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• Blender VSE Audio out-of-sync when animation (video) is rendered

  21 août 2021, par Siddhant Shenoy

  Ok, so I found out that Blender has this really cool video-editing interface and I was beginning to love it. Until, I created this awesome project composition and when I exported the animation as a video file, the audio was out of sync :(.

  



  Actual Problem

  



  Audio is in-sync with video when the animation is played in Blender but is out-of-sync in the rendered video.

  



  Solutions I tried out and failed

  



  

  • I used the 'Audio-Sync' option in the sequencer but that made no difference.

  


  • Then I thought that my scene audio frequency might have been an issue since it was initially 48kHz and my videos were at 24kHz, so I changed the scene audio frequency to 24kHz, this still failed to solve the issue.

  


  • Initially, I was combining videos with different frame rates and thought that might have been an issue (although animation played as expected in Blender), so I recreated the source videos to ensure all videos I was using in my project had the same frame rate, but this also did not work.

  


  • Someone online suggested exporting the video and audio separately and then combining them using a command-line tool like FFMPEG, this also failed.

  


  



  What's really frustrating

  



  


  • This lag (audio is a few frames ahead of the video) is noticeable only in longer videos (>12 mins, my video is 1 hr long) suggesting a very small rendered rate difference between the video and the audio.

  


  • Also, note that the animation plays absolutely fine in Blender, so all I could figure out was that this was a rendering issue.

  


  



  So if anyone figured this out please let me know. I am a noob in video/audio codecs so please forgive me if I used some incorrect nomenclature above.

  


• In spring manage threads created by one controller's different instances

  14 janvier 2014, par lubovbyc

  I have written a controller to deal with video upload. The hard part for me is to convert the video type to both mp4 and webm. I chose to new a thread in my controller and the thread will new a process which is a video convert software called "ffmpeg".

  The problem is that this thread will occupy too much resources(at least 25% CPU usage). So I guess I have to make these threads created by different controller instances execute in a shared queue. It is terrible to have these threads in concurrent execution.

  It seems that the taskExecutor in Spring can only manage threads created by one controller instance. And is there any way to manage threads among threads created by one controller class but different instances ? It seems like a public or shared thread pool..

• ffmpeg - caching ahead piped input as insurance while maintaining low latency and real-time output

  5 décembre 2020, par hedgehog90

  I'm piping a live transcoded stream into ffmpeg (simplified for brevity) :

  


  mpv playlist --o=- | ffmpeg -re -i - -tune zerolatency -f flv rtmp://blah.com/live

  


  The piped input usually runs above 1x encoding speed, but every now and then it can run a little slower than real-time (just a momentary 0.99x or 0.98x dip).
When this happens, the rtmp server (a popular streaming service with an audience) output will pause momentarily for a couple seconds usually.

  


  To overcome this I want ffmpeg to cache a few seconds in advance, so mpv's output (which outputs at whatever speed it's read, so potentially very fast) can supply ffmpeg with a little extra, and whenever mpv goes a little under 1x speed, there's a little insurance that ffmpeg has cached away. This should be doable while maintaining the lowest possible latency.

  


  Question is, how ?