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
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 = 1; _pCodecContext->frame_number = 1; //每包一个视频帧 _pCodecContext->codec_type = AVMEDIA_TYPE_VIDEO; _pCodecContext->bit_rate = 0; _pCodecContext->time_base.den = 25;//帧率 _pCodecContext->width = 0;//视频宽 _pCodecContext->height = 0;//视频高 _pCodecContext->pix_fmt = AV_PIX_FMT_YUVJ420P; _pCodecContext->color_range = AVCOL_RANGE_MPEG; if (avcodec_open2(_pCodecContext, _pH264VideoDecoder, NULL) >= 0) _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 = { 0 }; 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) == 0) { int height = _pCodecContext->height; int width = _pCodecContext->width; if (yuFormate == 1) { ////写入数据 int yLen = height * width; memcpy(buffer, _pFrameYuv->data[0], yLen); int uLen = yLen / 4; memcpy(buffer + yLen, _pFrameYuv->data[1], uLen); int vLen = uLen; memcpy(buffer + yLen + uLen, _pFrameYuv->data[2], vLen); return 0; } else { ////写入数据 int yLen = height * width; memcpy(buffer, _pFrameYuv->data[0], yLen); int uLen = yLen / 4; memcpy(buffer + yLen, _pFrameYuv->data[2], uLen); int vLen = uLen; memcpy(buffer + yLen + uLen, _pFrameYuv->data[1], vLen); return 0; } } return -1;}
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) == 0) { ResetRgbScale(width, height); int n = (_out_rgb_buffer_len == bufferLen); uint8_t * data[3]; data[0] = _pFrameYuv->data[0]; data[1] = _pFrameYuv->data[2]; //u v 向量互换 data[2] = _pFrameYuv->data[1]; _dst_dataTmp[0] = (uint8_t *)buffer; //少一次复制 int ret = sws_scale(_img_convert_ctx, (const unsigned char* const*)data, _pFrameYuv->linesize, 0, _pCodecContext->height, _dst_dataTmp, _dst_linesize); return 0; } return -1;}
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 = 0; long _handleDecode = 0; 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 == 0) return; H264DecodeWrapper.CloseHandle(_handleDecode); _handleDecode = 0; } 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 = 1, SWS_BILINEAR = 2, SWS_BICUBIC = 4, SWS_X = 8, 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 = 0; height = 0; byte[] width2 = new byte[4]; byte[] height2 = new byte[4]; 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 != 0) { return result; } width = BitConverter.ToInt32(width2, 0); height = BitConverter.ToInt32(height2, 0); 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 = 1, Y_V_U = 2, } }