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• Why Safari does not play mp4 though Chrome plays it ?

  30 octobre 2022, par János

  This mp4 is generated from a gif : https://t44-post-cover.s3.eu-central-1.amazonaws.com/gp2w.mp4

  


  It is playable on Chrom, not on Safari. Why ? What is the problem ?

  


  This is the conversion command :

  


          await new Promise<void>((resolve, reject) => {&#xA;            ffmpeg&#xA;                .input(`/tmp/input_${imgId}.gif`)&#xA;                .outputOptions([&#xA;                    &#x27;-c:v libx264&#x27;,&#xA;                    &#x27;-movflags &#x2B;faststart&#x27;,&#xA;                    &#x27;-movflags frag_keyframe&#x2B;empty_moov&#x27;,&#xA;                ])&#xA;                .noAudio()&#xA;                .output(`/tmp/output_${imgId}.mp4`)&#xA;                .on(&#x27;end&#x27;, () => {&#xA;                    console.log(&#x27;MP4 video generated&#x27;)&#xA;                    resolve()&#xA;                })&#xA;                .on(&#x27;error&#x27;, (e) => {&#xA;                    console.log(e)&#xA;                    reject()&#xA;                })&#xA;                .run()&#xA;        })&#xA;</void>

  


  Using ffmpeg-static :

  


  const pathToFfmpeg = require('ffmpeg-static')
const ffmpeg = require('fluent-ffmpeg')().setFfmpegPath(pathToFfmpeg)


  


• Merge/Blend/Composite transparent webm files with a jpg/png using ffmpeg

  13 avril 2021, par Lokanath

  I previously had generated color.webm and alpha.webm files withffmpeg using png images.
However, when I play the generated videos in my application it consumes quite some resources so I have decided to create a standard video(No alpha needed), I cannot re-record the videos as there are a lot of them at this point.

  


  I am generating the alpha and color video using the following command ffmpeg -framerate 30 -i img%d.png -filter_complex "alphaextract[a]" -map 0:v -c:v libvpx-vp9 -pix_fmt yuv420p -auto-alt-ref 0 -crf 15 -b:v 0 color.webm -map "[a]" -c:v libvpx-vp9 -pix_fmt yuv420p -auto-alt-ref 0 -crf 15 -b:v 0 alpha.webm

  


  I am looking to get a final video output where in alpha values are replaced with the png/jpg image, it's more like replacing the green screen with a background however in my case greenscreen is the alpha channel.

  


  Could any one let me know how to combine alpha.webm, color.webm with a jpg/png image without minimal or no quality loss ?
.

  


• How to identify exact type or variation of a .mp4 file

  5 octobre 2017, par Dave502619

  Can anyone tell me if there are different variations of mp4 file and if so, how to identify the exact type or variation of a mp4 file ?

  The reason I need to know this is if I pass an .mp4 through FFMPEG to create an uncompressed grayscale rgb24 avi file, depending on
  where the .mp4 file has been sourced from will produce a different internally structured avi file as output from FFMPEG. Ie, the file header
  and interframe header sizes differ.

  The ffmpeg command i am using is :
  ffmpeg.exe -i source.mp4 -b 1150 -r 20.97 -g 120 -an -vf format=gray -f rawvideo -pixfmt rgb24 -s 384x216 -vcode rawvideo -y fileX.avi

  So far I have identified that .mp4 files generated by my Samsung S5 mobile phone differ from .mp4 files generated by Power Director 14. So I suspect there are different variations of .mp4 files.

  I have written some software which steps into the FFMPEG output .avi file to extract video frames, but it requires fixed offset positions to work so I can only make it work for one variation of .mp4.