@Antony_Simonneau
The Wowza Team has posted the B-Frame Fix here -> Problems with Beamr Transcoding WSE 4.8.14+9
But i dont think that you have a Problem with B-Frames. Take a look into your transcode.xml. Why did you set the Keyframe-Interval to 15? Has your Source Stream only 7,5 FPS? I dont think so. At the Moment the Transcoder set a Keyframe every 0,5 Seconds, if your Source has 30 Frames / Sec. Set the Keyframe-Interval to 60. This adjusts your Keyframe-Interval to 2 Seconds and is a good Setting for Livestreaming.