Decoder box for reproducing an additional audio track

A decoder box comprising:

• an input arranged to be connected to a source producing an audio-video stream comprising an inbound audio stream and an inbound video stream, the inbound audio stream comprising a main inbound audio track, which is intended to be reproduced to form an ambient sound and an additional inbound audio track, distinct from the main inbound audio track, which comprises commentaries relating to the inbound video stream, and which is intended to be reproduced to one single user via earphones, the additional inbound audio track integrates at least an additional audio content which is an audio description content corresponding to said commentaries;
• a video output arranged to be connected to video reproduction equipment, a first audio output arranged to be connected to an audio reproduction output arranged to be connected to an audio reproduction module comprising at least one speaker, and a second audio output, distinct from the video output and from the first audio output, and arranged to be connected to the earphones;
• a video processing chain arranged to produce, from the inbound video stream, an outbound video stream, and to transmit the outbound video stream to the video reproduction equipment via the video output, the video processing chain comprising a decoding module;
• a main audio processing chain arranged to produce, from the main inbound audio track, a main outbound audio track synchronised with the outbound video stream, and to transmit the main outbound audio track to the audio reproduction module via the first audio output, the main audio processing chain comprising successively a decoding module, a shaping module and a control module, the control module providing a main audio track to the audio reproduction module via the first audio output;
• an additional audio processing chain arranged to produce, from the additional inbound audio track, an additional outbound audio track synchronised with the outbound video stream, and to transmit the additional outbound audio track to the earphones via the second audio output, the additional audio processing chain comprising successively a decoding module, a shaping module and a control module, the decoding module being potentially common to the one of the main audio processing chain, the control module providing the additional outbound audio track to the earphones via the second audio output so that the earphones reproduce only the additional audio content;
• a clock connected to the decoding module of the video processing chain and connected to the decoding module of the main audio processing chain.