FFmpeg Decode（解码）

首发地址，会更错

本文来自官方例子doc/examples/decode_audio.c 和 doc/examples/decode_video.c。

FFmpeg解码流程

其中，AVFormatContext、AVPacket等重要的结构体请看：FFmpeg重要结构体（转自雷神） 。

官方例子【Audio】

/**
 * @author 秦城季
 * @email xhunmon@126.com
 * @Blog https://qincji.gitee.io
 * @date 2021/01/06
 * description: 来自官方例子：doc/examples/decode_audio.c  <br>
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

extern "C"{
   
   
#include <libavutil/frame.h>
#include <libavutil/mem.h>

#include <libavcodec/avcodec.h>
}

#define AUDIO_INBUF_SIZE 20480
#define AUDIO_REFILL_THRESH 4096

static void decode(AVCodecContext *dec_ctx, AVPacket *pkt, AVFrame *frame,
                   FILE *outfile)
{
   
   
    int i, ch;
    int ret, data_size;

    //把AVPacket数据送去解码器
    ret = avcodec_send_packet(dec_ctx, pkt);
    if (ret < 0) {
   
   
        fprintf(stderr, "Error submitting the packet to the decoder\n");
        exit(1);
    }

    /* read all the output frames (in general there may be any number of them */
    while (ret >= 0) {
   
   
        //接到解码后的<AVPacket数据>，读取到AVFrame中
        ret = avcodec_receive_frame(dec_ctx, frame);
        if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
            return;
        else if (ret < 0) {
   
   
            fprintf(stderr, "Error during decoding\n");
            exit(1);
        }
        /*下面是得到解码后的裸流数据进行处理，根据裸流数据的特征做相应的处理，如AAC解码后是PCM，h264解码后是YUV等。*/
        data_size = av_get_bytes_per_sample(dec_ctx->sample_fmt);
        if (data_size < 0) {
   
   
            /* This should not occur, checking just for paranoia */
            fprintf(stderr, "Failed to calculate data size\n");
            exit(1);
        }
        for (i = 0; i < frame->nb_samples; i++)
            for (ch = 0; ch < dec_ctx->channels; ch++)
                fwrite(frame->data[ch] + data_size*i, 1, data_size, outfile);
    }
}

int main(int argc, char **argv)
{
   
   
    const char *outfilename, *filename;
    const AVCodec *codec;
    AVCodecContext *c= NULL;
    AVCodecParserContext *parser = NULL;
    int len, ret;
    FILE *f, *outfile;