Abstract:
An automotive multimedia entertainment system includes an integrated rear seat entertainment module in which audio signals coordinated with video entertainment devices in the rear seat can be reproduced using the vehicle&#39;s audio system. Multiplex control signals between an audio main control unit, rear seat entertainment module, and CD disc jockey allows free selection of sources for single and dual play modes. By sharing an external audio input of the main control unit, between the rear seat entertainment module and the CD disc jockey, a single version of the main control unit can be used in vehicles either with or without rear seat entertainment modules or CD disc jockeys.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates in general to a rear seat audio and video entertainment system for a passenger vehicle, and more specifically to an architecture for a multimedia entertainment system using a head unit adapted for easy expansion to include a rear seat audio and video entertainment system. 
     Audio and video entertainment systems integrated in vehicles such as cars, mini-vans, and sport utility vehicles are becoming popular. Special systems for rear seat passengers to watch videos and play video games have been developed. 
     Portable, self-contained audio and video units are available that can be used-in vehicles and which can even be connected to a vehicle power source. However, integration of audio and video entertainment products into or with a vehicle provide significant advantages in terms of usability and convenience. Furthermore, performance can be improved by interconnecting the entertainment components with the vehicle audio system so that audio can be reproduced over the main vehicle speakers. 
     Integrating these audio and video systems into a vehicle has an associated cost. Since not all purchasers of a particular model of vehicle may desire to purchase the enhanced video entertainment system, it becomes necessary to produce vehicles with and without such a system. On the other hand, nearly all vehicles are manufactured with an audio system, typically including a radio and at least one playback mechanism for prerecorded media such as audio cassettes or compact discs. The need to obtain distinct audio system components (i.e., an audio system main unit adapted to work with rear seat video entertainment enhancements and a different main unit which does not) and the necessity to coordinate manufacture of different vehicle installations further adds to the total manufacturing costs. 
     SUMMARY OF THE INVENTION 
     The present invention has the advantage of providing a flexible architecture for an automotive multimedia entertainment system which is adapted to easily include audio production for rear seat entertainment and rear seat video. 
     The present invention provides a front main control unit which is adapted to be configured either with or without rear seat video entertainment and provides an overall architecture which minimizes distinct components needed for vehicle manufacturing even though the overall multimedia entertainment system can have various configurations. More specifically, the present invention provides a multimedia entertainment system for a vehicle having a front seat and a rear seat. An audio media player is mounted as a self-contained unit within the vehicle and generates player audio signals. The audio media player may be a compact disc jockey (CDDJ), for example. The video unit generates video signals and coordinated audio signals. A display screen reproduces the video signals and is viewable from the rear seat. A main control unit is mounted for use by a first operator in the front seat and includes a source of main unit audio signals and a front audio processor generating front and rear audio output signals for reproduction by the multimedia entertainment system. The main control unit includes an external audio input that can normally be used for connecting to a CDDJ, but which can alternatively be connected to a rear seat entertainment system. The rear control unit is mounted for use by a second operator in the rear seat and is connected to the audio media player (e.g., CDDJ) and the video unit. The rear control unit includes a source switch for switchably coupling the player audio signals or the coordinated audio signals to the external audio input. A multiplex network interconnects the main control unit and the rear control unit and transmits multiplex messages therebetween. The main control unit sends control commands by transmitting appropriate multiplex messages to the rear control unit and to the audio media player via the multiplex network. The source switch is configured to select either the player audio signals or the coordinated audio signals in response to respective control commands sent by the main control unit. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram showing a multimedia entertainment system according to the present invention. 
     FIG. 2 is a schematic, block diagram showing the main control unit and rear control unit of FIG. 1 in greater detail. 
     FIG. 3 is a flowchart showing a method for changing a selected audio source in the multimedia entertainment system. 
     FIG. 4 is a flowchart showing a method for changing from a single play to a dual play mode. 
     FIG. 5 is a flowchart showing a method for changing from dual play mode to single play mode. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to FIG. 1, a multimedia entertainment system for a vehicle includes a main control unit  10 , a remotely-mounted audio media player such as a compact-disc disc jockey (CDDJ)  11 , and a rear seat entertainment console  12 . Main control unit  10  is mounted for use by a first operator in a front seat  13  while rear console  12  is mounted for use by a second operator in a rear seat  14 . Integrally mounted in rear console  12  are a rear control unit or rear seat entertainment module (RSEM)  15  connected to a video screen  16  and an integrated A/V source  17 , such as a video cassette player, a DVD player, or a video game unit. 
     The multimedia entertainment system employs main control unit  10  as the basic, fundamental piece of the system so that a vehicle can be easily produced either with or without the enhanced audio and video functions of rear console  12 . Furthermore, a remote media player, such as CDDJ  11 , can be connected to main control unit  10  either with RSEM  15  by passing the CDDJ audio output through RSEM  15  or without RSEM by connecting the CDDJ audio output directly to the external audio input of main unit  10 . 
     FIG. 1 shows an enhanced configuration wherein rear seat entertainment features are in place and wherein a dual play mode is available in which rear seat passengers may be listening to audio signals from one source (by using headphones) while the front seat passengers are listening to a different source of audio signals (through the front vehicle speakers). Thus, a left front main vehicle speaker  20  and a right front main speaker  21  are connected directly to main control unit  10 . A left rear main speaker  22  and a right rear main speaker  23  are connected to rear seat entertainment module  15 . RSEM  15  also includes a pair of headphone jacks  24  and  25  and a-switch  26  for selecting rear seat audio to be played over main speakers  22  and  23  (single play mode) or over headphone jacks  24  and  25  (dual play mode). RSEM  15  also includes push buttons  27  for remote control of audio functions including volume, media selection, memory preset selection, and radio station or media track seek. A plurality of back-lit media indicators  28  illuminate to show the current media selection for the rear seat. Rear seat entertainment module  15  also includes a connector port  30  for connecting to an auxiliary audio/video source  31 , such as a video game player, a portable DVD player, a camcorder, or any other source of standard signals (e.g., NTSC). 
     Main control unit  10 , media player  11 , and rear seat entertainment module  15  each include respective microcontrollers which communicate over a multiplex network  32 . Any known multiplex network may be used such as one using SAE recommended practice J1850 or the controller area network (CAN). 
     In order to minimize system costs, main control unit  10  is manufactured having only one external audio input. In a vehicle having a CDDJ installed but without rear seat entertainment, the CDDJ audio output can be connected directly to the external audio input of main control unit  10 . Likewise, in a vehicle having only a rear seat entertainment installation without an extra media player or CDDJ, an audio output from the rear seat entertainment module is connected to the external audio input of main control unit  10 . Where both an audio media player  11  and a rear seat entertainment module are installed in a single vehicle, the media player audio is coupled to rear seat entertainment module  15  and either the CDDJ audio or the coordinated audio signals from a video unit in the rear seat entertainment console, are selectively coupled to the single external audio input of main control unit  10  via a switch in RSEM  15 . 
     Details of the main control unit and the rear seat entertainment module are shown in FIG.  2 . The front main control unit  10  includes a tuner  35  and a media mechanism  36  such as an audio cassette player or a single disc CD player. A front channel audio processor  37  provides front audio signals to speakers  20  and  21 . A rear channel audio processor  38  provides rear audio signals to a rear speaker audio line  40  connected to RSEM  15 . A first source selector switch  41  has its output connected to the input of front channel audio processor  37  and a second source selector switch  42  has its output connected to the input of rear channel audio processor  38 . Selector switches  41  and  42  each have respective inputs connected to the output of tuner  35 , media mechanism  36 , and an audio outline  43  from RSEM  15 . Selector switches  41  and  42  are controlled by a microcontroller (not shown) in main control unit  10  and may be independently controlled to implement a dual play mode in which front and rear seat passengers listen to different sources. Single play mode is obtained by setting selector switches  41  and  42  to the same source. The selector switches are preferably comprised of electronic switches. 
     RSEM  15  includes a microprocessor  45  which communicates with main control unit  10  via multiplex network  32 . Microprocessor  45  also receives commands via the RSEM user interface buttons  26  and  27 . Microprocessor  45  transmits local control signals via control lines  46  to an audio switching block  47  and a video switch  48 . Video switch  48  selectively connects video signals from auxiliary jacks  30  or integrated video cassette player  17  to screen  16 . The coordinated audio signals from auxiliary jacks  30  and video cassette player  17  are connected to respective inputs of selector switches  50  and  51 . Analog audio signals from CDDJ  11  are coupled to respective inputs of selector switches  50  and  51 . The output of selector switch  50  is coupled via RSEM audio output line  43  to respective inputs of selector switches  41  and  42 . Yet another input of selector switch  51  is connected to rear speaker audio line  40  which is also connected to a rear speaker relay  52  (also preferably an electronic switch). The output of selector switch  51  is coupled to headphone jacks  24  and  25  via a headphone audio processor circuit  53  which controls headphone volume in response to microprocessor  45 . 
     As a result of the architecture shown in FIG. 2, main controller unit  10  has access to all rear audio sources using only one external audio input line  43 . Main control unit  10  sends a multiplex message via multiplex system  32  to microprocessor  45  in RSEM  15  for configuring source selector switch  50  to provide rear audio signals to be used as a source for the front channel by appropriately configuring selector switch  50 . Audio signals from a rear seat source can be used in either single play or dual play modes by appropriately configuring selector switches  41  and  42 . In single play mode, microprocessor  45  causes speaker relay  52  to be closed, but causes it to be open in dual play mode so that the rear main speakers are inactive and the headphone jacks are active. 
     In dual play mode, any sources can be applied to the headphone jacks via appropriate configuration of selector switches  42  and  51 . Furthermore, any combination of sources may be obtained as the front (i.e., primary) source and the rear (i.e., secondary) source in dual play mode, with the exception that tuner  35  produces only one broadcast signal at a time and cannot provide different radio stations simultaneously for dual play mode. 
     The operation of the present invention during a source change is shown by the flowchart of FIG.  3 . Whenever a selected source is being changed, a check is first made in step  60  to determine whether the multimedia entertainment system is currently in single play or dual play mode. If in single play mode, then a check is made in step  61  to determine whether a rear source (e.g., CDDJ, integrated video cassette player, or auxiliary video/game system) is selected. If a rear source is selected while in single play mode, then the rear external source selector switch is set in step  62  to provide the selected source to the main unit external input. If a rear source is not selected in step  61  or after setting of the rear source selector switch in step  62 , the front channel and rear channel audio processor selector switch inputs in the main unit are set to the selected source in step  63 . 
     If step  60  determines that the multimedia entertainment system is in dual play mode, then a check is performed in step  64  to determine whether a rear source is selected for the primary source (i.e., the source to be reproduced by the front channel audio processor). If a rear source is selected for the primary source, then the rear external source selector switch is set in step  65  to provide the selected rear source to the main unit external audio input. After setting the rear source selector switch, or if a rear source was not selected for the primary source in step  64 , the front channel selector switch in the main unit is set to the selected primary source in step  66 . In step  67 , a check is made to determine whether a front source has been selected for the secondary source (i.e., the source to be reproduced in dual play mode by the headphone jacks). If yes, then the rear channel selector switch in the main unit is set to provide that secondary source to the rear channel audio processor. Thereafter, the rear headphone selector switch is set to the desired secondary source in step  69  (either local input from a rear source or remote input from the main unit). 
     A method for changing mode from single play mode to dual play mode is shown in FIG.  4 . Such a change is initiated by pressing the mode change button  26  of FIG. 1, causing a multiplex message to be sent to the main control unit informing it of the button press. First, all audio is muted by the main control unit in step  71 . Also, the rear speaker relay is set to its off state in response to a control command sent by the main control unit to the rear control unit. This makes sure that the audio is muted when the relay changes state. In step  72 , a check is made to determine whether the previous secondary source (i.e., the source selected for rear seat entertainment the last time dual play mode was active) is valid. For example, if the previous secondary source was the CD player and no disc is currently loaded in the CD player, then the secondary source would not be valid. In that case, the secondary source is set to the currently active primary source in step  73 . Otherwise, the secondary source is set to the previous valid source in step  74 . After setting the secondary source, the rear headphone volume is restored to its previous level set during the last time dual play mode was active in step  75 . All audio is unmuted in step  76 . 
     A method for changing mode from dual play mode to single play mode is shown in FIG.  5 . All audio is muted in step  80  and the rear speaker relay is changed to its on state. Then, the secondary source currently selected and the current volume level for the rear headphones are stored in step  81 . The primary source is resumed for both the front and rear audio channels in step  82  and the main speakers are all unmuted in step  83 .