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• Burning subtitles into video with ffmpeg with specific margin not working

  17 mai 2024, par Anthony

  I am trying to build a tool where people can position their subtitles on an HTML5 video and then I will burn the subtitles into the video for them.

  


  I can easily get the position of the subtitles, in whatever format I need, that's easy. However, no combination of values that I feed to ffmpeg are working.

  


  My holy grail is an x and y offest (aka offset 5% from the left, 10% from the bottom, in terms of video height/width).

  


  To achieve this, I would like the subtitles to start in the very bottom-left corner.

  


  ffmpeg -y -i english.mp4 -vf "subtitles=english.srt:force_style='Alignment=1,OutlineColour=&H100000000,BorderStyle=3,Outline=1,Shadow=0,FontName=Arial,FontSize=24,MarginL=140,MarginV=0'"  -c:v libx264 -crf 23 -c:a copy output_video.mp4


  


  Here is something that is approaching working, but it's behaving very strangely. The video is 850x480 but when I do a margin of 140 it goes way past the midway point of the video.

  


  Am I missing something ? How can I start the margin in the bottom left, and then apply the margin I want to push it away from the left and away from the bottom ? I can do it either as a percentage of the video height/width if that API is supported or just pixels is fine too (but clearly doesn't seem to be working)

  


• ffmpg full album video - multiple audio files one after another

  21 août 2019, par Martin

  I am trying to write an ffmpeg command which will take an image (jpg) and multiple audio files (in this case, lets say 3 mp3 files) and create an mp4 video where each audio file comes one after another (first audio file, then second, then third, etc... no overlap, files play in order one after another).

  I am currently using this command to export a single mp3 file and jpg into an mp4 :

  ffmpeg -loop 1 -y -i "media/pic.jpg" -i "media/01 song name.mp3" -shortest -acodec copy -vcodec mjpeg -s 1920x1080 "outputVideo.mp4"

  Is it possible to combine multiple audio tracks into the video using one command ?

  In the past I was using this command seperately to generate a single audio track made up of multiple audio inputs in order :

   ffmpeg -i '01 - Funky Carla.mp3' -i '02 - Take This Day Away.mp3' -i '03 - Youre The One I Love.mp3' -filter_complex '[0:0][1:0][2:0]concat=n=3:v=0:a=1[out]' -map '[out]' -b:a 320k fullAudio.mp3

  And then just using that track to export one video, but this process takes two separate ffmpeg commands, is long and slow, and produced a huge video file.

  Should I use something like amix / amerge / map ? Any advice/ideas is appreciated, thanks.

• How to play video Media Source Extensions when the audio start is delayed ? Or how to fix it with ffmpeg ?

  11 décembre 2020, par sheodox

  I have a video that I'm splitting the individual video/audio streams out then dashing with MP4Box, then I'm playing them with Media Source Extensions and appending byte ranges to video/audio source buffers from the MPD files. It's all working nicely, but one video I have has audio that is delayed by about 1.1 second. I couldn't get it to sync up and the audio would always play ahead of the video.

  


  Currently I'm trying to set the audioBuffer.timestampOffset = 1.1 and that gets it to sync up perfectly. The issue I'm running into now though is the video refuses to play unless the audio source buffer has data. So the video stalls right away. If I skip a few seconds in (past the offset) everything works because both video/audio are buffered.

  


  Is there a way to get around this ? Either make it play without the audio loaded, somehow fill the audio buffer with silence (can I generate something with the Web Audio API) ? Add silence to the audio file in ffmpeg ? Something else ?

  


  I first tried adding a delay in ffmpeg with ffmpeg -i video.mkv -map 0:a:0 -acodec aac -af "adelay=1.1s:all=true" out.aac but nothing seemed to change. Was I doing something wrong ? Is there a better way to demux audio while keeping the exact same timing as when it was in the container with the video so I don't have to worry about delays/offsets at all ?