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• FFMpeg amix filter volume changes. Explanation request

  22 janvier 2020, par klodoma

  First, the question :
  IS THERE somewhere documented or explained how ffmpeg amix filter changes the volume in the mixed audio files ? I couldn’t find any good reference.

  There are several threads regarding this "issue" that the amix filter changes the volume of the input files. I played around with these and I just cannot explain what is going on. It makes a difference if you "mix" files like concatenate them at specific times or you overlap audio tracks and volume changes just doesn’t make any sense.

  Firstly, I don’t understand WHY the volumes need to be changed.

  Some related refs :

  • FFMPEG amix filter volume issue with inputs of different duration
  • FFMPEG set volume in amix

• ffplay cannot play more than one song

  5 février 2020, par Bernie gach

  i have taken ffplay.c file from http://ffmpeg.org/doxygen/trunk/ffplay_8c-source.html and re edited it to a cpp file to embed in my win32 gui application . i have made the following changes to it.

  1. made the int main function into a local function as follows, i can pass the HWND to embedd the player

  void Ffplay::play_song(string file, HWND parent, bool* successfull)
  
  {
  
      int flags;
  
      VideoState* is;
  
      input_filename = file; 
  
      /* register all codecs, demux and protocols */
  
  #if CONFIG_AVDEVICE
  
      avdevice_register_all();
  
  #endif
  
      //avformat_network_init();
  
      //check whether the filename is valid
  
      if (input_filename.empty())
  
      {
  
          logger.log(logger.LEVEL_ERROR, "filename %s is not valid\n", file);
  
          return;
  
      }
  
      if (display_disable)
  
      {
  
          video_disable = 1;
  
      }
  
      flags = SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER;
  
      if (audio_disable)
  
          flags &= ~SDL_INIT_AUDIO;
  
      else
  
      {
  
          /* Try to work around an occasional ALSA buffer underflow issue when the
  
           * period size is NPOT due to ALSA resampling by forcing the buffer size. */
  
          if (!SDL_getenv("SDL_AUDIO_ALSA_SET_BUFFER_SIZE"))
  
              SDL_setenv("SDL_AUDIO_ALSA_SET_BUFFER_SIZE", "1", 1);
  
      }
  
      if (display_disable)
  
          flags &= ~SDL_INIT_VIDEO;
  
      SDL_SetMainReady();
  
      if (SDL_Init(flags))
  
      {
  
          logger.log(logger.LEVEL_ERROR, "Could not initialize SDL - %s\n", SDL_GetError());
  
          logger.log(logger.LEVEL_ERROR, "(Did you set the DISPLAY variable?)\n");
  
          return;
  
      }
  
      //Initialize optional fields of a packet with default values.
  
      //Note, this does not touch the data and size members, which have to be initialized separately.
  
      av_init_packet(&flush_pkt);
  
      flush_pkt.data = (uint8_t*)&flush_pkt;
  
  
  
      if (!display_disable)
  
      {
  
          int flags = SDL_WINDOW_HIDDEN;
  
          if (alwaysontop)
  
  #if SDL_VERSION_ATLEAST(2,0,5)
  
              flags |= SDL_WINDOW_ALWAYS_ON_TOP;
  
  #else
  
              logger.log(logger.LEVEL_INFO, "SDL version doesn't support SDL_WINDOW_ALWAYS_ON_TOP. Feature will be inactive.\n");
  
  #endif
  
          if (borderless)
  
              flags |= SDL_WINDOW_BORDERLESS;
  
          else
  
              flags |= SDL_WINDOW_RESIZABLE;
  
          SDL_InitSubSystem(flags);
  
          ShowWindow(parent, true);
  
          //window = SDL_CreateWindow(program_name, SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, default_width, default_height, flags);
  
          window = SDL_CreateWindowFrom(parent);
  
          SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, "linear");
  
          if (window) {
  
              renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC);
  
              if (!renderer)
  
              {
  
                  logger.log(logger.LEVEL_ERROR, "Failed to initialize a hardware accelerated renderer: %s\n", SDL_GetError());
  
                  renderer = SDL_CreateRenderer(window, -1, 0);
  
              }
  
              if (renderer)
  
              {
  
                  if (!SDL_GetRendererInfo(renderer, &renderer_info))
  
                  {
  
                      logger.log(logger.LEVEL_INFO, "Initialized %s renderer.\n", renderer_info.name);
  
                  }
  
              }
  
          }
  
          if (!window || !renderer || !renderer_info.num_texture_formats)
  
          {
  
              logger.log(logger.LEVEL_ERROR, "Failed to create window or renderer: %s\n", SDL_GetError());
  
              return;
  
          }
  
      }
  
  
  
      is = stream_open(input_filename.c_str(), file_iformat);
  
      if (!is)
  
      {
  
          logger.log(logger.LEVEL_ERROR, "Failed to initialize VideoState!\n");
  
          return;
  
      }
  
      //the song is playing now
  
      *successfull = true;
  
      event_loop(is);
  
      //the song has quit;
  
      *successfull = false;
  
  }

  2. changed the callback functions as the static ones couldn’t be used by c++ eg,

  void Ffplay::static_sdl_audio_callback(void* opaque, Uint8* stream, int len)
  
  {
  
      static_cast(opaque)->sdl_audio_callback(opaque, stream, len);
  
  }

  closing doesn’t change from the main file to close the audio and sdl framework

  void Ffplay::do_exit(VideoState* is)
  
  {
  
      abort = true;
  
      if(is)
  
      {
  
          stream_close(is);
  
      }
  
      if (renderer)
  
          SDL_DestroyRenderer(renderer);
  
      if (window)
  
           SDL_DestroyWindow(window);
  
  #if CONFIG_AVFILTER
  
      av_freep(&vfilters_list);
  
  #endif
  
      avformat_network_deinit();
  
      SDL_Quit();
  
  
  
  }

  i call the functions as follows from main gui

  ft=std::async(launch::async, &Menu::play_song, this, songs_to_play.at(0));

  the menu::play_song function is :

  void Menu::play_song(wstring song_path)
  
  {
  
      ready_to_play_song = false;
  
      OutputDebugString(L"\nbefore song\n");
  
      using std::future;
  
      using std::async;
  
      using std::launch;
  
  
  
      string input{ song_path.begin(),song_path.end() };
  
      Ffplay ffplay;
  
      ffplay.play_song(input, h_sdl_window, &song_opened);
  
  
  
      OutputDebugString(L"\nafter song\n");
  
      ready_to_play_song = true;
  
  }

  THE PROBLEM is i can only play one song . if i call the menu::play_song function again the sound is missing and the video/art cover is occasionally missing also. it seems some resources are not been released or something like that.

  i have localised the proble to this function

  int Ffplay::packet_queue_get(PacketQueue* q, AVPacket* pkt, int block, int* serial)
  
  {
  
  
  
      MyAVPacketList* pkt1;
  
      int ret;
  
      int count=0;
  
      SDL_LockMutex(q->mutex);
  
  
  
      for (;;) 
  
      {
  
  
  
  
  
          if (q->abort_request)
  
          {
  
              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 + sizeof(*pkt1);
  
              q->duration -= pkt1->pkt.duration;
  
              *pkt = pkt1->pkt;
  
              if (serial)
  
                  *serial = pkt1->serial;
  
              av_free(pkt1);
  
              ret = 1;
  
              break;
  
          }
  
          else if (!block) {
  
              ret = 0;
  
              break;
  
          }
  
          else 
  
          {
  
              logger.log(logger.LEVEL_INFO, "packet_queue before");
  
              SDL_CondWait(q->cond, q->mutex);
  
              logger.log(logger.LEVEL_INFO, "packet_queue after");
  
  
  
          }
  
      }
  
      SDL_UnlockMutex(q->mutex);
  
      return ret;
  
  }

  the call to SDL_CondWait(q->cond, q->mutex); never returns

• Samples Archive Mirror

  27 février 2011, par Multimedia Mike — General

  I’m pleased to announce the first (to my knowledge) public mirror of the world-famous MPlayerHQ multimedia samples archive, hosted right here at multimedia.cx (can you think of a better place ?) :

  http://samples.multimedia.cx/

  Here’s hoping the load doesn’t crush my simple hosting plan (which actually claims quite a bit of bandwidth per month, but we’ll see).