Nyenzo za kifungu zimechukuliwa kutoka kwangu
Kuunda mita ya kiwango cha ishara
Zamani
Katika makala hii tutakusanya mzunguko wa mita ya kiwango cha ishara na kujifunza jinsi ya kusoma matokeo ya kipimo kutoka kwa chujio. Wacha tuchunguze usahihi wa kipimo.
Seti ya vichungi vinavyotolewa na kipeperushi cha media ni pamoja na kichujio, MS_VOLUME, ambacho kina uwezo wa kupima kiwango cha RMS cha ishara inayopita ndani yake, kupunguza ishara na kufanya kazi nyingi muhimu na zisizotarajiwa. Tutatoa nakala nzima kwa kichujio hiki baadaye. Lakini kwa sasa tutaitumia kama mita.
Tutatumia jenereta ya toni kama chanzo cha ishara, ishara ambayo itatumwa kwa kichujio cha MS_VOLUME, kwa matokeo ambayo kadi ya sauti imeunganishwa.
Katika mfano huu, tutatumia chujio cha jenereta kwa hali tofauti kidogo - itazalisha ishara ya toni moja kwa ajili yetu, i.e. ishara iliyo na oscillation moja tu ya sinusoidal.
Mbali na marudio na amplitude, tutahitaji kuweka muda ambao ishara itatolewa; lazima iwe ya kutosha ili idadi ya kutosha ya sampuli zipitie kwenye kichujio cha MS_VOLUME kwa kipimo. Ili kuhamisha mipangilio kwa jenereta, muundo wa MSDtmfGenCustomTone hutumiwa:
struct _MSDtmfGenCustomTone{
char tone_name[8]; /* Π’Π΅ΠΊΡΡΠΎΠ²ΠΎΠ΅ Π½Π°Π·Π²Π°Π½ΠΈΠ΅ ΡΠΈΠ³Π½Π°Π»Π° ΠΈΠ· 8 Π±ΡΠΊΠ².*/
int duration; /* ΠΠ»ΠΈΡΠ΅Π»ΡΠ½ΠΎΡΡΡ ΡΠΈΠ³Π½Π°Π»Π° Π² ΠΌΠΈΠ»Π»ΠΈΡΠ΅ΠΊΡΠ½Π΄Π°Ρ
.*/
int frequencies[2]; /* ΠΠ°ΡΠ° ΡΠ°ΡΡΠΎΡ ΠΈΠ· ΠΊΠΎΡΠΎΡΡΡ
Π΄ΠΎΠ»ΠΆΠ΅Π½ ΡΠΎΡΡΠΎΡΡΡ Π²ΡΡ
ΠΎΠ΄Π½ΠΎΠΉ ΡΠΈΠ³Π½Π°Π». */
float amplitude; /* ΠΠΌΠΏΠ»ΠΈΡΡΠ΄Π° ΡΠΎΠ½ΠΎΠ², 1.0 ΡΠΎΠΎΡΠ²Π΅ΡΡΡΠ²ΡΠ΅Ρ ΡΡΠΎΠ²Π½Ρ 0 Π΄Π ΠΎΡ ΠΌΠΈΠ»Π»ΠΈΠ²Π°ΡΡΠ° Π½Π° Π½Π°Π³ΡΡΠ·ΠΊΠ΅ 600 ΠΠΌ.*/
int interval; /* ΠΠ°ΡΠ·Π° Π² ΠΌΠΈΠ»Π»ΠΈΡΠ΅ΠΊΡΠ½Π΄Π°Ρ
ΠΏΠ΅ΡΠ΅Π΄ Π½Π°ΡΠ°Π»ΠΎΠΌ ΠΏΠΎΠ²ΡΠΎΡΠ½ΠΎΠ³ΠΎ ΠΏΡΠΎΠΈΠ³ΡΡΠ²Π°Π½ΠΈΡ ΡΠΈΠ³Π½Π°Π»Π°.*/
int repeat_count; /* ΠΠΎΠ»ΠΈΡΠ΅ΡΡΠ²ΠΎ ΠΏΠΎΠ²ΡΠΎΡΠΎΠ².*/
};
typedef struct _MSDtmfGenCustomTone MSDtmfGenCustomTone;
Ili kuanzisha jenereta, tutatumia mbinu yake ya MS_DTMF_GEN_PLAY_CUSTOM.
Mchoro wa kuzuia usindikaji wa ishara:
Msimbo wa programu unaotekeleza mpango huu umeonyeshwa hapa chini.
/* Π€Π°ΠΉΠ» mstest3.c */
#include <mediastreamer2/msfilter.h>
#include <mediastreamer2/msticker.h>
#include <mediastreamer2/dtmfgen.h>
#include <mediastreamer2/mssndcard.h>
#include <mediastreamer2/msvolume.h>
int main()
{
ms_init();
/* Π‘ΠΎΠ·Π΄Π°Π΅ΠΌ ΡΠΊΠ·Π΅ΠΌΠΏΠ»ΡΡΡ ΡΠΈΠ»ΡΡΡΠΎΠ². */
MSFilter *voidsource=ms_filter_new(MS_VOID_SOURCE_ID);
MSFilter *dtmfgen=ms_filter_new(MS_DTMF_GEN_ID);
MSFilter *volume=ms_filter_new(MS_VOLUME_ID);
MSSndCard *card_playback=ms_snd_card_manager_get_default_card(ms_snd_card_manager_get());
MSFilter *snd_card_write=ms_snd_card_create_writer(card_playback);
/* Π‘ΠΎΠ·Π΄Π°Π΅ΠΌ ΡΠΈΠΊΠ΅Ρ. */
MSTicker *ticker=ms_ticker_new();
/* Π‘ΠΎΠ΅Π΄ΠΈΠ½ΡΠ΅ΠΌ ΡΠΈΠ»ΡΡΡΡ Π² ΡΠ΅ΠΏΠΎΡΠΊΡ. */
ms_filter_link(voidsource, 0, dtmfgen, 0);
ms_filter_link(dtmfgen, 0, volume, 0);
ms_filter_link(volume, 0, snd_card_write, 0);
/* ΠΠΎΠ΄ΠΊΠ»ΡΡΠ°Π΅ΠΌ ΠΈΡΡΠΎΡΠ½ΠΈΠΊ ΡΠ°ΠΊΡΠΎΠ². */
ms_ticker_attach(ticker,voidsource);
MSDtmfGenCustomTone dtmf_cfg;
/* Π£ΡΡΠ°Π½Π°Π²Π»ΠΈΠ²Π°Π΅ΠΌ ΠΈΠΌΡ Π½Π°ΡΠ΅Π³ΠΎ ΡΠΈΠ³Π½Π°Π»Π°, ΠΏΠΎΠΌΠ½Ρ ΠΎ ΡΠΎΠΌ, ΡΡΠΎ Π² ΠΌΠ°ΡΡΠΈΠ²Π΅ ΠΌΡ Π΄ΠΎΠ»ΠΆΠ½Ρ
ΠΎΡΡΠ°Π²ΠΈΡΡ ΠΌΠ΅ΡΡΠΎ Π΄Π»Ρ Π½ΡΠ»Ρ, ΠΊΠΎΡΠΎΡΡΠΉ ΠΎΠ±ΠΎΠ·Π½Π°ΡΠ°Π΅Ρ ΠΊΠΎΠ½Π΅Ρ ΡΡΡΠΎΠΊΠΈ. */
strncpy(dtmf_cfg.tone_name, "busy", sizeof(dtmf_cfg.tone_name));
dtmf_cfg.duration=1000;
dtmf_cfg.frequencies[0]=440; /* ΠΡΠ΄Π΅ΠΌ Π³Π΅Π½Π΅ΡΠΈΡΠΎΠ²Π°ΡΡ ΠΎΠ΄ΠΈΠ½ ΡΠΎΠ½, ΡΠ°ΡΡΠΎΡΡ Π²ΡΠΎΡΠΎΠ³ΠΎ ΡΠΎΠ½Π° ΡΡΡΠ°Π½ΠΎΠ²ΠΈΠΌ Π² 0.*/
dtmf_cfg.frequencies[1]=0;
dtmf_cfg.amplitude=1.0; /* Π’Π°ΠΊΠΎΠΉ Π°ΠΌΠΏΠ»ΠΈΡΡΠ΄Π΅ ΡΠΈΠ½ΡΡΠ° Π΄ΠΎΠ»ΠΆΠ΅Π½ ΡΠΎΠΎΡΠ²Π΅ΡΡΡΠ²ΠΎΠ²Π°ΡΡ ΡΠ΅Π·ΡΠ»ΡΡΠ°Ρ ΠΈΠ·ΠΌΠ΅ΡΠ΅Π½ΠΈΡ 0.707.*/
dtmf_cfg.interval=0.;
dtmf_cfg.repeat_count=0.;
/* ΠΠΊΠ»ΡΡΠ°Π΅ΠΌ Π·Π²ΡΠΊΠΎΠ²ΠΎΠΉ Π³Π΅Π½Π΅ΡΠ°ΡΠΎΡ. */
ms_filter_call_method(dtmfgen, MS_DTMF_GEN_PLAY_CUSTOM, (void*)&dtmf_cfg);
/* ΠΠ°Π΅ΠΌ, Π²ΡΠ΅ΠΌΡ ΠΏΠΎΠ»ΠΎΠ²ΠΈΠ½Ρ ΡΠ΅ΠΊΡΠ½Π΄Ρ, ΡΡΠΎΠ±Ρ ΠΈΠ·ΠΌΠ΅ΡΠΈΡΠ΅Π»Ρ Π½Π°ΠΊΠΎΠΏΠΈΠ» Π΄Π°Π½Π½ΡΠ΅. */
ms_usleep(500000);
/* Π§ΠΈΡΠ°Π΅ΠΌ ΡΠ΅Π·ΡΠ»ΡΡΠ°Ρ ΠΈΠ·ΠΌΠ΅ΡΠ΅Π½ΠΈΡ. */
float level=0;
ms_filter_call_method(volume, MS_VOLUME_GET_LINEAR,&level);
printf("ΠΠΌΠΏΠ»ΠΈΡΡΠ΄Π΅ ΡΠΈΠ½ΡΡΠ° %f Π²ΠΎΠ»ΡΡ ΡΠΎΠΎΡΠ²Π΅ΡΡΡΠ²ΡΠ΅Ρ ΡΡΠ΅Π΄Π½Π΅ΠΊΠ²Π°Π΄ΡΠ°ΡΠΈΡΠ΅ΡΠΊΠΎΠ΅ Π·Π½Π°ΡΠ΅Π½ΠΈΠ΅ %f Π²ΠΎΠ»ΡΡ.n", dtmf_cfg.amplitude, level);
}
Tunakusanya mfano wetu, kama tulivyofanya hapo awali, kwa kutumia tu jina la faili mstst3. Wacha tuiendeshe na tupate matokeo:
ΠΠΌΠΏΠ»ΠΈΡΡΠ΄Π΅ ΡΠΈΠ½ΡΡΠ° 1.000000 Π²ΠΎΠ»ΡΡ ΡΠΎΠΎΡΠ²Π΅ΡΡΡΠ²ΡΠ΅Ρ ΡΡΠ΅Π΄Π½Π΅ΠΊΠ²Π°Π΄ΡΠ°ΡΠΈΡΠ΅ΡΠΊΠΎΠ΅ Π·Π½Π°ΡΠ΅Π½ΠΈΠ΅ 0.707733 Π²ΠΎΠ»ΡΡ.
Kama unavyoona, matokeo ya kipimo yalilingana na nafasi ya tatu ya desimali na thamani ya kinadharia sawa na mzizi wa mraba wa mbili zilizogawanywa katika nusu: sqr(2)/2=0,7071067811865475
Mkengeuko wa jamaa wa matokeo kutoka kwa thamani ya kweli ulikuwa 0.1%. Tulitathmini hitilafu ya kipimo katika kiwango cha juu cha mawimbi. Ipasavyo, kiwango kinapungua, kosa linapaswa kuongezeka. Ninapendekeza ujitathmini mwenyewe kwa viwango vya chini vya mawimbi.
Katika makala inayofuata tutakusanya mzunguko unaotambua kuwepo kwa ishara ya sauti ya mzunguko uliopewa kwenye pembejeo kwa kutumia detector ya tone. Pia tutajifunza jinsi ya kuchakata matukio yanayotokana na vichujio.
Chanzo: mapenzi.com