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• 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.)

  


• avcodec/ffv1 : Implement CRC with non zero initial and final value

  25 septembre 2024, par Michael Niedermayer

  avcodec/ffv1 : Implement CRC with non zero initial and final value
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/ffv1.h
  • [DH] libavcodec/ffv1dec.c
  • [DH] libavcodec/ffv1enc.c

• No audio in the final video when converting webm blobs to mp4 using ffmpeg

  28 septembre 2024, par alpecca

  I trying to record user camera and microphone and using MediaRecorder to convert the stream to blobs and sending the blobs every 2 second to the backend using websocket. Everything is working fine, but when I checked the final mp4 video in the backend, it doesn't have any audio to it, I try specifying the audio codec, but still no help.

  


  My frontend code :-

  


  const micStream = await navigator.mediaDevices.getUserMedia({ audio: true });

const recorder = new MediaRecorder(stream, {
   mimeType: 'video/webm;codecs=H264',
   videoBitsPerSecond: 8000000,
   audioBitsPerSecond : 8000000
});

recorder.ondataavailable = (e: BlobEvent) => {
    websocket.send(e.data)         
}  
recorder.start(2000);


  


  And here is the backend code :-

  


  @router.websocket("/streamaudio")
async def websocket_endpoint(websocket: WebSocket):
    await manager.connect(websocket)

    recordingFile = os.path.join(os.getcwd(), f"recording_.mp4")

    command = [
        'ffmpeg', 
        '-y',
        '-i', 
        '-', 
        '-codec:v', 
        'copy', 
        '-c:a', 'aac', 
        '-y',
        '-f', 'mp4',
        recordingFile,
        # "-"
        # f'output{queueNumber}.mp4',
    ]  

    
    try:
        while True:
            try:
           
                data = await websocket.receive_bytes()
                
                process.stdin.send(data)
               
            except RuntimeError:
                break      
    except WebSocketDisconnect:
        print(f"Client disconnected: {websocket.client.host}")
    finally:
        manager.disconnect(websocket)
        await process.stdin.aclose()
        await process.wait()