Dear Ant.com users,
Recently Ant.com had to change AVD downloads format due to switching YouTube HTML5 player to Opus audio.
For now videos will be saved in MP4, WEBM or MKV depending on YouTube player streams format supported by your browser and system configuration.
In case of video or audio playback problems with downloaded videos in your default system media player we recommend you to update your codecs with help of K-Lite Codec Pack Mega: http://www.codecguide.com/download_kl.htm
Either you can try to use third-party media player with Opus audio support. Ant.com recommends the last version of VLC player for this purpose: http://www.videolan.org/vlc/index.html
Meanwhile, temporarily you can force your browser to save videos in MP4 format with help of YouTube flash player switching add-ons or by making a few simple changes in the Firefox configuration.
You need to open "about:config" page in browser address bar, type "media.webm.enabled" in search field and change it to "false" by double-clicking.
Format should be changed after restarting Firefox.