Speaker : Chungyi WangAdvisor: Quincy WuDate : 2007.8.8

outlineIntroductionWhy Speex ?Speex Tools – WindowsSpeex API – LinuxReference

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IntroductionWhat is the Speex ?

One kind of compression software (or API)

What is the main advantage of the Speex ?Good compression ratio (and variable)

What kinds of application need the Speex ?Audio file (ex.ogg, spx)VoIP

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Why Speex ? (1/5)

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320 bytes

PCMRTP

• 320 x 50 = 16000 (15.625 kb/sec)• Need compression !!

Why Speex ? (2/5)

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Good compression ratio !!

Speex encode

Speex decode

PCMRTP

320 bytes

(6~62) bytes

320 bytes

Why Speex ? (3/5)

2007/8/8 6From : http://www.speex.org/comparison/

Why Speex ? (4/5)Speex is based on CELP and is designed to compress

voice at bitrates ranging from 2 to 44 kbps. Some of Speex's features include: - Narrowband (8 kHz), wideband (16 kHz), and

ultrawideband (32 kHz) compression in the same bitstream

- Intensity stereo encoding - Packet loss concealment - Variable bitrate operation (VBR) - Voice Activity Detection (VAD) - Discontinuous Transmission (DTX) - Fixed-point port - Acoustic echo canceller - Noise suppression

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Why Speex ? (5/5)Lossy

Depend on quality (and compression ratio)

From : http://en.wikipedia.org/wiki/Lossy_data_compression

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Speex Tools – Windows (1/4)Download

http://downloads.us.xiph.org/releases/speex/speex-tools-win32-v1.2beta1.zip

Speex Toolsspeexenc.exespeexdec.exe

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Speex Tools – Windows (2/4)speexenc.exe

speexenc [input_file] [outfile] input_file : wavoutfile_file : spx

speexenc –quality n [input_file] [outfile]n : Quality (10-0)

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Speex Tools – Windows (3/4)speexdec.exe

speexdec [input_file] [outfile] input_file : spxoutfile_file : wav

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Speex Tools – Windows (4/4)Demo

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Speex API – Linux (1/7)Download

http://downloads.us.xiph.org/releases/speex/speex-1.2beta1.tar.gz

SetupLinphone - 2007/01/08 http://ms11.voip.edu.tw/~webmaster/meeting/

http://ms11.voip.edu.tw/~chungyi/ncnu-research/linphone/install.html

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Speex API – Linux (2/7)#include <speex/speex.h>

For API of encoder and decoder

Compilegcc –lspeex source.c

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Speex API – Linux (3/7)

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Encoder Init

One round encode

Destory encoder

void *state = speex_encoder_init(&speex_nb_mode);SpeexBits bits;

speex_bits_init(&bits);speex_encoder_ctl(state, SPEEX_SET_QUALITY,

&quality);

speex_bits_reset(&bits);speex_encode(state, input, &bits);

int nbBytes = speex_bits_write(&bits, cbits, 200);

speex_encoder_destroy(state);speex_bits_destroy(&bits);

Speex API – Linux (4/7)Quality Frame_Size (Bytes)

0 6

1 10

2 15

3 20

4 20

5 28

6 28

7 38

8 38

9 46

10 62

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For every 320-bytes

Speex API – Linux (5/7)Demo

>>make >>gcc -lspeex speex_encode.c -o encode >>gcc -lspeex speex_decode.c -o decode

>>./encode

ResultMakefilespeex_encode.cspeex_encode.txt

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Speex API – Linux (6/7)

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Decoder Init

One round decode

Destory decoder

void *state speex_decoder_init(&speex_nb_mode);SpeexBits bits;

speex_bits_init(&bits);

speex_bits_read_from(&bits, cbits[j], nbBytes);speex_decode(state, &bits, output);

speex_decoder_destroy(state);speex_bits_destroy(&bits);

Speex API – Linux (7/7)Demo

>>./decode

Resultspeex_decode.cspeex_decode.txt

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Reference (1/2)Speex - mainhttp://www.speex.org/

Speex - windows toolshttp://downloads.us.xiph.org/releases/speex/speex-tools-

win32-v1.2beta1.zip

Speex - windows libhttp://downloads.us.xiph.org/releases/speex/libspeex-

win32-v1.2beta1.zip

Speex - Development RPMhttp://downloads.us.xiph.org/releases/speex/speex-devel-

1.2beta2-1.i386.rpm

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Reference (2/2)Speex – API documentation

(The Speex Codec Manual –very good!!)http://www.speex.org/docs/manual/speex-manual/

Speex – wikihttp://en.wikipedia.org/wiki/Speex

This ppt & demohttp://ms11.voip.edu.tw/~chungyi/ncnu-

research/Speex/Speex.zip

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