as part of the videodownloadhelper preference page there is an option to show the conversion log. it is there that i found the reference to ffmpeg. i have created an new firefox profile and i only installed the videodownloadhelper. in my default profile of firefox i could not open the conversion log but with the new one i can. i tried to convert the same video under the new profile and it still would not convert. i checked the conversion log. the ffmpeg version is unknown, but it did tell me that the failure is do to “cannot get resampling text”. by the way thank you for your help.