Bug#800396: iceweasel: Youtube HTML5: error try again later for most videos after transition to ffmpeg

[Beta Version]

Package: iceweasel
Version: 41.0-1
Severity: normal

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



-- Package-specific info:

-- Extensions information
Name: Default theme
Location:
/usr/lib/iceweasel/browser/extensions/{972ce4c6-7e08-4474-a285-3208198ce6fd}
Package: iceweasel
Status: user-disabled

Name: Russian (RU) Language Pack locale
Location: /usr/lib/iceweasel/browser/extensions/langpack-
ru at iceweasel.mozilla.org.xpi
Package: iceweasel-l10n-ru
Status: enabled

Name: the Moon Cat theme
Status: enabled

Name: uBlock
Location: ${PROFILE_EXTENSIONS}/{2b10c1c8-a11f-4bad-fe9c-1c11e82cac42}.xpi
Status: enabled

Name: YouTube™ HD Plus
Location: ${PROFILE_EXTENSIONS}/jid1-wkCmfgboni3B1Q at jetpack.xpi
Status: enabled

-- Plugins information

-- Addons package information
ii  iceweasel      41.0-1       amd64        Web browser based on Firefox
ii  iceweasel-l10n 1:41.0-1     all          Russian language package for Icew

-- System Information:
Debian Release: stretch/sid
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.1.0-2-amd64 (SMP w/4 CPU cores)
Locale: LANG=ru_RU.utf8, LC_CTYPE=ru_RU.utf8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages iceweasel depends on:
ii  debianutils               4.5.1
ii  fontconfig                2.11.0-6.3
ii  libasound2                1.0.29-1
ii  libatk1.0-0               2.16.0-2
ii  libc6                     2.19-22
ii  libcairo2                 1.14.2-2
ii  libdbus-1-3               1.10.0-3
ii  libdbus-glib-1-2          0.102-1
ii  libevent-2.0-5            2.0.21-stable-2
ii  libffi6                   3.2.1-3
ii  libfontconfig1            2.11.0-6.3
ii  libfreetype6              2.6-2
ii  libgcc1                   1:5.2.1-17
ii  libgdk-pixbuf2.0-0        2.32.0-1
ii  libglib2.0-0              2.44.1-1.1
ii  libgtk2.0-0               2.24.28-1
ii  libhunspell-1.3-0         1.3.3-3+b1
ii  libnspr4                  2:4.10.9-2
ii  libnss3                   2:3.20-1
ii  libpango-1.0-0            1.36.8-3
ii  libsqlite3-0              3.8.11.1-1
ii  libstartup-notification0  0.12-4
ii  libstdc++6                5.2.1-17
ii  libvpx2                   1.4.0-4
ii  libx11-6                  2:1.6.3-1
ii  libxcomposite1            1:0.4.4-1
ii  libxdamage1               1:1.1.4-2+b1
ii  libxext6                  2:1.3.3-1
ii  libxfixes3                1:5.0.1-2+b2
ii  libxrender1               1:0.9.8-1+b1
ii  libxt6                    1:1.1.4-1+b1
ii  procps                    2:3.3.10-2
ii  zlib1g                    1:1.2.8.dfsg-2+b1

Versions of packages iceweasel recommends:
pn  gstreamer1.0-libav         <none>
ii  gstreamer1.0-plugins-good  1.4.5-2+b2

Versions of packages iceweasel suggests:
pn  fonts-lmodern          <none>
pn  fonts-stix | otf-stix  <none>
ii  libcanberra0           0.30-2.1
ii  libgnomeui-0           2.24.5-3
ii  libgssapi-krb5-2       1.13.2+dfsg-2
pn  mozplugger             <none>