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• Black screen when playing a video with ffmpeg and SDL on iOS

  1er avril 2012, par patrick

  I'm attempting to create a video player on iOS using ffmpeg and SDL. I'm decoding the video stream and attempting to convert the pixel data into a SDL_Surface and then convert that over to an SDL_Texture and render it on screen. However, all I'm getting is a black screen. I know the video file is good and can be viewed fine from VLC. Any idea what I'm missing here ?

  Initialization code :

      // initialize SDL (Simple DirectMedia Layer) to playback the content
  
      if( SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER) ) 
  
      {
  
          DDLogError(@"Unable to initialize SDL");
  
          return NO; 
  
      }
  
  
  
      // create window and renderer 
  
      window = SDL_CreateWindow(NULL, 0, 0, SCREEN_WIDTH, SCREEN_HEIGHT,
  
                                SDL_WINDOW_OPENGL | SDL_WINDOW_BORDERLESS |
  
                                SDL_WINDOW_SHOWN);
  
      if ( window == 0 ) 
  
      {
  
          DDLogError(@"Unable to initialize SDL Window");
  
      }
  
  
  
      renderer = SDL_CreateRenderer(window, -1, 0);
  
      if ( !renderer ) 
  
      {
  
          DDLogError(@"Unable to initialize SDL Renderer");
  
      }
  
  
  
      // Initialize the FFMpeg and register codecs and their respected file formats
  
      av_register_all();

  Playback code :
  AVFormatContext *formatContext = NULL ;

  DDLogInfo(@"Opening media file at location:%@", filePath);
  
  
  
  const char *filename = [filePath cStringUsingEncoding:NSUTF8StringEncoding];
  
  // Open media file
  
  if( avformat_open_input(&formatContext, filename, NULL, NULL) != 0 )
  
  {
  
      DDLogWarn(@"Unable to open media file. [File:%@]", filePath);
  
  
  
      NSString *failureReason = NSLocalizedString(@"Unable to open file.", @"Media playback failed, unable to open file.");
  
  
  
      if ( error != NULL ) 
  
      {
  
          *error = [NSError errorWithDomain:MediaPlayerErrorDomain
  
                                       code:UNABLE_TO_OPEN 
  
                                   userInfo:[NSDictionary dictionaryWithObject:failureReason
  
                                                                        forKey:NSLocalizedFailureReasonErrorKey]];
  
      }
  
  
  
      return NO; // Couldn't open file
  
  }
  
  
  
  // Retrieve stream information
  
  if( avformat_find_stream_info(formatContext, NULL) <= 0 )
  
  {
  
      DDLogWarn(@"Unable to locate stream information for file. [File:%@]", filePath);
  
  
  
      NSString *failureReason = NSLocalizedString(@"Unable to find audio/video stream information.", @"Media playback failed, unable to find stream information.");
  
  
  
      if ( error != NULL ) 
  
      {
  
          *error = [NSError errorWithDomain:MediaPlayerErrorDomain
  
                                       code:UNABLE_TO_FIND_STREAM
  
                                   userInfo:[NSDictionary dictionaryWithObject:failureReason
  
                                                                        forKey:NSLocalizedFailureReasonErrorKey]];
  
      }
  
  
  
      return NO;  // Missing stream information
  
  }
  
  
  
  // Find the first video or audio stream
  
  int videoStream = -1;
  
  int audioStream = -1;
  
  
  
  DDLogInfo(@"Locating stream information for media file");
  
  
  
  for( int index=0; index<(formatContext->nb_streams); index++)
  
  {
  
      if( formatContext->streams[index]->codec->codec_type==AVMEDIA_TYPE_VIDEO ) 
  
      {
  
          DDLogInfo(@"Found video stream");
  
          videoStream = index;
  
          break;
  
      }
  
      else if( mediaType == AUDIO_FILE && 
  
              (formatContext->streams[index]->codec->codec_type==AVMEDIA_TYPE_AUDIO) )
  
      {
  
          DDLogInfo(@"Found audio stream");
  
          audioStream = index;
  
          break;
  
      }
  
  }
  
  
  
  if( videoStream == -1 && (audioStream == -1) )
  
  {
  
      DDLogWarn(@"Unable to find video or audio stream for file");
  
  
  
      NSString *failureReason = NSLocalizedString(@"Unable to locate audio/video stream.", @"Media playback failed, unable to locate media stream.");
  
  
  
      if ( error != NULL ) 
  
      {
  
          *error = [NSError errorWithDomain:MediaPlayerErrorDomain
  
                                       code:UNABLE_TO_FIND_STREAM
  
                                   userInfo:[NSDictionary dictionaryWithObject:failureReason
  
                                                                        forKey:NSLocalizedFailureReasonErrorKey]];
  
      }
  
  
  
      return NO; // Didn't find a video or audio stream
  
  }
  
  
  
  // Get a pointer to the codec context for the video/audio stream
  
  AVCodecContext *codecContext;
  
  
  
  DDLogInfo(@"Attempting to locate the codec for the media file");
  
  
  
  if ( videoStream > -1 ) 
  
  {
  
      codecContext = formatContext->streams[videoStream]->codec;
  
  
  
  }
  
  else 
  
  {
  
      codecContext = formatContext->streams[audioStream]->codec;
  
  }
  
  
  
  // Now that we have information about the codec that the file is using,
  
  // we need to actually open the codec to decode the content
  
  
  
  DDLogInfo(@"Attempting to open the codec to playback the media file");
  
  
  
  AVCodec *codec;
  
  
  
  // Find the decoder for the video stream
  
  codec = avcodec_find_decoder(codecContext->codec_id);
  
  if( codec == NULL ) 
  
  {
  
      DDLogWarn(@"Unsupported codec! Cannot playback meda file [File:%@]", filePath);
  
  
  
      NSString *failureReason = NSLocalizedString(@"Unsupported file format. Cannot playback media.", @"Media playback failed, unsupported codec.");
  
      if ( error != NULL ) 
  
      {
  
          *error = [NSError errorWithDomain:MediaPlayerErrorDomain
  
                                       code:UNSUPPORTED_CODEC
  
                                   userInfo:[NSDictionary dictionaryWithObject:failureReason
  
                                                                        forKey:NSLocalizedFailureReasonErrorKey]];
  
      }
  
  
  
      return NO; // Codec not found
  
  }
  
  
  
  // Open codec
  
  if( avcodec_open2(codecContext, codec, NULL) < 0 )
  
  {
  
      DDLogWarn(@"Unable to open codec! Cannot playback meda file [File:%@]", filePath);
  
  
  
      NSString *failureReason = NSLocalizedString(@"Unable to open media codec. Cannot playback media.", @"Media playback failed, cannot open codec.");
  
      if ( error != NULL ) 
  
      {
  
          *error = [NSError errorWithDomain:MediaPlayerErrorDomain
  
                                       code:UNABLE_TO_LOAD_CODEC
  
                                   userInfo:[NSDictionary dictionaryWithObject:failureReason
  
                                                                        forKey:NSLocalizedFailureReasonErrorKey]];
  
      }
  
  
  
      return NO; // Could not open codec
  
  }
  
  
  
  // Allocate player frame
  
   AVFrame *playerFrame=avcodec_alloc_frame();
  
  
  
  // Allocate an AVFrame structure
  
  AVFrame *RGBframe=avcodec_alloc_frame();
  
  if( RGBframe==NULL )
  
  {
  
      // could not create a frame to convert our video frame
  
      // to a 16-bit RGB565 frame.
  
  
  
      DDLogWarn(@"Unable to convert video frame. Cannot playback meda file [File:%@]", filePath);
  
  
  
      NSString *failureReason = NSLocalizedString(@"Problems interpreting video frame information.", @"Media playback failed, cannot convert frame.");
  
      if ( error != NULL ) 
  
      {
  
          *error = [NSError errorWithDomain:MediaPlayerErrorDomain
  
                                       code:UNABLE_TO_LOAD_FRAME
  
                                   userInfo:[NSDictionary dictionaryWithObject:failureReason
  
                                                                        forKey:NSLocalizedFailureReasonErrorKey]];
  
      }
  
  
  
      return NO; // Could not open codec
  
  }
  
  
  
  int frameFinished = 0;
  
  AVPacket packet;
  
  
  
  // Figure out the destination width/height based on the screen size
  
  int destHeight = codecContext->height;
  
  int destWidth  = codecContext->width;
  
  if ( destHeight > SCREEN_HEIGHT || (destWidth > SCREEN_WIDTH) ) 
  
  {
  
      if ( destWidth > SCREEN_WIDTH ) 
  
      {
  
          float percentDiff = ( destWidth - SCREEN_WIDTH ) / (float)destWidth;
  
          destWidth  = destWidth  - (int)(destWidth * percentDiff );
  
          destHeight = destHeight - (int)(destHeight * percentDiff );
  
      }
  
  
  
      if ( destHeight > SCREEN_HEIGHT ) 
  
      {
  
          float percentDiff = (destHeight - SCREEN_HEIGHT ) / (float)destHeight;
  
          destWidth  = destWidth  - (int)(destWidth * percentDiff );
  
          destHeight = destHeight - (int)(destHeight * percentDiff );
  
      }
  
  }
  
  
  
  SwsContext *swsContext = sws_getContext(codecContext->width, codecContext->height, codecContext->pix_fmt, destWidth, destHeight, PIX_FMT_RGB565, SWS_BICUBIC, NULL, NULL, NULL);
  
  
  
  while( av_read_frame(formatContext, &packet) >= 0 ) 
  
  {
  
      // Is this a packet from the video stream?
  
      if( packet.stream_index == videoStream ) 
  
      {
  
          // Decode video frame
  
          avcodec_decode_video2(codecContext, playerFrame, &frameFinished, &packet);
  
  
  
          // Did we get a video frame?
  
          if( frameFinished != 0 ) 
  
          {
  
              // Convert the content over to RGB565 (16-bit RGB) to playback with SDL
  
  
  
              uint8_t *dst[3];
  
              int dstStride[3];
  
  
  
              // Set the destination stride
  
              for (int plane = 0; plane < 3; plane++) 
  
              {
  
                  dstStride[plane] = codecContext->width*2;
  
                  dst[plane]= (uint8_t*) malloc(dstStride[plane]*destHeight);
  
              }
  
  
  
              sws_scale(swsContext, playerFrame->data, 
  
                        playerFrame->linesize, 0, 
  
                        destHeight, 
  
                        dst, dstStride);
  
  
  
              // Create the SDL surface frame that we are going to use to draw our video
  
  
  
              // 16-bit RGB so 2 bytes per pixel (pitch = width*(bytes per pixel))
  
              int pitch = destWidth*2;
  
              SDL_Surface *frameSurface = SDL_CreateRGBSurfaceFrom(dst[0], destWidth, destHeight, 16, pitch, 0, 0, 0, 0);
  
  
  
              // Clear the old frame first
  
              SDL_RenderClear(renderer);
  
  
  
              // Move the frame over to a texture and render it on screen
  
              SDL_Texture *texture = SDL_CreateTextureFromSurface(renderer, frameSurface);
  
              SDL_SetTextureBlendMode(texture, SDL_BLENDMODE_BLEND);
  
  
  
              // Draw the new frame on the screen
  
              SDL_RenderPresent(renderer);
  
  
  
              SDL_DestroyTexture(texture);
  
              SDL_FreeSurface(frameSurface);
  
          }

• Video Overlay not returning to black once video stopped

  24 septembre 2020, par Matt Nelson

  I am combining multiple videos from a webrtc call and aligning the "user-terminal" videos to the left, and the "user-visitor" videos to the right. As the visitor feed can start and strop, they have multiple videos so I'm offsetting them by the timestamp.

  


  This is working, however crazy it looks !

  


  The one last issue I have is that when the first visitor video stop on the right, it shows the last frame of that video until the next video starts on the left. Can I have it return o the black background ?

  


  Here is the command passed to ffmpeg :

  


  ffmpeg -y 
-i /recordings/process/5f6c9c3/videoroom-5f6c9c3-user-terminal-1600953586531366-audio.mjr.opus 
-i /recordings/process/5f6c9c3/videoroom-5f6c9c3-user-visitor-1600953592694430-audio.mjr.opus 
-i /recordings/process/5f6c9c3/videoroom-5f6c9c3-user-visitor-1600953609873223-audio.mjr.opus 
-i /recordings/process/5f6c9c3/videoroom-5f6c9c3-user-visitor-1600953628668227-audio.mjr.opus 
-i /recordings/process/5f6c9c3/videoroom-5f6c9c3-user-visitor-1600953663905342-audio.mjr.opus 
-i /recordings/process/5f6c9c3/videoroom-5f6c9c3-user-MasterTerminal-52350116-1600953681107272-audio.mjr.opus 
-i /recordings/process/5f6c9c3/videoroom-5f6c9c3-user-visitor-1600953697832165-audio.mjr.opus 
-i /recordings/process/5f6c9c3/videoroom-5f6c9c3-user-MasterTerminal-52350116-1600953723320364-audio.mjr.opus 
-i /recordings/process/5f6c9c3/videoroom-5f6c9c3-user-visitor-1600953725307043-audio.mjr.opus 
-filter_complex [1:a]adelay=6163|6163[1adelay];[2:a]adelay=23341|23341[2adelay];[3:a]adelay=42136|42136[3adelay];[4:a]adelay=77373|77373[4adelay];[5:a]adelay=94575|94575[5adelay];[6:a]adelay=111300|111300[6adelay];[7:a]adelay=136788|136788[7adelay];[8:a]adelay=138775|138775[8adelay];[0:a][1adelay][2adelay][3adelay][4adelay][5adelay][6adelay][7adelay][8adelay]amix=inputs=9:duration=longest[a] 
-map [a] -ac -2 /recordings/process/5f6c9c3/5f6c9c3.mp3


  


• Rendering YUV420P ffmpeg decoded images on QT with OpenGL, only see black screen

  17 février 2019, par Lucas Zanella

  I’ve found this QT OpenGL Widget which should render a 420PYUV image on screen. I’m feeding a ffmpeg decoded buffer into its paintGL() function but I see nothing. Neither noises or correct images, only a black screen. I’m trying to understand why.

  I want to exclude the possibilities of other things being wrong, but I need to be sure first that my code will produce anything. I std::couted some bytes from the ffmpeg just to see if they were arriving and they were. So I should see at least some noise.

  Can you see anything wrong with my code that wouldn’t make it able to render images on screen ?

  This is the widget that should output the image :

  #include "XVideoWidget.h"
  
  #include <qdebug>
  
  #include <qtimer>
  
  #include <iostream>
  
  //自动加双引号
  
  #define GET_STR(x) #x
  
  #define A_VER 3
  
  #define T_VER 4
  
  
  
  //顶点shader
  
  const char *vString = GET_STR(
  
      attribute vec4 vertexIn;
  
      attribute vec2 textureIn;
  
      varying vec2 textureOut;
  
      void main(void)
  
      {
  
          gl_Position = vertexIn;
  
          textureOut = textureIn;
  
      }
  
  );
  
  
  
  
  
  //片元shader
  
  const char *tString = GET_STR(
  
      varying vec2 textureOut;
  
      uniform sampler2D tex_y;
  
      uniform sampler2D tex_u;
  
      uniform sampler2D tex_v;
  
      void main(void)
  
      {
  
          vec3 yuv;
  
          vec3 rgb;
  
          yuv.x = texture2D(tex_y, textureOut).r;
  
          yuv.y = texture2D(tex_u, textureOut).r - 0.5;
  
          yuv.z = texture2D(tex_v, textureOut).r - 0.5;
  
          rgb = mat3(1.0, 1.0, 1.0,
  
              0.0, -0.39465, 2.03211,
  
              1.13983, -0.58060, 0.0) * yuv;
  
          gl_FragColor = vec4(rgb, 1.0);
  
      }
  
  
  
  );
  
  
  
  
  
  
  
  //准备yuv数据
  
  // ffmpeg -i v1080.mp4 -t 10 -s 240x128 -pix_fmt yuv420p  out240x128.yuv
  
  XVideoWidget::XVideoWidget(QWidget * parent)
  
  {
  
     // setWindowFlags (Qt::WindowFullscreenButtonHint);
  
    //  showFullScreen();
  
  
  
  }
  
  
  
  XVideoWidget::~XVideoWidget()
  
  {
  
  }
  
  
  
  //初始化opengl
  
  void XVideoWidget::initializeGL()
  
  {
  
      //qDebug() &lt;&lt; "initializeGL";
  
      std::cout &lt;&lt; "initializing gl" &lt;&lt; std::endl;
  
      //初始化opengl （QOpenGLFunctions继承）函数
  
      initializeOpenGLFunctions();
  
  
  
      this->m_F  = QOpenGLContext::currentContext()->functions();
  
  
  
      //program加载shader（顶点和片元）脚本
  
      //片元（像素）
  
      std::cout &lt;&lt; program.addShaderFromSourceCode(QOpenGLShader::Fragment, tString) &lt;&lt; std::endl;
  
      //顶点shader
  
      std::cout &lt;&lt; program.addShaderFromSourceCode(QOpenGLShader::Vertex, vString) &lt;&lt; std::endl;
  
  
  
      //设置顶点坐标的变量
  
      program.bindAttributeLocation("vertexIn",A_VER);
  
  
  
      //设置材质坐标
  
      program.bindAttributeLocation("textureIn",T_VER);
  
  
  
      //编译shader
  
      std::cout &lt;&lt; "program.link() = " &lt;&lt; program.link() &lt;&lt; std::endl;
  
  
  
      std::cout &lt;&lt; "program.bind() = " &lt;&lt; program.bind() &lt;&lt; std::endl;
  
  
  
      //传递顶点和材质坐标
  
      //顶点
  
      static const GLfloat ver[] = {
  
          -1.0f,-1.0f,
  
          1.0f,-1.0f,
  
          -1.0f, 1.0f,
  
          1.0f,1.0f
  
      };
  
  
  
      //材质
  
      static const GLfloat tex[] = {
  
          0.0f, 1.0f,
  
          1.0f, 1.0f,
  
          0.0f, 0.0f,
  
          1.0f, 0.0f
  
      };
  
  
  
      //顶点
  
      glVertexAttribPointer(A_VER, 2, GL_FLOAT, 0, 0, ver);
  
      glEnableVertexAttribArray(A_VER);
  
  
  
      //材质
  
      glVertexAttribPointer(T_VER, 2, GL_FLOAT, 0, 0, tex);
  
      glEnableVertexAttribArray(T_VER);
  
  
  
      //glUseProgram(&amp;program);
  
      //从shader获取材质
  
      unis[0] = program.uniformLocation("tex_y");
  
      unis[1] = program.uniformLocation("tex_u");
  
      unis[2] = program.uniformLocation("tex_v");
  
  
  
      //创建材质
  
      glGenTextures(3, texs);
  
  
  
      //Y
  
      glBindTexture(GL_TEXTURE_2D, texs[0]);
  
      //放大过滤，线性插值   GL_NEAREST(效率高，但马赛克严重)
  
      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
  
      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  
      //创建材质显卡空间
  
      glTexImage2D(GL_TEXTURE_2D, 0, GL_RED, width, height, 0, GL_RED, GL_UNSIGNED_BYTE, 0);
  
  
  
      //U
  
      glBindTexture(GL_TEXTURE_2D, texs[1]);
  
      //放大过滤，线性插值
  
      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
  
      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  
      //创建材质显卡空间
  
      glTexImage2D(GL_TEXTURE_2D, 0, GL_RED, width/2, height / 2, 0, GL_RED, GL_UNSIGNED_BYTE, 0);
  
  
  
      //V
  
      glBindTexture(GL_TEXTURE_2D, texs[2]);
  
      //放大过滤，线性插值
  
      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
  
      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  
      //创建材质显卡空间
  
      glTexImage2D(GL_TEXTURE_2D, 0, GL_RED, width / 2, height / 2, 0, GL_RED, GL_UNSIGNED_BYTE, 0);
  
  
  
      ///分配材质内存空间
  
      datas[0] = new unsigned char[width*height];     //Y
  
      datas[1] = new unsigned char[width*height/4];   //U
  
      datas[2] = new unsigned char[width*height/4];   //V
  
  }
  
  
  
  //刷新显示
  
  void XVideoWidget::paintGL(unsigned char**data)
  
  //void QFFmpegGLWidget::updateData(unsigned char**data)
  
  {
  
      std::cout &lt;&lt; "painting!" &lt;&lt; std::endl;
  
      memcpy(datas[0], data[0], width*height);
  
      memcpy(datas[1], data[1], width*height/4);
  
      memcpy(datas[2], data[2], width*height/4);
  
  
  
      glActiveTexture(GL_TEXTURE0);
  
      glBindTexture(GL_TEXTURE_2D, texs[0]); //0层绑定到Y材质
  
      //修改材质内容(复制内存内容)
  
      glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, width, height, GL_RED, GL_UNSIGNED_BYTE, datas[0]);
  
      //与shader uni遍历关联
  
      glUniform1i(unis[0], 0);
  
  
  
  
  
      glActiveTexture(GL_TEXTURE0+1);
  
      glBindTexture(GL_TEXTURE_2D, texs[1]); //1层绑定到U材质
  
                                             //修改材质内容(复制内存内容)
  
      glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, width/2, height / 2, GL_RED, GL_UNSIGNED_BYTE, datas[1]);
  
      //与shader uni遍历关联
  
      glUniform1i(unis[1],1);
  
  
  
  
  
      glActiveTexture(GL_TEXTURE0+2);
  
      glBindTexture(GL_TEXTURE_2D, texs[2]); //2层绑定到V材质
  
                                             //修改材质内容(复制内存内容)
  
      glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, width / 2, height / 2, GL_RED, GL_UNSIGNED_BYTE, datas[2]);
  
      //与shader uni遍历关联
  
      glUniform1i(unis[2], 2);
  
  
  
      glDrawArrays(GL_TRIANGLE_STRIP,0,4);
  
      qDebug() &lt;&lt; "paintGL";
  
  }
  
  
  
  
  
  // 窗口尺寸变化
  
  void XVideoWidget::resizeGL(int width, int height)
  
  {
  
      m_F->glViewport(0, 0, width, height);
  
  
  
      qDebug() &lt;&lt; "resizeGL "&lt;code></iostream></qtimer></qdebug>

  Here’s a bit of code from my MainWindow :

  MainWindow::MainWindow(QWidget *parent):
  
      QMainWindow(parent)
  
      {
  
          FfmpegDecoder* ffmpegDecoder = new FfmpegDecoder();
  
          if(!ffmpegDecoder->Init()) {
  
              std::cout << "problem with ffmpeg decoder init"  << std::endl;
  
          } else {
  
              std::cout << "fmmpeg decoder initiated"  << std::endl;
  
          }
  
          XVideoWidget * xVideoWidget = new XVideoWidget(parent);
  
          ffmpegDecoder->setOpenGLWidget(xVideoWidget);
  
  
  
          mediaStream = new MediaStream(uri, ffmpegDecoder, videoConsumer);//= new MediaStream(uri, ffmpegDecoder, videoConsumer);
  
          //...
  
      }
  
      void MainWindow::run()
  
      {
  
          mediaStream->receiveFrame();
  
      }

  My main.cpp makes sure my window run() method runs in the background.

      MainWindow w;
  
      w.setFixedSize(1280,720);
  
      w.show();
  
      boost::thread mediaThread(&MainWindow::run, &w);
  
      std::cout << "mediaThread running"  << std::endl;

  If someone wants to view the entire code, please feel free to visit the commit I just did : https://github.com/lucaszanella/orwell/tree/bbd74e42bd42df685bacc5d51cacbee3a178689f