1. The status quo
In the era of national live broadcast, anyone can pick up the device in their hands to broadcast live. The live broadcast brings jobs to a group of people, and brings huge benefits to major live broadcast platforms. It must have high quality in the face of a huge market. Only low-cost live broadcast technology can stand out from the competition and become a leader in the live broadcast industry. Five key processes of live video streaming: 1. Recording 2. Encoding 3. Network transmission 4. Decoding 5. Playback. Each of these links will affect the quality and delay time of the live broadcast. Below we will mainly talk about the third point of optimizing the delay.
The current live broadcast technology generally uses protocols such as RTMP, HLS, HDL (HTTP-FLV), and RTP. The most common protocol among these protocols is the rtmp protocol. Now many live broadcast platforms in China are still in use, and there is also HLS. It is also a very many agreement. Make some brief introductions to the above-mentioned agreements.
2. Agreement
(1) RTMP protocol
It is a patent agreement of Adobe, which is not supported by most foreign CDNs. Popularity in the country is very high. There are several reasons:
1) The support of open source software and open source libraries is stable and complete. For example, OBS software commonly used by Douyu anchors, open source librtmp library, and nginx-rtmp plug-in on the server side.
2) The installation rate of the player is high. As long as the browser supports FlashPlayer, RTMP live broadcast can be played very easily, and the detailed protocol can be understood by Google. Compared with other protocols, the handshake process is too complicated when the RTMP protocol establishes a connection for the first time (the bottom layer is based on TCP, here is the interaction of the RTMP protocol itself), depending on different network conditions, it will bring more than 100ms delay to the first opening. RTMP-based live broadcasts generally have a delay of 2 to 5 seconds.
(2) HTTP-FLV protocol
That is, use HTTP protocol to stream media content. Compared to RTMP, HTTP is simpler and well-known, and there is no fear of being kidnapped by Adobe's patents. The content delay can also be achieved for 2~5 seconds, and the opening speed is faster, because HTTP itself does not have complex state interaction. So from the perspective of latency, HTTP-FLV is better than RTMP.
(3) HLS agreement
HLS stands for Http Live Streaming, which is a streaming media transmission protocol based on HTTP proposed by Apple. HLS has a very big advantage: HTML5 can be opened and played directly; this means that a live link can be forwarded and shared through WeChat, etc., without installing any independent APP, just a browser, so it is very popular. Social live streaming APP, HLS can be said to be just needed, let's analyze its principles. To
The basic principle of HLS is that when the collection and push end pushes the video stream to the streaming media server, the server will buffer the received stream information into a new ts file every time it is cached for a period of time, and the server will create an m3u8 index file to Maintain the index of the latest ts fragments. When the player gets the live broadcast, it obtains the latest ts video file fragments from the m3u8 index file to play, so as to ensure that the user will see newer content whenever he connects in, realizing a similar live broadcast experience. Compared with common live streaming protocols, such as RTMP and RTSP, the biggest difference of HLS is that what the live broadcast client gets is not a complete data stream, but a continuous, short-duration media file. Download and play these small files. The theoretical minimum delay of this method is the duration of one ts file, and generally the duration of 2-3 ts files. HLS's segmentation strategy is basically recommended to be a segment of 10 seconds
(4) RTP protocol
RTP is Real-time Transport Protocol, a transport layer protocol for multimedia data streaming on the Internet. In actual application scenarios, RTCP (RTP Control Protocol) is often required to be used together. It can be simply understood as RTCP transmits interactive control signaling, and RTP transmits actual media data. To
RTP has a wide range of applications in video surveillance, video conferencing, and IP telephony, because an important experience in video conferencing and IP telephony: real-time content.
Compared with the above three or actually two protocols, there is an important difference between RTP and them that the default is to use UDP protocol to transmit data, while RTMP and HTTP are based on TCP protocol transmission. Why can UDP achieve such real-time effects? I searched a lot of articles about the analysis of the difference between TCP and UDP. I won’t repeat them here, but briefly summarize:
1) UDP: A single datagram, no need to establish a connection, simple, unreliable, packet loss, and disorder;
2) TCP: streaming, need to establish a connection, complex, reliable, and orderly. To
The scene of real-time audio and video streaming does not need to be reliably guaranteed, so there is no need to have a retransmission mechanism. Real-time viewing of images and sounds, some content lost when the network shakes, blurry and blurred screens are completely unimportant. TCP will cause delay and unsynchronization for retransmission. If a certain content is retransmitted and will arrive after 1 second, then the entire conversation will be delayed by 1 second. As the network jitters, the delay will increase to 2 seconds or 3 Seconds, if the client's playback is not processed, it will seriously affect the live broadcast experience. To
To sum up: In the choice of live broadcast protocol, if you choose RTMP or HTTP-FLV, it means that there is a content delay of 2~5 seconds, but when the delay is turned on, HTTP-FLV is better than RTMP. HLS has a content delay of 5-7 seconds. Selecting RTP for live broadcast can achieve a live broadcast delay within 1 second. But as far as I know, the major CDN manufacturers do not support RTP-based live broadcast, so the current domestic mainstream is still RTMP or HTTP-FLV, and there is also the emerging HLS.
(5) Comparison of HLS and RTMP
1) HLS
① Disadvantages of HLS:
Generally, the HLS live broadcast delay will reach 20-30s, and high delay is unacceptable for live broadcasts that require real-time interactive experience.
HLS is based on short connection HTTP, HTTP is based on TCP, which means that HLS needs to continuously establish a connection with the server. TCP three-way handshake every time a connection is established, slow start process, and four waves of hands when disconnecting will cause consumption .
② Advantages of HLS:
Data is transmitted via HTTP protocol, so there is no need to consider firewall or proxy issues when using HLS.
Using short-duration fragmented files for playback, the client can smoothly switch the bit rate to adapt to playback under different bandwidth conditions.
HLS is a streaming media protocol launched by Apple. It can be naturally supported on the iOS platform. It can be played directly by using the AVPlayer provided by the system, without having to develop a player by itself.
2) RTMP
Compared with HLS, when the RTMP protocol is adopted, it is a data stream from the collection and push end to the streaming media server and then to the playback end, so there will be no landing files on the server. In this way, RTMP has these advantages relatively:
① The delay is small, usually 1-3s.
② Based on TCP long connection, there is no need to establish a connection multiple times.
Therefore, most live broadcast services in the industry will choose RTMP as the streaming media protocol. Usually the data stream is encapsulated into FLV and provided through HTTP. However, there are some problems that need to be resolved:
① The iOS platform does not provide a player that natively supports RTMP or HTTP-FLV, which requires the development of a player that supports related protocols.
3.HLS delay optimization
The delay of hls is mainly composed of the following three parts:
(1) The time for the server-side encoder and stream splitter to generate TS files
(2) The time for the client to download the TS file, and usually requires two TS media files to be downloaded
(3) Client decode and play time
|
|
|
|
How far(long) the transmitter cover?
The transmission range depends on many factors. The true distance is based on the antenna installing height , antenna gain, using environment like building and other obstructions , sensitivity of the receiver, antenna of the receiver . Installing antenna more high and using in the countryside , the distance will much more far.
EXAMPLE 5W FM Transmitter use in the city and hometown:
I have a USA customer use 5W fm transmitter with GP antenna in his hometown ,and he test it with a car, it cover 10km(6.21mile).
I test the 5W fm transmitter with GP antenna in my hometown ,it cover about 2km(1.24mile).
I test the 5W fm transmitter with GP antenna in Guangzhou city ,it cover about only 300meter(984ft).
Below are the approximate range of different power FM Transmitters. ( The range is diameter )
0.1W ~ 5W FM Transmitter ：100M ~1KM
5W ~15W FM Ttransmitter : 1KM ~ 3KM
15W ~ 80W FM Transmitter : 3KM ~10KM
80W ~500W FM Transmitter : 10KM ~30KM
500W ~1000W FM Transmitter : 30KM ~ 50KM
1KW ~ 2KW FM Transmitter : 50KM ~100KM
2KW ~5KW FM Transmitter : 100KM ~150KM
5KW ~10KW FM Transmitter : 150KM ~200KM
How to contact us for the transmitter?
Call me +8618078869184 OR
Email me [email protected]
1.How far you want to cover in diameter ?
2.How tall of you tower ?
3.Where are you from ?
And we will give you more professional advice.
About Us
FMUSER.ORG is a system integration company focusing on RF wireless transmission / studio video audio equipment / streaming and data processing .We are providing everything from advice and consultancy through rack integration to installation, commissioning and training.
We offer FM Transmitter, Analog TV Transmitter, Digital TV transmitter, VHF UHF Transmitter, Antennas, Coaxial Cable Connectors, STL, On Air Processing, Broadcast Products for the Studio, RF Signal Monitoring, RDS Encoders, Audio Processors and Remote Site Control Units, IPTV Products, Video / Audio Encoder / Decoder, designed to meet the needs of both large international broadcast networks and small private stations alike.
Our solution has FM Radio Station / Analog TV Station / Digital TV Station / Audio Video Studio Equipment / Studio Transmitter Link / Transmitter Telemetry System / Hotel TV System / IPTV Live Broadcasting / Streaming Live Broadcast / Video Conference / CATV Broadcasting system.
We are using advanced technology products for all the systems, because we know the high reliability and high performance are so important for the system and solution . At the same time we also have to make sure our products system with a very reasonable price.
We have customers of public and commercial broadcasters, telecom operators and regulation authorities , and we also offer solution and products to many hundreds of smaller, local and community broadcasters .
FMUSER.ORG has been exporting more than 15 years and have clients all over the world. With 13 years experience in this field ,we have a professional team to solve customer's all kinds of problems. We dedicated in supplying the extremely reasonable pricing of professional products & services. Contact email : [email protected]
Our Factory
We have modernization of the factory . You are welcome to visit our factory when you come to China.
At present , there are already 1095 customers around the world visited our Guangzhou Tianhe office . If you come to China , you are welcome to visit us .
At Fair
This is our participation in 2012 Global Sources Hong Kong Electronics Fair . Customers from all over the world finally have a chance to get together.
Where is Fmuser ?
You can search this numbers " 23.127460034623816,113.33224654197693 " in google map , then you can find our fmuser office .
FMUSER Guangzhou office is in Tianhe District which is the center of the Canton . Very near to the Canton Fair , guangzhou railway station, xiaobei road and dashatou , only need 10 minutes if take TAXI . Welcome friends around the world to visit and negotiate .
Contact: Sky Blue
Cellphone: +8618078869184
WhatsApp: +8618078869184
Wechat: +8618078869184
E-mail: [email protected]
QQ: 727926717
Skype: sky198710021
Address: No.305 Room HuiLan Building No.273 Huanpu Road Guangzhou China Zip:510620
|
|
|
|
English: We accept all payments , such as PayPal, Credit Card, Western Union, Alipay, Money Bookers, T/T, LC, DP, DA, OA, Payoneer, If you have any question , please contact me [email protected] or WhatsApp +8618078869184
-
PayPal.  www.paypal.com
We recommend you use Paypal to buy our items ,The Paypal is a secure way to buy on internet .
Every of our item list page bottom on top have a paypal logo to pay.
Credit Card.If you do not have paypal,but you have credit card,you also can click the Yellow PayPal button to pay with your credit card.
---------------------------------------------------------------------
But if you have not a credit card and not have a paypal account or difficult to got a paypal accout ,You can use the following:
Western Union.  www.westernunion.com
Pay by Western Union to me :
First name/Given name: Yingfeng
Last name/Surname/ Family name: Zhang
Full name: Yingfeng Zhang
Country: China
City: Guangzhou
|
---------------------------------------------------------------------
T/T . Pay by T/T (wire transfer/ Telegraphic Transfer/ Bank Transfer)
First BANK INFORMATION (COMPANY ACCOUNT):
SWIFT BIC: BKCHHKHHXXX
Bank name: BANK OF CHINA (HONG KONG) LIMITED, HONG KONG
Bank Address: BANK OF CHINA TOWER, 1 GARDEN ROAD, CENTRAL, HONG KONG
BANK CODE: 012
Account Name : FMUSER INTERNATIONAL GROUP LIMITED
Account NO. : 012-676-2-007855-0
---------------------------------------------------------------------
Second BANK INFORMATION (COMPANY ACCOUNT):
Beneficiary: Fmuser International Group Inc
Account Number: 44050158090900000337
Beneficiary's Bank: China Construction Bank Guangdong Branch
SWIFT Code: PCBCCNBJGDX
Address: NO.553 Tianhe Road, Guangzhou, Guangdong,Tianhe District, China
**Note: When you transfer money to our bank account, please DO NOT write anything in the remark area, otherwise we won't be able to receive the payment due to government policy on international trade business.
|
|
|
|
* It will be sent in 1-2 working days when payment clear.
* We will send it to your paypal address. If you want to change address, please send your correct address and phone number to my email [email protected]
* If the packages is below 2kg,we will be shipped via post airmail, it will take about 15-25days to your hand.
If the package is more than 2kg,we will ship via EMS , DHL , UPS, Fedex fast express delivery,it will take about 7~15days to your hand.
If the package more than 100kg , we will send via DHL or air freight. It will take about 3~7days to your hand.
All the packages are form China guangzhou.
* Package will be sent as a "gift" and declear as less as possible,buyer don't need to pay for "TAX".
* After ship, we will send you an E-mail and give you the tracking number.
|
|
|
For Warranty .
Contact US--->>Return the item to us--->>Receive and send another replace .
Name: Liu xiaoxia
Address: 305Fang HuiLanGe HuangPuDaDaoXi 273Hao TianHeQu Guangzhou China.
ZIP:510620
Phone: +8618078869184
Please return to this address and write your paypal address,name,problem on note: |
|
