c++ 使用ffmpeg实现h264硬编码代码

以下是使用FFmpeg实现H.264硬编码的C++代码示例：

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

extern "C" {
    #include <libavcodec/avcodec.h>
    #include <libavformat/avformat.h>
    #include <libavutil/opt.h>
    #include <libavutil/imgutils.h>
}

#define INBUF_SIZE 4096

int main(int argc, char **argv) {
    AVCodec *codec;
    AVCodecContext *codec_context = NULL;
    int ret, i, j, k, got_output;
    FILE *f;
    AVFrame *frame;
    AVPacket pkt;
    uint8_t inbuf[INBUF_SIZE + AV_INPUT_BUFFER_PADDING_SIZE];
    AVFormatContext *format_context = NULL;
    AVStream *stream = NULL;
    AVIOContext *io_context = NULL;

    if (argc <= 2) {
        std::cout << "Usage: " << argv[0] << " <input file> <output file>" << std::endl;
        return 0;
    }

    av_register_all();
    avcodec_register_all();

    // Open input file
    if (avformat_open_input(&format_context, argv[1], NULL, NULL) < 0) {
        std::cerr << "Could not open input file" << std::endl;
        return -1;
    }

    // Find stream info
    if (avformat_find_stream_info(format_context, NULL) < 0) {
        std::cerr << "Could not find stream info" << std::endl;
        return -1;
    }

    // Find video stream
    for (i = 0; i < format_context->nb_streams; i++) {
        if (format_context->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
            stream = format_context->streams[i];
            break;
        }
    }

    if (stream == NULL) {
        std::cerr << "Could not find video stream" << std::endl;
        return -1;
    }

    // Find decoder
    codec = avcodec_find_decoder(stream->codecpar->codec_id);
    if (codec == NULL) {
        std::cerr << "Could not find codec" << std::endl;
        return -1;
    }

    // Allocate codec context
    codec_context = avcodec_alloc_context3(codec);
    if (codec_context == NULL) {
        std::cerr << "Could not allocate codec context" << std::endl;
        return -1;
    }

    // Fill codec context with stream parameters
    if (avcodec_parameters_to_context(codec_context, stream->codecpar) < 0) {
        std::cerr << "Could not fill codec context with stream parameters" << std::endl;
        return -1;
    }

    // Open codec
    if (avcodec_open2(codec_context, codec, NULL) < 0) {
        std::cerr << "Could not open codec" << std::endl;
        return -1;
    }

    // Open output file
    if (avio_open(&io_context, argv[2], AVIO_FLAG_WRITE) < 0) {
        std::cerr << "Could not open output file" << std::endl;
        return -1;
    }

    // Allocate frame
    frame = av_frame_alloc();
    if (frame == NULL) {
        std::cerr << "Could not allocate frame" << std::endl;
        return -1;
    }

    // Initialize packet
    av_init_packet(&pkt);
    pkt.data = NULL;
    pkt.size = 0;

    // Read frames from input file
    while (av_read_frame(format_context, &pkt) >= 0) {
        // Decode frame
        ret = avcodec_send_packet(codec_context, &pkt);
        if (ret < 0) {
            std::cerr << "Error decoding frame" << std::endl;
            break;
        }

        while (ret >= 0) {
            ret = avcodec_receive_frame(codec_context, frame);
            if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
                break;
            } else if (ret < 0) {
                std::cerr << "Error decoding frame" << std::endl;
                break;
            }

            // Convert frame to YUV420P format
            AVFrame *tmp_frame = av_frame_alloc();
            if (tmp_frame == NULL) {
                std::cerr << "Could not allocate temporary frame" << std::endl;
                break;
            }

            tmp_frame->format = AV_PIX_FMT_YUV420P;
            tmp_frame->width = codec_context->width;
            tmp_frame->height = codec_context->height;

            ret = av_frame_get_buffer(tmp_frame, 32);
            if (ret < 0) {
                std::cerr << "Could not allocate temporary frame data" << std::endl;
                break;
            }

            ret = av_frame_copy(tmp_frame, frame);
            if (ret < 0) {
                std::cerr << "Error copying frame data" << std::endl;
                break;
            }

            ret = av_frame_copy_props(tmp_frame, frame);
            if (ret < 0) {
                std::cerr << "Error copying frame props" << std::endl;
                break;
            }

            // Encode frame
            ret = avcodec_send_frame(codec_context, tmp_frame);
            if (ret < 0) {
                std::cerr << "Error encoding frame" << std::endl;
                break;
            }

            while (ret >= 0) {
                AVPacket outpkt;
                av_init_packet(&outpkt);
                outpkt.data = NULL;
                outpkt.size = 0;

                ret = avcodec_receive_packet(codec_context, &outpkt);
                if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
                    break;
                } else if (ret < 0) {
                    std::cerr << "Error encoding frame" << std::endl;
                    break;
                }

                // Write packet to output file
                avio_write(io_context, outpkt.data, outpkt.size);
                av_packet_unref(&outpkt);
            }

            av_frame_free(&tmp_frame);
        }

        av_packet_unref(&pkt);
    }

    // Flush encoder
    ret = avcodec_send_frame(codec_context, NULL);
    if (ret < 0) {
        std::cerr << "Error flushing encoder" << std::endl;
        return -1;
    }

    while (ret >= 0) {
        AVPacket outpkt;
        av_init_packet(&outpkt);
        outpkt.data = NULL;
        outpkt.size = 0;

        ret = avcodec_receive_packet(codec_context, &outpkt);
        if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
            break;
        } else if (ret < 0) {
            std::cerr << "Error flushing encoder" << std::endl;
            return -1;
        }

        // Write packet to output file
        avio_write(io_context, outpkt.data, outpkt.size);
        av_packet_unref(&outpkt);
    }

    // Close output file
    avio_close(io_context);

    // Free resources
    avcodec_free_context(&codec_context);
    av_frame_free(&frame);
    avformat_close_input(&format_context);

    return 0;
}

此代码使用FFmpeg库打开输入文件，并将其解码为AVFrame。然后，它将AVFrame转换为YUV420P格式，将其编码为H.264并将其写入输出文件。