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SRS librtmp

librtmp is a client side library, seems from rtmpdump.

Use Scenarios

The use scenarios of librtmp:

• Play or suck RTMP stream: For example rtmpdump, dvr RTMP stream to flv file.
• Publish RTMP stream: Publish RTMP stream to server.
• Use sync block socket: It's ok for client.
• ARM: Can used for linux arm, for some embed device, to publish stream to server.

Note: About the openssl, complex and simple handshake, read RTMP protocol

Note: To cross build srs-librtmp for ARM cpu, read srs-arm

librtmp For Server

librtmp or srs-librtmp only for client side application, impossible for server side.

Why SRS provides srs-librtmp

SRS provides different librtmp:

• The code of librtmp is hard to maintain.
• The interface of librtmp is hard to use.
• No example, while srs-librtmp provides lots of examples at trunk/research/librtmp.
• Min depends, SRS extract core/kernel/rtmp modules for srs-librtmp.
• Min library requires, srs-librtmp only depends on stdc++.
• NO ST, srs-librtmp does not depends on st.
• Provides bandwidth api, to get the bandwidth data to server, read Bandwidth Test
• Provides tracable log, to get the information on server of client, read Tracable log

In a word, SRS provides more efficient and simple client library srs-librtmp.

Build srs-librtmp

When make SRS, the srs-librtmp will auto generated when configure with librtmp:

./configure --with-librtmp --without-ssl && make

All examples are built, read Examples.

Note: Recomment to disable ssl, for librtmp does not depends on ssl.

Note: srs-librtmp provides only simple handshake, without complex handshake, eventhough configure with ssl.

When build ok, user can use .h and .a library to build client application.

Build srs-librtmp on Windows

srs-librtmp only depends on libc++, so can be build on windows:

• Build on linux: ./configure --disable-all --with-librtmp && make
• Copy the files to build on windows:

objs/srs_auto_headers.hpp
src/core/*
src/kernel/*
src/rtmp/*
src/libs/*

Note: Donot need ssl and st. Note: SRS2.0 can directly export srs-librtmp to a single project, or .h+.cpp file, read export srs-librtmp.

RTMP packet specification

This section descrips the RTMP packet specification, for the srs-librtmp api to read or write data.

The api about data:

• Read RTMP packet from server: int srs_read_packet(int* type, u_int32_t* timestamp, char** data, int* size)
• Write RTMP packet to server: int srs_write_packet(int type, u_int32_t timestamp, char* data, int size)

The RTMP packet(char* data) for api, is format in flv Video/Audio, read the trunk/doc video_file_format_spec_v10_1.pdf

• Audio data, read E.4.2.1 AUDIODATA，p76, for example, the aac codec audio data.
• Video data, read E.4.3.1 VIDEODATA，p78, for example, the h.264 video data.
• Script data, read E.4.4.1 SCRIPTDATA，p80, for example, onMetadata call.

The RTMP packet type(int type) defines (in E.4.1 FLV Tag，page 75)：

• Audio: 8, the macro SRS_RTMP_TYPE_AUDIO
• Video: 9, the macro SRS_RTMP_TYPE_VIDEO
• Script: 18, the macro SRS_RTMP_TYPE_SCRIPT

Other parameters, for instance, the timestamp, pass by args.

About the flv specification:

• flv header format: E.2 The FLV header，p74。
• flv body format: E.3 The FLV File Body，p74。
• tag tag header: E.4.1 FLV Tag，p75。

Why use flv format as srs-librtmp api data format:

• Flv is simple enough.
• FFMPEG also use flv for rtmp.
• Only need to add flv tag header, then we can write to flv file.
• When publish flv file to server, only need to parse the tag header, the tag body is the data.

Note: SRS2.0 supports directly write h.264 raw stream, read publish h.264 raw data

srs-librtmp Examples

The examples for srs-librtmp, automatically build when build SRS:

• research/librtmp/srs_play.c: Use srs-librtmp to play RTMP stream.
• research/librtmp/srs_publish.c: Use srs-librtmp to publish RTMP stream.
• research/librtmp/srs_ingest_flv.c: Use srs-librtmp to read local flv to publish as RTMP stream.
• research/librtmp/srs_ingest_rtmp.c: Use srs-librtmp to read RTMP then publish as RTMP stream.
• research/librtmp/srs_bandwidth_check.c: Use srs-librtmp to check bandwidth to server.
• research/librtmp/srs_flv_injecter.c: Use srs-librtmp to inject flv keyframes offset for flv vod stream.
• research/librtmp/srs_flv_parser.c: Use srs-librtmp to show the flv file.
• research/librtmp/srs_detect_rtmp.c: Use srs-librtmp to detect the RTMP stream status.

Run Examples

Start SRS:

make && ./objs/srs -c srs.conf 

The publish example:

make && ./objs/research/librtmp/objs/srs_publish rtmp://127.0.0.1:1935/live/livestream

Note: the publish stream send random data, cannot play by player.

The play example:

make && ./objs/research/librtmp/objs/srs_play rtmp://ossrs.net/live/livestreamsuck rtmp stream like rtmpdump

Winlin 2014.11