C# 使用FFmpeg.Autogen对byte[]进行编解码

C# 使用FFmpeg.Autogen对byte[]进行编解码，参考：https://github.com/vanjoge/CSharpVideoDemo

入口调用类：

using System;
using System.IO;
using System.Drawing;
using System.Runtime.InteropServices;
using FFmpeg.AutoGen;

namespace FFmpegAnalyzer
{
    public class FFmpegWrapper
    {
        /// <summary>
        /// 默认的编码格式
        /// </summary>
        public AVCodecID DefaultCodecFormat { get; set; } = AVCodecID.AV_CODEC_ID_H264;

        /// <summary>
        /// 注册FFmpeg
        /// </summary>
        public static void RegisterFFmpeg()
        {
            FFmpegBinariesHelper.RegisterFFmpegBinaries();

            // 初始化注册ffmpeg相关的编码器
            ffmpeg.av_register_all();
            ffmpeg.avcodec_register_all();
            ffmpeg.avformat_network_init();
        }

        /// <summary>
        /// 注册日志
        /// <exception cref="NotSupportedException">.NET Framework 不支持日志注册</exception>
        /// </summary>
        private unsafe void RegisterFFmpegLogger()
        {
            // 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);
        }

        #region 编码器

        /// <summary>
        /// 创建编码器
        /// </summary>
        /// <param name="frameSize">编码前一帧原始数据的大小</param>
        /// <param name="isRgb">rgb数据</param>
        public void CreateEncoder(Size frameSize, bool isRgb = true)
        {
            _fFmpegEncoder = new FFmpegEncoder(frameSize, isRgb);
            _fFmpegEncoder.CreateEncoder(DefaultCodecFormat);
        }

        /// <summary>
        /// 编码
        /// </summary>
        /// <param name="frameBytes">编码帧数据</param>
        /// <returns></returns>
        public byte[] EncodeFrames(byte[] frameBytes)
        {
            return _fFmpegEncoder.EncodeFrames(frameBytes);
        }

        /// <summary>
        /// 释放编码器
        /// </summary>
        public void DisposeEncoder()
        {
            _fFmpegEncoder.Dispose();
        }
        #endregion

        #region 解码器

        /// <summary>
        /// 创建解码器
        /// </summary>
        /// <param name="decodedFrameSize">解码后数据的大小</param>
        /// <param name="isRgb">Rgb数据</param>
        public void CreateDecoder(Size decodedFrameSize, bool isRgb = true)
        {
            _fFmpegDecoder = new FFmpegDecoder(decodedFrameSize, isRgb);
            _fFmpegDecoder.CreateDecoder(DefaultCodecFormat);
        }

        /// <summary>
        /// 解码
        /// </summary>
        /// <param name="frameBytes">解码帧数据</param>
        /// <returns></returns>
        public byte[] DecodeFrames(byte[] frameBytes)
        {
            return _fFmpegDecoder.DecodeFrames(frameBytes);
        }

        /// <summary>
        /// 释放解码器
        /// </summary>
        public void DisposeDecoder()
        {
            _fFmpegDecoder.Dispose();
        }
        #endregion

        /// <summary>编码器</summary>
        private FFmpegEncoder _fFmpegEncoder;

        /// <summary>解码器</summary>
        private FFmpegDecoder _fFmpegDecoder;
    }
}

其它业务类：

using System;
using System.IO;
using System.Runtime.InteropServices;

namespace FFmpegAnalyzer
{
    internal class FFmpegBinariesHelper
    {
        private const string LD_LIBRARY_PATH = "LD_LIBRARY_PATH";

        internal static void RegisterFFmpegBinaries()
        {
            switch (Environment.OSVersion.Platform)
            {
                case PlatformID.Win32NT:
                case PlatformID.Win32S:
                case PlatformID.Win32Windows:
                    var current = AppDomain.CurrentDomain.BaseDirectory;
                    var probe = $"FFmpeg/bin/{(Environment.Is64BitProcess ? @"x64" : @"x86")}";
                    while (current != null)
                    {
                        var ffmpegDirectory = Path.Combine(current, probe);
                        if (Directory.Exists(ffmpegDirectory))
                        {
                            Console.WriteLine($"FFmpeg binaries found in: {ffmpegDirectory}");
                            RegisterLibrariesSearchPath(ffmpegDirectory);
                            return;
                        }
                        current = Directory.GetParent(current)?.FullName;
                    }
                    break;
                case PlatformID.Unix:
                case PlatformID.MacOSX:
                    var libraryPath = Environment.GetEnvironmentVariable(LD_LIBRARY_PATH);
                    RegisterLibrariesSearchPath(libraryPath);
                    break;
            }
        }
        private static void RegisterLibrariesSearchPath(string path)
        {
            switch (Environment.OSVersion.Platform)
            {
                case PlatformID.Win32NT:
                case PlatformID.Win32S:
                case PlatformID.Win32Windows:
                    SetDllDirectory(path);
                    break;
                case PlatformID.Unix:
                case PlatformID.MacOSX:
                    string currentValue = Environment.GetEnvironmentVariable(LD_LIBRARY_PATH);
                    if (string.IsNullOrWhiteSpace(currentValue) == false && currentValue.Contains(path) == false)
                    {
                        string newValue = currentValue + Path.PathSeparator + path;
                        Environment.SetEnvironmentVariable(LD_LIBRARY_PATH, newValue);
                    }
                    break;
            }
        }
        
        [DllImport("kernel32", SetLastError = true)]
        private static extern bool SetDllDirectory(string lpPathName);
    }
}

using System;
using System.Drawing;
using System.Runtime.InteropServices;
using FFmpeg.AutoGen;

namespace FFmpegAnalyzer
{
    /// <summary>
    /// 解码器
    /// </summary>
    internal unsafe class FFmpegDecoder
    {
        /// <param name="decodedFrameSize">解码后数据的大小</param>
        /// <param name="isRgb">Rgb数据</param>
        public FFmpegDecoder(Size decodedFrameSize, bool isRgb = true)
        {
            _decodedFrameSize = decodedFrameSize;
            _isRgb = isRgb;
        }

        /// <summary>
        /// 创建解码器
        /// </summary>
        /// <param name="codecFormat">解码格式</param>
        public void CreateDecoder(AVCodecID codecFormat)
        {
            var originPixelFormat = AVPixelFormat.AV_PIX_FMT_YUV420P;
            var destinationPixelFormat = _isRgb ? AVPixelFormat.AV_PIX_FMT_RGB24 : AVPixelFormat.AV_PIX_FMT_BGRA; 

            //获取解码器
            _pDecodec = ffmpeg.avcodec_find_decoder(codecFormat);
            if (_pDecodec == null) throw new InvalidOperationException("Codec not found.");

            _pDecodecContext = ffmpeg.avcodec_alloc_context3(_pDecodec);
            _pDecodecContext->width = _decodedFrameSize.Width;
            _pDecodecContext->height = _decodedFrameSize.Height;
            _pDecodecContext->time_base = new AVRational { num = 1, den = 30 };
            _pDecodecContext->pix_fmt = AVPixelFormat.AV_PIX_FMT_YUV420P;
            _pDecodecContext->framerate = new AVRational { num = 30, den = 1 };                        
            _pDecodecContext->gop_size = 30;
            // 设置预测算法
            _pDecodecContext->flags |= ffmpeg.AV_CODEC_FLAG_PSNR;
            _pDecodecContext->flags2 |= ffmpeg.AV_CODEC_FLAG2_FAST;
            _pDecodecContext->max_b_frames = 0;
            ffmpeg.av_opt_set(_pDecodecContext->priv_data, "preset", "veryfast", 0);
            ffmpeg.av_opt_set(_pDecodecContext->priv_data, "tune", "zerolatency", 0);
            //打开解码器
            ffmpeg.avcodec_open2(_pDecodecContext, _pDecodec, null);
            _pConvertContext = ffmpeg.sws_getContext(
                _decodedFrameSize.Width,
                _decodedFrameSize.Height,
                originPixelFormat,
                _decodedFrameSize.Width,
                _decodedFrameSize.Height,
                destinationPixelFormat,
               ffmpeg.SWS_FAST_BILINEAR,
                null, null, null);
            if (_pConvertContext == null)
                throw new ApplicationException("Could not initialize the conversion context.");

            var convertedFrameBufferSize = ffmpeg.av_image_get_buffer_size(destinationPixelFormat, _decodedFrameSize.Width, _decodedFrameSize.Height, 1);
            _convertedFrameBufferPtr = Marshal.AllocHGlobal(convertedFrameBufferSize);
            _dstData = new byte_ptrArray4();
            _dstLineSize = new int_array4();

            ffmpeg.av_image_fill_arrays(ref _dstData, ref _dstLineSize, (byte*)_convertedFrameBufferPtr, destinationPixelFormat,
                _decodedFrameSize.Width, _decodedFrameSize.Height, 1);
            _isCodecRunning = true;
        }

        /// <summary>
        /// 解码
        /// </summary>
        /// <param name="frameBytes"></param>
        /// <returns></returns>
        public  byte[] DecodeFrames(byte[] frameBytes)
        {
            if (!_isCodecRunning)
            {
                throw new InvalidOperationException("解码器未运行!");
            }
            var waitDecodePacket = ffmpeg.av_packet_alloc();
            var waitDecoderFrame = ffmpeg.av_frame_alloc();
            ffmpeg.av_frame_unref(waitDecoderFrame);
            fixed (byte* waitDecodeData = frameBytes)
            {
                waitDecodePacket->data = waitDecodeData;
                waitDecodePacket->size = frameBytes.Length;
                ffmpeg.av_frame_unref(waitDecoderFrame);
                try
                {
                    int error;
                    do
                    {
                        ffmpeg.avcodec_send_packet(_pDecodecContext, waitDecodePacket);
                        error = ffmpeg.avcodec_receive_frame(_pDecodecContext, waitDecoderFrame);
                    } while (error == ffmpeg.AVERROR(ffmpeg.EAGAIN));
                }
                finally
                {
                    ffmpeg.av_packet_unref(waitDecodePacket);
                }

                var decodeAfterFrame = ConvertToRgb(waitDecoderFrame);

                var length = _isRgb
                    ? decodeAfterFrame.height * decodeAfterFrame.width * 3
                    : decodeAfterFrame.height * decodeAfterFrame.width * 4;

                byte[] buffer = new byte[length];
                Marshal.Copy((IntPtr)decodeAfterFrame.data[0], buffer, 0, buffer.Length);
                return buffer;
            }
        }

        /// <summary>
        /// 释放
        /// </summary>
        public  void Dispose()
        {
            _isCodecRunning = false;
            //释放解码器
            ffmpeg.avcodec_close(_pDecodecContext);
            ffmpeg.av_free(_pDecodecContext);
            //释放转换器
            Marshal.FreeHGlobal(_convertedFrameBufferPtr);
            ffmpeg.sws_freeContext(_pConvertContext);
        }

        /// <summary>
        /// 转换成Rgb
        /// </summary>
        /// <param name="waitDecoderFrame"></param>
        /// <returns></returns>
        private  AVFrame ConvertToRgb(AVFrame* waitDecoderFrame)
        {
            ffmpeg.sws_scale(_pConvertContext, waitDecoderFrame->data, waitDecoderFrame->linesize, 0, waitDecoderFrame->height, _dstData, _dstLineSize);
            var decodeAfterData = new byte_ptrArray8();
            decodeAfterData.UpdateFrom(_dstData);
            var lineSize = new int_array8();
            lineSize.UpdateFrom(_dstLineSize);

            ffmpeg.av_frame_unref(waitDecoderFrame);
            return new AVFrame
            {
                data = decodeAfterData,
                linesize = lineSize,
                width = _decodedFrameSize.Width,
                height = _decodedFrameSize.Height
            };
        }

        //解码器
        private AVCodec* _pDecodec;
        private AVCodecContext* _pDecodecContext;
        //转换缓存区
        private IntPtr _convertedFrameBufferPtr;
        private byte_ptrArray4 _dstData;
        private int_array4 _dstLineSize;
        //格式转换
        private SwsContext* _pConvertContext;
        private Size _decodedFrameSize;
        private readonly bool _isRgb;
        //解码器正在运行
        private bool _isCodecRunning;
    }
}

using System;
using System.Runtime.InteropServices;
using System.Drawing;
using FFmpeg.AutoGen;

namespace FFmpegAnalyzer
{
    /// <summary>
    /// 编码器
    /// </summary>
    internal unsafe class FFmpegEncoder
    {
        /// <param name="frameSize">编码前一帧原始数据的大小</param>
        /// <param name="isRgb">rgb数据</param>
        public FFmpegEncoder(Size frameSize, bool isRgb = true)
        {
            _frameSize = frameSize;
            _isRgb = isRgb;
            _rowPitch = isRgb ? _frameSize.Width * 3 : _frameSize.Width * 4;
        }

        /// <summary>
        /// 创建编码器
        /// </summary>
        public  void CreateEncoder(AVCodecID codecFormat)
        {
            var originPixelFormat = _isRgb ? AVPixelFormat.AV_PIX_FMT_RGB24 : AVPixelFormat.AV_PIX_FMT_BGRA;
            var destinationPixelFormat = AVPixelFormat.AV_PIX_FMT_YUV420P;
            _pCodec = ffmpeg.avcodec_find_encoder(codecFormat);
             
            if (_pCodec == null)
                throw new InvalidOperationException("Codec not found.");
            _pCodecContext = ffmpeg.avcodec_alloc_context3(_pCodec);
            _pCodecContext->width = _frameSize.Width;
            _pCodecContext->height = _frameSize.Height;

            _pCodecContext->framerate = new AVRational { num = 30, den = 1 };
            _pCodecContext->time_base = new AVRational {num = 1, den = 30};
            _pCodecContext->gop_size = 30;
            _pCodecContext->pix_fmt = destinationPixelFormat;
            // 设置预测算法
            _pCodecContext->flags |= ffmpeg.AV_CODEC_FLAG_PSNR;
            _pCodecContext->flags2 |= ffmpeg.AV_CODEC_FLAG2_FAST;
            _pCodecContext->max_b_frames = 0;

            ffmpeg.av_opt_set(_pCodecContext->priv_data, "preset", "veryfast", 0);
            ffmpeg.av_opt_set(_pCodecContext->priv_data, "tune", "zerolatency", 0);

            //打开编码器
            ffmpeg.avcodec_open2(_pCodecContext, _pCodec, null);
            _pConvertContext = ffmpeg.sws_getContext(_frameSize.Width, _frameSize.Height, originPixelFormat, _frameSize.Width, _frameSize.Height, destinationPixelFormat,
            ffmpeg.SWS_FAST_BILINEAR, null, null, null);
            if (_pConvertContext == null)
                throw new ApplicationException("Could not initialize the conversion context.");

            var convertedFrameBufferSize = ffmpeg.av_image_get_buffer_size(destinationPixelFormat, _frameSize.Width, _frameSize.Height, 1);
            _convertedFrameBufferPtr = Marshal.AllocHGlobal(convertedFrameBufferSize);
            _dstData = new byte_ptrArray4();
            _dstLineSize = new int_array4();

            ffmpeg.av_image_fill_arrays(ref _dstData, ref _dstLineSize, (byte*)_convertedFrameBufferPtr, destinationPixelFormat, _frameSize.Width, _frameSize.Height, 1);
            _isCodecRunning = true;
        }

        /// <summary>
        /// 释放
        /// </summary>
        public  void Dispose()
        {
            if (!_isCodecRunning) return;
            _isCodecRunning = false;
            //释放编码器
            ffmpeg.avcodec_close(_pCodecContext);
            ffmpeg.av_free(_pCodecContext);
            //释放转换器
            Marshal.FreeHGlobal(_convertedFrameBufferPtr);
            ffmpeg.sws_freeContext(_pConvertContext);
        }

        /// <summary>
        /// 编码
        /// </summary>
        /// <param name="frameBytes"></param>
        /// <returns></returns>
        public  byte[] EncodeFrames(byte[] frameBytes)
        {
            if (!_isCodecRunning)
            {
                 throw new InvalidOperationException("编码器未运行!");
            }
            fixed (byte* pBitmapData = frameBytes)
            {
                var waitToYuvFrame = new AVFrame
                {
                    data = new byte_ptrArray8 { [0] = pBitmapData },
                    linesize = new int_array8 { [0] = _rowPitch },
                    height = _frameSize.Height
                };

                var rgbToYuv = ConvertToYuv(waitToYuvFrame, _frameSize.Width, _frameSize.Height);

                byte[] buffer;
                var pPacket = ffmpeg.av_packet_alloc();
                try
                {
                    int error;
                    do
                    {
                        ffmpeg.avcodec_send_frame(_pCodecContext, &rgbToYuv);
                        error = ffmpeg.avcodec_receive_packet(_pCodecContext, pPacket);
                    } while (error == ffmpeg.AVERROR(ffmpeg.EAGAIN));
                    buffer = new byte[pPacket->size];
                    Marshal.Copy(new IntPtr(pPacket->data), buffer, 0, pPacket->size);
                }
                finally
                {
                    ffmpeg.av_frame_unref(&rgbToYuv);
                    ffmpeg.av_packet_unref(pPacket);
                }

                return buffer;
            }
        }

        /// <summary>
        /// 转换成Yuv格式
        /// </summary>
        /// <param name="waitConvertYuvFrame"></param>
        /// <param name="width"></param>
        /// <param name="height"></param>
        /// <returns></returns>
        private  AVFrame ConvertToYuv(AVFrame waitConvertYuvFrame, int width, int height)
        {
            ffmpeg.sws_scale(_pConvertContext, waitConvertYuvFrame.data, waitConvertYuvFrame.linesize, 0, waitConvertYuvFrame.height, _dstData, _dstLineSize);

            var data = new byte_ptrArray8();
            data.UpdateFrom(_dstData);
            var lineSize = new int_array8();
            lineSize.UpdateFrom(_dstLineSize);
            ffmpeg.av_frame_unref(&waitConvertYuvFrame);
            return new AVFrame
            {
                data = data,
                linesize = lineSize,
                width = width,
                height = height
            };
        }

        //编码器
        private AVCodec* _pCodec;
        private AVCodecContext* _pCodecContext;
        //转换缓存区
        private IntPtr _convertedFrameBufferPtr;
        private byte_ptrArray4 _dstData;
        private int_array4 _dstLineSize;
        //格式转换
        private SwsContext* _pConvertContext;
        private Size _frameSize;
        private readonly int _rowPitch;
        private readonly bool _isRgb;

        //编码器正在运行
        private bool _isCodecRunning;
    }
}

using FFmpeg.AutoGen;
using System;
using System.Drawing;
using System.Runtime.InteropServices;
using System.Windows;

namespace FFmpegAnalyzer
{
    public sealed unsafe class VideoFrameConverter : IDisposable
    {
        private readonly IntPtr _convertedFrameBufferPtr;
        private readonly System.Drawing.Size _destinationSize;
        private readonly byte_ptrArray4 _dstData;
        private readonly int_array4 _dstLinesize;
        private readonly SwsContext* _pConvertContext;
        /// <summary>
        /// 帧格式转换
        /// </summary>
        /// <param name="sourceSize"></param>
        /// <param name="sourcePixelFormat"></param>
        /// <param name="destinationSize"></param>
        /// <param name="destinationPixelFormat"></param>
        public VideoFrameConverter(System.Drawing.Size sourceSize, AVPixelFormat sourcePixelFormat,
            System.Drawing.Size destinationSize, AVPixelFormat destinationPixelFormat)
        {
            _destinationSize = destinationSize;
            //分配并返回一个SwsContext。您需要它使用sws_scale()执行伸缩/转换操作
            //主要就是使用SwsContext进行转换！！！
            _pConvertContext = ffmpeg.sws_getContext((int)sourceSize.Width, (int)sourceSize.Height, sourcePixelFormat,
                (int)destinationSize.Width,
                (int)destinationSize.Height
                , destinationPixelFormat,
                ffmpeg.SWS_FAST_BILINEAR //默认算法 还有其他算法
                , null
                , null
                , null //额外参数 在flasgs指定的算法，而使用的参数。如果  SWS_BICUBIC  SWS_GAUSS  SWS_LANCZOS这些算法。  这里没有使用
                );
            if (_pConvertContext == null) throw new ApplicationException("Could not initialize the conversion context.");
            //获取媒体帧所需要的大小
            var convertedFrameBufferSize = ffmpeg.av_image_get_buffer_size(destinationPixelFormat
                , (int)destinationSize.Width, (int)destinationSize.Height
                , 1);
            //申请非托管内存,unsafe代码
            _convertedFrameBufferPtr = Marshal.AllocHGlobal(convertedFrameBufferSize);

            //转换帧的内存指针
            _dstData = new byte_ptrArray4();
            _dstLinesize = new int_array4();

            //挂在帧数据的内存区把_dstData里存的的指针指向_convertedFrameBufferPtr
            ffmpeg.av_image_fill_arrays(ref _dstData, ref _dstLinesize
                , (byte*)_convertedFrameBufferPtr
                , destinationPixelFormat
                , (int)destinationSize.Width, (int)destinationSize.Height
                , 1);
        }

        public void Dispose()
        {
            Marshal.FreeHGlobal(_convertedFrameBufferPtr);
            ffmpeg.sws_freeContext(_pConvertContext);
        }

        public AVFrame Convert(AVFrame sourceFrame)
        {
            //转换格式
            ffmpeg.sws_scale(_pConvertContext
                , sourceFrame.data
                , sourceFrame.linesize
                , 0, sourceFrame.height
                , _dstData, _dstLinesize);

            var data = new byte_ptrArray8();
            data.UpdateFrom(_dstData);
            var linesize = new int_array8();
            linesize.UpdateFrom(_dstLinesize);

            return new AVFrame
            {
                data = data,
                linesize = linesize,
                width = (int)_destinationSize.Width,
                height = (int)_destinationSize.Height
            };
        }
    }
}

using System;
using System.Collections.Generic;
using System.Drawing;
using System.IO;
using System.Runtime.InteropServices;
using System.Windows;
using FFmpeg.AutoGen;

namespace FFmpegAnalyzer
{
    public sealed unsafe class VideoStreamDecoder : IDisposable
    {
        private readonly AVCodecContext* _pCodecContext;
        private readonly AVFormatContext* _pFormatContext;
        private readonly int _streamIndex;
        //
        private readonly AVFrame* _pFrame;
        //
        private readonly AVFrame* _receivedFrame;
        private readonly AVPacket* _pPacket;
        /// <summary>
        /// 视频解码器
        /// </summary>
        /// <param name="url">视频流URL</param>
        /// <param name="HWDeviceType">硬件解码器类型（默认AVHWDeviceType.AV_HWDEVICE_TYPE_NONE）</param>
        public VideoStreamDecoder(string url, AVHWDeviceType HWDeviceType = AVHWDeviceType.AV_HWDEVICE_TYPE_NONE)
        {
            //分配一个AVFormatContext
            _pFormatContext = ffmpeg.avformat_alloc_context();
            //分配一个AVFrame
            _receivedFrame = ffmpeg.av_frame_alloc();

            var pFormatContext = _pFormatContext;
            //将源音视频流传递给ffmpeg即ffmpeg打开源视频流
            ffmpeg.avformat_open_input(&pFormatContext, url, null, null);
            //获取音视频流信息
            ffmpeg.avformat_find_stream_info(_pFormatContext, null);
            AVCodec* codec = null;
            //在源里找到最佳的流，如果指定了解码器，则根据解码器寻找流，将解码器传递给codec
            _streamIndex = ffmpeg.av_find_best_stream(_pFormatContext, AVMediaType.AVMEDIA_TYPE_VIDEO, -1, -1, &codec, 0);
            //根据解码器分配一个AVCodecContext ，仅仅分配工具，还没有初始化。
            _pCodecContext = ffmpeg.avcodec_alloc_context3(codec);
            //如果硬解码
            if (HWDeviceType != AVHWDeviceType.AV_HWDEVICE_TYPE_NONE)
            {
                //根据硬件编码类型创建AVHWDeviceContext，存在AVFormatContext.hw_device_ctx (_pCodecContext->hw_device_ctx)
                ffmpeg.av_hwdevice_ctx_create(&_pCodecContext->hw_device_ctx, HWDeviceType, null, null, 0);
            }
            //将最佳流的格式参数传递给codecContext
            ffmpeg.avcodec_parameters_to_context(_pCodecContext, _pFormatContext->streams[_streamIndex]->codecpar);
            //根据codec初始化pCodecContext 。与_pCodecContext = ffmpeg.avcodec_alloc_context3(codec);对应
            ffmpeg.avcodec_open2(_pCodecContext, codec, null);

            CodecName = ffmpeg.avcodec_get_name(codec->id);
            FrameSize = new System.Drawing.Size(_pCodecContext->width, _pCodecContext->height);
            PixelFormat = _pCodecContext->pix_fmt;
            //分配AVPacket
            /* AVPacket用于存储压缩的数据，分别包括有音频压缩数据，视频压缩数据和字幕压缩数据。
                       它通常在解复用操作后存储压缩数据，然后作为输入传给解码器。或者由编码器输出然后传递给复用器。
                       对于视频压缩数据，一个AVPacket通常包括一个视频帧。对于音频压缩数据，可能包括几个压缩的音频帧。
             */
            _pPacket = ffmpeg.av_packet_alloc();

            //分配AVFrame
            /*AVFrame用于存储解码后的音频或者视频数据。
                    AVFrame必须通过av_frame_alloc进行分配，通过av_frame_free释放。
            */
            _pFrame = ffmpeg.av_frame_alloc();
        }

        public string CodecName { get; }
        public System.Drawing.Size FrameSize { get; }
        public AVPixelFormat PixelFormat { get; }

        public void Dispose()
        {
            ffmpeg.av_frame_unref(_pFrame);
            ffmpeg.av_free(_pFrame);

            ffmpeg.av_packet_unref(_pPacket);
            ffmpeg.av_free(_pPacket);

            ffmpeg.avcodec_close(_pCodecContext);
            var pFormatContext = _pFormatContext;
            ffmpeg.avformat_close_input(&pFormatContext);
        }

        /// <summary>
        /// 解码下一帧帧
        /// </summary>
        /// <param name="frame">参数返回解码后的帧</param>
        /// <returns></returns>
        public bool TryDecodeNextFrame(out AVFrame frame)
        {
            //取消帧的引用。帧将不会被任何资源引用
            ffmpeg.av_frame_unref(_pFrame);
            ffmpeg.av_frame_unref(_receivedFrame);
            int error;
            do
            {


                try
                {
                    #region 读取帧忽略无效帧
                    do
                    {

                        //读取无效帧
                        error = ffmpeg.av_read_frame(_pFormatContext, _pPacket);//根据pFormatContext读取帧，返回到Packet中
                        if (error == ffmpeg.AVERROR_EOF)//如果已经是影视片流末尾则返回
                        {
                            frame = *_pFrame;
                            return false;
                        }
                    } while (_pPacket->stream_index != _streamIndex); //忽略掉音视频流里面与有效流（初始化（构造函数）时标记的_streamIndex）不一致的流
                    #endregion

                    //将帧数据放入解码器
                    ffmpeg.avcodec_send_packet(_pCodecContext, _pPacket);  //将原始数据数据（_pPacket）作为输入提供给解码器（_pCodecContext）
                }
                finally
                {
                    //消除对_pPacket的引用
                    ffmpeg.av_packet_unref(_pPacket);
                }



                //读取解码器里解码（_pCodecContext）后的帧通过参数返回（_pFrame）
                error = ffmpeg.avcodec_receive_frame(_pCodecContext, _pFrame);

            } while (error == ffmpeg.AVERROR(ffmpeg.EAGAIN));//当返回值等于 EAGAIN(再试一次)，
            if (_pCodecContext->hw_device_ctx != null)//如果配置了硬件解码则调用硬件解码器解码
            {
                //将_pFrame通过硬件解码后放入_receivedFrame
                ffmpeg.av_hwframe_transfer_data(_receivedFrame, _pFrame, 0);
                frame = *_receivedFrame;
            }
            else
            {
                frame = *_pFrame;
            }
            return true;
        }

        /// <summary>
        /// 获取媒体TAG信息
        /// </summary>
        /// <returns></returns>
        public IReadOnlyDictionary<string, string> GetContextInfo()
        {
            AVDictionaryEntry* tag = null;
            var result = new Dictionary<string, string>();
            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);
                result.Add(key, value);
            }

            return result;
        }
    }
}

需要将ffmpeg的类库复制到生成目录上（对应FFmpegBinariesHelper.RegisterFFmpegBinaries()中的生成路径）

 使用代码：

FFmpegWrapper.RegisterFFmpeg();
_ffMpegWrapper = new FFmpegWrapper();
_ffMpegWrapper.CreateEncoder(new System.Drawing.Size(1920, 1080), true);

_ffMpegWrapper1 = new FFmpegWrapper();
_ffMpegWrapper1.CreateDecoder(new System.Drawing.Size(1920, 1080), true);

var encodeFrames = _ffMpegWrapper.EncodeFrames(Data);
var decodeFrames = _ffMpegWrapper1.DecodeFrames(encodeFrames);