please change videoQuality to videoBitrate.
This is @brion answer
Originally I think there was some concept that nobody would ever try to *stream* HD videos live, so they are 'for download' and use a fixed quality setting, which means they may have a much higher actual bitrate if there's a lot of high-frequency data or motion in the video, or a lower actual bitrate if they don't.
See also T70418.
My recommendation is to switch them to a fixed bitrate (or at least a constrained maximum bitrate) to make them friendlier to HD streaming.
Please see below on it being used.
WebVideoTranscode::ENC_WEBM_480P =>
array(
'maxSize' => '854x480',
'videoBitrate' => '1024',
'audioQuality' => '2',
'samplerate' => '44100',
'noUpscaling' => 'true',
'twopass' => 'true',
'keyframeInterval' => '128',
'bufDelay' => '256',
'videoCodec' => 'vp8',
'type' => 'video/webm; codecs="vp8, vorbis"',
),
and 720p looks like
WebVideoTranscode::ENC_WEBM_720P =>
array(
'maxSize' => '1280x720',
'videoQuality' => 7,
'audioQuality' => 3,
'noUpscaling' => 'true',
'videoCodec' => 'vp8',
'type' => 'video/webm; codecs="vp8, vorbis"',
),