Abstract:
A technique for extending battery life and reducing noise in a portable music player storing tracks on a hard drive reads a track from the disk to a buffer and plays the track from the buffer while the disk is spun down to a power-saving state. Noise and vibration is also reduced when the disk is spun down.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
         [0001]    This application is related to application No. _/_,_, entitled “System for Selecting and Playing Songs in a Playback Device with a Limited User Interface,” (Atty. Docket No. 17002-020800); and application No. _/_,_, entitled “Automatic Hierarchical Categorization of Music by Metadata,” (Atty. Docket No. 17002-022500), all filed Jan. 5, 2001, the disclosures of which are incorporated herein by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    Today, portable consumer electronic devices are more powerful than ever. For example, small, portable music playback devices can store hundreds, even thousands, of compressed songs and can play back the songs at high quality. With the capacity for so many songs, a playback device can store many songs from different albums, artists, styles of music, etc.  
           [0003]    As users desire to store more songs on the portable music player different storage media are being used. A hard disk drive (HDD) has many benefits in terms of capacity, access time, cost. However, HDDs consume power and quickly drain batteries used in a portable music player.  
           [0004]    Accordingly, HDDs have power saving modes, such as the STANDBY mode and the SLEEP mode. In both the STANDBY and SLEEP modes the motor is turned off and the disk spins down. Additionally, is SLEEP mode most of the electronic subsystems of the HDD are powered down to save additional power. However, to recover from SLEEP mode the drive must be reset which adds additional time to the recover. Typical recovery times are several seconds to transition from a power-saving mode to the IDLE mode.  
           [0005]    In the IDLE mode the HDD is ready to transfer data and the disk is spinning. During reading or writing the HDD is in the ACTIVE mode.  
           [0006]    Some HDDs automatically transition to a power saving mode from the IDLE mode if no read or write requests are received during a set time interval, e.g., 30 seconds.  
           [0007]    Additionally, jitter is a problem when reading data from an HDD in portable device because the device is subject to jarring or bumping which causes glitches. Further, when the disk is spinning noise and vibration is present which may be noticeable to a listener.  
           [0008]    Accordingly, techniques for extending battery life and reducing jitter and noise in portable music players are being actively developed.  
         SUMMARY OF THE INVENTION  
         [0009]    According to one aspect of the present invention, battery life is extended in a portable music player using an HDD to store audio tracks by transitioning the HDD to a power-saving mode when the a track is stored in the play buffer.  
           [0010]    According to another aspect of the invention, the HDD is transitioned out of the power-saving mode when the buffer reaches a low threshold level so that a next audio track can be read from the HDD to the buffer before the present track is through playing.  
           [0011]    According to another aspect of the invention, the HDD is not transitioned to the power-saving mode if the battery voltage is below a critical level to avoid a large current drain on the batteries occurring when the HDD transitions from the power-saving mode.  
           [0012]    Other features and advantages of the invention will be apparent in view of the following detailed description and appended drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a block diagram of a system for implementing an embodiment of the invention;  
         [0014]    [0014]FIG. 2 is a state diagram depicting the transitions between modes of the HDD; and  
         [0015]    FIGS.  3 A- 3 D are schematic diagrams depicting a buffer at various points in time. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]    An embodiment of the invention implemented in the Nomad® Jukebox portable music player will now be described by way of example, not limitation. The principles of the invention are broadly applicable to portable music players in general.  
         [0017]    [0017]FIG. 1 is a block diagram of a system  10  including a hard-disk drive (HDD)  12  and interface  14 , central processing unit  16 , a buffer  18 , system memory  20 , and audio subsystem  22  connected to bus  24 . As is well-known in the art, the buffer  18  may be a part of the system memory  20  and various components may be integrated on a single chip or be part of chip set.  
         [0018]    In a preferred embodiment the act described are implemented under control of the CPU which executes program code stored in the system memory. The program code can be stored in any computer readable medium including magnetic storage, CD ROM, optical media, or digital data encoded on an electromagnetic signal.  
         [0019]    The CPU executes software to implement a power management system. As described above, the HDD may be in the IDLE, STANDBY, or SLEEP states. In the IDLE state the disk is spinning and data may be read from the disk. In the presently described embodiment, the data is compressed digital music, for example, music encoded in the MP3 format.  
         [0020]    In the STANDBY and SLEEP states the disk is not spinning and the states differ by the amount of power consumed, the time required to transition back to IDLE, and the amount of power required to transition back to IDLE. SLEEP mode consumes less power but has a longer recovery time.  
         [0021]    Typical power consumption numbers for an HDD used in the Nomad® Jukebox are:  
         [0022]    spin-up (from standby or sleep)-900 mA max  
         [0023]    active mode-460 mA  
         [0024]    idle mode-170 mA  
         [0025]    standby mode-56 mA  
         [0026]    sleep mode-20 mA  
         [0027]    In the presently described embodiment, in response to a user request to play a track or a list of tracks, a block track data is transferred to the buffer until the buffer is full. In the presently described embodiment the buffer is implemented in system memory and may vary in sized depending on how much of system memory is used for other purposes. As depicted in FIG. 2, when the block is loaded into the buffer the HDD transitions from the IDLE mode to the SLEEP mode. The track data is then played from the buffer, that is, the track data is transferred from the buffer to the audio subsystem where the digital music data is transformed into an audio output signal utilizing techniques known in the art.  
         [0028]    When the buffer data remaining to be played reaches a low threshold level the HDD transitions from the SLEEP mode to the IDLE mode. An exemplary buffer management system for triggering this transition is depicted in FIG. 3.  
         [0029]    Referring to FIG. 2 FIGS.  3 A-D, a first block is read from the HDD and stored in the buffer as depicted in FIG. 3A. Data is read from the storage location as depicted by the READ pointer and a subsequent writing of data will commence at the location indicated by the WRITE pointer. Subsequent to reading data from the disk the HDD transitions to the SLEEP mode.  
         [0030]    As depicted in FIG. 3B and FIG. 2, when the READ pointer reaches a threshold value the software causes the HDD to transition to the IDLE mode from the SLEEP mode. This threshold can be set as a number of addresses from the beginning of the block because the amount of data read from the buffer translates as a known duration of audio. The threshold is set to take into account amount of time required to spin-up the disk to the IDLE mode and to read the next track into the buffer.  
         [0031]    As depicted in FIG. 3C, when the read pointer is reaching the end of the first block the second block is being stored in the buffer and the HDD transitions to the SLEEP mode again.  
         [0032]    Finally, as depicted in FIG. 3D, the READ pointer is positioned to read block 2  and the HDD is again in SLEEP mode.  
         [0033]    If the portable music player is being powered by an external supply then STANDBY mode may be utilized instead of SLEEP mode since a faster transition to IDLE may be more important then lowest power drain. Alternatively, STANDBY mode can also be utilized when using battery power albeit with a large current drain on the batteries.  
         [0034]    As set forth above, a large current drain on the batteries occurs during spin-up. If the battery is low this power drain could cause the voltage output from the battery to drop to a low value that could cause the system to crash.  
         [0035]    Accordingly, in one embodiment of the invention, if the voltage reading from the batteries indicates that battery life is very low then HDD is not put into SLEEP mode between disk reads to avoid the large current drain required to spin the disk back up to IDLE.  
         [0036]    The invention has now been described with reference to the preferred embodiments. Alternatives and substitutions will now be apparent to persons of skill in the art. For example, alternative buffer management techniques can be utilized to trigger the transitions to the power-saving mode. Further, in the embodiment described, a single track is read from the buffer between spin-downs. However, depending on the size of the buffer and characteristics of the HDD different size blocks of audio data may be stored in the buffer between spin downs. Accordingly, it is not intended to limit the invention except as provided by the appended claims.