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Estudamos o mecanismo VoIP do Mediastreamer2. Parte 1

Material do artigo retirado do meu canal zen .



Introdução


Este artigo é o início de uma série de artigos sobre processamento de mídia em tempo real usando o mecanismo Mediastreamer2. Durante a apresentação, serão utilizadas habilidades mínimas de trabalho no terminal Linux e programação C.


O Mediastreamer2 é o mecanismo de VoIP subjacente ao projeto de código aberto popular do telefone de voz do software Linphone . No Linphone, o Mediastreamer2 implementa todas as funções associadas ao áudio e vídeo. Uma lista detalhada dos recursos do mecanismo pode ser vista nesta página do Mediastreamer. O código fonte está aqui: GitLab .


Mais adiante no texto, por conveniência, em vez da palavra Mediastreamer2, usaremos sua notação russa: "media streamer".


, , Glib, , GStreamer. . Linphone 2001 , 20 .


"Data flow" ( ). .


Arquitetura "Fluxo de dados"


, () , . .


, RTP- VoIP-.


, , , . , VoIP, .


, . , . :




  • Alsa (Linux): MS_ALSA_WRITE, MS_ALSA_READ
  • Android native sound (libmedia): MS_ANDROID_SOUND_WRITE, MS_ANDROID_SOUND_READ
  • Audio Queue Service (Mac OS X): MS_AQ_WRITE, MS_AQ_READ
  • Audio Unit Service (Mac OS X)
  • Arts (Linux): MS_ARTS_WRITE, MS_ARTS_READ
  • DirectSound (Windows): MS_WINSNDDS_WRITE, MS_WINSNDDS_READ
  • (raw/wav/pcap ) (Linux): MS_FILE_PLAYER
  • (raw/wav ) (Windows): MS_WINSND_READ
  • (wav ) (Linux): MS_FILE_REC
  • (wav ) (Windows): MS_WINSND_WRITE
  • Mac Audio Unit (Mac OS X)
  • MME (Windows)
  • OSS (Linux): MS_OSS_WRITE, MS_OSS_READ
  • PortAudio (Mac OS X)
  • PulseAudio (Linux): MS_PULSE_WRITE, MS_PULSE_READ
  • Windows Sound (Windows)

/


  • G.711 a-: MS_ALAW_DEC, MS_ALAW_ENC
  • G.711 µ-: MS_ULAW_DEC, MS_ULAW_ENC
  • G.722: MS_G722_DEC, MS_G722_ENC
  • G.726: MS_G726_32_ENC, MS_G726_24_ENC, MS_G726_16_ENC
  • GSM: MS_GSM_DEC, MS_GSM_ENC
  • : MS_L16_ENC, MS_L16_DEC
  • Speex: MS_SPEEX_ENC, MS_SPEEX_DEC


  • (->, ->): MS_CHANNEL_ADAPTER
  • : MS_CONF
  • DTMF: MS_DTMF_GEN
  • (speex): MS_SPEEX_EC
  • : MS_EQUALIZER
  • : MS_MIXER
  • (PLC): MS_GENERIC_PLC
  • : MS_RESAMPLE
  • : MS_TONE_DETECTOR
  • : MS_VOLUME



  • Android
  • Android
  • AV Foundation (iOS)
  • AV Foundation (iOS)
  • DirectShow (Windows)
  • DrawDib (Windows)
  • External —
  • GLX (Linux): MS_GLXVIDEO
  • Mire — Synthetic moving picture: MS_MIRE
  • OpenGL (Mac OS X)
  • OpenGL ES2 (Android)
  • Quicktime (Mac OS X)
  • SDL : MS_SDL_OUT
  • : MS_STATIC_IMAGE
  • Video For Linux (V4L) (Linux): MS_V4L
  • Video For Linux 2 (V4L2) (Linux): MS_V4L2_CAPTURE
  • Video4windows (DirectShow) (Windows)
  • Video4windows (DirectShow) (Windows CE)
  • Video For Windows (vfw) (Windows)
  • XV (Linux)

/


  • H.263, H.263-1998, MP4V-ES, JPEG, MJPEG, Snow: MS_MJPEG_DEC, MS_H263_ENC, MS_H263_DEC
  • H.264 ( ): MS_H264_DEC
  • Theora: MS_THEORA_ENC, MS_THEORA_DEC
  • VP8: MS_VP8_ENC, MS_VP8_DEC


  • JPEG snapshot
  • Pixel format converter: MS_PIX_CONV
  • : MS_ITC_SOURCE, MS_ITC_SINK
  • : MS_JOIN
  • RTP /: MS_RTP_SEND, MS_RTP_RECV
  • : MS_TEE
  • : MS_VOID_SINK
  • : MS_VOID_SOURCE



  • AMR-NB /


  • G.729 /


  • iLBC /


  • SILK /



  • H.264


  • H.264 V4L2 /



, . .


Linux Ubuntu


.


Mediastremer2 Ubuntu . "$" shell . .. , .


, , .


libmediastremer-dev


:


$ sudo apt-get update

, . :


$ sudo apt-get install libmediastreamer-dev

.


deb- 35 . :


$ dpkg -s libmediastreamer-dev

:


Package: libmediastreamer-dev
Status: install ok installed
Priority: optional
Section: libdevel
Installed-Size: 244
Maintainer: Ubuntu Developers <ubuntu-devel-discuss@lists.ubuntu.com>
Architecture: amd64
Source: linphone
Version: 3.6.1-2.5
Depends: libmediastreamer-base3 (= 3.6.1-2.5), libortp-dev
Description: Linphone web phone's media library - development files
Linphone is an audio and video internet phone using the SIP protocol. It
has a GTK+ and console interface, includes a large variety of audio and video
codecs, and provides IM features.
.
This package contains the development libraries for handling media operations.
Original-Maintainer: Debian VoIP Team <pkg-voip-maintainers@lists.alioth.debian.org>
Homepage: http://www.linphone.org/


:


$ sudo apt-get install gcc

, :


$ gcc --version

:


gcc (Ubuntu 5.4.0-6ubuntu1~16.04.12) 5.4.0 20160609
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.


home , mstutorial:


$ mkdir ~/mstutorial

- mstest.c :


#include "stdio.h"
#include <mediastreamer2/mscommon.h>
int main()
{
  ms_init();
  printf ("Mediastreamer is ready.\n");
}

, .


:


$ gcc mstest.c -o mstest `pkg-config mediastreamer --libs --cflags`

,


`pkg-config mediastreamer --libs --cflags`

, "".


, mstest. :


$ ./mstest

:


ALSA lib conf.c:4738:(snd_config_expand) Unknown parameters 0
ALSA lib control.c:954:(snd_ctl_open_noupdate) Invalid CTL default:0
ortp-warning-Could not attach mixer to card: Invalid argument
ALSA lib conf.c:4738:(snd_config_expand) Unknown parameters 0
ALSA lib pcm.c:2266:(snd_pcm_open_noupdate) Unknown PCM default:0
ALSA lib conf.c:4738:(snd_config_expand) Unknown parameters 0
ALSA lib pcm.c:2266:(snd_pcm_open_noupdate) Unknown PCM default:0
ortp-warning-Strange, sound card HDA Intel PCH does not seems to be capable of anything, retrying with plughw...
Mediastreamer is ready.

, ALSA, . , . .


. , , , .


No próximo artigo, criaremos um aplicativo que coleta e inicia o processamento de um sinal de áudio em uma cadeia de vários filtros.

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