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• Speed advantage in combining FFmpeg filters ?

  4 mai 2020, par lach_codes

  I'm currently using five separate FFmpeg processes to do the following :

  



  

  1. trim & crop Vid B

  


  2. scale Vid B to height of Vid A

  


  3. combine Vid B & Vid A

  


  4. add a fade-in/fade-out to Combined Vid

  


  5. add an overlay to fade in/out vid

  


  



  I have them all set to ultrafast but it still takes a long time - about 40 seconds when each video is 10 seconds long.

  



  I initially explored combining some of the filters but couldn't get it working in the timeframe I had available. I also wasn't sure if the time spent figuring out how to combine all the filters would pay off in a faster processing time.

  



  Any thoughts/insights from you brilliant FFmpeg gurus ? Would this speed up processing, and if so, should I combine all the commands together or are there some I should combine and others I should leave separate ?

  



  Here are my current commands, all of which are working :

  



  // trimming 200ms off begining of vid B + cropping frame (note that I have previously retrieved dimensions and duration of both videos with ffprobe)
1. `ffmpeg -i vidB.mov -ss 200 -t ${vidB.duration} -async 1 -filter:v "crop=iw:${vidB.croppedHeight}:0:${vidB.offset}" -preset ultrafast -c:a copy croppedVidB.mov`

// scale Vid B up to Vid A's height
2. `ffmpeg -i croppedVidB.mov -vf scale=-2:${vidA.height} vidBScaled.mov`

// combine videos
3. `ffmpeg -i vidA.mov -i vidBScaled.mov -filter_complex "[0:v][1:v] hstack=inputs=2[v]; [0:a][1:a]amix[a]" -map "[v]" -map "[a]" -preset ultrafast -ac 2 combined.mov`

// add fade in & out
4. `ffmpeg -i combined.mov -sseof -1 -copyts -i combined.mov -filter_complex "[1]fade=out:0:30[t];[0][t]overlay,fade=in:0:30[v]; anullsrc,atrim=0:1[at];[0][at]acrossfade=d=1,afade=d=1[a]" -map "[v]" -map "[a]" -c:v libx264 -crf 22 -preset ultrafast -shortest fadeInOut.mov`

// add overlay
5. `ffmpeg -i fadeInOut.mov -i overlay.png -filter_complex overlay=W-w-10:H-h-10 -codec:a copy -preset ultrafast -async 1 overlay.mov`


  



  Thanks in advance for your thoughts !

  


• How to remove silence from an audio file while leaving a bit of the otherwise deleted portion ?

  26 février 2020, par A Question Asker

  Pardon the title, it’s a bit difficult to explain concisely !

  I have a bunch of short (1s-4s) recordings of people reading sentences. They were recorded themselves. Often, there is a bit of silence at the beginning or end, and I would like to automate removing that.

  As a first pass, I used this command :

  sox original.mp3 edited.mp3 silence 1 0.1 2% reverse silence 1 0.1 2% reverse

  The problem is that when people speak, sometimes the very beginning of their speech is quiet and quickly ramps up. This command thus clipped the very beginning of a number of sentences.

  So what I would like to do is essentially the same as what the sox command does, but ideally once it detects the boundary, it leaves 50ms before the boundary, in recognition that there may be some quiet but important sounds.

  I think that ffmpeg might be a good tool for this, as I don’t think sox can be configured like that. I’m tool agnostic. I don’t know ffmpeg at all though, so I appreciate any help putting together a command given ffmpeg’s rather arcane syntax !

  Another nice to have over the aforementioned sox command is for it only to remove silence at the beginning and end (if it exists) — not from the middle of the recording.

  UPDATE : based on time spent with ffmpeg, it looks like I want something like this

  ffmpeg -i input.mp3 -af "silenceremove=start_periods=1:start_threshold=0.02:start_silence=0.1:detection=peak,areverse,silenceremove=start_periods=1:start_threshold=0.02:start_silence=0.1:detection=peak,areverse" output.mp3

  Oddly, this comes out garbled. I thought that it wasn’t reversing properly, but when I try to do something like

  ffmpeg -i input.mp3 -af areverse output.mp3

  It doesn’t work — I just get the input back. I’m not sure what is going wrong ?

  If I just do the beginning,

  ffmpeg -i input.mp3 -af "silenceremove=start_periods=1:start_threshold=0.02:start_silence=0.1:detection=peak" output.mp3

  It works fine — for the beginning. But not sure why the reverse trick is resulting in a garbled output.

  UPDATE2 : it actually looks like the command works, but it changes the metadata in a way that makes itunes wonky. If I use VLC instead, it works fine.

• Game Music Appreciation

  16 juillet 2012, par Multimedia Mike — Game Hacking

  A little over a year ago, I was prototyping a method to leverage Google Chrome’s Native Client technology in order to play old chiptunes (video game music) directly in a web browser. The last time I posted on the matter, I said that I might have something ready for public consumption by the time Google Chrome 21 rolled around. I thought I was being facetious but I wasn’t too far off. Chrome 20 is the current release version as I write this.

  Anyway, I did it : I created a chiptune music player in Native Client by leveraging existing C/C++ libraries such as Game Music Emu, Audio Overload SDK, and Vio2sf. Then I packaged up the player into into a Google Chrome extension and published it on the Chrome Web Store. Then I made a website cataloging as many chiptunes as I could find for 7 different systems :

  http://gamemusic.multimedia.cx/
  

  Check it out if you have any affinity for old game music or you want to hear how music was made using a limited range of bleeps and bloops. Thus far, the site catalogs NES, SNES, Game Boy, Nintendo DS, Genesis, Saturn, and Dreamcast songs. I’m hoping to add support and catalogs for many more systems, though, eventually bringing support in line with the Chipamp plugin for Winamp.