RK3568上使用C++结合V4L2拉流，并RKMPP硬件编解码，并保存为MP4文件

在RK3568平台上使用C++结合V4L2捕获视频流，并通过RKMPP进行硬件编码后保存为MP4文件，可以按照以下步骤实现：

1. 环境准备

硬件：RK3568开发板、摄像头模块。
软件依赖：
- Linux内核支持V4L2。
- Rockchip MPP库（RKMPP）。
- FFmpeg库（用于MP4封装，可选）。

V4L2_13">2. V4L2视频捕获

初始化V4L2设备并配置视频捕获参数：

#include <linux/videodev2.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/mman.h>int init_v4l2(const char* device, int width, int height) {int fd = open(device, O_RDWR);if (fd < 0) return -1;// 设置视频格式struct v4l2_format fmt = {0};fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;fmt.fmt.pix.width = width;fmt.fmt.pix.height = height;fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV; // 根据摄像头支持调整fmt.fmt.pix.field = V4L2_FIELD_NONE;if (ioctl(fd, VIDIOC_S_FMT, &fmt) < 0) {close(fd);return -1;}// 申请缓冲区struct v4l2_requestbuffers req = {0};req.count = 4;req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;req.memory = V4L2_MEMORY_MMAP;if (ioctl(fd, VIDIOC_REQBUFS, &req) < 0) {close(fd);return -1;}// 映射内存并入队for (int i = 0; i < req.count; ++i) {struct v4l2_buffer buf = {0};buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;buf.memory = V4L2_MEMORY_MMAP;buf.index = i;if (ioctl(fd, VIDIOC_QUERYBUF, &buf) < 0) {close(fd);return -1;}void* ptr = mmap(NULL, buf.length, PROT_READ | PROT_WRITE, MAP_SHARED, fd, buf.m.offset);// 保存缓冲区指针...ioctl(fd, VIDIOC_QBUF, &buf);}// 启动视频流enum v4l2_buf_type type = V4L2_BUF_TYPE_VIDEO_CAPTURE;ioctl(fd, VIDIOC_STREAMON, &type);return fd;
}

RKMPP_72">3. RKMPP编码器初始化

配置RKMPP的H.264编码器：

#include <rockchip/rk_mpi.h>MppCtx init_rkmpp_encoder(int width, int height) {MppCtx ctx = NULL;MppApi *mpi = NULL;MppParam param = NULL;mpp_create(&ctx, &mpi);mpi->control(ctx, MPP_SET_OUTPUT_FORMAT, MPP_FMT_YUV420SP); // 输入格式需与V4L2一致// 配置编码参数MppEncCodecCfg codec_cfg = {0};codec_cfg.coding = MPP_VIDEO_CodingAVC;mpi->control(ctx, MPP_ENC_SET_CODEC_CFG, &codec_cfg);MppEncPrepCfg prep_cfg = {0};prep_cfg.width = width;prep_cfg.height = height;prep_cfg.format = MPP_FMT_YUV420SP;mpi->control(ctx, MPP_ENC_SET_PREP_CFG, &prep_cfg);MppEncRcCfg rc_cfg = {0};rc_cfg.rc_mode = MPP_ENC_RC_MODE_CBR;rc_cfg.bps_target = 4000000; // 码率4Mbpsmpi->control(ctx, MPP_ENC_SET_RC_CFG, &rc_cfg);return ctx;
}

4. FFmpeg封装MP4文件

初始化FFmpeg用于写入MP4容器：

extern "C" {
#include <libavformat/avformat.h>
}AVFormatContext* init_mp4_writer(const char* filename, int width, int height) {avformat_alloc_output_context2(&fmt_ctx, NULL, NULL, filename);AVStream* stream = avformat_new_stream(fmt_ctx, NULL);stream->codecpar->codec_id = AV_CODEC_ID_H264;stream->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;stream->codecpar->width = width;stream->codecpar->height = height;stream->time_base = (AVRational){1, 30};avio_open(&fmt_ctx->pb, filename, AVIO_FLAG_WRITE);avformat_write_header(fmt_ctx, NULL);return fmt_ctx;
}

5. 主循环处理

捕获、编码、写入循环：

void capture_encode_save(int v4l2_fd, MppCtx encoder, AVFormatContext* mp4_ctx) {AVStream* stream = mp4_ctx->streams[0];int64_t pts = 0;while (true) {// 从V4L2捕获一帧struct v4l2_buffer v4l2_buf = {0};v4l2_buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;v4l2_buf.memory = V4L2_MEMORY_MMAP;ioctl(v4l2_fd, VIDIOC_DQBUF, &v4l2_buf);void* frame_data = ...; // 获取映射的缓冲区地址// 编码（伪代码，需适配RKMPP API）MppBuffer mpp_buf;mpp_buffer_put(mpp_buf, frame_data, v4l2_buf.length);mpi->encode_put_frame(encoder, mpp_buf);MppPacket packet;while (mpi->encode_get_packet(encoder, &packet) == MPP_OK) {AVPacket av_pkt = {0};av_pkt.data = mpp_packet_get_data(packet);av_pkt.size = mpp_packet_get_length(packet);av_pkt.pts = pts++;av_pkt.stream_index = stream->index;av_write_frame(mp4_ctx, &av_pkt);}ioctl(v4l2_fd, VIDIOC_QBUF, &v4l2_buf);}
}

6. 资源清理

退出时释放资源：

void cleanup(int v4l2_fd, MppCtx encoder, AVFormatContext* mp4_ctx) {// 停止V4L2enum v4l2_buf_type type = V4L2_BUF_TYPE_VIDEO_CAPTURE;ioctl(v4l2_fd, VIDIOC_STREAMOFF, &type);close(v4l2_fd);// 销毁RKMPP编码器mpp_destroy(encoder);// 结束MP4写入av_write_trailer(mp4_ctx);avio_closep(&mp4_ctx->pb);avformat_free_context(mp4_ctx);
}