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• ffmpeg continue streaming to twitch use case

  11 juin 2023, par Hassan M. Amin

  So I have a weird use case that I'm struggling with. Here's the situation :

  


  I have 2 video files, each 1 hour long. I want to stream the first file to twitch in a process, and when that file ends, the ffmpeg process will end and then I want to pickup the other video and continue the stream with that one.

  


  Why should the process end ? because after the first video ends, I need to check via code if the 2nd video is available to be streamed, otherwise I'll re-stream the first video again.

  


  I understand that this can be done via concatenating the two videos, but again, the 2nd video might not be available just yet so we need to end the process right after the 1st video ends streaming and check if it's there.

  


  This works great on YouTube, but the issue I'm facing is that Twitch specifically, when we start streaming the 2nd video, thinks that it's a totally new live stream and resets the live duration counter.

  


  Here's the million dollar question : How can we make twitch think that the data being sent from the 2nd video is the remainder of the first video ? I think it has something to do with the timestamps being sent ? any pointers or other way to look at this ?

  


  Tried updating the pts to be the previous video length + current pts

  


• convert 16bit grayscale raw video by ffmpeg for analysis in openCV

  15 février 2015, par user3730845

  I have 16bit grayscale stream of scientific data which I want to analyse in openCV. I tried to look for some conversion of data, however it seems that grayscale is a trouble for ffmpeg and available codecs.

  My idea is to use 3 colours of video wisely and stream my grayscales into 3 colours, one by one and then in openCV access each colour and do my analysis there. Is such a thing possible ?

  When I convert stream by : ffmpeg -f rawvideo -y -s 256x256 -pix_fmt gray16be -i rawfile.bin -an -vcodec ffv1 video.avi, I get weird colour space but I can open the result in openCV.

  If there is any other way to do such a thing can you point me towards libraries/howtos, ultimately I need to do thresholding, cross-correlation, edge filtering, centre of gravity types of functions and I need to do this as quickly as possible for datasets of >10GB

  My raw files/streams are set of 256x256 16bit b&w images, with 256 bytes header and gaps

• FFMPEG aspect parameter cannot actually set aspect ratio [on hold]

  8 août 2014, par yasi

  I want to generate an h264 (avc) file by a jpg file. I generated it by command :

  • ffmpeg -f image2 -i img%d.jpg -vcodec libx264 sample.h264
  • mv avatar.h264 sample-320.avc

  the img%d.jpg is 0.jpg, 1.jpg, 2.jpg ... 24.jpg, all of which is the same, resolution is 320x180

  When sample.avc is generated, I checked information of it by ESEyE, it’s like below.
  

  As you can see, the resolution is correct, but aspect ratio is weird since original jpg sequence is 320x180, whose aspect ratio is 16:9. So, I tried to keep 16:9 by the command below

  • ffmpeg -r 25 -f image2 -i img%d.jpg -vcodec libx264 -profile:v baseline -level:v 1.1 -aspect "16:9" sample.h264

  However, it doesn’t work, the generated avc aspect ratio is still 5x3.

  How can I keep aspect ratio of 16:9 ?

  P.S.
  I guess h264 miminal block is 16x16, and avc width could be padded as 192 (16 * 12), so aspect ratio is 320:192 = 5:3.