ffmpeg read file function call read 函数吗?

Question

ffmpeg read file function call read 函数吗

Answer 1

av_read_frame()的声明位于libavformat\avformat.h，如下所示。/*** Return the next frame of a stream.* This function returns what is stored in the file, and does not validate* that what is there are valid frames for the decoder. It will split what is* stored in the file into frames and return one for each call. It will not* omit invalid data between valid frames so as to give the decoder the maximum* information possible for decoding.** If pkt->buf is NULL, then the packet is valid until the next* av_read_frame() or until avformat_close_input(). Otherwise the packet* is valid indefinitely. In both cases the packet must be freed with* av_free_packet when it is no longer needed. For video, the packet contains* exactly one frame. For audio, it contains an integer number of frames if each* frame has a known fixed size (e.g. PCM or ADPCM data). If the audio frames* have a variable size (e.g. MPEG audio), then it contains one frame.** pkt->pts, pkt->dts and pkt->duration are always set to correct* values in AVStream.time_base units (and guessed if the format cannot* provide them). pkt->pts can be AV_NOPTS_VALUE if the video format* has B-frames, so it is better to rely on pkt->dts if you do not* decompress the payload.** @return 0 if OK, < 0 on error or end of file*/int av_read_frame(AVFormatContext *s, AVPacket *pkt);av_read_frame()使用方法在注释中写得很详细，用中文简单描述一下它的两个参数：s：输入的AVFormatContextpkt：输出的AVPacket如果返回0则说明读取正常。