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Mot : - Tags -/Christian Nold

Autres articles (56)

  • Des sites réalisés avec MediaSPIP

    2 mai 2011, par

    Cette page présente quelques-uns des sites fonctionnant sous MediaSPIP.
    Vous pouvez bien entendu ajouter le votre grâce au formulaire en bas de page.

  • Support de tous types de médias

    10 avril 2011

    Contrairement à beaucoup de logiciels et autres plate-formes modernes de partage de documents, MediaSPIP a l’ambition de gérer un maximum de formats de documents différents qu’ils soient de type : images (png, gif, jpg, bmp et autres...) ; audio (MP3, Ogg, Wav et autres...) ; vidéo (Avi, MP4, Ogv, mpg, mov, wmv et autres...) ; contenu textuel, code ou autres (open office, microsoft office (tableur, présentation), web (html, css), LaTeX, Google Earth) (...)

  • Other interesting software

    13 avril 2011, par

    We don’t claim to be the only ones doing what we do ... and especially not to assert claims to be the best either ... What we do, we just try to do it well and getting better ...
    The following list represents softwares that tend to be more or less as MediaSPIP or that MediaSPIP tries more or less to do the same, whatever ...
    We don’t know them, we didn’t try them, but you can take a peek.
    Videopress
    Website : http://videopress.com/
    License : GNU/GPL v2
    Source code : (...)

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  • fate : add tests for cdxl video

    21 février 2012, par Paul B Mahol

    fate : add tests for cdxl video

  • Decode audio and video and process both streams — ffmpeg, sdl, opencv

    6 mai 2013, par Eric

    My goal is to proceed on audio and video of mpeg-2 file independently, and to keep synchronicity on both flows. Duration of video is about 1 or 2 minutes maximum.

    1. First, following this post "opencv for reading videos (and do the process),ffmpeg for audio , and SDL used to play both" sounds perfect. I have done some modification on the code considering recent ffmpeg naming changes. Compilation with cmake on 64-bits machine is fine. I get an error "Unsupported codec [3]" when opening codec.
      The code is following.

    2. Second, I looking for code dealing with synchronicity on both flows.


    #include "opencv/highgui.h"
    #include "opencv/cv.h"

    #ifndef INT64_C
    #define INT64_C(c) (c ## LL)
    #define UINT64_C(c) (c ## ULL)
    #endif

    extern "C"{
    #include <sdl></sdl>SDL.h>
    #include <sdl></sdl>SDL_thread.h>
    #include <libavcodec></libavcodec>avcodec.h>
    #include <libavformat></libavformat>avformat.h>
    }

    #include <iostream>
    #include
    #include

    using namespace cv;

    #define SDL_AUDIO_BUFFER_SIZE 1024

    typedef struct PacketQueue
    {
      AVPacketList *first_pkt, *last_pkt;
      int nb_packets;
      int size;
      SDL_mutex *mutex;
      SDL_cond *cond;
    } PacketQueue;
    PacketQueue audioq;

    int audioStream = -1;
    int videoStream = -1;
    int quit = 0;

    SDL_Surface* screen = NULL;
    SDL_Surface* surface = NULL;

    AVFormatContext* pFormatCtx = NULL;
    AVCodecContext* aCodecCtx = NULL;
    AVCodecContext* pCodecCtx = NULL;

    void show_frame(IplImage* img){
      if (!screen){
         screen = SDL_SetVideoMode(img->width, img->height, 0, 0);
         if (!screen){
            fprintf(stderr, "SDL: could not set video mode - exiting\n");
            exit(1);
         }
      }
      // Assuming IplImage packed as BGR 24bits
      SDL_Surface* surface = SDL_CreateRGBSurfaceFrom((void*)img->imageData,
                                                      img->width,
                                                      img->height,
                                                      img->depth * img->nChannels,
                                                      img->widthStep,
                                                      0xff0000, 0x00ff00, 0x0000ff, 0
                                                     );

      SDL_BlitSurface(surface, 0, screen, 0);
      SDL_Flip(screen);
    }

    void packet_queue_init(PacketQueue *q){
      memset(q, 0, sizeof(PacketQueue));
      q->mutex = SDL_CreateMutex();
      q->cond = SDL_CreateCond();
    }

    int packet_queue_put(PacketQueue *q, AVPacket *pkt){
      AVPacketList *pkt1;
      if (av_dup_packet(pkt) &lt; 0){
         return -1;
      }

      pkt1 = (AVPacketList*) av_malloc(sizeof(AVPacketList));
      //pkt1 = (AVPacketList*) malloc(sizeof(AVPacketList));
      if (!pkt1) return -1;
      pkt1->pkt = *pkt;
      pkt1->next = NULL;

      SDL_LockMutex(q->mutex);

      if (!q->last_pkt)
         q->first_pkt = pkt1;
      else
         q->last_pkt->next = pkt1;

      q->last_pkt = pkt1;
      q->nb_packets++;
      q->size += pkt1->pkt.size;
      SDL_CondSignal(q->cond);

      SDL_UnlockMutex(q->mutex);
      return 0;
    }

    static int packet_queue_get(PacketQueue *q, AVPacket *pkt, int block){
      AVPacketList *pkt1;
      int ret;

      SDL_LockMutex(q->mutex);
      for (;;){
         if( quit){
            ret = -1;
            break;
         }

         pkt1 = q->first_pkt;
         if (pkt1){
            q->first_pkt = pkt1->next;
            if (!q->first_pkt)
               q->last_pkt = NULL;

            q->nb_packets--;
            q->size -= pkt1->pkt.size;
            *pkt = pkt1->pkt;
            av_free(pkt1);
            //free(pkt1);
            ret = 1;
            break;
         }

         else if (!block){
            ret = 0;
            break;
         }
         else{
            SDL_CondWait(q->cond, q->mutex);
         }
      }

      SDL_UnlockMutex(q->mutex);
      return ret;
    }

    int audio_decode_frame(AVCodecContext *aCodecCtx, uint8_t *audio_buf, int buf_size){
      static AVPacket pkt;
      static uint8_t *audio_pkt_data = NULL;
      static int audio_pkt_size = 0;

      int len1, data_size;

      for (;;){
         while (audio_pkt_size > 0){
            data_size = buf_size;
            len1 = avcodec_decode_audio3(aCodecCtx, (int16_t*)audio_buf, &amp;data_size, &amp;pkt);
            if (len1 &lt; 0){
               // if error, skip frame
               audio_pkt_size = 0;
               break;
            }
            audio_pkt_data += len1;
            audio_pkt_size -= len1;
            if (data_size &lt;= 0){
               // No data yet, get more frames
               continue;
            }
            // We have data, return it and come back for more later
            return data_size;
        }

        if (pkt.data)
           av_free_packet(&amp;pkt);
        if (quit) return -1;
        if (packet_queue_get(&amp;audioq, &amp;pkt, 1) &lt; 0) return -1;
        audio_pkt_data = pkt.data;
        audio_pkt_size = pkt.size;
     }
    }

    void audio_callback(void *userdata, Uint8 *stream, int len){
     AVCodecContext *aCodecCtx = (AVCodecContext *)userdata;
     int len1, audio_size;

     static uint8_t audio_buf[(AVCODEC_MAX_AUDIO_FRAME_SIZE * 3) / 2];
     static unsigned int audio_buf_size = 0;
     static unsigned int audio_buf_index = 0;

     while (len > 0){
        if (audio_buf_index >= audio_buf_size){
           // We have already sent all our data; get more
           audio_size = audio_decode_frame(aCodecCtx, audio_buf, sizeof(audio_buf));
           if(audio_size &lt; 0){
              // If error, output silence
              audio_buf_size = 1024; // arbitrary?
              memset(audio_buf, 0, audio_buf_size);
           }
           else{
              audio_buf_size = audio_size;
           }
           audio_buf_index = 0;
       }

       len1 = audio_buf_size - audio_buf_index;
       if (len1 > len)
          len1 = len;
       memcpy(stream, (uint8_t *)audio_buf + audio_buf_index, len1);
       len -= len1;
       stream += len1;
       audio_buf_index += len1;
     }
    }

        void setup_ffmpeg(char* filename)
        {
           if (avformat_open_input(&amp;pFormatCtx, filename, NULL, NULL) != 0){
              fprintf(stderr, "FFmpeg failed to open file %s!\n", filename);
              exit(-1);
           }

           if (av_find_stream_info(pFormatCtx) &lt; 0){
              fprintf(stderr, "FFmpeg failed to retrieve stream info!\n");
              exit(-1);
           }

           // Dump information about file onto standard error
           av_dump_format(pFormatCtx, 0, filename, 0);

           // Find the first video stream
           int i = 0;
           for (i; i &lt; pFormatCtx->nb_streams; i++){
              if (pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO &amp;&amp; videoStream &lt; 0){
                 videoStream = i;
              }

              if (pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO &amp;&amp; audioStream &lt; 0){
                 audioStream = i;
              }
           }

           if (videoStream == -1){
              fprintf(stderr, "No video stream found in %s!\n", filename);
              exit(-1);
           }

           if (audioStream == -1){
              fprintf(stderr, "No audio stream found in %s!\n", filename);
              exit(-1);
           }

           // Get a pointer to the codec context for the audio stream
           aCodecCtx = pFormatCtx->streams[audioStream]->codec;

           // Set audio settings from codec info
           SDL_AudioSpec wanted_spec;
           wanted_spec.freq = aCodecCtx->sample_rate;
           wanted_spec.format = AUDIO_S16SYS;
           wanted_spec.channels = aCodecCtx->channels;
           wanted_spec.silence = 0;
           wanted_spec.samples = SDL_AUDIO_BUFFER_SIZE;
           wanted_spec.callback = audio_callback;
           wanted_spec.userdata = aCodecCtx;

           SDL_AudioSpec spec;
           if (SDL_OpenAudio(&amp;wanted_spec, &amp;spec) &lt; 0){
              fprintf(stderr, "SDL_OpenAudio: %s\n", SDL_GetError());
              exit(-1);
           }

           AVCodec* aCodec = avcodec_find_decoder(aCodecCtx->codec_id);
           if (!aCodec){
              fprintf(stderr, "Unsupported codec [1]!\n");
              exit(-1);
           }
           avcodec_open(aCodecCtx, aCodec);

           // audio_st = pFormatCtx->streams[index]
           packet_queue_init(&amp;audioq);
           SDL_PauseAudio(0);

           // Get a pointer to the codec context for the video stream
           pCodecCtx = pFormatCtx->streams[videoStream]->codec;

           // Find the decoder for the video stream
           AVCodec* pCodec = avcodec_find_decoder(pCodecCtx->codec_id);
           if (pCodec == NULL){
              fprintf(stderr, "Unsupported codec [2]!\n");
              exit(-1); // Codec not found
           }

           // Open codec
           if (avcodec_open(pCodecCtx, pCodec) &lt; 0){
              fprintf(stderr, "Unsupported codec [3]!\n");
              exit(-1); // Could not open codec
           }
        }


        int main(int argc, char* argv[])
        {
           if (argc &lt; 2){
               std::cout &lt;&lt; "Usage: " &lt;&lt; argv[0] &lt;&lt; " <video>" &lt;&lt; std::endl;
               return -1;
           }

           av_register_all();

           // Init SDL
           if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER))
           {
              fprintf(stderr, "Could not initialize SDL - %s\n", SDL_GetError());
              return -1;
           }

           // Init ffmpeg and setup some SDL stuff related to Audio
           setup_ffmpeg(argv[1]);

           VideoCapture cap(argv[1]);
           if (!cap.isOpened()){
              std::cout &lt;&lt; "Failed to load file!" &lt;&lt; std::endl;
              return -1;
           }

           AVPacket packet;
           while (av_read_frame(pFormatCtx, &amp;packet) >= 0)
           {
              if (packet.stream_index == videoStream)
              {
                 // Actually this is were SYNC between audio/video would happen.
                 // Right now I assume that every VIDEO packet contains an entire video frame, and that&#39;s not true. A video frame can be made by multiple packets!
                 // But for the time being, assume 1 video frame == 1 video packet,
                 // so instead of reading the frame through ffmpeg, I read it through OpenCV.

                 Mat frame;
                 cap >> frame; // get a new frame from camera

                 // do some processing on the frame, either as a Mat or as IplImage.
                 // For educational purposes, applying a lame grayscale conversion
                 IplImage ipl_frame = frame;
                 for (int i = 0; i &lt; ipl_frame.width * ipl_frame.height * ipl_frame.nChannels; i += ipl_frame.nChannels)
                 {
                    ipl_frame.imageData[i] = (ipl_frame.imageData[i] + ipl_frame.imageData[i+1] + ipl_frame.imageData[i+2])/3;   //B
                    ipl_frame.imageData[i+1] = (ipl_frame.imageData[i] + ipl_frame.imageData[i+1] + ipl_frame.imageData[i+2])/3; //G
                    ipl_frame.imageData[i+2] = (ipl_frame.imageData[i] + ipl_frame.imageData[i+1] + ipl_frame.imageData[i+2])/3; //R
                 }

                 // Display it on SDL window
                 show_frame(&amp;ipl_frame);

                 av_free_packet(&amp;packet);
              }
              else if (packet.stream_index == audioStream)
              {
                 packet_queue_put(&amp;audioq, &amp;packet);
              }
              else
              {
                 av_free_packet(&amp;packet);
              }

              SDL_Event event;
              SDL_PollEvent(&amp;event);
              switch (event.type)
              {
              case SDL_QUIT:
                 SDL_FreeSurface(surface);
                 SDL_Quit();
                 break;

              default:
                 break;
              }
           }

           // the camera will be deinitialized automatically in VideoCapture destructor

           // Close the codec
           avcodec_close(pCodecCtx);

           // Close the video file
           av_close_input_file(pFormatCtx);

           return 0;
        }
    </video></iostream>
  • Decode audio and video and process both flows — ffmpeg, sdl, opencv

    24 février 2012, par Eric

    My goal is to proceed on audio and video of mpeg-2 file independently, and to keep synchronicity on both flows. Duration of video is about 1 or 2 minutes maximum.

    1. First, following this post "opencv for reading videos (and do the process),ffmpeg for audio , and SDL used to play both" sounds perfect. I have done some modification on the code considering recent ffmpeg naming changes. Compilation with cmake on 64-bits machine is fine. I get an error "Unsupported codec [3]" when opening codec.
      The code is following.

    2. Second, I looking for code dealing with synchronicity on both flows.


    #include "opencv/highgui.h"
    #include "opencv/cv.h"

    #ifndef INT64_C
    #define INT64_C(c) (c ## LL)
    #define UINT64_C(c) (c ## ULL)
    #endif

    extern "C"{
    #include <sdl></sdl>SDL.h>
    #include <sdl></sdl>SDL_thread.h>
    #include <libavcodec></libavcodec>avcodec.h>
    #include <libavformat></libavformat>avformat.h>
    }

    #include <iostream>
    #include
    #include

    using namespace cv;

    #define SDL_AUDIO_BUFFER_SIZE 1024

    typedef struct PacketQueue
    {
      AVPacketList *first_pkt, *last_pkt;
      int nb_packets;
      int size;
      SDL_mutex *mutex;
      SDL_cond *cond;
    } PacketQueue;
    PacketQueue audioq;

    int audioStream = -1;
    int videoStream = -1;
    int quit = 0;

    SDL_Surface* screen = NULL;
    SDL_Surface* surface = NULL;

    AVFormatContext* pFormatCtx = NULL;
    AVCodecContext* aCodecCtx = NULL;
    AVCodecContext* pCodecCtx = NULL;

    void show_frame(IplImage* img){
      if (!screen){
         screen = SDL_SetVideoMode(img->width, img->height, 0, 0);
         if (!screen){
            fprintf(stderr, "SDL: could not set video mode - exiting\n");
            exit(1);
         }
      }
      // Assuming IplImage packed as BGR 24bits
      SDL_Surface* surface = SDL_CreateRGBSurfaceFrom((void*)img->imageData,
                                                      img->width,
                                                      img->height,
                                                      img->depth * img->nChannels,
                                                      img->widthStep,
                                                      0xff0000, 0x00ff00, 0x0000ff, 0
                                                     );

      SDL_BlitSurface(surface, 0, screen, 0);
      SDL_Flip(screen);
    }

    void packet_queue_init(PacketQueue *q){
      memset(q, 0, sizeof(PacketQueue));
      q->mutex = SDL_CreateMutex();
      q->cond = SDL_CreateCond();
    }

    int packet_queue_put(PacketQueue *q, AVPacket *pkt){
      AVPacketList *pkt1;
      if (av_dup_packet(pkt) &lt; 0){
         return -1;
      }

      pkt1 = (AVPacketList*) av_malloc(sizeof(AVPacketList));
      //pkt1 = (AVPacketList*) malloc(sizeof(AVPacketList));
      if (!pkt1) return -1;
      pkt1->pkt = *pkt;
      pkt1->next = NULL;

      SDL_LockMutex(q->mutex);

      if (!q->last_pkt)
         q->first_pkt = pkt1;
      else
         q->last_pkt->next = pkt1;

      q->last_pkt = pkt1;
      q->nb_packets++;
      q->size += pkt1->pkt.size;
      SDL_CondSignal(q->cond);

      SDL_UnlockMutex(q->mutex);
      return 0;
    }

    static int packet_queue_get(PacketQueue *q, AVPacket *pkt, int block){
      AVPacketList *pkt1;
      int ret;

      SDL_LockMutex(q->mutex);
      for (;;){
         if( quit){
            ret = -1;
            break;
         }

         pkt1 = q->first_pkt;
         if (pkt1){
            q->first_pkt = pkt1->next;
            if (!q->first_pkt)
               q->last_pkt = NULL;

            q->nb_packets--;
            q->size -= pkt1->pkt.size;
            *pkt = pkt1->pkt;
            av_free(pkt1);
            //free(pkt1);
            ret = 1;
            break;
         }

         else if (!block){
            ret = 0;
            break;
         }
         else{
            SDL_CondWait(q->cond, q->mutex);
         }
      }

      SDL_UnlockMutex(q->mutex);
      return ret;
    }

    int audio_decode_frame(AVCodecContext *aCodecCtx, uint8_t *audio_buf, int buf_size){
      static AVPacket pkt;
      static uint8_t *audio_pkt_data = NULL;
      static int audio_pkt_size = 0;

      int len1, data_size;

      for (;;){
         while (audio_pkt_size > 0){
            data_size = buf_size;
            len1 = avcodec_decode_audio3(aCodecCtx, (int16_t*)audio_buf, &amp;data_size, &amp;pkt);
            if (len1 &lt; 0){
               // if error, skip frame
               audio_pkt_size = 0;
               break;
            }
            audio_pkt_data += len1;
            audio_pkt_size -= len1;
            if (data_size &lt;= 0){
               // No data yet, get more frames
               continue;
            }
            // We have data, return it and come back for more later
            return data_size;
        }

        if (pkt.data)
           av_free_packet(&amp;pkt);
        if (quit) return -1;
        if (packet_queue_get(&amp;audioq, &amp;pkt, 1) &lt; 0) return -1;
        audio_pkt_data = pkt.data;
        audio_pkt_size = pkt.size;
     }
    }

    void audio_callback(void *userdata, Uint8 *stream, int len){
     AVCodecContext *aCodecCtx = (AVCodecContext *)userdata;
     int len1, audio_size;

     static uint8_t audio_buf[(AVCODEC_MAX_AUDIO_FRAME_SIZE * 3) / 2];
     static unsigned int audio_buf_size = 0;
     static unsigned int audio_buf_index = 0;

     while (len > 0){
        if (audio_buf_index >= audio_buf_size){
           // We have already sent all our data; get more
           audio_size = audio_decode_frame(aCodecCtx, audio_buf, sizeof(audio_buf));
           if(audio_size &lt; 0){
              // If error, output silence
              audio_buf_size = 1024; // arbitrary?
              memset(audio_buf, 0, audio_buf_size);
           }
           else{
              audio_buf_size = audio_size;
           }
           audio_buf_index = 0;
       }

       len1 = audio_buf_size - audio_buf_index;
       if (len1 > len)
          len1 = len;
       memcpy(stream, (uint8_t *)audio_buf + audio_buf_index, len1);
       len -= len1;
       stream += len1;
       audio_buf_index += len1;
     }
    }

        void setup_ffmpeg(char* filename)
        {
           if (avformat_open_input(&amp;pFormatCtx, filename, NULL, NULL) != 0){
              fprintf(stderr, "FFmpeg failed to open file %s!\n", filename);
              exit(-1);
           }

           if (av_find_stream_info(pFormatCtx) &lt; 0){
              fprintf(stderr, "FFmpeg failed to retrieve stream info!\n");
              exit(-1);
           }

           // Dump information about file onto standard error
           av_dump_format(pFormatCtx, 0, filename, 0);

           // Find the first video stream
           int i = 0;
           for (i; i &lt; pFormatCtx->nb_streams; i++){
              if (pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO &amp;&amp; videoStream &lt; 0){
                 videoStream = i;
              }

              if (pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO &amp;&amp; audioStream &lt; 0){
                 audioStream = i;
              }
           }

           if (videoStream == -1){
              fprintf(stderr, "No video stream found in %s!\n", filename);
              exit(-1);
           }

           if (audioStream == -1){
              fprintf(stderr, "No audio stream found in %s!\n", filename);
              exit(-1);
           }

           // Get a pointer to the codec context for the audio stream
           aCodecCtx = pFormatCtx->streams[audioStream]->codec;

           // Set audio settings from codec info
           SDL_AudioSpec wanted_spec;
           wanted_spec.freq = aCodecCtx->sample_rate;
           wanted_spec.format = AUDIO_S16SYS;
           wanted_spec.channels = aCodecCtx->channels;
           wanted_spec.silence = 0;
           wanted_spec.samples = SDL_AUDIO_BUFFER_SIZE;
           wanted_spec.callback = audio_callback;
           wanted_spec.userdata = aCodecCtx;

           SDL_AudioSpec spec;
           if (SDL_OpenAudio(&amp;wanted_spec, &amp;spec) &lt; 0){
              fprintf(stderr, "SDL_OpenAudio: %s\n", SDL_GetError());
              exit(-1);
           }

           AVCodec* aCodec = avcodec_find_decoder(aCodecCtx->codec_id);
           if (!aCodec){
              fprintf(stderr, "Unsupported codec [1]!\n");
              exit(-1);
           }
           avcodec_open(aCodecCtx, aCodec);

           // audio_st = pFormatCtx->streams[index]
           packet_queue_init(&amp;audioq);
           SDL_PauseAudio(0);

           // Get a pointer to the codec context for the video stream
           pCodecCtx = pFormatCtx->streams[videoStream]->codec;

           // Find the decoder for the video stream
           AVCodec* pCodec = avcodec_find_decoder(pCodecCtx->codec_id);
           if (pCodec == NULL){
              fprintf(stderr, "Unsupported codec [2]!\n");
              exit(-1); // Codec not found
           }

           // Open codec
           if (avcodec_open(pCodecCtx, pCodec) &lt; 0){
              fprintf(stderr, "Unsupported codec [3]!\n");
              exit(-1); // Could not open codec
           }
        }


        int main(int argc, char* argv[])
        {
           if (argc &lt; 2){
               std::cout &lt;&lt; "Usage: " &lt;&lt; argv[0] &lt;&lt; " <video>" &lt;&lt; std::endl;
               return -1;
           }

           av_register_all();

           // Init SDL
           if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER))
           {
              fprintf(stderr, "Could not initialize SDL - %s\n", SDL_GetError());
              return -1;
           }

           // Init ffmpeg and setup some SDL stuff related to Audio
           setup_ffmpeg(argv[1]);

           VideoCapture cap(argv[1]);
           if (!cap.isOpened()){
              std::cout &lt;&lt; "Failed to load file!" &lt;&lt; std::endl;
              return -1;
           }

           AVPacket packet;
           while (av_read_frame(pFormatCtx, &amp;packet) >= 0)
           {
              if (packet.stream_index == videoStream)
              {
                 // Actually this is were SYNC between audio/video would happen.
                 // Right now I assume that every VIDEO packet contains an entire video frame, and that&#39;s not true. A video frame can be made by multiple packets!
                 // But for the time being, assume 1 video frame == 1 video packet,
                 // so instead of reading the frame through ffmpeg, I read it through OpenCV.

                 Mat frame;
                 cap >> frame; // get a new frame from camera

                 // do some processing on the frame, either as a Mat or as IplImage.
                 // For educational purposes, applying a lame grayscale conversion
                 IplImage ipl_frame = frame;
                 for (int i = 0; i &lt; ipl_frame.width * ipl_frame.height * ipl_frame.nChannels; i += ipl_frame.nChannels)
                 {
                    ipl_frame.imageData[i] = (ipl_frame.imageData[i] + ipl_frame.imageData[i+1] + ipl_frame.imageData[i+2])/3;   //B
                    ipl_frame.imageData[i+1] = (ipl_frame.imageData[i] + ipl_frame.imageData[i+1] + ipl_frame.imageData[i+2])/3; //G
                    ipl_frame.imageData[i+2] = (ipl_frame.imageData[i] + ipl_frame.imageData[i+1] + ipl_frame.imageData[i+2])/3; //R
                 }

                 // Display it on SDL window
                 show_frame(&amp;ipl_frame);

                 av_free_packet(&amp;packet);
              }
              else if (packet.stream_index == audioStream)
              {
                 packet_queue_put(&amp;audioq, &amp;packet);
              }
              else
              {
                 av_free_packet(&amp;packet);
              }

              SDL_Event event;
              SDL_PollEvent(&amp;event);
              switch (event.type)
              {
              case SDL_QUIT:
                 SDL_FreeSurface(surface);
                 SDL_Quit();
                 break;

              default:
                 break;
              }
           }

           // the camera will be deinitialized automatically in VideoCapture destructor

           // Close the codec
           avcodec_close(pCodecCtx);

           // Close the video file
           av_close_input_file(pFormatCtx);

           return 0;
        }
    </video></iostream>