qt ffmpeg C++ 对磁盘指定文件视频进行h264编码

要对磁盘上的视频文件进行编码，需要做一些修改以读取视频文件并将编码后的数据写入新的文件中。以下是一个示例代码，演示了如何对指定的视频文件进行编码：

#include <QtCore/QCoreApplication>
#include <QDebug>

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

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    // Open input file
    AVFormatContext *inputContext;
    avformat_open_input(&inputContext, "input.mp4", NULL, NULL);
    avformat_find_stream_info(inputContext, NULL);

    // Find video stream
    int videoStreamIdx = -1;
    for (int i = 0; i < inputContext->nb_streams; i++) {
        if (inputContext->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
            videoStreamIdx = i;
            break;
        }
    }
    if (videoStreamIdx == -1) {
        qWarning() << "No video stream found in input file!";
        return -1;
    }

    // Set up codec parameters
    AVCodecParameters *codecParams = inputContext->streams[videoStreamIdx]->codecpar;
    codecParams->codec_id = AV_CODEC_ID_H264;
    codecParams->bit_rate = 400000;

    // Set up output file
    AVFormatContext *outputContext;
    avformat_alloc_output_context2(&outputContext, NULL, NULL, "output.mp4");
    AVStream *outputStream = avformat_new_stream(outputContext, NULL);
    outputStream->codecpar = codecParams;

    // Open codec
    AVCodec *codec = avcodec_find_encoder(codecParams->codec_id);
    AVCodecContext *codecContext = avcodec_alloc_context3(codec);
    avcodec_parameters_to_context(codecContext, codecParams);
    avcodec_open2(codecContext, codec, NULL);

    // Open output file
    avio_open(&outputContext->pb, "output.mp4", AVIO_FLAG_WRITE);
    avformat_write_header(outputContext, NULL);

    // Set up scaling context
    SwsContext *imgConvertCtx = sws_getContext(codecParams->width, codecParams->height, codecParams->format,
                                               codecParams->width, codecParams->height, codecParams->format,
                                               SWS_BICUBIC, NULL, NULL, NULL);

    // Loop through frames
    AVPacket *inputPacket = av_packet_alloc();
    AVFrame *inputFrame = av_frame_alloc();
    AVPacket *outputPacket = av_packet_alloc();
    while (av_read_frame(inputContext, inputPacket) >= 0) {
        if (inputPacket->stream_index == videoStreamIdx) {
            // Decode frame
            avcodec_send_packet(codecContext, inputPacket);
            avcodec_receive_frame(codecContext, inputFrame);

            // Convert frame to codec format
            AVFrame *outputFrame = av_frame_alloc();
            outputFrame->width = codecParams->width;
            outputFrame->height = codecParams->height;
            outputFrame->format = codecParams->format;
            av_image_alloc(outputFrame->data, outputFrame->linesize, codecParams->width, codecParams->height, codecParams->format, 32);
            sws_scale(imgConvertCtx, inputFrame->data, inputFrame->linesize, 0, codecParams->height,
                      outputFrame->data, outputFrame->linesize);

            // Encode frame
            avcodec_send_frame(codecContext, outputFrame);
            avcodec_receive_packet(codecContext, outputPacket);

            // Write encoded frame to output file
            av_interleaved_write_frame(outputContext, outputPacket);

            // Clean up
            av_packet_unref(outputPacket);
            av_frame_unref(outputFrame);
        }
        av_packet_unref(inputPacket);
    }

    // Flush codec
    avcodec_send_frame(codecContext, NULL);
    while (avcodec_receive_packet(codecContext, outputPacket) == 0) {
        av_interleaved_write_frame(outputContext, outputPacket);
        av_packet_unref(outputPacket);
    }

    // Close codec, input file, output file, and cleanup
    avcodec_close(codecContext);
    avformat_close_input(&inputContext);
    avio_close(outputContext->pb);
    avformat_free_context(outputContext);
    sws_freeContext(imgConvertCtx);
    av_packet_free(&inputPacket);
    av_frame_free(&inputFrame);
    av_packet_free(&outputPacket);

    return a.exec();
}

这个示例代码会打开一个名为 "input.mp4" 的视频文件，并将编码数据写入一个名为 "output.mp4" 的新文件中。请注意，这只是一个大致的示例，可能需要根据您的具体情况进行修改。此外，为了简化代码，一些错误检查和异常处理可能被省略了。