Dear Maintainer,

After a recent transition to ffmpeg all old and more than a half of new videos
on youtube cannot be played. If i set "media.fragmented-mp4.use-blank-decoder"
to "true", videos can be played, but without sound.

youtube.com/html5 shows everything as supported.

Disabling addons does not help.

media.mediasource.enabled - true
media.mediasource.mp4.enabled - true
media.mediasource.webm.enabled - true
media.fragmented-mp4.enabled - true
media.fragmented-mp4.exposed - true
media.fragmented-mp4.ffmpeg.enabled - true

Installed gstreamer packages:

gstreamer0.10-alsa
gstreamer0.10-gconf
gstreamer0.10-plugins-bad
gstreamer0.10-plugins-base
gstreamer0.10-plugins-good
gstreamer0.10-x
gstreamer1.0-alsa
gstreamer1.0-plugins-bad
gstreamer1.0-plugins-base
gstreamer1.0-plugins-good
gstreamer1.0-x
libgstreamer-plugins-bad0.10-0
libgstreamer-plugins-bad1.0-0
libgstreamer-plugins-base0.10-0
libgstreamer-plugins-base1.0-0
libgstreamer0.10-0
libgstreamer1.0-0

Installing gstreamer1.0-libav with dependencies and disabling
media.fragmented-mp4.exposed solved this problem.

​I was having this same problem​.

Can confirm
​ ​
disabling
​ ​
media.fragmented-mp4.exposed
​ works.​

src:iceweasel has been superseded by src:firefox-esr in version
45.0esr-1 in March 2016. Transitional packages to ease upgrades were
provided in the wheezy, jessie, stretch and buster releases. The
transitional packages have been removed finally before the bullseye
release in August 2021.
After regular security support for buster ended in August 2022 and LTS
support ended in June 2024, I'm closing the remaining bug reports now.

Andreas