发布：2021/3/19 17:31:01作者：管理员 来源：本站 浏览次数：833

    1. 项目添加ffmpeg.autogen引用，nuget可以直接获取到，因为我用的FFmpeg是3.4版本，ffmpeg.autogen也用的3.4版本，如图。

• 2.创建一个frmPlayer窗体，来显示图像，为了方便，我这里用一个PictureBox来显示图像。

FFmpeg解码后是YUV图像，需通过sws_scale转会成RGB，然后构造成 System.Drawing.Bitmap给PictureBox显示。

3. FFmpeg拉流和解码类 里面有详细注释。

using FFmpeg.AutoGen;
using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Runtime.InteropServices;
 
namespace FFmpegDemo
{
    public unsafe class tstRtmp
    {
        /// <summary>
        /// 显示图片委托
        /// </summary>
        /// <param name="bitmap"></param>
        public delegate void ShowBitmap(Bitmap bitmap);
        /// <summary>
        /// 执行控制变量
        /// </summary>
        bool CanRun;
        /// <summary>
        /// 对读取的264数据包进行解码和转换
        /// </summary>
        /// <param name="show">解码完成回调函数</param>
        /// <param name="url">播放地址，也可以是本地文件地址</param>
        public unsafe void Start(ShowBitmap show, string url)
        {
            CanRun = true;
 
            Console.WriteLine(@"Current directory: " + Environment.CurrentDirectory);
            Console.WriteLine(@"Runnung in {0}-bit mode.", Environment.Is64BitProcess ? @"64" : @"32");
            //FFmpegDLL目录查找和设置
            FFmpegBinariesHelper.RegisterFFmpegBinaries();
 
            #region ffmpeg 初始化
            // 初始化注册ffmpeg相关的编码器
            ffmpeg.av_register_all();
            ffmpeg.avcodec_register_all();
            ffmpeg.avformat_network_init();
 
            Console.WriteLine($"FFmpeg version info: {ffmpeg.av_version_info()}");
            #endregion
 
            #region ffmpeg 日志
            // 设置记录ffmpeg日志级别
            ffmpeg.av_log_set_level(ffmpeg.AV_LOG_VERBOSE);
            av_log_set_callback_callback logCallback = (p0, level, format, vl) =>
            {
                if (level > ffmpeg.av_log_get_level()) return;
 
                var lineSize = 1024;
                var lineBuffer = stackalloc byte[lineSize];
                var printPrefix = 1;
                ffmpeg.av_log_format_line(p0, level, format, vl, lineBuffer, lineSize, &printPrefix);
                var line = Marshal.PtrToStringAnsi((IntPtr)lineBuffer);
                Console.Write(line);
            };
            ffmpeg.av_log_set_callback(logCallback);
 
            #endregion
 
            #region ffmpeg 转码
 
 
            // 分配音视频格式上下文
            var pFormatContext = ffmpeg.avformat_alloc_context();
 
            int error;
 
            //打开流
            error = ffmpeg.avformat_open_input(&pFormatContext, url, null, null);
            if (error != 0) throw new ApplicationException(GetErrorMessage(error));
 
            // 读取媒体流信息
            error = ffmpeg.avformat_find_stream_info(pFormatContext, null);
            if (error != 0) throw new ApplicationException(GetErrorMessage(error));
 
            // 这里只是为了打印些视频参数
            AVDictionaryEntry* tag = null;
            while ((tag = ffmpeg.av_dict_get(pFormatContext->metadata, "", tag, ffmpeg.AV_DICT_IGNORE_SUFFIX)) != null)
            {
                var key = Marshal.PtrToStringAnsi((IntPtr)tag->key);
                var value = Marshal.PtrToStringAnsi((IntPtr)tag->value);
                Console.WriteLine($"{key} = {value}");
            }
 
            // 从格式化上下文获取流索引
            AVStream* pStream = null, aStream;
            for (var i = 0; i < pFormatContext->nb_streams; i++)
            {
                if (pFormatContext->streams[i]->codec->codec_type == AVMediaType.AVMEDIA_TYPE_VIDEO)
                {
                    pStream = pFormatContext->streams[i];
 
                }
                else if (pFormatContext->streams[i]->codec->codec_type == AVMediaType.AVMEDIA_TYPE_AUDIO)
                {
                    aStream = pFormatContext->streams[i];
 
                }
            }
            if (pStream == null) throw new ApplicationException(@"Could not found video stream.");
 
            // 获取流的编码器上下文
            var codecContext = *pStream->codec;
 
            Console.WriteLine($"codec name: {ffmpeg.avcodec_get_name(codecContext.codec_id)}");
            // 获取图像的宽、高及像素格式
            var width = codecContext.width;
            var height = codecContext.height;
            var sourcePixFmt = codecContext.pix_fmt;
 
            // 得到编码器ID
            var codecId = codecContext.codec_id;
            // 目标像素格式
            var destinationPixFmt = AVPixelFormat.AV_PIX_FMT_BGR24;
 
 
            // 某些264格式codecContext.pix_fmt获取到的格式是AV_PIX_FMT_NONE 统一都认为是YUV420P
            if (sourcePixFmt == AVPixelFormat.AV_PIX_FMT_NONE && codecId == AVCodecID.AV_CODEC_ID_H264)
            {
                sourcePixFmt = AVPixelFormat.AV_PIX_FMT_YUV420P;
            }
 
            // 得到SwsContext对象：用于图像的缩放和转换操作
            var pConvertContext = ffmpeg.sws_getContext(width, height, sourcePixFmt,
                width, height, destinationPixFmt,
                ffmpeg.SWS_FAST_BILINEAR, null, null, null);
            if (pConvertContext == null) throw new ApplicationException(@"Could not initialize the conversion context.");
 
            //分配一个默认的帧对象:AVFrame
            var pConvertedFrame = ffmpeg.av_frame_alloc();
            // 目标媒体格式需要的字节长度
            var convertedFrameBufferSize = ffmpeg.av_image_get_buffer_size(destinationPixFmt, width, height, 1);
            // 分配目标媒体格式内存使用
            var convertedFrameBufferPtr = Marshal.AllocHGlobal(convertedFrameBufferSize);
            var dstData = new byte_ptrArray4();
            var dstLinesize = new int_array4();
            // 设置图像填充参数
            ffmpeg.av_image_fill_arrays(ref dstData, ref dstLinesize, (byte*)convertedFrameBufferPtr, destinationPixFmt, width, height, 1);
 
            #endregion
 
            #region ffmpeg 解码
            // 根据编码器ID获取对应的解码器
            var pCodec = ffmpeg.avcodec_find_decoder(codecId);
            if (pCodec == null) throw new ApplicationException(@"Unsupported codec.");
 
            var pCodecContext = &codecContext;
 
            if ((pCodec->capabilities & ffmpeg.AV_CODEC_CAP_TRUNCATED) == ffmpeg.AV_CODEC_CAP_TRUNCATED)
                pCodecContext->flags |= ffmpeg.AV_CODEC_FLAG_TRUNCATED;
 
            // 通过解码器打开解码器上下文:AVCodecContext pCodecContext
            error = ffmpeg.avcodec_open2(pCodecContext, pCodec, null);
            if (error < 0) throw new ApplicationException(GetErrorMessage(error));
 
            // 分配解码帧对象：AVFrame pDecodedFrame
            var pDecodedFrame = ffmpeg.av_frame_alloc();
 
            // 初始化媒体数据包
            var packet = new AVPacket();
            var pPacket = &packet;
            ffmpeg.av_init_packet(pPacket);
 
            var frameNumber = 0;
            while (CanRun)
            {
                try
                {
                    do
                    {
                        // 读取一帧未解码数据
                        error = ffmpeg.av_read_frame(pFormatContext, pPacket);
                        Console.WriteLine(pPacket->dts);
                        if (error == ffmpeg.AVERROR_EOF) break;
                        if (error < 0) throw new ApplicationException(GetErrorMessage(error));
 
                        if (pPacket->stream_index != pStream->index) continue;
 
                        // 解码
                        error = ffmpeg.avcodec_send_packet(pCodecContext, pPacket);
                        if (error < 0) throw new ApplicationException(GetErrorMessage(error));
                        // 解码输出解码数据
                        error = ffmpeg.avcodec_receive_frame(pCodecContext, pDecodedFrame);
                    } while (error == ffmpeg.AVERROR(ffmpeg.EAGAIN) && CanRun);
                    if (error == ffmpeg.AVERROR_EOF) break;
                    if (error < 0) throw new ApplicationException(GetErrorMessage(error));
 
                    if (pPacket->stream_index != pStream->index) continue;
 
                    Console.WriteLine($@"frame: {frameNumber}");
                    // YUV->RGB
                    ffmpeg.sws_scale(pConvertContext, pDecodedFrame->data, pDecodedFrame->linesize, 0, height, dstData, dstLinesize);
                }
                finally
                {
                    ffmpeg.av_packet_unref(pPacket);//释放数据包对象引用
                    ffmpeg.av_frame_unref(pDecodedFrame);//释放解码帧对象引用
                }
 
                // 封装Bitmap图片
                var bitmap = new Bitmap(width, height, dstLinesize[0], PixelFormat.Format24bppRgb, convertedFrameBufferPtr);
                // 回调
                show(bitmap);
                //bitmap.Save(AppDomain.CurrentDomain.BaseDirectory + "\\264\\frame.buffer."+ frameNumber + ".jpg", ImageFormat.Jpeg);
                
                frameNumber++;
            }
            //播放完置空播放图片
            show(null);
 
            #endregion
 
            #region 释放资源
            Marshal.FreeHGlobal(convertedFrameBufferPtr);
            ffmpeg.av_free(pConvertedFrame);
            ffmpeg.sws_freeContext(pConvertContext);
 
            ffmpeg.av_free(pDecodedFrame);
            ffmpeg.avcodec_close(pCodecContext);
            ffmpeg.avformat_close_input(&pFormatContext);
            
 
            #endregion
        }
 
        /// <summary>
        /// 获取ffmpeg错误信息
        /// </summary>
        /// <param name="error"></param>
        /// <returns></returns>
        private static unsafe string GetErrorMessage(int error)
        {
            var bufferSize = 1024;
            var buffer = stackalloc byte[bufferSize];
            ffmpeg.av_strerror(error, buffer, (ulong)bufferSize);
            var message = Marshal.PtrToStringAnsi((IntPtr)buffer);
            return message;
        }
 
        public void Stop()
        {
            CanRun = false;
        }
    }
}

4.调用代码

public partial class frmPlayer : Form
    {
        public frmPlayer()
        {
            InitializeComponent();
        }
        tstRtmp rtmp = new tstRtmp();
        Thread thPlayer;
        private void btnStart_Click(object sender, EventArgs e)
        {
            btnStart.Enabled = false;
            if (thPlayer != null)
            {
                rtmp.Stop();
 
                thPlayer = null;
            }
            else
            {
                thPlayer = new Thread(DeCoding);
                thPlayer.IsBackground = true;
                thPlayer.Start();
                btnStart.Text = "停止播放";
                btnStart.Enabled = true;
            }
        }
 
        /// <summary>
        /// 播放线程执行方法
        /// </summary>
        private unsafe void DeCoding()
        {
            try
            {
                Console.WriteLine("DeCoding run...");
                Bitmap oldBmp = null;
 
 
                // 更新图片显示
                tstRtmp.ShowBitmap show = (bmp) =>
                {
                    this.Invoke(new MethodInvoker(() =>
                    {
                        this.pic.Image = bmp;
                        if (oldBmp != null)
                        {
                            oldBmp.Dispose();
                        }
                        oldBmp = bmp;
                    }));
                };
                rtmp.Start(show, txtUrl.Text.Trim());
 
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex);
            }
            finally
            {
                Console.WriteLine("DeCoding exit");
                this.Invoke(new MethodInvoker(() =>
                {
                    btnStart.Text = "开始播放";
                    btnStart.Enabled = true;
                }));
            }
        }
    }

5.最终运行效果

     其他说明：

    构造Bitmap给PictureBox显示的方式效率比较低，可以采用SDL_NET版本直接显示YUV；
    音频这里没处理，音频播放可以用DirectSound 或者SDL_NET；
    因为这里用到了指针，所以在项目中需要勾选允许不安全代码；
    网上C#调用FFmpeg的API例子很少，大多是C/C++的，因为ffmpeg.autogen的名称与FFmpeg完全一样，所以C#中可以直接复制C/C++代码，然后在FFmpeg的方法前加入 ffmpeg. 即可；
    ffmpeg.autogen也支持.net core 和mono。