Recherche avancée

Sur d’autres sites (3004)

• How can I seek to frame No. X with ffmpeg ?

  27 août 2018, par Giumo

  I’m writing a video editor, and I need to seek to exact frame, knowing the frame number.

  Other posts on stackoverflow told me that ffmpeg may give me a few broken frames after seeking, which is not a problem for playback but a big problem for video editors.

  And I need to seek by frame number, not by time, which will become inaccurate when converted to frame number.

  I’ve read dranger’s tuts (which is outdated now), and end up with :

  av_seek_frame(fmt_ctx, video_stream_id, frame, AVSEEK_FLAG_ANY);

  It always seek to frame No. 0, and always return 0 which means success.
  Then I tried to read Blender’s source code and found it really complex(maybe I should implement an image buffer ?).

  So, is there any simple way to seek to a frame with just a simple call like seek(context, frame_number)(while getting a full frame, not a broken one) ? Or, is there any lightweight library that simplifies this ?

  EDIT :
  Thanks to praks411，I found the solution :

  void AV_seek(AV * av, size_t frame)
  
  {
  
      int frame_delta = frame - av->frame_id;
  
      if (frame_delta < 0 || frame_delta > 5)
  
          av_seek_frame(av->fmt_ctx, av->video_stream_id,
  
                  frame, AVSEEK_FLAG_BACKWARD);
  
      while (av->frame_id != frame)
  
          AV_read_frame(av);
  
  }
  
  
  
  void AV_read_frame(AV * av)
  
  {
  
      AVPacket packet;
  
      int frame_done;
  
  
  
      while (av_read_frame(av->fmt_ctx, &packet) >= 0) {
  
          if (packet.stream_index == av->video_stream_id) {
  
              avcodec_decode_video2(av->codec_ctx, av->frame, &frame_done, &packet);
  
              if (frame_done) {
  
                  ...
  
                  av->frame_id = packet.dts;
  
                  av_free_packet(&packet);
  
                  return;
  
              }
  
          }
  
          av_free_packet(&packet);
  
      }
  
  }

  EDIT2 :
  Turns out there is a library for this : FFMS2.
  It is "an FFmpeg based source library [...] for easy frame accurate access", and is portable (at least across Windows and Linux).

• Recording ip camera stream writing video file [closed]

  10 décembre 2020, par Marc

  We are implementing a camera surveillance system project using python with openCV/ffmpeg and Cuda based on client-server architecture, this system should hold up to 40-60 IP cameras for live, record and playback features.

  


  The problem is that their is delay in live view between our program and the web page of the camera and problem in writing frames into video files(recording).

  


  Does the problem due to the used language or a hardware issue, and does python represents the efficient language for this type of projects ?

  


• ffmpeg No NVENC capable devices found if run on multiple GPUs [duplicate]

  25 octobre 2017, par Marco Pardo

  This question is an exact duplicate of :

  • ffmpeg - cuda encode - OpenEncodeSessionEx failed : out of memory
    
    1 answer
    

  i have 4 Geforce 1060 GPUs and a running ffmpeg with cuvid on ubuntu server.

  If i run this :

  /bin/ffmpeg -hwaccel cuvid -i 0.mkv -c:v hevc_nvenc -profile:v main -rc vbr_hq -qmin 18 -qmax 24 -b:v 1000k -maxrate 3000k -preset slow -rc-lookahead 32 -g 250 -c:a copy -c:s copy -map 0 -gpu 0 out0.mkv null

  (notice -gpu 0) it works like a charm. I can run 2 conversions at once (on differend GPUs) :

  /bin/ffmpeg -hwaccel cuvid -i 1.mkv -c:v hevc_nvenc -profile:v main -rc vbr_hq -qmin 18 -qmax 24 -b:v 1000k -maxrate 3000k -preset slow -rc-lookahead 32 -g 250 -c:a copy -c:s copy -map 0 -gpu 1 out1.mkv null
  
  /bin/ffmpeg -hwaccel cuvid -i 2.mkv -c:v hevc_nvenc -profile:v main -rc vbr_hq -qmin 18 -qmax 24 -b:v 1000k -maxrate 3000k -preset slow -rc-lookahead 32 -g 250 -c:a copy -c:s copy -map 0 -gpu 2 out2.mkv null

  all of this works perfectly and i see via nvidia-smi that the processes use the named GPUs.

  But if i run all three commands together the first two started normal and the third creashed with :

  # [hevc_nvenc @ 0x5601103ca560] OpenEncodeSessionEx failed: out of memory (10) 
  
  # [hevc_nvenc @ 0x5601103ca560] No NVENC capable devices
  
  # found Error initializing output stream 0:0 -- Error while opening
  
  # encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height

  The memory (on GPUs and system) is more than enough !

  can anyone help me by this ?