Try : https://support.mozilla.org/en-US/kb/html5-audio-and-video-firefox and https://support.mozilla.org/en-US/kb/fix-video-audio-problems-firefox-windows

Please update to 57.0.2 https://support.mozilla.org/en-US/kb/update-firefox-latest-version

Please let us know if this solved your issue or if need further assistance.

Hi, I said that I followed the instructions from https://support.mozilla.org/en-US/kb/html5-audio-and-video-firefox: I downloaded this updates And for video from http://camendesign.com/code/video_for_everybody/test.html I can't do anything with volume. Its disabled.

Ok you're missing your AAC Audio codec, which was a bug from the last M$ Win10 update.

Go and download the newest videocard drivers directly from Intel/AMD/nVidia, install them then restart.

Start Firefox and type "about:support" in the url bar then "refresh Firefox" on the top right, it will restart and now it should be working.

NOTE: If your version of Win10 is the "N" version then you have to download a special codec package for your version of windows.

I updated videocard drivers. Made a full cleanup of mozilla and I lost all of my data:( Also I downloaded windows drivers from https://support.mozilla.org/en-US/kb/fix-video-audio-problems-firefox-windows Ok, I understood that I don't have AAC Audio codec, I installed K-lite codec pack for this too, didn't help. The problem is still here.

I downloaded h264/mp4 video from https://www.quirksmode.org/html5/tests/video.html downloaded video has sound, but if I play it in FF it still don't have any sound.

I played it in FF58.0.1 and have audio. How did you download the video I don't see how you would get that option on the site.

right click on a video, then "save video as"

Must've missed that I have to check on FF58 at home to see again. Ok I downloaded in chrome and did see the video and audio. Have try back at home since they don't have FF here. So do you have codec or other audio Addon installed as well?

As I said before, I don't have any custom add-ons and I have 3 default plugins . Please, take a look at the attached screenshots.

I just played all three online and the audio and sound were in-sync no lags. Didn't download unless the online lagged.

I have sound in 2 of 3 videos: first one without sound and other videos with it. I downloaded these videos and all 3 have sound If I play them online from browser I'll hear sound in first video. In my opinion If I have sound in downloaded videos, it means that all is fine with codec in OS and smth wrong with integration browser-codec. I hear sound in all videos in Chrome for example.

I don't use integrated codec that could also be the cause as well. My codec is independent of the browser and only from WMP12.

Do you know how can I use WMP codecs instead of integrated one? I tried to disable it, but I still not have any sound in h264 video.

First you need to remove all other codes before installing new codec otherwise you will have more problems. This is the site I use for coded and so far I haven't had any troubles.

http://www.codecguide.com/download_kl.htm

Just remember use CUSTOM install and go slow and when your almost at the end there will be a option to install some other software but you would choose "Decline" and continue the install. I tried many other codec in the past but this one seems to be stable and doesn't give me headaches.

I have these codecs already. I re-installed them to have the latest. BUT FF still not have sound in that h264 video

alexfallout said

I have these codecs already. I re-installed them to have the latest. BUT FF still not have sound in that h264 video

Then you got more problems going on here then FF forum can fix. I use those same codecs and have no issues.

WestEnd said

alexfallout said

I have these codecs already. I re-installed them to have the latest. BUT FF still not have sound in that h264 video

Then you got more problems going on here then FF forum can fix. I use those same codecs and have no issues.

I don't think so, because 1) in any other browser I have sound in these videos 2) I have sound even if I download them and open in video players (windows media, k-lite, winamp also)