Recently made an Android project to use the encoding and decoding function. The general requirements are: take a video through the camera, then extract frames, generate a short video, and reverse video. At the beginning, it directly uses H.264 encoding format, without using MP4 container packaging. After doing these functions, I feel that MP4 format is more compatible with all models and reduces bugs. Take an obvious example: when Android is hard coded, the combination of mediacodec and mediaextractor is often used. However, if you use the H.264 naked video file, the setsource function of mediaextractor will report an exception. It can't parse the video file on some models (such as Meizu Note2, system is 5.1).
After getting the general requirements, we initially used ffmpeg to do video codec, so-called software codec. Due to the slow processing speed and the need for fast display after decoding, the scheme can not achieve our desired effect (a ffmpeg video decoding and saved as JPEG example: https://github.com/xiaoxiaoqingyi/ffmpeg-android-video-decoder )。 But it also has some advantages, such as good compatibility and color conversion. After all, it's not hardware codec (so many models in China, you know). Secondly, ffmpeg can output the specified frame, while mediacodec can't output the specified frame. You need to input several frames to the decoder to decode one frame. At present, I still haven't found a scheme to input a frame and solve a frame, which God knows can guide.
In the case of software codec is not suitable, we can only consider using hardware codec. A few days ago, I attended the Tencent 2017live live Developer Conference and learned that most of the live broadcast now uses hardware to encode and decode. Just said, some models can't use mediaextractor to parse H.264 files. In order to be compatible with most models, they need to parse them by themselves. By analyzing each byte of the H.264 file, they can distinguish the position of each frame and what type of frame it is. To achieve this requirement, first of all, the data obtained from the camera is set to nv21 format if camera is used, but some people use Camera2 and the format is image. No matter which format it is, it needs to be converted to yuv420sp or yuv420p (Note: when transcoding, it's better to use JNI, use C / C + + to convert the format, the efficiency will be many times higher), so that it can be encoded by mediacodec, and then save the H.264 file. When creating an instance of mediacodec, in addition to setting the required parameters, you should also pay attention to some aspects, such as which encoder to choose. Generally, you will choose the following:
MediaCodec.createEncoderByType ("video/avc");
This seems to be no problem. The basic principle is to get the best encoder, the first one in the Android system's encoder registry, which is usually hardware decoding (mediacodec can also call software codec). In fact, it's not very reliable to create an encoder in this way. Although the official website also recommends it, in many domestic android models, some mobile phones will have problems, some codes will have a blue screen, and some will flash back directly. There is a foreign example, which roughly means to obtain the "video / AVC" type encoder first, and then test one by one through try catch. If there is no problem, choose this encoder. Source code: mediacodec_ rtsp_ h264
Another problem is that when I-frame interval is set, some mobile phones do not work. The settings are as follows:
mediaFormat.setInteger ( MediaFormat.KEY_ I_ FRAME_ INTERVAL, interval);
In view of this situation, we need to use another way to set the I frame, which is mandatory setting:
Bundle params = new Bundle();
params.putInt ( MediaCodec.PARAMETER_ KEY_ REQUEST_ SYNC_ FRAME, 0);
mMediaCodec.setParameters (params);
In encoding and decoding, when all the data are input into the codec, remember to input the end character, then the codec will output all the frames.
There is also a frame extraction problem. If mediacodec is used to extract frames, a new video will be generated. Can I just remove the frame from the H.264 file? It doesn't work like this. There's usually a splash screen. This needs to re input the H.264 file to the decoder, and then get the frame you want, and then input it into a new encoder to generate the H.264 file you want. There is also a format problem here. It is not that the data decoded from the decoder can be directly encoded by the encoder. Some mobile phones can, and some will have blue screen or even flash back. In this case, we need to unify the format of the decoder. If you use this form to get:
mMediaCodec.getOutputBuffer ()
There are all kinds of formats out there, and it's hard for you to be compatible. Google has launched a new format:
mMediaCodec.getOutputImage (outIndex)
The result is an image object, which can be saved as a JPEG image or converted to nv21, like the shooting part above, converted to YUV422 format, and then input to the encoder. So no matter what model can be compatible (I try more than 10 different manufacturers of mobile phones), although a lot of detours.
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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
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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
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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.
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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
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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
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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.
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* 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.
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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: |
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