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• Blank out video frames for last two minutes of MP4 (while keeping audio intact)

  13 juillet 2020, par fourells5

  I am trying to make a copy of one of my mp4 movies with audio intact, but blacking out video frames only on the last few minutes. Basically I want to keep the end credit music but without the artifacted video.

  


  I found this answer : which works perfectly for an entire mp4 file (including a test fragment I made of the above ending credits sequence), but I need it applied as I stated above to just the end of the entire copied full mp4.

  


  In this case I don't want to start blanking the video stream frames until after 2h 7m 30s. I messed around with combinations of the -ss, -start_time and -timecode 02:07:31 params, but I'm an ffmpeg noob and couldn't get it to produce anything but cut-out sections or the whole copy blanked.

  


  Any guidance would be greatly appreciated !

  


• How to do precise frame cut with ffmpeg ?

  25 juillet 2020, par Menglun Li

  I tried to cut multiple big videos into many small pieces. I know I can cut and export the small pieces one by one with "Premiere Elements", however that takes a lot time to export them manually. I couldn't find a way to do batch export in "Premiere Elements".

  


  I wrote down the starting and ending points of the small videos from Premiere Elements' timeline viewer, then I created a batch file to use ffmpeg for batch cutting. Below is one of the cutting command in the batch file.

  


  ffmpeg -i input.mp4 -ss 00:20:45.09 -to 00:23:01.00 -c:v libx264 -c:a aac output5.mp4 


  


  I compared the video that was cut by ffmpeg and the video was exported by Premiere Elements. I found sometime they are not starting and ending at the same frame, and it is not consistent either. Both the starting and ending frame that was cut by ffmpeg can drift forward or backward 6-9 frames from the frame number showed in Premiere Elements.

  


  How do I make sure ffmpeg has the precise frame cut ? Thanks in advance.

  


• HLS live stream stops working with AbortError after running fine for a while

  20 juillet 2020, par mandrakey

  Before I go file a bug with Video.js I wanted to see if I maybe have gotten something wrong. The situation is this :

  


  

  • I have a RTSP live stream, which I convert to HLS using ffmpeg (works)

  


  • I want to play that HLS stream using Video.js in the browser

  


  


  After I start ffmpeg, all works as expected and I can watch the live stream in the browser. This was, say, around 4pm. I go home for the day and when I try to access the stream again in the morning (around 8am, freshly started browser) I just get a black image (Firefox) or a still (Chrome) and a never ending loading animation.

  


  The browser console shows the following output every 6 seconds (which is my chunk length) :

  


  AbortError: The operation was aborted. 
XHR GET http://server/hls/live/stream1/720p6.ts [HTTP/1.1 200  71ms]
XHR GET http://server/hls/live/stream1/720p7.ts [HTTP/1.1 200  64ms]
XHR GET http://server/hls/live/stream1/720p8.ts [HTTP/1.1 200  62ms]
XHR GET http://server/hls/live/stream1/720p9.ts [HTTP/1.1 200  57ms]
XHR GET http://server/hls/live/stream1/720p0.ts [HTTP/1.1 200  63ms]


  


  Note : The chunk numbers in the end do change correctly, so it does not look like an infinite loop where video.js tries to access the same files over and over again.

  


  I have compared the m3u8 contents from a time when this happens to just after I restarted ffmpeg. The only difference I can spot is that the sequence number has increased :

  


  Working version

  


  #EXTM3U
#EXT-X-VERSION:3
#EXT-X-TARGETDURATION:6
#EXT-X-MEDIA-SEQUENCE:2
#EXTINF:6.000011,
720p2.ts
#EXTINF:5.999989,
720p3.ts
#EXTINF:6.000000,
720p4.ts
#EXTINF:6.000000,
720p5.ts
#EXTINF:6.000000,
720p6.ts


  


  Not working version

  


  #EXTM3U
#EXT-X-VERSION:3
#EXT-X-TARGETDURATION:6
#EXT-X-MEDIA-SEQUENCE:45255
#EXTINF:6.000011,
720p5.ts
#EXTINF:5.999989,
720p6.ts
#EXTINF:6.000000,
720p7.ts
#EXTINF:6.000011,
720p8.ts
#EXTINF:5.999989,
720p9.ts


  


  What I have confirmed so far :

  


  

  • The video chunks ffmpeg creates work. I have downloaded newly generated chunks and played them using VLC : Got a 6 second video as expected.

  


  • This also means the source stream still works as expected.

  


  • It does not seem to be an issue with the browser as both Firefox and Chrome show the same behaviour.

  


  • When I restart ffmpeg, which as far as I can see only resets the sequence number, everything works fine again after I reload the video.js player.

  


  • It is no one time issue : I have tried this more than 4 days in a row now. Happens every time.

  


  


  Have I stumbled upon a bug in video.js here or am I missing something ?

  


  For reference, this is how I start ffmpeg :

  


  ffmpeg -v info -rtsp_transport tcp -i rtsp://source/stream -c:v copy -c:a copy -hls_time 6 -hls_wrap 10 -start_number 1 /path/to/stream1/720p.m3u8


  


  Thank you very much for reading and taking the time so far. Any help will be much appreciated :)