In the insertHTTPFile() function of eZVideoFLVType there are two bugs:
1) The line 368 of datatypes/ezvideoflv/ezvideoflvtype.php:
if ( !$httpFile->store( "original", false, false ) )
should be replaced with:
if ( !$httpFile->store( "original", $mimeData['suffix'], false ) )
Otherwise the stored file doesn't get the suffix and therefore eZVideoFLV::convert() function cannot determine the mime type of the file and the conversion is aborted.
2) The line 388 of datatypes/ezvideoflv/ezvideoflvtype.php:
$ffmpeg = eZVideoFLV::getFFMPEGObject( $http->attribute( 'filename' ) );
should be replaced with:
$ffmpeg = eZVideoFLV::getFFMPEGObject( $httpFile->attribute( 'filename' ) );
because there's no $http which produces fatal error.
P.S. With this two bugs fixed this extension works really great when combined with the multiupload extension.