User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:37.0) Gecko/20100101 Firefox/37.0 Build ID: 20141128080044 Steps to reproduce: Installed Nightly from mozilla.org, installed most of the component for gstreamer0.10 and 1.0 from this place https://www.archlinux.org/packages/?q=gstreamer (bad, ugly, good etc), tried with OMTC on, OMTC off, addon on, addons off. Actual results: Youtube VP8 and VP9 videos work fine, youtube mp4 videos worked fine (even new 60fps) till two weeks ago I think, now I get black screen with sound. Expected results: Youtube videos should show image, they don't.
You say this started about two weeks ago. Can you try downloading an older Nightly build to see if that corrects the issue? You can get older nightly builds from ftp://ftp.mozilla.org/pub/firefox/nightly
Hmmm... Tried Firefox Nightly from month ago when it most definetly worked and now I get same issue (new profile, no addons). Video playback in every other corner of my system works just fine, html5 .mp4 youtube works with Chromium, so I'm not sure what's going on.
Enabling following options in about:config fixed this issue (even 60fps playback works now): media.fragmented-mp4.exposed media.fragmented-mp4.ffmpeg.enabled media.mediasource.mp4.enabled
Component: Untriaged → Video/Audio
Product: Firefox → Core
Component: Audio/Video → Audio/Video: Playback
Status: UNCONFIRMED → RESOLVED
Last Resolved: 3 years ago
Resolution: --- → WORKSFORME
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