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• How to merge webm video with mp4 video with transperency ?

  30 novembre 2017, par kostya572

  I have 1080p webm video and 500x300 mp4 video. How could I place muted mp4 video on top-center position of webm video with transparency ? The output file format needed ".webm". Here what similar code I found, but it uses two mp4 videos and second video scales full width on front of first one :

  ffmpeg \
       -i in1.mp4 -i in2.mp4 \
       -filter_complex " \
           [0:v]setpts=PTS-STARTPTS, scale=480x360[top]; \
           [1:v]setpts=PTS-STARTPTS, scale=480x360, \
                format=yuva420p,colorchannelmixer=aa=0.5[bottom]; \
           [top][bottom]overlay=shortest=1" \
       -vcodec libx264 out.mp4

  Output log :
  

• Detect if "faststart" has been applied to video

  26 juin 2024, par Will Ashworth

  When running "qt-faststart" on an MP4, you're essentially taking the meta data from the back and placing it at the front of the file. In my case, so Flash can properly start playing the video before it's fully done loading.

  



  I have a large number of videos that I'm running through a shell script to encode overnight. When I upload, however, I won't necessarily know in my final folder of videos (on the server) have "qt-faststart" run on it.

  



  My goal is to find the straggler videos and run qt-faststart on them manually, but I'll need a way to compile a list. Is there any way to check for this meta data information with PHP or something ? Wondering how I can tell if a video has already had qt-faststart run on it or not.

  


• FFplay : WASAPI can't initialize audio client (FFmpeg 3.4 binaries)

  9 juillet 2022, par fve

  I am trying to playback a stream that is multicasted over RTP using ffplay on Windows 7 64 bits.
The computer that serves the audio over RTP runs :

  



  ffmpeg -re -f dshow -audio_buffer_size 15 -ac 1 -i audio="Mic in at front Mic-in (Realtek" -ar 8k -acodec pcm_alaw -vn -f rtp rtp://127.0.0.1:5000


  



  The client runs :

  



  ffplay rtp://127.0.0.1:5000


  



  While this was working correctly in release 3.3, release 3.4 fails with this error :

  



  SDL_OpenAudio (1 channels, 8000 Hz): WASAPI can't initialize audio client: CoInitialize has not been called.

No more combinations to try, audio open failed
Failed to open file 'rtp://127.0.0.1:5000' or configure filtergraph


  



  Anyone has an idea of whats going on ?

  



  Thanks

  



  UPDATE #1 :

  



  A workaround is to specify an alternate output driver.
Set SDL_AUDIODRIVER environment variable value to the driver you want to use.
Under windows 7, directsound and winmm both solved my issue.