Illustration: The function avformat_open_input of FFMPEG to open the media

The process of enabling FFMPEG to open a media set starts with avformat_open_input. Therefore, the importance of this function cannot be ignored.

In this function, FFMPEG is completed:

Initialization of the input/output structure AVIOContext;

The input data protocol, such as RTMP or file, is identified by a scoring mechanism.) 1. Determine the suffix of the file name. 2. Read the data from the file header for comparison;

Use the URLProtocol corresponding to the file protocol with the highest score, and use the function pointer to connect with FFMPEG for non-professional terms );

The rest is to call the URLProtocol function for open and read operations.

The following figure shows the function call relationship diagram obtained by debugging FFMPEG source code through eclipse + MinGW.

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It can be seen that all function pointers in the URLProtocol struct are finally called.

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