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• Merging audio channels by FFmpeg libraries C++

  13 juin 2023, par Elija

  C/C++ project. There are several audio tracks with an individual number of channels. Each is processed using a avresampler. The avresampler converts all tracks to the same format. At the output of the avresampler, we get a set of channels from all audio tracks. Do the FFmpeg libraries have any standard means to merge all these audio channels into another set of audio channels using AVFrame::ch_layout to form a single audio track ? That is, no additional processing is required, except for copying channels buffers from several AVFrames of different audio tracks to new positions of one AVFrame according to the new layout and aligning the timestamps of different audio tracks, since different audio tracks can have audio frames of different sizes with different timestamps.

  


  For example, 1 audio track with 2 channels and 2 audio tracks with 6 channels will be merged into 16 channels with silence in the "missing" channels. Or 4 audio tracks with 2 channels merged into 8 channels. Etc...

  


  Is there a way to use a avresampler for this ? Or a avfilter ? Or something else ?

  


  Any source code or any reading source that can help me is welcome.

  


• ffmpeg create thumbnail image of multiple images from video

  21 janvier 2018, par Michael Yousef

  So I want to create a thumbnail image that consists of multiple images from a single video. I’m looking to make them 4x8, and I want to spread out the images uniformly throughout the video.

  Ideally the final product should show 32 image captures, all downscaled to a reasonable size so they can fit on screen at the same time. Also, I’d like to have the final product have some overhead text like the video title, and I’d like to put the timestamp in the images as well.

  

  This is an example of what I want to do. The text at the top and the timestamp in the images. This one’s 6x4 and I want 4x8 but other than that it looks about what I want.

  I think ffmpeg probably has something to do this but I can’t seem to figure it out. I can generate individual screens but not collapse them into one. It’s also slower than programs I’ve used to do this in the past, not sure how they can do it as fast as they do. If I can’t get ffmpeg to do this, I’m open to using Python to accomplish this.

• How to get FFMPEG to use more GPU when encoding

  24 mars 2023, par Entropy

  so the situation is as following

  


  Im receiging 20/30 uncompressed image per second. format is either PNG or Bitmap. Each individual photo size is between 40 and 50 mb (all have same size since uncompressed).

  


  I want to encode them to a 265 lossless video and stream them to a http server using FFMPEG.
The output video is 1920x1080, so there is some downsampling.
Compression is allowed but nothing is allowed to be lost other than the down sampling.

  


  now i m still in the testing phase. i have a 500 sample image. and i m tryng to encode them as effeciently as possible.
Im using commands such as :

  


  ffmpeg  -hwaccel cuvid -f  image2  -i "0(%01d).png" -framerate 30 / 
-pix_fmt p010le -c:v hevc_nvenc -preset lossless -rc vbr_hq /
-b:v 6M -maxrate:v 10M  -vf scale=1920:1080  -c:a aac -b:a 240k result.mp4


  


  I have a powerfull modern quadro GPU and a 6 cores intel CPU and an Nvme hard drive.

  


  The usuage of the GPU when encoding is exactly 10%, CPU is circa 30-40%

  


  How can i get GPU usuage to 80% ? The machine on which im going to run the code will have at leat a quadro 4000 (maybe stronger) and i want to use it to the fullest