使用ffmpeg实现对h264视频解码 -- （实现了一个易于使用的c++封装库）

H264是当今流行的视频压缩格式；ffmpeg是一个开源库，实现了对h264视频文件的解压缩。

为了降低使用ffmpeg的复杂性，尽量隐藏实现细节，我写了一个封装库。c#也可以很方便的使用此库。解压后的数据可以为yuv格式，也可以为rgb格式。同时可以对rgb格式视频做缩放。

类H264Decode实现了所有解码功能。最后，再把此类封装成c函数，以便于与c#交互。

代码下载地址 https://download.csdn.net/download/qq_29939347/10674597

下面讲述一下此类的实现细节：

1 BOOL H264Decode::Init()

 初始化解码库，打开h264解码器。

BOOL H264Decode::Init()
{
    if (_init)
        return TRUE;

    _init = TRUE;
    if (!_av_register)
    {
        _av_register = TRUE;
        av_register_all();
    }

    _pCodecContext = avcodec_alloc_context3(NULL);
    _pH264VideoDecoder = avcodec_find_decoder(AV_CODEC_ID_H264);
    if (_pH264VideoDecoder == NULL)
    {
        return FALSE;
    }    

    //初始化参数，下面的参数应该由具体的业务决定  AV_PIX_FMT_YUV420P;
    _pCodecContext->time_base.num = ;
    _pCodecContext->frame_number = ; //每包一个视频帧
    _pCodecContext->codec_type = AVMEDIA_TYPE_VIDEO;
    _pCodecContext->bit_rate = ;
    _pCodecContext->time_base.den = ;//帧率
    _pCodecContext->width = ;//视频宽
    _pCodecContext->height = ;//视频高
    _pCodecContext->pix_fmt = AV_PIX_FMT_YUVJ420P;
    _pCodecContext->color_range = AVCOL_RANGE_MPEG;

    if (avcodec_open2(_pCodecContext, _pH264VideoDecoder, NULL) >= )
        _pFrameYuv = av_frame_alloc();
    else
        return FALSE;

    return TRUE;
}

2 向解码器输入数据

INT32 H264Decode::H264_PutVideoStream(char* buffer, INT32 bufferLen)
{
    AVPacket packet = {  };
    packet.data = (uint8_t*)buffer;    //这里填入一个指向完整H264数据帧的指针
    packet.size = bufferLen;        //这个填入H264数据帧的大小  

    int ret = avcodec_send_packet(_pCodecContext, &packet);
    return ret;
}

3 读取解压后的数据 yuv格式

INT32 H264Decode::H264_GetNextVideoFrame(char* buffer, INT32 bufferLen, INT32 yuFormate)
{
    if (avcodec_receive_frame(_pCodecContext, _pFrameYuv) == )
    {
        int height = _pCodecContext->height;
        int width = _pCodecContext->width;

        if (yuFormate == )
        {
            ////写入数据
            int yLen = height * width;
            memcpy(buffer, _pFrameYuv->data[], yLen);

            int uLen = yLen / ;
            memcpy(buffer + yLen, _pFrameYuv->data[], uLen);

            int vLen = uLen;
            memcpy(buffer + yLen + uLen, _pFrameYuv->data[], vLen);
            return ;
        }
        else
        {
            ////写入数据
            int yLen = height * width;
            memcpy(buffer, _pFrameYuv->data[], yLen);

            int uLen = yLen / ;
            memcpy(buffer + yLen, _pFrameYuv->data[], uLen);

            int vLen = uLen;
            memcpy(buffer + yLen + uLen, _pFrameYuv->data[], vLen);
            return ;
        }
    }
    return -;
}

4 获取RGB格式视频；可同时，根据需要的大小，对视频做缩放。

INT32 H264Decode::H264_GetNextVideoFrame_Rgb(char* buffer, INT32 bufferLen, INT32 width, INT32 height)
{
    if (avcodec_receive_frame(_pCodecContext, _pFrameYuv) == )
    {
        ResetRgbScale(width, height);

        int n = (_out_rgb_buffer_len == bufferLen);

        uint8_t * data[];
        data[] = _pFrameYuv->data[];
        data[] = _pFrameYuv->data[]; //u v 向量互换
        data[] = _pFrameYuv->data[];

        _dst_dataTmp[] = (uint8_t *)buffer; //少一次复制
        int ret = sws_scale(_img_convert_ctx, (const unsigned char* const*)data, _pFrameYuv->linesize, , _pCodecContext->height,
            _dst_dataTmp, _dst_linesize);
        return ;
    }
    return -;
}

C语言封装接口

extern "C"
{
    LibFfmpegWrapper_API INT64 H264_CreateHandle();
    LibFfmpegWrapper_API INT32 H264_CloseHandle(INT64 handle);

    LibFfmpegWrapper_API INT32 H264_SetDefaultAlgorithm(INT32 flag);
    LibFfmpegWrapper_API INT32 H264_SetAlgorithm(INT64 handle, INT32 flag);

    LibFfmpegWrapper_API INT32 H264_PutVideoStream(INT64 handle, char* buffer, INT32 bufferLen);
    LibFfmpegWrapper_API INT32 H264_GetVideoParam(INT64 handle, INT32& width, INT32& height);

    LibFfmpegWrapper_API INT32 H264_GetVideoFrameSize(INT64 handle);
    LibFfmpegWrapper_API INT32 H264_GetVideoFrameFormate(INT64 handle);

    LibFfmpegWrapper_API INT32 H264_GetNextVideoFrame(INT64 handle, char* buffer, INT32 bufferLen, INT32 yuFormate);

    LibFfmpegWrapper_API INT32 H264_GetVideoFrameSize_Rgb(INT64 handle);
    LibFfmpegWrapper_API INT32 H264_GetNextVideoFrame_Rgb(INT64 handle, char* buffer, INT32 bufferLen);

    LibFfmpegWrapper_API INT32 H264_GetVideoFrameSize_Rgb2(INT64 handle,INT32 width, INT32 height);
    LibFfmpegWrapper_API INT32 H264_GetNextVideoFrame_Rgb2(INT64 handle, char* buffer, INT32 bufferLen, INT32 width, INT32 height);
}

c# 调用封装

class H264Decode
    {
        public const int Decode_Result_OK = ;

        long _handleDecode = ;

        public static void SetDefaultAlgorithm(EN_H264Algorithm flag)
        {
            H264DecodeWrapper.SetDefaultAlgorithm((int)flag);
        }

        ~H264Decode()
        {
            Close();
        }

        public void Init()
        {
            _handleDecode = H264DecodeWrapper.CreateHandle();
        }

        public Int32 SetAlgorithm(EN_H264Algorithm flag)
        {
            return H264DecodeWrapper.SetAlgorithm(_handleDecode, (int)flag);
        }

        public void Close()
        {
            if (_handleDecode == )
                return;
            H264DecodeWrapper.CloseHandle(_handleDecode);
            _handleDecode = ;
        }

        public int PutVideoStream(byte[] buffer)
        {
            return PutVideoStream(buffer, buffer.Length);
        }

        public int PutVideoStream(byte[] buffer, Int32 bufferLen)
        {
            return H264DecodeWrapper.PutVideoStream(_handleDecode, buffer, bufferLen);
        }

        public int GetVideoOrgSize(out int width, out int height)
        {
            int result = H264DecodeWrapper.GetVideoParam(_handleDecode, out width, out height);
            return result;
        }

        public int GetVideoFrameSize()
        {
            int result = H264DecodeWrapper.GetVideoFrameSize(_handleDecode);
            return result;
        }
        public AVPixelFormat GetVideoFrameFormate()
        {
            int result = H264DecodeWrapper.GetVideoFrameFormate(_handleDecode);
            return (AVPixelFormat)result;
        }

        public int GetNextVideoFrame(byte[] buffer, Int32 bufferLen, EN_H264_YU_Formate formate)
        {
            int result = H264DecodeWrapper.GetNextVideoFrame(_handleDecode, buffer, bufferLen, formate);
            return result;
        }
        public int GetNextVideoFrame(byte[] buffer, EN_H264_YU_Formate formate)
        {
            int result = H264DecodeWrapper.GetNextVideoFrame(_handleDecode, buffer, buffer.Length, formate);
            return result;
        }

        public int GetVideoFrameSize_Rgb()
        {
            int result = H264DecodeWrapper.GetVideoFrameSize_Rgb(_handleDecode);
            return result;
        }

        public int GetNextVideoFrame_Rgb(byte[] buffer, Int32 bufferLen)
        {
            int result = H264DecodeWrapper.GetNextVideoFrame_Rgb(_handleDecode, buffer, bufferLen);
            return result;
        }

        public int GetVideoFrameSize_Rgb2(Int32 width, Int32 height)
        {
            int result = H264DecodeWrapper.GetVideoFrameSize_Rgb2(_handleDecode, width, height);
            return result;
        }

        public int GetNextVideoFrame_Rgb2(byte[] buffer, Int32 bufferLen, Int32 width, Int32 height)
        {
            int result = H264DecodeWrapper.GetNextVideoFrame_Rgb2(_handleDecode, buffer, bufferLen, width, height);
            return result;
        }

    }

    public enum EN_H264Algorithm
    {
        SWS_FAST_BILINEAR = ,
        SWS_BILINEAR = ,
        SWS_BICUBIC = ,
        SWS_X = ,
        SWS_POINT = 0x10,
        SWS_AREA = 0x20,
        SWS_BICUBLIN = 0x40,
        SWS_GAUSS = 0x80,
        SWS_SINC = 0x100,
        SWS_LANCZOS = 0x200,
        SWS_SPLINE = 0x400,
    }

    public class H264DecodeWrapper
    {
        private const string DLLName = "LibFfmpegWrapper.dll";

        [DllImport(DLLName, EntryPoint = "H264_CreateHandle", CallingConvention = CallingConvention.Cdecl)]
        private static extern long H264_CreateHandle();

        [DllImport(DLLName, EntryPoint = "H264_CloseHandle", CallingConvention = CallingConvention.Cdecl)]
        private static extern Int32 H264_CloseHandle(long handle);

        [DllImport(DLLName, EntryPoint = "H264_PutVideoStream", CallingConvention = CallingConvention.Cdecl)]
        private static extern Int32 H264_PutVideoStream(long handle, IntPtr buffer, Int32 bufferLen);

        [DllImport(DLLName, EntryPoint = "H264_GetVideoParam", CallingConvention = CallingConvention.Cdecl)]
        private static extern Int32 H264_GetVideoParam(long handle, IntPtr width, IntPtr height);

        [DllImport(DLLName, EntryPoint = "H264_GetVideoFrameSize", CallingConvention = CallingConvention.Cdecl)]
        private static extern Int32 H264_GetVideoFrameSize(long handle);

        [DllImport(DLLName, EntryPoint = "H264_GetVideoFrameFormate", CallingConvention = CallingConvention.Cdecl)]
        private static extern Int32 H264_GetVideoFrameFormate(long handle);

        [DllImport(DLLName, EntryPoint = "H264_GetNextVideoFrame", CallingConvention = CallingConvention.Cdecl)]
        private static extern Int32 H264_GetNextVideoFrame(long handle, IntPtr buffer, Int32 bufferLen, Int32 yuFormate);

        [DllImport(DLLName, EntryPoint = "H264_GetVideoFrameSize_Rgb", CallingConvention = CallingConvention.Cdecl)]
        private static extern Int32 H264_GetVideoFrameSize_Rgb(long handle);

        [DllImport(DLLName, EntryPoint = "H264_GetNextVideoFrame_Rgb", CallingConvention = CallingConvention.Cdecl)]
        private static extern Int32 H264_GetNextVideoFrame_Rgb(long handle, IntPtr buffer, Int32 bufferLen);

        [DllImport(DLLName, EntryPoint = "H264_GetVideoFrameSize_Rgb2", CallingConvention = CallingConvention.Cdecl)]
        private static extern Int32 H264_GetVideoFrameSize_Rgb2(long handle, Int32 width, Int32 height);

        [DllImport(DLLName, EntryPoint = "H264_GetNextVideoFrame_Rgb2", CallingConvention = CallingConvention.Cdecl)]
        private static extern Int32 H264_GetNextVideoFrame_Rgb2(long handle, IntPtr buffer, Int32 bufferLen, Int32 width, Int32 height);

        [DllImport(DLLName, EntryPoint = "H264_SetDefaultAlgorithm", CallingConvention = CallingConvention.Cdecl)]
        private static extern Int32 H264_SetDefaultAlgorithm(Int32 flag);

        [DllImport(DLLName, EntryPoint = "H264_SetAlgorithm", CallingConvention = CallingConvention.Cdecl)]
        private static extern Int32 H264_SetAlgorithm(long handle,Int32 flag);

        public static long CreateHandle()
        {
            return H264_CreateHandle();
        }

        public static long CloseHandle(long handle)
        {
            return H264_CloseHandle(handle);
        }

        public static int PutVideoStream(long handle, byte[] buffer, Int32 bufferLen)
        {
            GCHandle hin = GCHandle.Alloc(buffer, GCHandleType.Pinned);
            int result = H264_PutVideoStream(handle, hin.AddrOfPinnedObject(), bufferLen);
            hin.Free();
            return result;
        }

        public static int GetVideoParam(long handle, out int width, out int height)
        {
            width = ;
            height = ;
            byte[] width2 = new byte[];
            byte[] height2 = new byte[];

            GCHandle hin_width = GCHandle.Alloc(width2, GCHandleType.Pinned);
            GCHandle hin_height = GCHandle.Alloc(height2, GCHandleType.Pinned);
            int result = H264_GetVideoParam(handle, hin_width.AddrOfPinnedObject(), hin_height.AddrOfPinnedObject());
            hin_width.Free();
            hin_height.Free();

            if (result != )
            {
                return result;
            }

            width = BitConverter.ToInt32(width2, );
            height = BitConverter.ToInt32(height2, );
            return result;
        }

        public static int GetVideoFrameSize(long handle)
        {
            int result = H264_GetVideoFrameSize(handle);
            return result;
        }
        public static int GetVideoFrameFormate(long handle)
        {
            int result = H264_GetVideoFrameFormate(handle);
            return result;
        }

        public static int GetNextVideoFrame(long handle, byte[] buffer, Int32 bufferLen, EN_H264_YU_Formate formate)
        {
            GCHandle hin = GCHandle.Alloc(buffer, GCHandleType.Pinned);
            int result = H264_GetNextVideoFrame(handle, hin.AddrOfPinnedObject(), bufferLen, (int)formate);
            hin.Free();
            return result;
        }

        public static int GetVideoFrameSize_Rgb(long handle)
        {
            int result = H264_GetVideoFrameSize_Rgb(handle);
            return result;
        }

        public static int GetNextVideoFrame_Rgb(long handle, byte[] buffer, Int32 bufferLen)
        {
            GCHandle hin = GCHandle.Alloc(buffer, GCHandleType.Pinned);
            int result = H264_GetNextVideoFrame_Rgb(handle, hin.AddrOfPinnedObject(), bufferLen);
            hin.Free();
            return result;
        }

        public static int GetVideoFrameSize_Rgb2(long handle, Int32 width, Int32 height)
        {
            int result = H264_GetVideoFrameSize_Rgb2(handle, width, height);
            return result;
        }

        public static  Int32 SetDefaultAlgorithm(Int32 flag)
        {
            return H264_SetDefaultAlgorithm(flag);
        }

        public static Int32 SetAlgorithm(long handle, Int32 flag)
        {
            return H264_SetAlgorithm(handle,flag);
        }

        public static int GetNextVideoFrame_Rgb2(long handle, byte[] buffer, Int32 bufferLen, Int32 width, Int32 height)
        {
            GCHandle hin = GCHandle.Alloc(buffer, GCHandleType.Pinned);
            int result = H264_GetNextVideoFrame_Rgb2(handle, hin.AddrOfPinnedObject(), bufferLen, width, height);
            hin.Free();
            return result;
        }

        public enum EN_H264_YU_Formate
        {
            Y_U_V = ,
            Y_V_U = ,
        }
    }