ffmpeng 读取h264文件

要使用FFmpeg读取H.264文件，您需要使用FFmpeg的API。以下是一些基本的代码示例，可以帮助您开始：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <errno.h>

// FFmpeg libraries
#include <libavformat/avformat.h>
#include <libavcodec/avcodec.h>
#include <libswscale/swscale.h>

int main(int argc, char *argv[]) {
    AVFormatContext *pFormatCtx = NULL;
    AVCodecContext *pCodecCtx = NULL;
    AVCodec *pCodec = NULL;
    AVPacket packet;
    AVFrame *pFrame = NULL;
    int i, videoStream, frameFinished;
    struct SwsContext *sws_ctx = NULL;

    // Open video file
    if (avformat_open_input(&pFormatCtx, argv[1], NULL, NULL) != 0) {
        printf("Error: Could not open input file.\n");
        return -1;
    }

    // Retrieve stream information
    if (avformat_find_stream_info(pFormatCtx, NULL) < 0) {
        printf("Error: Could not find stream information.\n");
        return -1;
    }

    // Find the first video stream
    videoStream = -1;
    for (i = 0; i < pFormatCtx->nb_streams; i++) {
        if (pFormatCtx->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
            videoStream = i;
            break;
        }
    }
    if (videoStream == -1) {
        printf("Error: Could not find video stream.\n");
        return -1;
    }

    // Get a pointer to the codec context for the video stream
    pCodecCtx = avcodec_alloc_context3(NULL);
    if (pCodecCtx == NULL) {
        printf("Error: Could not allocate codec context.\n");
        return -1;
    }
    avcodec_parameters_to_context(pCodecCtx, pFormatCtx->streams[videoStream]->codecpar);

    // Find the decoder for the video stream
    pCodec = avcodec_find_decoder(pCodecCtx->codec_id);
    if (pCodec == NULL) {
        printf("Error: Unsupported codec.\n");
        return -1;
    }

    // Open codec
    if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0) {
        printf("Error: Could not open codec.\n");
        return -1;
    }

    // Allocate video frame
    pFrame = av_frame_alloc();
    if (pFrame == NULL) {
        printf("Error: Could not allocate video frame.\n");
        return -1;
    }

    // Read frames and convert to RGB
    while (av_read_frame(pFormatCtx, &packet) >= 0) {
        // Is this a packet from the video stream?
        if (packet.stream_index == videoStream) {
            // Decode video frame
            avcodec_send_packet(pCodecCtx, &packet);
            while (avcodec_receive_frame(pCodecCtx, pFrame) == 0) {
                // Convert the image from its native format to RGB
                sws_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt,
                                         pCodecCtx->width, pCodecCtx->height, AV_PIX_FMT_RGB24,
                                         SWS_BILINEAR, NULL, NULL, NULL);
                if (sws_ctx == NULL) {
                    printf("Error: Could not initialize conversion context.\n");
                    return -1;
                }
                sws_scale(sws_ctx, pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pFrameRGB->data, pFrameRGB->linesize);
                sws_freeContext(sws_ctx);
            }
        }
        av_packet_unref(&packet);
    }

    // Free resources
    av_frame_free(&pFrame);
    avcodec_close(pCodecCtx);
    avformat_close_input(&pFormatCtx);

    return 0;
}

这个例子假设您已经安装了FFmpeg，并且具有H.264解码器。如果没有，请先安装FFmpeg和H.264解码器。