Atmel AVR32840: AVR UC3 Audio Player
MAD MP3 Decoder
Features
32-bit Atmel
Microcontroller
• Software MAD MP3 decoder implementation
– Player implementation
– Player configuration
– Licensing
Application Note
1. Introduction
This application note is an extension of the Atmel® AVR32839: AVR® UC3 Audio
Player application note.
The aim is to give the reader all he needs about implementation and configuration of
the Underbit Technologies™ MPEG Audio Decoder (MAD) MP3 decoder in the Atmel
AVR UC3 Audio Player.
32173A–AVR32–10/11
2. UC3 audio player
2.1
Overview
The Atmel AVR UC3 audio player is a generic audio player interface and is designed to support
multiple audio formats like MP3, WMA, AAC…
This document details the implementation of the MAD decoder in this player.
2.2
Package
The UC3 audio player package implementing the MAD decoder is the:
audio_player-evk1104-evk1105-MP3-<version>.zip file.
2.3
2.3.1
MAD decoder
Overview
MAD is a high-quality MPEG audio decoder. It currently supports MPEG-1 and the MPEG-2
extension to lower sampling frequencies, as well as the de facto MPEG 2.5 format. All three
audio layers — Layer I, Layer II, and Layer III (that is, MP3) — are fully implemented.
MAD has the following special features:
•
24-bit PCM output
•
100% fixed-point (integer) computation
•
Implementation based on the ISO/IEC standards
More information can be retrieved
http://www.underbit.com/products/mad/.
2.3.2
from
the
MAD
home
page:
Source code
The source code for the UC3 specific parts of the libmad decoder is available from [1] and binaries can be built from [2].
Notes:
2.3.3
2.4
2.4.1
1. http://git.buildroot.net/buildroot/tree/package/multimedia/libmad/libmad-0.15.1boptimization.patch.avr32.
2. http://git.buildroot.net/buildroot/tree/package/multimedia/libmad.
Supported devices
The MAD decoder can be ported to any Atmel AVR UC3 devices, assuming parts has enough
flash and RAM resources.
Player implementation
Source code
As highlighted in Figure 2-1, the MAD decoder source code is implemented in /thirdparty/libmad
directory. The optimized UC3 library is available in /thirparty/libmad/libs directory.
2.4.2
Player layer
The MP3 player layer is located in /avr32/services/audio/players/mp3/mp3_libmad_player.[c,h].
2
AVR32840
32173A–AVR32–10/11
AVR32840
Figure 2-1.
Player software architecture.
Audio Player Application
main.c
Audio Interface
Task (AI)
Communication
Task (HMI)
GUI
Task (specific)
_gui.c
Controller
ai_task.c
Audio Decoding
Audio Interface
audio_interface.c
SD Card Audio interface
host_mass_storage_task.c
codec_mp3_task.c
_controller.c
com_task.c
Host Mass Storage
Codec(s)
ai_sd_mmc.c
/thirdparty/libmad
ai_usb_ms.c
usb_task.c
USB Host task
MP3 MAD Decoder
Mass Storage Audio interface
USB
usb_host_task.c
Decoder 2
/thirdparty/decoder2
File System
Decoder 3
/services/fs/fat/
/thirdparty/decoder3
Decoder 2 and above are optional
Drivers
usart.c, spi.c, twi.c, ssc_i2s.c, flashc.c, pm.c, gpio.c
2.5
Player configuration
As detailed in the Atmel AVR32839: AVR UC3 Audio Player application note, the task() function
is in charge of calling the software “tasks” to perform audio decoding.
The task() is macro based and defined in /config/conf_audio_player.h file where the call to the
MP3 task is defined:
#define task()
\
{
\
task_usb();
\
task_usb_ms();
\
task_mp3();
\
}
The MP3 support is then enabled by defining the MP3_SUPPORT to true:
#define SUPPORT_MP3
true
The MP3 file extension filtering is enabled in the following section of the conf_audio_player.h
file:
// ***** MP3 Support *******************************************
#if defined(SUPPORT_MP3) && SUPPORT_MP3 == true
#include "ai_usb_ms_mp3_support.h"
#define task_mp3()
\
{
\
extern void codec_mp3_task(void);
\
codec_mp3_task();
\
}
#define file_format_mp3
MP3_FILE_FORMAT,
#else
3
32173A–AVR32–10/11
#define task_mp3()
#define file_format_mp3
#endif
2.6
Decoder license
The MAD decoder is distributed under the terms of the GNU General Public License (GPL). The
license is located in /thirdparty/libmad/license.txt.
2.7
Performance
Table 2-1 shows the memory requirement for the MP3 MAD decoder implementation.
Table 2-1.
MP3 MAD decoder performance.
Compiler
(1)
RAM [KB]
(2)
GCC 4.4.3 (3)
67.1 / 59.4
31.9 / 31.2
IAR EWAVR32 3.31.1
60.4 / 57.7
31.3 / 31.3
1.
2.
3.
4
Flash [KB]
Speed / Size optimization
Speed / Size optimization
AVR 32-bit GNU Toolchain 3.3.1 build 285
AVR32840
32173A–AVR32–10/11
Atmel Corporation
2325 Orchard Parkway
San Jose, CA 95131
USA
Tel: (+1)(408) 441-0311
Fax: (+1)(408) 487-2600
www.atmel.com
Atmel Asia Limited
Unit 1-5 & 16, 19/F
BEA Tower, Millennium City 5
418 Kwun Tong Road
Kwun Tong, Kowloon
HONG KONG
Tel: (+852) 2245-6100
Fax: (+852) 2722-1369
Atmel Munich GmbH
Business Campus
Parkring 4
D-85748 Garching b. Munich
GERMANY
Tel: (+49) 89-31970-0
Fax: (+49) 89-3194621
Atmel Japan
9F, Tonetsu Shinkawa Bldg.
1-24-8 Shinkawa
Chuo-ku, Tokyo 104-0033
JAPAN
Tel: (+81)(3) 3523-3551
Fax: (+81)(3) 3523-7581
© 2011 Atmel Corporation. All rights reserved.
Atmel ®, Atmel logo and combinations thereof, AVR ® and others are registered trademarks or trademarks of Atmel Corporation or its
subsidiaries. Other terms and product names may be trademarks of others.
Disclaimer: The information in this document is provided in connection with Atmel products. No license, express or implied, by estoppel or otherwise, to
any intellectual property right is granted by this document or in connection with the sale of Atmel products. EXCEPT AS SET FORTH IN THE ATMEL
TERMS AND CONDITIONS OF SALES LOCATED ON THE ATMEL WEBSITE, ATMEL ASSUMES NO LIABILITY WHATSOEVER AND DISCLAIMS ANY
EXPRESS, IMPLIED OR STATUTORY WARRANTY RELATING TO ITS PRODUCTS INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTY OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT. IN NO EVENT SHALL ATMEL BE LIABLE FOR ANY DIRECT,
INDIRECT, CONSEQUENTIAL, PUNITIVE, SPECIAL OR INCIDENTAL DAMAGES (INCLUDING, WITHOUT LIMITATION, DAMAGES FOR LOSS AND PROFITS, BUSINESS INTERRUPTION, OR LOSS OF INFORMATION) ARISING OUT OF THE USE OR INABILITY TO USE THIS DOCUMENT, EVEN IF ATMEL
HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. Atmel makes no representations or warranties with respect to the accuracy or completeness of the contents of this document and reserves the right to make changes to specifications and product descriptions at any time without notice.
Atmel does not make any commitment to update the information contained herein. Unless specifically provided otherwise, Atmel products are not suitable for, and shall not be used in, automotive applications. Atmel products are not intended, authorized, or warranted for use as components in applications intended to support or sustain life.
32173A–AVR32–10/11