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• FFmpeg covering H264 to H265 without loosing quality

  5 septembre 2022, par drekka

  I'm looking to convert some mkv files with H264 streams to mkv with H265 streams to save some space. Currently I'm doing this :

  


  ffmpeg -i test.mkv -map 0:v -map 0:m:language:eng -c:v libx265 -c:a copy -c:s copy test-2.mkv


  


  But I notice that the progress is displaying with a low q like this

  


  frame=  484 fps=3.2 q=32.6 size=    2560kB time=00:00:20.70 bitrate=1012.9kbits/s speed=0.136x


  


  Not an expert here, but it's my understanding that high quality is around q22-18 with a lower number being better.

  


  So if I want H265 without any lose of quality should I add a q argument to set it lower ? Or is that just going to do nothing because the original material isn't great and it's that q I'm seeing in the progress display ?

  


  Follow up : The encoding's now finished and much to my surprise the H265 file is not just smaller, but massively smaller. My original test file was 29G in size, the resulting H265 is 1.5G in size. Way smaller than I was expected.

  


• Can I stream a static image feed into a video with Node.js ?

  5 juillet 2022, par Quentin Lamotte

  I want to create a small PoC where I can stream a static image source into a video. The idea behind that is that I have an (old) IP camera that only serves snapshots on an HTTP endpoint. When calling that endpoint, you get a static JPEG picture. Let's say, the URL I want to "convert" is : http://mycamera.local/live.jpg

  


  Now, I want to create a script using Node.js to quickly call that URL over and over in order to form some sort of video stream. I'm not an expert into media encoding and stuff, but I guess that the variable refresh rate induced by HTTP latency, the camera's FPS... would make it a bit trickier to pipe images into a video response ?

  


  I thought I'd go with Express and Axios to serve and query HTTP content. I've also read that FFmpeg could play a role in there. But, I am open to any suggestion. I could even switch languages if that's required. This question is so specific I think, that any response would do.

  


  A couple of requirements I cannot change :

  


  

  • The camera can only serve static pictures on a single endpoint.

  


  • I have no other protocol than HTTP on the camera.

  


  • I am not buying or modifying the existing hardware, even though I know there are very cheap units out there.

  


  • My server must serve a live video that could be streamed by VLC for instance.

  


  


• Segmenting .flac files with ffmpeg truncates audio but not file length

  5 avril 2022, par Yan White

  I am trying to get Twitter spaces audio (.ts) files into a format I can easily edit, on OSX.

  


  So far I was able to convert the files in bulk to .flac with this :

  


  for i in *.ts;
do name=`echo "$i" | cut -d'.' -f1`
echo "$name"
ffmpeg -i "$i" -sample_fmt s16 -ar 41000 "${name}.flac"
done


  


  That worked, and reduced the file sizes somewhat, but..
Because most of the files are around 7 hours long, my editor of choice cannot process that much audio in one file.

  


  So I looked around and was able to find this command to segment the files into 3hr long sections.

  


  ffmpeg -i space-1OdKrBealBqKX_0.flac -map 0 -f segment -segment_time 10800 -c copy space-1OdKrBealBqKX_0__%03d.flac


  


  This works, but each file contains as much empty / silent space at the end as the orginal file. That's going to be a problem for sharing with a team that will help edit these files, as each file has the original file's length and file size. There are a lot of files.
The audio segments and naming did work though.

  


  How to truncate the actual length of the file to the audio segment ?

  


  Caveat : I am no expert on any of these matters, I just managed to google and get this far, so if someone knows and wants to provide working code that would be very much appreciated !