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• Google Lato Font Display discrepancies between platforms/software [closed]

  5 juin 2024, par CRAIG

  Using Google's Lato font with 400 weight, is giving me some inconsistent results between Photoshop/Web on MacOS and Linux Imagemagick & Linux ffmpeg.

  


  I have printed out some text on my linux server using the font using both imagemagick (v6.9.10-68) and ffmpeg's (v6.0) drawtext feature and in both cases, I get some extra space between the T and the e. (Image below)

  


  At first I was only testing ffmpeg and thought it was related to drawtext, but now that imagemagick is doing the same, I am thinking it may be somehow related to how the server is managing the font ?

  


  I did download the exact same font to test on my Mac and installed it, but I still get the original photoshop results I was getting before. So I don't think it is inherently the font unless I missed a step. I did completely uninstall the font and then install the downloaded one to be sure.

  


  However, the same word, font, font-size combo used in Photoshop and on the web does not produce the same space between the T and the e.

  


  Here is an image I put together showing the results :

  


  

  


  For reference, here is the imagemagick command :

  


  convert -size 900x900 xc:black -font /fonts/Lato:400.ttf -pointsize 261.6 -fill white -gravity center -annotate +0+0 'Text' testoutput.png

  


  And the ffmpeg command :

  


  /usr/local/bin/ffmpeg -f  lavfi  -i  color=c=black@0.0:s=953x953:r=30:d=5,format=rgba  -filter_complex  "drawtext=expansion=none:enable='between(t,0,5)':fontfile='/fonts/Lato\:400.ttf':fontcolor=0xffffffff:fontsize=294:text='Text':x=(w-text_w)/2+0:y=476.5-(max_glyph_a)+(294/2.8)"  -copyts  -threads  1  -c:v  png  -pix_fmt  rgba  -movflags  faststart  -r  30  -t  8  -y  testoutput.mov

  


• How to extract fully synced audio with ffmpeg ?

  2 janvier 2023, par Brendan Hill

  I have an MP4 file with video and audio. I need to extract the audio stream only to an MP3 file.

  


  However it is critical for our application that the timing / synchronization of the audio file is exactly aligned with the original video, as we cross-correlate audio features based on timing.

  


  I currently use this command :

  


  ffmpeg -y 
   -v error 
   -map 0:a ./the-output-file-mp3
   -map 0:v ~/a-dummy-video-output-file.mp4
   -i ~/the-input-file.mp4
   -acodec copy 
  


  


  as I read somewhere that mapping both 0:a and 0:v would guarantee alignment & synchronization. I then discard the video file as it is not needed.

  


  However it is orders of magnitude faster to just extract the audio instead :

  


  ffmpeg -y 
   -v error 
   -map 0:a ./the-output-file-mp3
   -i ~/the-input-file.mp4
   -acodec copy 


  


  But I don't know if this guarantees alignment, because I read on this page that :

  


  If you only extract audio from a video stream, the length of the audio may be shorter than the length of the video. To make sure this doesn't happen, extract both audio AND video with the same call to ffmpeg, e.g. "ffmpeg -i vid.avi -map 0:a audio.wav -map 0:v onlyvideo.avi

  


  However perhaps I am putting too much weight on that comment. I don't care if the audio clip finishes early, but it is critical that it does not start late, or get de-synced from the original video at any point.

  


  What is the most efficient way with ffmpeg to extract the audio stream with a guarantee that it is 100% aligned in time to the video (and starts at exactly the same time) ?

  


  Will this method guarantee alignment ?

  


  ffmpeg -y 
   -v error 
   -i ~/the-input-file.mp4
   -vn
   -acodec copy 
   ~/the-output-file.mp4
   


  


• lavu/riscv : add optimisations

  12 septembre 2022, par Rémi Denis-Courmont

  lavu/riscv : add <intmath.h> optimisations
  This provides some micro-optimisations for signed integer clipping, and
  
  support for bit weight with the Zbb extension.
  

  • [DH] libavutil/intmath.h
  • [DH] libavutil/riscv/intmath.h