1. Steps to realize screen recording and push streaming
1) Collect data
It is mainly to collect the screen to obtain video data, and to collect the microphone to obtain audio data. If it can be realized, we can also collect some built-in audio data of the application.
2) Data format conversion
It is mainly to convert the obtained video and audio into a common standard format of push streaming, which can ensure that the viewing terminal can watch normally.
3) Encoding
If it is not encoded, the amount of data will be very large, which not only wastes bandwidth, but also wastes the performance of the viewing terminal, so it is necessary to encode audio and video data.
4) Packet & Push
This piece of logic can be encapsulated and streamed in a common live broadcast method.
Summary: Actually, the difference between the screen-recording push-streaming live broadcast and the ordinary live broadcast is that the collection source has changed, and at the technical level, what we really need to do is to process the data obtained from the screen-recording into a stable encoding format.
2, Android's idea of realizing the screen recording function
Android's technical solutions to achieve the function of screen recording are mainly the following two at this stage:
1) Under Android 5.0, obtain root permission and use the adb shell screenrecord command function to record.
2) Above Android5.0, use system Api functions: MediaProjection and VirtualDisplay.
The current mainstream implementation and use of ideas are: MediaProjection + VirtualDisplay method.
In fact, the underlying implementation mechanism of these two methods is the same, because before 5.0, Google may have a certain risk of recording the screen function, so this function has not been opened. After the release of Android 5.0, Google opened the screen capture interface, and we can use VirtualDisplay to obtain the video source data of the screen recording.
When writing the App, if you don't want the pages of some applications to be captured by the screen recording software, you can add the WindowManager.LayoutParams.FLAG_SECURE property to the code of the page where it is located.
1) Use the command line to record the screen
Below Android 5.0, we can use the adb shell screencap command to take screenshots, and use adb shell screenrecord to record the screen.
Here we talk about how to use the command line to record the screen:
(1). Basic use
adb shell screenrecord /sdcard/demo.mp4
Command description: Record the phone screen, the video format is mp4, and store it in the phone's sd card. The default recording time is 180s.
(2). Limit the recording time
Parameters: --time-limit
adb shell screenrecord --time-limit 10 /sdcard/demo.mp4
Command description: limit the video recording time to 10s, if not limited, the default is 180s
(3). Specify the video resolution size:
Parameters: --size
adb shell screenrecord --size 1280*720 /sdcard/demo.mp4
Command description: Record video with a resolution of 1280*720. If you do not specify the default resolution of the mobile phone, for best results, please use the size supported by the Advanced Video Coding (AVC) on the device
(4). Specify the bit rate of the video:
Parameters: --bit-rate
adb shell screenrecord --bit-rate 6000000 /sdcard/demo.mp4
Command description: Specify the bit rate of the video to be 6Mbps, if not specified, the default is 4Mbps. You can increase the bit rate to improve the video quality or reduce the bit rate in order to make the file smaller
Remarks:
1. This recording method does not support sound and needs to be recorded separately.
2. The use of this command requires Root permission, which limits its use to a large extent.
3. As the version of Android continues to upgrade, we recommend using the MediaProjection class for screen recording.
4. Use MediaProjection+VirtualDiaplay to record the screen
