How to cleverly avoid delays in mobile live broadcast scenes

For live broadcasts, avoiding delays has always been a difficult bone to chew, but this "bone" has carved out "pits" one after another for the development of mobile live broadcast source code. According to the experience summarized in practice, the video on the mobile platform There are two main aspects of live broadcast: equipment differences, and technical tests brought about by these scenarios in the network environment. So how to effectively avoid these pits, let's take a look at it in detail below.

1. Understand the coding differences on different chip platforms

Regardless of whether it is hard-coded or soft-coded on the iOS platform, since it is made by Apple, there are almost no coding differences due to different chip platforms.
However, on the Android platform, the MediaCodec encoder provided by the Android Framework SDK has very different performance on different chip platforms. Different manufacturers use different chips, and the performance of Android MediaCodec on different chip platforms is slightly different. The cost of achieving full platform compatibility is not low.
In addition, the H.264 encoding image quality parameters at the hard-coded level of Android MediaCodec are a fixed baseline, so the image quality is usually average. Therefore, under the Android platform, it is recommended to use soft editing. The advantage is that the image quality can be adjusted and the compatibility is better.

2. High-performance acquisition and coding on low-end equipment

For example, what the Camera collects and outputs may be pictures, and the volume of a picture is not small. If the acquisition frequency is very high, the encoded frame rate is very high, and each picture passes through the encoder, the encoder may be overloaded.
At this time, you can consider to perform selective frame loss before encoding without affecting the image quality (we talked about the microscopic meaning of the frame rate before), so as to reduce the power consumption of the encoding link.

3. Ensure smooth HD streaming in a weak network environment

In the mobile network, it is usually easy to encounter network instability, the connection is reset, and the connection is disconnected. On the one hand, frequent reconnections require overhead to establish a connection. On the other hand, especially when GPRS / 2G / 3G / 4G handover occurs, bandwidth bottlenecks may appear. When the bandwidth is not enough, the content with higher frame rate/higher bit rate is more difficult to send out. At this time, variable bit rate support is required.
That is, at the push end, the network status and simple speed measurement can be detected, and the bit rate can be dynamically switched to ensure smooth push during network switching.
Secondly, the logic of encoding, packetization, and streaming can also be fine-tuned. You can try to selectively drop frames, such as preferentially dropping video reference frames (not losing I-frames and audio frames), which can also reduce the data content to be transmitted, but At the same time, the goal of not affecting the picture quality and the smoothness of the audiovisual version is achieved.

Doing the above in the development process of the live broadcast source code can cleverly avoid the delay "pits" in the mobile live broadcast scene.

 

 

 

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