Video live broadcasting technology: experience summary of low delay live broadcasting

The core idea to solve the problem of low latency: no buffer
Low latency: as the name suggests, it means that the smaller the time difference between the playback end and the streaming end, the better. So how to achieve low latency? One word summary: no buffer

First of all, let's explain the flow direction of video stream: push stream end --- CDN server --- pull stream end

1. No buffer on the push side, that is to ensure the minimum buffer on the push side. This basically ensures that in the case of network jitter or sudden deterioration at the streaming end, it can discard the buffered buffer and continue to push new generated video frames. This ensures that the video content is up-to-date when the network begins to transmit.

2. CDN nobuffer, adjust the configuration of CDN to make the GOP cached by CDN server as less as possible, so as to ensure that the streaming end gets the latest content.

3. The pull side nobuffer. Since the push and transfer CDN have nobuffer set, the meaning of setting nobuffer on the pull side should not be explained too much.

One thing to remember: the solution to the low latency problem is not a matter of one end. The configuration of three ends will affect the effect of latency.

Experience of low delay live broadcast at streaming end (based on ijkplayer)

In the process of live broadcast, there are first delay and content delay. The first start delay can be controlled at about 100ms; the content delay based on RTMP can be controlled at about 2 ~ 5 seconds according to the situation of CDN. Because RTMP is based on TCP protocol, it will be affected by network conditions in the process of playing, resulting in increased delay. By understanding the relevant knowledge of live streaming push and pull, we can know that according to the different control settings of push side (push strategy) and server (cache strategy), we are likely to get the content a few seconds ago (even more than ten seconds), which can be known by comparing the content of pull side and push side. For these contents, the data cached by the CDN server will be pulled over at the streaming end, and the buffer queue becomes larger. Then, the larger the buffer queue, the greater the delay between the pull end and the push end.

The core reason for the delay of the pull end is that the buffer queue becomes larger and the delay of the difference between the content played by the pull end and the push end increases.
terms of settlement:
1. Control max_ buffer_ Size, set Max reasonably_ buffer_ Size, so that the streaming end will not cache the content for a long time (after testing, it is found that it is not very practical, because the content delay can only be achieved by catching up with or discarding the currently played content and quickly skipping to the latest data)
2. Double speed playback is used to consume buffer queue quickly. After the consumption reaches a reasonable range, normal playback is performed (monitor and dynamically control buffer queue, which requires the decoding performance of the device to be able to support).
3. Use packet loss (frame loss) strategy. Strategy description:
In the case of audio stream and video stream, or only audio stream, when the audioq reaches a certain duration, the previous part of the packets will be lost, because the default is av_ SYNC_ AUDIO_ Master, the video will catch up.
Only in the case of video streaming, when the video Q reaches a certain duration, some of the previous packets will be lost.

 

 

 

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:

Our other product:

Professional lightning protection system for Tower	Professional FM Radio Station Equipment Package	FMUSER FU-1000C 1000W FM Transmitter With USB Audio Input Interface
FMUSER 200W FM Radio Broadcasting Package	Hotel IPTV Solution	FMUSER FSN-1000T V5.0 1KW FM Radio Broadcast Transmitter