Recherche avancée

Sur d’autres sites (11017)

• How to insert bullet screen comments into a video by using ffmpeg ?

  7 septembre 2019, par Saeron Meng

  I would like to add some real-time comments in my video but I do not know how to use ffmpeg to realize this. The comments are like screen bullets through the screen, scrolling from right to left.

  My thought is to count the length of the comments and define speeds for them to move. Don’t worry about the source of the comments, I have already gotten them saved as an xml file. Also, I can transfer it into srt. For instance :

  <chat timestamp="671.195">
  
      <ems utctime="1562584080" sender="Bill">
  
          <richtext></richtext>
  
      </ems>
  
  </chat>
  
  <chat timestamp="677.798">
  
      <ems utctime="1562584086" sender="Jack">
  
          <richtext></richtext>
  
      </ems>
  
  </chat>

  The final result is like this (I did not find an example displayed in English), these fancy characters can move horizontally :

  

  I have searched some solutions on the Internet, most of which talk about how to write ass/srt files and add motionless subtitles. Like this :

  3
  
  00:00:39,770 --> 00:00:41,880
  
  When I was lying there in the VA hospital ...
  
  
  
  4
  
  00:00:42,550 --> 00:00:44,690
  
  ... with a big hole blown through the middle of my life,
  
  
  
  5
  
  00:00:45,590 --> 00:00:48,120
  
  ... I started having these dreams of flying.

  ffmpeg -i infile.mp4 -i infile.srt -c copy -c:s mov_text outfile.mp4

  But I need another kind of "subtitles" which can move.

  So my question is, how to modify the ffmpeg command and the template of srt file so as to arrange the subtitles from the top to the bottom and let them move from right to left ?

• Java sound vs C sound api in sound result

  18 août 2019, par Ahmed

  i finish developing a conference chat app using java, and i used mp3 as encoder and javacv ( ffmpeg ) as a library, but the sound i get not sonorous like Paltalk app

  i used java sound api to capture the sound then store the sound in a buffer , send it to the encoder and get the compressed bytes and send it via socket then decode it and play it in speaker.
  the sound format was like 44100 sample rate when i capture the sound in java and in encoder it generate 11025 sound.
  here how i get sound from java api

   AudioFormat format = new AudioFormat(44100.0f, 16 , 1, true, false);        
  
   // target dataline  (Mic)
  
  DataLine.Info info = new DataLine.Info(TargetDataLine.class, format);
  
  targetDataLine = (TargetDataLine) AudioSystem.getLine(info);
  
  targetDataLine.open();

  i want to know what the thing making sound sonorous ?

• FFmpeg streaming low CRF results in low quality

  12 août 2019, par Max Paython

  I am streaming(live chat) with FFmpeg using the following parameters.

  ffmpeg -f dshow -rtbufsize 100M -i video="device":audio="device" \
  
  -c:v libx264 -crf 30 -preset ultrafast -tune zerolatency \
  
  -c:a aac -f mpegts udp://127.0.0.1:1234

  Unexpectedly, when CRF is lowered from 30 to 20, step-by-step. The stream quality decreases dramatically. When the CRF is about 20, sudden changes in the picture (like a head movement), seems to make the image green, gray or very distorted. I tried using CRF 30, and the problems seems to be gone. Why is this happening ?

  I don’t think it is a bandwidth issue given that I am on localhost. Also I didn’t change anything based on I-frames.

  Edit : I checked the file sizes given CRF 20 and CRF 30 on libx265.

  10 Second video.

  CRF 20 : 1.7M

  CRF 30 : 350kb

  Is 1.7M really bad for a 10 second stream that localhost or any other live streaming sevice can’t handle ?