1. Yongchang, Kai, Justin, Rama
Audio Processing
Yongchang, Kai, Justin, Rama

2. Audio Processing

4. System Analysis Input: Raw WAV Format Data
Output: Normalized Wave Signal

5. System Analysis (continued) Step 1: Preprocessing
Input: Raw WAV Format Data
Output: Preprocessed Wave Data Set
Sample Rate: 8k Hz
Channels: 1 = Mono
Bits Per Sample: 8 bits

6. System Analysis (continued) Step 2: Audio Processing
Input: Preprocessed Wave Data Set
Output: Single Wave Signal

7. Audio Processing Preprocessing Channel
Preprocessed Wave Data
Audio Processing
Each Signal to Be Played
Raw WAV Format Data
Preprocessing
Channel

8. System Analysis (continued)
Preprocessed input data:
Illegal format – thrown away
Legal format – converted to the suitable format
Preprocessing is very important
Save the cost of the satellite
Time
Space
Decrease risk: illegal data can make the satellite system crash

9. System Analysis (continued)
Preprocessed input data:
Illegal format – thrown away
Legal format – converted to the suitable format
Preprocessing is very important
Save the cost of the satellite
Time
Space
Decrease risk: illegal data can make the satellite system crash

10. Basic Wave File Format The “RIFF” Chunk The “fmt” Sub-chunk
The “data” Sub-chunk

11. Basic Wave File Format The “RIFF” Chunk The “fmt” Sub-chunk
Unit: Byte( s )
"WAVE"
36 + SubChunk2Size
"RIFF"
Comment 4
ChunckSize
Format 8
ChunkID
Size
Field
Offset
The “data” Sub-chunk
The “fmt” Sub-chunk
The “RIFF” Chunk

12. Basic Wave File Format The “RIFF” Chunk The “fmt” Sub-chunk
8 bits = 8,
16 bits = 16, etc 2
BitsPerSample 34
NC * BPS / 8
BlockAlign 32
SR*NC*BPS/8 4
ByteRate 28
8k, 44.1k, etc
SampleRate 24
Mono = 1, Stereo = 2, etc
NumChannels 22
PCM = 1
16 for PCM
"fmt "
Comment
Subchunk1Size 16
AudioFormat 20
Subchunk1ID 12
Size
Field
Offset
The “data” Sub-chunk
The “fmt” Sub-chunk
The “RIFF” Chunk
SR = SampleRate, NC = NumChannels
BPS = BitsPerSample

13. Basic Wave File Format The “RIFF” Chunk The “fmt” Sub-chunk
The actual sound data
NumSamples * NumChannels * BitsPerSample/8
“data"
Comment 4
Subchunk2Size 40 *
Data 44
Subchunk2ID 36
Size
Field
Offset
The “data” Sub-chunk
The “fmt” Sub-chunk
The “RIFF” Chunk

14. Preprocessed Wave Format
Offset
Field
Size
Comment
DataSize 4
Little Endian, (uint32)
Data *
The actual sound data :
Sample Rate: 8k Hz
Channels: 1 = Mono
Bits Per Sample: 8 bits
Normalized Data

15. System Design for Preprocessor
Raw Data
Legal Format ?
Report Error No
Yes
Preprocessing
Preprocessed Data

16. System Design for Preprocessor
int LoadRawFile( char * apchRawFileName );
Load the raw format wave file and check it.
pchRawFileName: File name of the raw wave file.
Return value:
0 – Successfully
Negative value – There exists error
int ConvertTo( char * apchNewFormatFile );
Convert the legal wave data to the preprocessed format
pchNewFormatFile: File name of the preprocessed data.

17. System Design for AudioProcessor ( Concept )
File ID
Is playing ?
Yes No
Initializing
playing Over?
Play
Ignore and Return
Finally process
and Return

18. System Design for AudioProcessor ( Implement )
File ID
Is playing ?
Yes No
Initializing
Hardware and Software
Ignore
Start Timer
Return
playing Over?
Yes No
Send One Byte
to DAC
Stop Timer
and Return
OnTimer
Return

19. System Design for AudioProcessor
int play_audio( char * apchFileID );
Initialize hardware and software and be ready for playing.
apchFileID: Wave file to be played.
Return value:
0 – To be played.
-1 – Request is ignored
void write_data_onto_DAC( void );
To be called when TimerB18000 interrupt occurs
void initialise_hw( void );
Initialize hardware for playing sound

20. System Design for AudioProcessor ( About DAC )
DAC12_1CTL = DAC12IR + DAC12AMP_5 + DAC12ENC;
DAC12IR:
In DAC12_xCTL, DAC12 Control Register. Bit 8.
DAC12 input range. This bit sets the reference input and voltage output range.
0 DAC12 full-scale output = 3x reference voltage
1 DAC12 full-scale output = 1x reference voltage
DAC12AMPx:
DAC12ENC:

21. System Design for AudioProcessor ( About DAC )
DAC12_1CTL = DAC12IR + DAC12AMP_5 + DAC12ENC;
DAC12IR:
DAC12AMPx:
In DAC12_xCTL, DAC12 Control Register. Bits : 7-5
DAC12 amplifier setting. These bits select settling time vs. current consumption for the DAC12 input and output amplifiers.
DAC12ENC:

22. System Design for AudioProcessor ( About DAC )
DAC12_1CTL = DAC12IR + DAC12AMP_5 + DAC12ENC;
DAC12IR:
DAC12AMPx:
DAC12ENC:
In DAC12_xCTL, DAC12 Control Register. Bit 1.
DAC12 enable conversion. This bit enables the DAC12 module when DAC12LSELx > 0. when DAC12LSELx = 0, DAC12ENC is ignored.
0 DAC12 disabled
1 DAC12 enabled

23. Testing
Preprocessor passed testing
AudioProcessor passed testing

24. Demo of Preprocessor I

25. Demo of Preprocessor II
The output file is a *.h file, so that we can directly include this file and get the data.

26. Status Problem: Solution:
There is no file system API, so real audio files can’t be processed.
Solution:
Now we use a char array to simulate an audio file. ( less flexibility )
Maybe resolving packets directly will be more elegant.

27. Future Wait for the file system APIs? ( or solve it ourselves )
Re-design audio processing APIs?
Flexible ( not only play 8k Hz audio )
Extensible ( multimedia processing )
Available ( non-stop service )
Reliable ( not a toy )
Maintainable

28. Thanks for your attention