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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

  


• How to implement multiple video resolutions on front and back-end

  25 février 2021, par LanGuu

  I need a solution or hint on how should I handle multiple resolutions on front-end and back-end. I have been reading about hls, dash, and mse for last few days but the more information I read, the more lost I am.

  


  Right now I have only a microservice for downscaling video using FFmpeg. The FFmpeg returns mp4 with no hls or dash, 4 video resolutions with no sound, and 2 different audio quality.
On front-end, I use react-player. The hardest part is that I need to merge audio and video, synchronize and handle change quality events.
I have found Media source extensions but it won't work I am not sure, but probably because I am using raw mp4 files.

  


  I would like to ask you a few questions

  


  

  1. It is possible to combine video and audio sources without MSE and still keep video and audio separate

  


  2. Do I need HLS or Dash to use MSE ?

  


  3. What is a difference between progressive download and progressive streaming ?

  


  4. If I have to choose what is better right now hls or dash ? what is much easier to implement ?

  


  


• Can I pipe multiple ffmpeg outputs to different pipes ?

  4 mars 2021, par mr. rogers

  I have an AWS workflow that streams an audio or video file from S3 to ffmpeg inside a lambda. Which then streams the encoded output back to S3. I want to extend that flow to generate DASH content. On my local device, I can generate the MPD file and the encoded AV files. And there's the problem. Encoding to dash generates at least two files, even with the -single_file flag.

  


  Can I limit the dash export to just the video or MPD file ? Or can I somehow pipe the multiple outputs separately through some flag magic ?

  


  Thanks in advance.