ffmpeg+qsv 硬编码成yuv420p的数据，给些代码示例

这里提供一个使用FFmpeg和QSV硬编码器将视频文件编码为YUV420P格式数据的C++代码示例：

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

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

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

    AVFormatContext* input_ctx = NULL;
    int ret = avformat_open_input(&input_ctx, argv[1], NULL, NULL);
    if (ret < 0) {
        fprintf(stderr, "Failed to open input file: %s\n", argv[1]);
        return 1;
    }

    ret = avformat_find_stream_info(input_ctx, NULL);
    if (ret < 0) {
        fprintf(stderr, "Failed to find stream information\n");
        return 1;
    }

    int video_stream_idx = -1;
    for (int i = 0; i < input_ctx->nb_streams; i++) {
        if (input_ctx->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
            video_stream_idx = i;
            break;
        }
    }

    if (video_stream_idx < 0) {
        fprintf(stderr, "No video stream found\n");
        return 1;
    }

    AVCodec* codec = avcodec_find_decoder(input_ctx->streams[video_stream_idx]->codecpar->codec_id);
    if (!codec) {
        fprintf(stderr, "Unsupported codec!\n");
        return 1;
    }

    AVCodecContext* codec_ctx = avcodec_alloc_context3(codec);
    if (!codec_ctx) {
        fprintf(stderr, "Failed to allocate codec context\n");
        return 1;
    }

    ret = avcodec_parameters_to_context(codec_ctx, input_ctx->streams[video_stream_idx]->codecpar);
    if (ret < 0) {
        fprintf(stderr, "Failed to copy codec parameters to context\n");
        return 1;
    }

    ret = avcodec_open2(codec_ctx, codec, NULL);
    if (ret < 0) {
        fprintf(stderr, "Failed to open codec\n");
        return 1;
    }

    AVFrame* frame = av_frame_alloc();
    if (!frame) {
        fprintf(stderr, "Failed to allocate frame\n");
        return 1;
    }

    AVPacket packet;
    av_init_packet(&packet);

    AVCodec* enc_codec = avcodec_find_encoder_by_name("h264_qsv");
    if (!enc_codec) {
        fprintf(stderr, "Failed to find QSV encoder\n");
        return 1;
    }

    AVCodecContext* enc_ctx = avcodec_alloc_context3(enc_codec);
    if (!enc_ctx) {
        fprintf(stderr, "Failed to allocate encoder context\n");
        return 1;
    }

    enc_ctx->width = codec_ctx->width;
    enc_ctx->height = codec_ctx->height;
    enc_ctx->time_base = codec_ctx->time_base;
    enc_ctx->framerate = codec_ctx->framerate;
    enc_ctx->pix_fmt = AV_PIX_FMT_NV12; // set output pixel format to NV12
    enc_ctx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;

    ret = avcodec_open2(enc_ctx, enc_codec, NULL);
    if (ret < 0) {
        fprintf(stderr, "Failed to open encoder\n");
        return 1;
    }

    FILE* output_file = fopen("output.yuv", "wb");
    if (!output_file) {
        fprintf(stderr, "Failed to open output file\n");
        return 1;
    }

    while (av_read_frame(input_ctx, &packet) >= 0) {
        if (packet.stream_index != video_stream_idx) {
            av_packet_unref(&packet);
            continue;
        }

        ret = avcodec_send_packet(codec_ctx, &packet);
        if (ret < 0) {
            fprintf(stderr, "Failed to send packet to decoder\n");
            break;
        }

        while (ret >= 0) {
            ret = avcodec_receive_frame(codec_ctx, frame);
            if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
                break;
            }
            else if (ret < 0) {
                fprintf(stderr, "Failed to receive frame from decoder\n");
                goto end;
            }

            AVFrame* enc_frame = av_frame_alloc();
            if (!enc_frame) {
                fprintf(stderr, "Failed to allocate encoder frame\n");
                goto end;
            }

            enc_frame->format = enc_ctx->pix_fmt;
            enc_frame->width = enc_ctx->width;
            enc_frame->height = enc_ctx->height;

            ret = av_frame_get_buffer(enc_frame, 32);
            if (ret < 0) {
                fprintf(stderr, "Failed to allocate encoder frame buffer\n");
                av_frame_free(&enc_frame);
                goto end;
            }

            ret = av_hwframe_transfer_data(enc_frame, frame, 0);
            if (ret < 0) {
                fprintf(stderr, "Failed to transfer frame data to encoder\n");
                av_frame_free(&enc_frame);
                goto end;
            }

            AVPacket enc_packet;
            av_init_packet(&enc_packet);

            ret = avcodec_send_frame(enc_ctx, enc_frame);
            if (ret < 0) {
                fprintf(stderr, "Failed to send frame to encoder\n");
                av_packet_unref(&enc_packet);
                av_frame_free(&enc_frame);
                goto end;
            }

            while (ret >= 0) {
                ret = avcodec_receive_packet(enc_ctx, &enc_packet);
                if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
                    break;
                }
                else if (ret < 0) {
                    fprintf(stderr, "Failed to receive packet from encoder\n");
                    av_packet_unref(&enc_packet);
                    av_frame_free(&enc_frame);
                    goto end;
                }

                fwrite(enc_packet.data, 1, enc_packet.size, output_file);

                av_packet_unref(&enc_packet);
            }

            av_frame_free(&enc_frame);
        }

        av_packet_unref(&packet);
    }

end:
    fclose(output_file);

    avcodec_free_context(&enc_ctx);
    avcodec_free_context(&codec_ctx);
    avformat_close_input(&input_ctx);
    av_frame_free(&frame);

    return 0;
}

这个示例代码使用H.264 QSV硬编码器将输入文件编码为YUV420P格式数据，并将结果保存到输出文件output.yuv中。