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• What are the correct conversion steps to generate a video from PDF with ffmpeg and mp4box

  25 juin 2020, par Michael Rall

  I need to convert a PDF-Document to a DASH-compatible stream. Every page of the PDF should be displayed for one second. Quality should be rather good, so that text and line graphics can still be read clearly. Additionally I want to be able to seek every page, so keyframes(?) should be (exactly) every second.

  


  Im using poppler-tools to extract the pdf-pages as png's -> works

  


  Im using ffmpeg to convert the single images to an x264 encoded mp4 video -> works (but maybe problematic)

  


  string.Format("-r 1 -i \"{0}.page_%d.png\" -r 24 -vcodec libx264 -pix_fmt yuv420p {0}.output.mp4", basePath)


  


  Im using MP4Box to convert that video to dash -> works (but needs improvement)

  


  string.Format("-dash 1000 -frag 1000 -rap -segment-name {1}_dash_$RepresentationID$_$Number$ -url-template {0}.output.mp4 -out \"{0}.{2}\"", basePath, tempDataId, STREAM_MANIFEST_FILE_POSTFIX)


  


  Now I have 2 Problems/Questions

  


  

  1. Are the settings for framerate, quality, outputformat correct for the goals I want to achieve

  


  2. When displaying the resulting DASH-Stream in the Demo-Player from https://github.com/Dash-Industry-Forum/dash.js/wiki it plays the stream, but as soon as I try to seek the player starts loading forever. Setting the position to start and let it play again works. The network tab in my browser-debugger shows that the player tries to load the segments and gets them successfully.

  


  


  I guess its a problem with keyframes, fragments or similar. Can somebody correct my conversion steps ?

  


  kind regards

  


• Anomalie #3380 : Un rédacteur peut attacher un document à un article qu’il n’a pas le droit de mod...

  8 juin 2015, par b b

  Pour info, cette modification a introduit un bug signalé dans #3452.

• How to raw TS packets off a file/url — Without decoding

  15 août 2019, par Znura

  New to ffmpeg and playing around that to understand better. I’m trying to use ffmpeg code base to get TS packets from a HLS Streaming server. I don’t need any decoding as I just have to store the TS packets to be processed later.

  First I built a minimal FFMPEG as outlined in https://zeranoe.com/forum/viewtopic.php?f=5&t=7426. No decoders and only hls and mpegts demuxers. Then using the following code to receive the frames. While inspecting it doesn’t seem to be MPEG-TS packets while looking into buffers thru GDB. Attaching the code here..

  Two Questions :

  1. Shouldn’t the av_recv_frame get me the TS packets ? However When I trace all the way to playlists (off HLSContext), the read_buffer there contains TS packets. IS there any example I could look into to get TS packets in this scenario without decoders ?

  2. If I get answer for (1), How to get the best stream off the HLS server ? when looking into ffplay, av_find_best_stream() sounds like the one to look into.. But again without needing to decode, is there a way to get best one according to the network condition ?

  Thanks..

  I dumped whatever I got off av_recv_frame() and stored in file. This file is not playable with VLC but Windows Movies & TV player could play the sound with missing frames..

  int main(int argc, char *argv[]) { 
  
      AVFormatContext * ifmt_ctx = NULL; 
  
      char *in_filename = NULL; 
  
      int ret = 0; 
  
      AVPacket pkt; 
  
      if (argc != 2) { return 1; } 
  
      in_filename = argv[1]; 
  
      av_register_all();
  
  
  
      if (!(ifmt_ctx = avformat_alloc_context())) { goto end; } 
  
      if ((ret = avformat_open_input(&ifmt_ctx, in_filename, 0, 0)) < 0) { 
  
          fprintf(stderr, "Could not open input file '%s'", in_filename); 
  
          goto end; 
  
      } 
  
      if ((ret = avformat_find_stream_info(ifmt_ctx, 0)) < 0) { 
  
          fprintf(stderr, "Failed to retrieve input stream information"); 
  
          goto end; 
  
      }
  
  
  
      av_dump_format(ifmt_ctx, 0, in_filename, 0); 
  
      while (1) { 
  
          ret = av_read_frame(ifmt_ctx, &pkt); 
  
          if (ret < 0) break; 
  
          av_free_packet(&pkt); 
  
      } 
  
      end: avformat_close_input(&ifmt_ctx); return 0; 
  
  }