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• FFmpeg convert time to frame

  3 décembre 2013, par William Seemann

  Does anyone know how to convert a timestamp into a frame ? For example, if I wanted the frame number at 2 seconds in a video with a framerate of 30/fps it would be the 60th frame. Here is the code I have so far. However, I don't think it's correct since seek_time has a value of 90 (for a 1 sec target) using a video with a framerate of 23.98 :

  int timeUs = 1000000; // 1 sec
  
  AVPacket packet;
  
  AVPacket *pkt = NULL;
  
  int64_t desired_frame_number = -1;
  
  
  
  State *state = *ps;
  
  
  
  Options opt = option;
  
  
  
  int stream_index = state->video_stream;
  
  int64_t seek_time = av_rescale_q(timeUs, AV_TIME_BASE_Q, state->pFormatCtx->streams[stream_index]->time_base);
  
  int64_t seek_stream_duration = state->pFormatCtx->streams[stream_index]->duration;
  
  
  
  int flags = 0;
  
  int ret = -1;
  
  
  
  // Convert time into frame number
  
  seek_time /= 1000;
  
  printf("seek time: %" PRId64 "\n", seek_time);

• How to reduce latency when streaming x264

  10 janvier 2014, par tobsen

  I would like to produce a zerolatency live video stream and play it in VLC player with as little latency as possible.

  This are the settings I currently use :

  x264_param_default_preset( &m_Params, "veryfast", "zerolatency" );
  
  
  
  m_Params.i_threads              =   2;
  
  m_Params.b_sliced_threads       =   true;
  
  m_Params.i_width                =   m_SourceWidth;
  
  m_Params.i_height               =   m_SourceHeight;
  
  
  
  m_Params.b_intra_refresh        =   1;
  
  
  
  m_Params.b_vfr_input            =   true;
  
  m_Params.i_timebase_num         =   1;
  
  m_Params.i_timebase_den         =   1000;
  
  
  
  m_Params.i_fps_num              =   1;
  
  m_Params.i_fps_den              =   60;
  
  
  
  m_Params.rc.i_vbv_max_bitrate   =   512;
  
  m_Params.rc.i_vbv_buffer_size   =   256;
  
  m_Params.rc.f_vbv_buffer_init   =   1.1f;
  
  
  
  m_Params.rc.i_rc_method         =   X264_RC_CRF;
  
  m_Params.rc.f_rf_constant       =   24;
  
  m_Params.rc.f_rf_constant_max   =   35;
  
  
  
  m_Params.b_annexb               =   0;
  
  m_Params.b_repeat_headers       =   0;
  
  m_Params.b_aud                  =   0;
  
  
  
  x264_param_apply_profile( &m_Params, "high" );

  Using those settings, I have the following issues :

  • VLC shows lots of missing frames (see screenshot, "verloren"). I am not sure if this is an issue.
  • If I set a value <200ms for the network stream delay in VLC, VLC renders a few frames and than stops to decode/render frames.
  • If I set a value >= 200ms for the network stream delay in VLC, everything looks good so far but the latency is, obviously, 200ms, which is too high.

  Question :
  Which settings (x264lib and VLC) should I use in order to encode and stream with as little latency as possible ?

  

• How to reduce latency when streaming x264

  10 janvier 2014, par tobsen

  I would like to produce a zerolatency live video stream and play it in VLC player with as little latency as possible.

  This are the settings I currently use :

  x264_param_default_preset( &m_Params, "veryfast", "zerolatency" );
  
  
  
  m_Params.i_threads              =   2;
  
  m_Params.b_sliced_threads       =   true;
  
  m_Params.i_width                =   m_SourceWidth;
  
  m_Params.i_height               =   m_SourceHeight;
  
  
  
  m_Params.b_intra_refresh        =   1;
  
  
  
  m_Params.b_vfr_input            =   true;
  
  m_Params.i_timebase_num         =   1;
  
  m_Params.i_timebase_den         =   1000;
  
  
  
  m_Params.i_fps_num              =   1;
  
  m_Params.i_fps_den              =   60;
  
  
  
  m_Params.rc.i_vbv_max_bitrate   =   512;
  
  m_Params.rc.i_vbv_buffer_size   =   256;
  
  m_Params.rc.f_vbv_buffer_init   =   1.1f;
  
  
  
  m_Params.rc.i_rc_method         =   X264_RC_CRF;
  
  m_Params.rc.f_rf_constant       =   24;
  
  m_Params.rc.f_rf_constant_max   =   35;
  
  
  
  m_Params.b_annexb               =   0;
  
  m_Params.b_repeat_headers       =   0;
  
  m_Params.b_aud                  =   0;
  
  
  
  x264_param_apply_profile( &m_Params, "high" );

  Using those settings, I have the following issues :

  • VLC shows lots of missing frames (see screenshot, "verloren"). I am not sure if this is an issue.
  • If I set a value <200ms for the network stream delay in VLC, VLC renders a few frames and than stops to decode/render frames.
  • If I set a value >= 200ms for the network stream delay in VLC, everything looks good so far but the latency is, obviously, 200ms, which is too high.

  Question :
  Which settings (x264lib and VLC) should I use in order to encode and stream with as little latency as possible ?