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• ffmpeg is setting start_time to a negative value on output

  16 mai 2016, par Éric

  We’ve been using an old version of ffmpeg for a while and now we need to upgrade to a more recent version (e.g. 2.6) and we have issues with it while converting .mov to .mp4.

  For instance I have a .mov video file that has two streams, video and audio, both with start_time=0 and when I convert it using :

  ffmpeg -i my_file.mov my_file.mp4

  the output mp4 has an audio stream with start_time=-0.021333.

  The FORMAT section, as shown by ffprobe -show_format -show_streams my_file.mp4
  also has start_time=-0.021333

  The previous version of ffmpeg we were using didn’t have this issue...

  When we play the output mp4 file in a web browser using < video > it’s all good while playing but if we pause the video and seek here and there we notice that all the frames are off by 1. The first frame is duplicated and the last frame is missing !

  In other words :

  dom.currentTime = 0 shows the first frame
  
  dom.currentTime = 1/24 (fps is 24) shows the first frame again
  
  dom.currentTime = 2/24 shows the second frame instead of the third frame
  
  dom.currentTime = 3/24 shows the third frame instead of the fourth frame
  
  ...

  We believe this is caused by the field start_time=-0.021333

  This is a major issue for us...

  It’s repro on chrome and firefox but somehow safari is not having issues with this...

  After googling this we found that we’re not the only one with this issue but it’s not clear what the solution is.

  Someone suggested to use the "-c:a copy" arguments and it worked on some files but gave an error on some others :

  Could not write header for output file #0 (incorrect codec parameters ?) : Invalid argument

  So this doesn’t seem to be a robust solution...

  Any help would be appreciated.

• Merge multiple videos without using command line-FFMPEG [on hold]

  19 avril 2018, par Valgrind1691

  I am developing an android application which has video processing features involved.
  For video processing I have been working with FFMPEG library. As for now ffmpeg is directly being consumed by android and the processing is being done by
  framing commands and executing it using ffmpeg executable running in the background.
  This approach has two drawbacks :

  1) Video Processing time is huge even after trying ultrafast and other options to reduce processing

  2) APK size is large

  For solving two major problems we seek c/c++ native implementation for video processing by using the ffmpeg code.
  The C/C++ code will be cross compiled for android and iOS platforms and provided to mobile platform as a library (.so file in case of Android)
  The .so file will have

  1. jni for communication between Android(java) and c/c+

  2. c++ code for functionality implementation of video processing. All
     the video processing i.e scaling, transcoding, merging,
     cropping etc will be done by C/C++ code.

  I have a query around the C/C++ side , how can we use ffmpeg not to process using command line rather we can define algorithms for the process. Transcoding, muxing etc I have achieved looking into the examples of ffmpeg but I am still unable to figure out algorithm for merging of multiple(upto 6) videos in a single video file.
  I have looked into every question posted in this context and none helped.
  Can someone help me merge videos using source code of ffmpeg without using command line ? Any help is appreciated.

• Ffmpeg hls live stream video freezes for a second but audio continues and video catches up

  13 décembre 2022, par Bluchip Studio

  I am using the latest version of ffmpeg to create a hls live stream todo this i am using the following command

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  /root/ffmpeg -y -loglevel debug -threads 0 -probesize 512000 -analyzeduration 512000 -user_agent "Chrome/98.0.4758.102" -i https://example.com/input.m3u8 -c:v copy -c:a copy -async 1 -tune zerolatency -fflags +genpts -hls_init_time 2.002 -hls_time 2.002 -hls_list_size 20 -hls_flags delete_segments+append_list -hls_segment_type mpegts -hls_segment_filename "/var/www/html/hls/segment_%05d.ts" -f hls "/var/www/html/hls/playlist.m3u8"


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  I initially tried using fmp4 but i noticed the video would lag behind major and the audio would end up well ahead so i switched to mpegts

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  i managed to fix the audio issue here using -async 1 on fmp4 this made no diffrence now i have a small issue where my stream will open and play but the video will freez every few seconds while the audio continues and then the video will jump to catch back up and continue then it will do it again and again and again

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  dose anyone know what may be causing this issue i tried swapping to x264 in stead of copying the video stream and using force key frames to set a key frame every 2 seconds but this resulted in well the same issue if not a little worse

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  i kind of expected the stream to play perfect with the settings i have and with the logs set to debug i cant see any errors at all

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