Newbie friendliness 35/100

w3c/media-source#369 · 1 reaction · Opened Oct 24, 2025
Clarification on returning to selection algorithm from end-of-stream Open

Difficulty 4/5 3-5 days Newbie friendliness 25/100

w3c/media-source#365 · 1 comment · Opened Apr 16, 2025
Clarification on removeSourceBuffer Open

Difficulty 5/5 Over a week Newbie friendliness 25/100

w3c/media-source#364 · 2 comments · Opened Mar 25, 2025
Accidental trimming of overlapping text cues Open

timed-text

Difficulty 5/5 Over a week Newbie friendliness 35/100

w3c/media-source#363 · 1 comment · Opened Mar 10, 2025
Multiple attachable/detachable SourceBuffers Open

Difficulty 5/5 Over a week Newbie friendliness 25/100

w3c/media-source#360 · 3 comments · Opened Jan 8, 2025
Dynamic addition/removal of SourceBuffers Open

Difficulty 5/5 Over a week Newbie friendliness 25/100

w3c/media-source#359 · 5 comments · 2 reactions · Opened Jan 8, 2025
Support timed text in MSE Open

timed-text TPAC2024

Difficulty 5/5 Over a week Newbie friendliness 25/100

w3c/media-source#358 · Opened Sep 27, 2024
Proposal: Have a detachable MediaSource object Open

TPAC2024

w3c/media-source#357 · 5 comments · 1 assignee · Opened Sep 19, 2024
Horizontal reviews Open

Difficulty 4/5 3-5 days Newbie friendliness 25/100

w3c/media-source#356 · Opened Aug 27, 2024
Deprecate isTypeSupported in favor of Media Capabilities Open

Difficulty 5/5 Over a week Newbie friendliness 25/100

w3c/media-source#355 · 2 comments · Opened Jul 4, 2024
BufferedChangeEventInit shouldn't be optional in BufferedChangeEvent constructor Open

w3c/media-source#349 · 2 comments · 1 assignee · Opened Mar 6, 2024
No handling for when the MediaSource constructed in a DedicatedWorkerGlobalScope goes out of scope Open

mse-in-workers

Difficulty 5/5 Over a week Newbie friendliness 30/100

w3c/media-source#348 · Opened Feb 18, 2024
Specify constructor for MediaSource, ManagedMediaSource, BufferedChangeEvent Open

Difficulty 5/5 Over a week Newbie friendliness 30/100

w3c/media-source#345 · Opened Dec 20, 2023
Describe eviction policy Open

Difficulty 3/5 1-2 days Newbie friendliness 35/100

w3c/media-source#341 · 1 comment · Opened Dec 5, 2023
HTMLMediaElement Extensions missing WebIDL? Open

Difficulty 3/5 1-2 days Newbie friendliness 28/100

w3c/media-source#338 · 1 comment · Opened Nov 14, 2023
Editorial: bullet numbering skips over numbers and renders poorly, needs rework to comply with [Infra] #algorithm-conditional-statements Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

w3c/media-source#334 · 1 comment · Opened Nov 8, 2023
Redundancies, duplications, and general spec health Open

Difficulty 5/5 Over a week Newbie friendliness 20/100

w3c/media-source#325 · 7 comments · Opened Oct 17, 2023
Move extensions to HTML to HTML spec Open

Difficulty 5/5 Over a week Newbie friendliness 25/100

w3c/media-source#324 · Opened Oct 17, 2023
Proposal: Add quality attribute to ManagedMediaSource API Open

Difficulty 5/5 Over a week Newbie friendliness 30/100

w3c/media-source#322 · Opened Aug 14, 2023
Broken link on random access points section of ISO BMFF Byte Stream Format Open

Difficulty 1/5 Under an hour Newbie friendliness 50/100

w3c/media-source#318 · 1 comment · Opened Nov 15, 2022
Editorial: Add image description text for the audio splice rendering image (in current WD section 4.5.12) Open

a11y-tracker

w3c/media-source#312 · 1 comment · 1 assignee · Opened May 6, 2022
MSE-for-WebCodecs: detection of mismatch of append format (WC vs BSF) is deferred and could produce decode err Open

mse-webcodecs

Difficulty 5/5 Over a week Newbie friendliness 25/100

w3c/media-source#301 · Opened Oct 1, 2021
Standardize expectations around endOfStream followed by later re-opening of MediaSource Open

Difficulty 5/5 Over a week Newbie friendliness 25/100

w3c/media-source#299 · Opened Sep 23, 2021
Add more type information for internal slots and variables Open

Difficulty 3/5 1-2 days Newbie friendliness 20/100

w3c/media-source#297 · Opened Sep 22, 2021
Add a change log to the specification Open

w3c/media-source#294 · 3 comments · 1 reaction · 1 assignee · Opened Sep 1, 2021
Consider defining clearly the PTS and DTS sourcing in each bytestream spec Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

w3c/media-source#292 · 1 comment · Opened Aug 13, 2021
Live stream with live seekable range and removal of buffered media around currentTime can cause currentTime to be outside of HTMLME.seekable Open

needs author input

Difficulty 5/5 Over a week Newbie friendliness 25/100

w3c/media-source#291 · 1 comment · Opened Aug 4, 2021
Coded Frame Removal algorithm steps need fixing to match actual intent Open

w3c/media-source#290 · 1 assignee · Opened Aug 4, 2021
Editorial? Coded Frame eviction algorithm needs to note that "buffer full flag" may be updated immediately based on |new data| Open

w3c/media-source#289 · 1 assignee · Opened Aug 4, 2021
Editorial? Prepare append algorithm's caller needs to abort if the algorithm aborted Open

w3c/media-source#288 · 2 comments · 1 assignee · Opened Aug 4, 2021
MSE-in-Workers: Track enable/selection change behavior needs clarity Open

mse-in-workers

w3c/media-source#281 · 1 comment · 1 assignee · Opened Jun 25, 2021
MSE-in-Workers: Clarify window/worker coherency/communication of track instance creation/removal and track enabled/selected changes Open

mse-in-workers

Difficulty 5/5 Over a week Newbie friendliness 25/100

w3c/media-source#278 · Opened Jun 18, 2021
MSE-in-Workers: Consider (eventually) transitioning attached element to error upon termination of MediaSource's worker/what should media element do? Open

mse-in-workers

w3c/media-source#277 · 4 comments · 1 assignee · Opened Jun 17, 2021
MSE-in-Workers: Consider adding a "closing" readyState to explain new `InvalidStateError` exception when closing underway Open

mse-in-workers

Difficulty 5/5 Over a week Newbie friendliness 20/100

w3c/media-source#276 · Opened May 26, 2021
Consider relaxing timing of initial HAVE_METADATA transitioning Open

TPAC-2022-discussion

w3c/media-source#275 · 5 comments · 1 assignee · Opened May 22, 2021
Consider removing confusing rec-track and redundant GH repo links from SOTD of BSF registry and BSF specs Open

Difficulty 3/5 1-2 days Newbie friendliness 30/100

w3c/media-source#273 · Opened May 17, 2021
Interoperable buffered.start(0) fudge room Open

TPAC-2022-discussion

Difficulty 5/5 Over a week Newbie friendliness 25/100

w3c/media-source#267 · 1 comment · 1 reaction · Opened Feb 5, 2021
Add "Security Considerations" and "Privacy Considerations" sections to the spec Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

w3c/media-source#261 · 1 comment · Opened Nov 23, 2020
Consider adding support for apps to get metadata about what is currently buffered Open

introspection-api TPAC-2022-discussion

Difficulty 5/5 Over a week Newbie friendliness 25/100

w3c/media-source#259 · 3 comments · Opened Oct 20, 2020
Compatibility with WebTransport Open

backlog question

Difficulty 5/5 Over a week Newbie friendliness 25/100

w3c/media-source#256 · 4 comments · 2 reactions · Opened Sep 21, 2020
Add vp09 codec string with relevant references similar to the webm vp09 codec string, to ISOBMFF Byte Stream Format Open

Difficulty 4/5 3-5 days Newbie friendliness 25/100

w3c/media-source#255 · Opened Sep 11, 2020
VideoPlaybackQuality is moving to Media Playback Quality spec Open

Difficulty 2/5 1-3 hours Newbie friendliness 45/100

w3c/media-source#253 · Opened Jun 9, 2020

w3c/media-source

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