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• How should one start with ffmpeg's API ?

  20 mai 2018, par JoeDough

  I’d like to make a real time streaming program that takes input from a webcamera, ffmpeg looks like a good library for encoding a stream of images but there is no documentation or community tutorials (there is just a doxygen API reference).Where should I start if there’s no official documentation ?

• How to convert VP8 track with different frame resolution to h264

  13 septembre 2016, par Nikita

  I have a .webm file with VP8 track, recorded from WebRTC stream by external service (TokBox Archiving). The stream is adaptive, so each frame in track could have different resolution. Most players (in webkit browsers) use video resolution from track description (which is always 640x480) and scale frames to this resolution. Firefox and VLC player uses real frame resolution, changing video resolution respectively.

  I want to achieve 2 goals :

  1. play this video in Internet Explorer 9+ without additional plugin installation.
  2. change frames resolution to one fixed resolution, so the video will look identically in different browsers.

  So, my plan is :

  • extract frames from source webm file to images with real frame resolution (e.g. PNG or BMP) (how could I do that ?)
  • find max width and max height of images
  • add black padding to images, so smaller frames will be in the center of a new frame (of size MAX_WIDHTxMAX_HEIGHT)
  • combine images to h264 track using ffmpeg

  Is all correct ? How can I achieve this ? Can this algorithm be optimized some way ?

  I tried ffmpeg to extract images, but it does not parse real frame resolution, using resolution from track header.
  I think some libwebm functions can help me (to parse frame headers and extract images). Maybe someone has some code snippets to do this ?

  Example .webm (download source, do not play google-converted version) : https://drive.google.com/file/d/0BwFZRvYNn9CKcndhMzlVa0psX00/view?usp=sharing

  Official description of adaptive stream from TokBox support : https://support.tokbox.com/hc/en-us/community/posts/206241666-Archived-video-resolution-is-supposed-to-be-720x1280-but-reports-as-640x480

• How to add dynamic captions with animations on a video in a cross-platform Android & iOS app and export it as a final video ? [closed]

  29 avril, par Danial Qsk

  I'm building a cross-platform mobile app using Flutter (or React Native) where users can :

  


  Add dynamic text captions with animations over a video, similar to TikTok

  


  See these changes in real-time during video playback

  


  Export the video with the animated captions burned into the output (e.g., MP4)

  


  What I’ve implemented so far :

  


  Video playback using video_player in Flutter (or react-native-video).

  


  Captions are rendered using Canvas/UI layer during playback.

  


  Problem : While I can overlay animated text in the UI, I can't figure out how to include these in the exported video. I’m considering using FFmpeg to burn in the captions, but I’m unclear how to integrate it with the animated UI overlays or render them into a final video on both Android and iOS.

  


  What I want to achieve :

  


  Efficient way to render animated text overlays onto a video and export it as a final video file on both Android and iOS.

  


  Maintain good performance for real-time playback and smooth export.

  


  What approaches or processing pipelines could achieve this ?
(For example, rendering the UI layer to an offscreen video, integrating with FFmpeg, or using native rendering techniques.)