Some features of the software are:

• Browse by directory or album (playlist)
• Supports bit rates up to 256Kbps
• Resumes where it left off on power up
• Track, Album, Artist, volume and progress display
• Preferences system
• IR remote control

The LCD display has four basic 'modes': Play Mode, Album Select, Directory Select and Prefs. Shown on the right are the loading screen (only shown for a few seconds), play mode and album select mode. I can flip between each mode using the number keys on my remote.   Play mode shows the track name, album and artist. On the bottom line of the LCD, the current volume (shown as a percentage or 'MAX' for 100%) and a progress bar are show. The progress bar shows how much of the MP3 has been decoded. From here I can also skip to the next/previous track, or pause/stop the music.   The album and directory select modes allow me to choose an a group of MP3s using the fast forward and rewind buttons on my remote. Pressing play will load the current album/directory list and start playing the first MP3.   The final mode is the prefs mode. Here I can set various options, such as bass and treble control, display contrast, backlight brightness, analogue volume control accuracy and volume update timing. This is the least often used mode.

LCD Display

  Of course, the music will keep playing regardless of the current mode, and the pause/stop buttons keep working.

  For decoding the MPEG stream and output, AmiMPC uses my own MHI drivers for the MAS Player Pro. MHI was developed by myself and Thomas Wenzel to provide a standard API for accessing MPEG audio decoders (both hardware and software) on the Amiga. Drivers and an SDK can be found on Aminet, search for 'MHI'.

  For volume control I used an analogue pot (see the hardware section). To read this I used an interrupt on the vertical blank (int5) which periodically checks the value of the pot. It then checks to see if it has changed enough to be more than just a random fluctuation, and if so signals the main task to perform a volume change.

  The software was developed on my A4000 060, and tested on the actual A1200 030 I used. The program code itself is only 34K, and along with the OS only uses around 100k of RAM. The program allocates 1MB of memory for buffering, which is split in to 128k chunks. This keeps HD access down, as 128K is approximately 8 seconds of audio at 128Kb/sec, or 6 at 192Kb/sec. The HD then only has to access every time a buffer becomes empty, and the 1MB total of buffering ensures that the music never skips. I also used PFS3 on the HD, which has 100K of buffers.