简介
之前写了一遍提取MP4中的音视频并且解码,这一篇引入SDL2.0来显示解码后的视频序列 实现一个简易的 视频播放器。
我这里用的FFMPEG和SDL2.0都是最新版的 可能网上的资料不是很多,API接口也变了很多,不过大体的思路还是一样的。
分析几个FFMPEG函数
在这之前我们分析几个代码中可能引起疑问的FFMPEG几个函数的源代码,我已经尽我的能力添加了注释,因为实在没有文档可能有的地方也不是很详尽 不过大体还是能看懂的
av_image_alloc (分配图片缓冲区)
我们在FFMPEG中引用了此函数,下面列举的函数都是这个函数里所引用到的 我都 添加了注释 这里注意下面的
[cpp] view plaincopyprint?
- pointers 参数是一个指针数组 实际上他在初始化完毕之后会被赋值成连续的内存序列 具体看源代码
[cpp] view plaincopyprint?
- int av_image_alloc(uint8_t *pointers[4], int linesizes[4],
- int w, int h, enum AVPixelFormat pix_fmt, int align)
- {
- //获取描述符
- const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(pix_fmt);
- //
- int i, ret;
- uint8_t *buf;
- //如果不存在描述符那么返回错误
- if (!desc)
- return AVERROR(EINVAL);
- //检测图像宽度 高度
- if ((ret = av_image_check_size(w, h, 0, NULL)) < 0)
- return ret;
- //填充line sizes
- if ((ret = av_image_fill_linesizes(linesizes, pix_fmt, align>7 ? FFALIGN(w, 8) : w)) < 0)
- return ret;
- //初始化0
- for (i = 0; i < 4; i++)
- linesizes[i] = FFALIGN(linesizes[i], align);
- //如果计算的缓冲区尺寸<0
- if ((ret = av_image_fill_pointers(pointers, pix_fmt, h, NULL, linesizes)) < 0)
- return ret;
- //如果失败 重新分配buf
- buf = av_malloc(ret + align);
- if (!buf)
- return AVERROR(ENOMEM);
- //再次调用 分配连续缓冲区 赋值给 pointers
- if ((ret = av_image_fill_pointers(pointers, pix_fmt, h, buf, linesizes)) < 0) {
- //如果分配失败那么释放 缓冲区
- av_free(buf);
- return ret;
- }
- //检测像素描述符 AV_PIX_FMT_FLAG_PAL 或AV_PIX_FMT_FLAG_PSEUDOPAL
- //Pixel format has a palette in data[1], values are indexes in this palette.
- /**
- The pixel format is "pseudo-paletted". This means that FFmpeg treats it as
- * paletted internally, but the palette is generated by the decoder and is not
- * stored in the file. *
- */
- if (desc->flags & AV_PIX_FMT_FLAG_PAL || desc->flags & AV_PIX_FMT_FLAG_PSEUDOPAL)
- //设置系统调色板
- avpriv_set_systematic_pal2((uint32_t*)pointers[1], pix_fmt);
- return ret;
- }
avpriv_set_systematic_pal2(设置系统调色板)
//设置系统化调色板根据不同像素格式
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- int avpriv_set_systematic_pal2(uint32_t pal[256], enum AVPixelFormat pix_fmt)
- {
- int i;
- for (i = 0; i < 256; i++) {
- int r, g, b;
- switch (pix_fmt) {
- case AV_PIX_FMT_RGB8:
- r = (i>>5 )*36;
- g = ((i>>2)&7)*36;
- b = (i&3 )*85;
- break;
- case AV_PIX_FMT_BGR8:
- b = (i>>6 )*85;
- g = ((i>>3)&7)*36;
- r = (i&7 )*36;
- break;
- case AV_PIX_FMT_RGB4_BYTE:
- r = (i>>3 )*255;
- g = ((i>>1)&3)*85;
- b = (i&1 )*255;
- break;
- case AV_PIX_FMT_BGR4_BYTE:
- b = (i>>3 )*255;
- g = ((i>>1)&3)*85;
- r = (i&1 )*255;
- break;
- case AV_PIX_FMT_GRAY8:
- r = b = g = i;
- break;
- default:
- return AVERROR(EINVAL);
- }
- pal[i] = b + (g << 8) + (r << 16) + (0xFFU << 24);
- }
- return 0;
- }
av_image_fill_pointers(填充av_image_alloc传递的unsigned char** data和linesize)
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- //返回图像所需的大小
- //并且分配了连续缓冲区 将 data 拼接成一个内存连续的 序列
- int av_image_fill_pointers(uint8_t *data[4], enum AVPixelFormat pix_fmt, int height,
- uint8_t *ptr, const int linesizes[4])
- {
- int i, total_size, size[4] = { 0 }, has_plane[4] = { 0 };
- //获取描述符
- const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(pix_fmt);
- //清空指针数组
- memset(data , 0, sizeof(data[0])*4);
- //如果不存在描述符 返回错误
- if (!desc || desc->flags & AV_PIX_FMT_FLAG_HWACCEL)
- return AVERROR(EINVAL);
- //data[0]初始化为ptr
- data[0] = ptr;
- //如果每行的像素 大于INT类型最大值 -1024/高度 返回
- if (linesizes[0] > (INT_MAX - 1024) / height)
- return AVERROR(EINVAL);
- //初始化size[0]
- size[0] = linesizes[0] * height;
- //如果 描述符的标志是AV_PIX_FMT_FLAG_PAL或者AV_PIX_FMT_FLAG_PSEUDOPAL 那么表明调色板放在data[1]并且是 256 32位置
- if (desc->flags & AV_PIX_FMT_FLAG_PAL ||
- desc->flags & AV_PIX_FMT_FLAG_PSEUDOPAL)
- {
- size[0] = (size[0] + 3) & ~3;
- data[1] = ptr + size[0];
- return size[0] + 256 * 4;
- }
- /**
- * Parameters that describe how pixels are packed.
- * If the format has 2 or 4 components, then alpha is last.
- * If the format has 1 or 2 components, then luma is 0.
- * If the format has 3 or 4 components,
- * if the RGB flag is set then 0 is red, 1 is green and 2 is blue;
- * otherwise 0 is luma, 1 is chroma-U and 2 is chroma-V.
- */
- for (i = 0; i < 4; i++)
- has_plane[desc->comp[i].plane] = 1;
- //下面是计算总的需要的缓冲区大小
- total_size = size[0];
- for (i = 1; i < 4 && has_plane[i]; i++) {
- int h, s = (i == 1 || i == 2) ? desc->log2_chroma_h : 0;
- data[i] = data[i-1] + size[i-1];
- h = (height + (1 << s) - 1) >> s;
- if (linesizes[i] > INT_MAX / h)
- return AVERROR(EINVAL);
- size[i] = h * linesizes[i];
- if (total_size > INT_MAX - size[i])
- return AVERROR(EINVAL);
- total_size += size[i];
- }
- //返回总的缓冲区 大小
- return total_size;
- }
av_image_fill_linesizes(填充行线宽)
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- //填充LineSize数组 ,linesize代表每一刚的线宽 像素为单位
- int av_image_fill_linesizes(int linesizes[4], enum AVPixelFormat pix_fmt, int width)
- {
- int i, ret;
- //获取格式描述符
- const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(pix_fmt);
- int max_step [4]; /* max pixel step for each plane */
- int max_step_comp[4]; /* the component for each plane which has the max pixel step */
- //初始化指针数组 0
- memset(linesizes, 0, 4*sizeof(linesizes[0]));
- //如果不存在那么返回错误
- if (!desc || desc->flags & AV_PIX_FMT_FLAG_HWACCEL)
- return AVERROR(EINVAL);
- //下面的代码都是填充线宽的代码
- av_image_fill_max_pixsteps(max_step, max_step_comp, desc);
- for (i = 0; i < 4; i++) {
- if ((ret = image_get_linesize(width, i, max_step[i], max_step_comp[i], desc)) < 0)
- return ret;
- linesizes[i] = ret;
- }
- return 0;
- }
例子 提取MP4文件的视频,并播放实现简易视频播放器
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- #include "stdafx.h"
- /************************************************************************/
- /* 利用分流器分流MP4文件音视频并进行解码输出
- Programmer小卫-USher 2014/12/17
- /************************************************************************/
- //打开
- #define __STDC_FORMAT_MACROS
- #ifdef _CPPRTTI
- extern "C"
- {
- #endif
- #include "libavutil/imgutils.h" //图像工具
- #include "libavutil/samplefmt.h" // 音频样本格式
- #include "libavutil/timestamp.h" //时间戳工具可以 被用于调试和日志目的
- #include "libavformat/avformat.h" //Main libavformat public API header 包含了libavf I/O和 Demuxing 和Muxing 库
- #include "SDL.h"
- #ifdef _CPPRTTI
- };
- #endif
- //音视频编码器上下文
- static AVCodecContext *pVideoContext,*pAudioContext;
- static FILE *fVideoFile,*fAudioFile; //输出文件句柄
- static AVStream *pStreamVideo,*pStreamAudio; //媒体流
- static unsigned char * videoDstData[4]; //视频数据
- static int videoLineSize[4]; //
- static int videoBufferSize; //视频缓冲区大小
- static AVFormatContext *pFormatCtx=NULL; //格式上下文
- static AVFrame*pFrame=NULL ; //
- static AVPacket pkt; //解码媒体包
- static int ret=0; //状态
- static int gotFrame; //获取到的视频流
- //音视频流的索引
- static int videoStreamIndex,audioStreamIndex;
- //解码媒体包
- //SDL定义
- SDL_Window * pWindow = NULL;
- SDL_Renderer *pRender = NULL;
- SDL_Texture *pTexture = NULL;
- SDL_Rect dstrect = {0,0,800,600};
- int frame = 0;
- int indexFrameVideo=0;
- static int decode_packet(int* gotFrame, int param2)
- {
- int ret = 0 ;
- //解码数据大小
- int decodedSize=pkt.size ;
- //初始化获取的数据帧为0
- *gotFrame=0;
- //如果是视频流那么 解包视频流
- if(pkt.stream_index==videoStreamIndex)
- {
- //解码数据到视频帧
- if((ret=avcodec_decode_video2(pVideoContext,pFrame,gotFrame,&pkt))<0)
- {
- //解码视频帧失败
- return ret ;
- }
- indexFrameVideo++;
- //copy 解压后的数据到我们分配的空间中
- if(*gotFrame)
- {
- //拷贝数据
- av_image_copy(videoDstData,videoLineSize, (const uint8_t **)(pFrame->data), pFrame->linesize,pVideoContext->pix_fmt, pVideoContext->width, pVideoContext->height);
- //写入数据到缓冲区
- //fwrite(videoDstData[0], 1, videoBufferSize, fVideoFile);
- printf("输出当前第%d帧,大小:%d\n",indexFrameVideo,videoBufferSize);
- int n = SDL_BYTESPERPIXEL(pStreamVideo->codec->pix_fmt);
- //更新纹理
- SDL_UpdateTexture(pTexture, &dstrect, (const void*)videoDstData[0], videoLineSize[0]);
- //拷贝纹理到2D模块
- SDL_RenderCopy(pRender, pTexture,NULL, &dstrect);
- //延时 1000ms*1/25
- SDL_Delay(1000 * 1 / frame);
- //显示Render渲染曾
- SDL_RenderPresent(pRender);
- }else
- {
- printf("第%d帧,丢失\n",indexFrameVideo);
- }
- }
- //音频不管
- else if(pkt.stream_index==audioStreamIndex)
- {
- ///解码音频信息
- // if ((ret = avcodec_decode_audio4(pAudioContext, pFrame, gotFrame, &pkt)) < 0)
- // return ret;
- // decodedSize = FFMIN(ret, pkt.size);
- // //算出当前帧的大小
- // size_t unpadded_linesize = pFrame->nb_samples * av_get_bytes_per_sample((AVSampleFormat)pFrame->format);
- // ///写入数据到音频文件
- // fwrite(pFrame->extended_data[0], 1, unpadded_linesize, fAudioFile);
- }
- //取消所有引用 并且重置frame字段
- av_frame_unref(pFrame);
- return decodedSize ;
- }
- int Demuxing(int argc, char** argv)
- {
- if (argc < 4)
- {
- printf("Parameter Error!\n");
- return 0;
- }
- //注册所有混流器 过滤器
- av_register_all();
- //注册所有编码器
- avcodec_register_all();
- //媒体输入源头
- char*pInputFile = argv[1];
- //视频输出文件
- char*pOutputVideoFile = argv[3];
- //音频输出文件
- char*pOutputAudioFile = argv[2];
- //分配环境上下文
- pFormatCtx = avformat_alloc_context();
- //打开输入源 并且读取输入源的头部
- if (avformat_open_input(&pFormatCtx, pInputFile, NULL, NULL) < 0)
- {
- printf("Open Input Error!\n");
- return 0;
- }
- //获取流媒体信息
- if (avformat_find_stream_info(pFormatCtx, NULL) < 0)
- {
- printf("获取流媒体信息失败!\n");
- return 0;
- }
- //打印媒体信息
- av_dump_format(pFormatCtx, 0, pInputFile, 0);
- for (unsigned i = 0; i < pFormatCtx->nb_streams; i++)
- {
- AVStream *pStream = pFormatCtx->streams[i];
- AVMediaType mediaType = pStream->codec->codec_type;
- //提取不同的编解码器
- if (mediaType == AVMEDIA_TYPE_VIDEO)
- {
- videoStreamIndex = i;
- pVideoContext = pStream->codec;
- pStreamVideo = pStream;
- fVideoFile = fopen(pOutputVideoFile, "wb");
- frame = pVideoContext->framerate.num;
- if (!fVideoFile)
- {
- printf("con‘t open file!\n");
- goto end;
- }
- //计算解码后一帧图像的大小
- //int nsize = avpicture_get_size(PIX_FMT_YUV420P, 1280, 720);
- //分配计算初始化 图像缓冲区 调色板数据
- int ret = av_image_alloc(videoDstData, videoLineSize, pVideoContext->width, pVideoContext->height, pVideoContext->pix_fmt, 1);
- if (ret < 0)
- {
- printf("Alloc video buffer error!\n");
- goto end;
- }
- //avpicture_fill((AVPicture *)pFrame, videoDstData[0], PIX_FMT_YUV420P, 1280, 720);
- videoBufferSize = ret;
- }
- else if (mediaType == AVMEDIA_TYPE_AUDIO)
- {
- audioStreamIndex = i;
- pAudioContext = pStream->codec;
- pStreamAudio = pStream;
- fAudioFile = fopen(pOutputAudioFile, "wb");
- if (!fAudioFile)
- {
- printf("con‘t open file!\n");
- goto end;
- }
- //分配视频帧
- pFrame = av_frame_alloc();
- if (pFrame == NULL)
- {
- av_freep(&videoDstData[0]);
- printf("alloc audio frame error\n");
- goto end;
- }
- }
- AVCodec *dec;
- //根据编码器id查找编码器
- dec = avcodec_find_decoder(pStream->codec->codec_id);
- if (dec == NULL)
- {
- printf("查找编码器失败!\n");
- goto end;
- }
- if (avcodec_open2(pStream->codec, dec, nullptr) != 0)
- {
- printf("打开编码器失败!\n");
- goto end;
- }
- }
- av_init_packet(&pkt);
- pkt.data = NULL;
- pkt.size = 0;
- //读取媒体数据包 数据要大于等于0
- while (av_read_frame(pFormatCtx, &pkt) >= 0)
- {
- AVPacket oriPkt = pkt;
- do
- {
- //返回每个包解码的数据
- ret = decode_packet(&gotFrame, 0);
- if (ret < 0)
- break;
- //指针后移 空闲内存减少
- pkt.data += ret;
- pkt.size -= ret;
- //
- } while (pkt.size > 0);
- //释放之前分配的空间 读取完毕必须释放包
- av_free_packet(&oriPkt);
- }
- end:
- //关闭视频编码器
- avcodec_close(pVideoContext);
- //关闭音频编码器
- avcodec_close(pAudioContext);
- avformat_close_input(&pFormatCtx);
- fclose(fVideoFile);
- fclose(fAudioFile);
- //释放编码帧
- avcodec_free_frame(&pFrame);
- //释放视频数据区
- av_free(videoDstData[0]);
- return 0;
- }
- int _tmain(int argc, char*argv[])
- {
- SDL_Init(SDL_INIT_VIDEO);
- //创建窗口
- pWindow = SDL_CreateWindow("YUV420P", 200, 100, 800, 600, 0);
- //启用硬件加速
- pRender=SDL_CreateRenderer(pWindow, -1, 0);
- dstrect.x = 0;
- dstrect.y = 0;
- dstrect.w = 1280;
- dstrect.h = 720;
- //创建一个纹理 设置可以Lock YUV420P 格式 1280*720
- pTexture = SDL_CreateTexture(pRender, SDL_PIXELFORMAT_IYUV, SDL_TEXTUREACCESS_STREAMING, 1280, 720);
- Demuxing(argc, argv);
- //释放
- SDL_RenderClear(pRender);
- SDL_DestroyTexture(pTexture);
- SDL_DestroyRenderer(pRender);
- SDL_DestroyWindow(pWindow);
- SDL_Quit();
- return 0;
- }
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时间: 2024-08-06 03:20:32