ffmpeg 编码程序

FFmpeg是一个开源的跨平台音视频编解码库和工具集，可用于录制、转换和流式传输音视频文件。以下是一个简单的FFmpeg编码程序示例，将输入文件转换为H.264格式的输出文件：

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

extern "C" {
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libswscale/swscale.h"
#include "libavutil/imgutils.h"
}

int main(int argc, char** argv) {
    AVFormatContext *pFormatCtx;
    AVCodecContext *pCodecCtx;
    AVCodec *pCodec;
    AVFrame *pFrame, *pFrameRGB;
    AVPacket packet;
    int frameFinished;
    int numBytes;
    uint8_t *buffer;

    if (argc < 3) {
        printf("Usage: %s <input file> <output file>\n", argv[0]);
        return -1;
    }

    av_register_all();

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

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

    av_dump_format(pFormatCtx, 0, argv[1], 0);

    int videoStream = -1;

    for (int i = 0; i < pFormatCtx->nb_streams; i++) {
        if (pFormatCtx->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
            videoStream = i;
            break;
        }
    }

    if (videoStream == -1) {
        printf("Could not find video stream.\n");
        return -1;
    }

    pCodecCtx = avcodec_alloc_context3(NULL);
    avcodec_parameters_to_context(pCodecCtx, pFormatCtx->streams[videoStream]->codecpar);
    pCodec = avcodec_find_decoder(pCodecCtx->codec_id);

    if (pCodec == NULL) {
        printf("Unsupported codec.\n");
        return -1;
    }

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

    pFrame = av_frame_alloc();
    pFrameRGB = av_frame_alloc();

    if (pFrame == NULL || pFrameRGB == NULL) {
        printf("Could not allocate frames.\n");
        return -1;
    }

    numBytes = av_image_get_buffer_size(AV_PIX_FMT_RGB24, pCodecCtx->width, pCodecCtx->height, 1);
    buffer = (uint8_t*)av_malloc(numBytes * sizeof(uint8_t));

    if (buffer == NULL) {
        printf("Could not allocate buffer.\n");
        return -1;
    }

    av_image_fill_arrays(pFrameRGB->data, pFrameRGB->linesize, buffer, AV_PIX_FMT_RGB24, pCodecCtx->width, pCodecCtx->height, 1);

    int frameCount = 0;

    FILE *fp = fopen(argv[2], "wb");

    if (fp == NULL) {
        printf("Could not open output file.\n");
        return -1;
    }

    struct SwsContext *sws_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height,
        pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height,
        AV_PIX_FMT_RGB24, SWS_BILINEAR, NULL, NULL, NULL);

    while (av_read_frame(pFormatCtx, &packet) >= 0) {
        if (packet.stream_index == videoStream) {
            avcodec_send_packet(pCodecCtx, &packet);

            while (avcodec_receive_frame(pCodecCtx, pFrame) == 0) {
                sws_scale(sws_ctx, (uint8_t const * const *)pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pFrameRGB->data, pFrameRGB->linesize);

                int y_size = pCodecCtx->width * pCodecCtx->height;
                fwrite(pFrameRGB->data[0], 1, y_size * 3, fp);

                frameCount++;
            }

            av_packet_unref(&packet);
        }
    }

    sws_freeContext(sws_ctx);
    fclose(fp);

    av_frame_free(&pFrame);
    av_frame_free(&pFrameRGB);
    avcodec_close(pCodecCtx);
    avformat_close_input(&pFormatCtx);

    printf("Converted %d frames.\n", frameCount);

    return 0;
}

以上示例代码仅供参考，并不能保证完全可用和正确。如果您需要使用FFmpeg进行音视频编解码，请仔细阅读官方文档，并参考更多示例代码。