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• Trying to concat videos from different sources with ffmpeg and get different broken results every time (partly no audio and/or fast forward video)

  30 octobre 2022, par Oliver

  I am using ffmpeg for years to create (merge and render) big video files from the (vaction) clips my sony camcorder produces. My basic workflow is to copy the mp4 files from the camcorder over to my pc, put the names in a file (file 'filename') and use the following command to create one big file that is playable by my apple tv :

  


  ffmpeg -f concat -safe 0 -i filelist.txt -c:v libx265 -preset slow -x265-params strong-intra-smoothing=0:merange=58 -crf 24 -c:a aac -b:a 320k -tag:v hvc1 output.mp4


  


  i cannot explain most of the arguments in total detail but i know that it works.
My problem occurred as i wanted to prepend some video clips recorded with an iphone to one of those files. So the first part seemed easy, the sony camcorder files have a resolution of 3840x2160 and the iphone video clips have a resolution of 1280x720 so at first i upscaled the iphone files using this command (i would have rather done in just one step but i do not know how to do that) :

  


  ffmpeg -i IMG_1182.MP4 -vf scale=3840:2160 IMG_1182_3840x2160.MP4


  


  then i just tried to add those upscaled video files to the filelist from the first command and ran the command for all clips again. Sadly that did not worked, as the resulting file contained all clips but only the iphone part had audio ! For the rest of the video the audio was missing. At this point i also did not noticed that the second part was played much faster (like played in fast forward mode). So guessed that i have to render the iphone and sony camcorder clips separately using the first command. That worked and i got two video files with perfect audio and video. My next step was to concatenate the resulting files using the following simple command :

  


  ffmpeg -f concat -safe 0 -i concatlist.txt -c copy output.mp4


  


  where concatlist contained both files.
Sadly that also did not worked. I do got a file containing both parts, this time with audio, but the video of the second part still was fast forward !

  


  I do not know what to do at this point, and i also do not understand enough to experiment with the options any more. Can someone explain to my what could be the problems here and how to solve them ?

  


• How do I convert videos to mp4 for use on Android ? [on hold]

  11 avril 2014, par user3525211

  I am trying to use ffmpeg to convert videos (flv,mov,etc) to mp4 for use on android mobile phones. The conversion seemingly works fine. I can see the mp4s on my iphone. But when I test it out on android phones it does not work. I have been googling this problem for two weeks now and I have tried probably 50 different variations of ffmpeg command lines, but without success. I tried upgrading to the latest ffmpeg on my linux server, but I am not linux savvy and am not sure that it did what it was supposed to. I am at my wits end. Am I going about this wrong ? Is ffmpeg the right tool ? Any ideas ?

  Here is the command line I have used to successfully convert to mp4s that work on iphone :
  ffmpeg -y -i input.mov -s 480x270 -r 30000/1001 -b 128k -vcodec libx264 -vpre slow -vpre ipod320 -acodec libfaac -ac 2 -ar 44100 -ab 128k output.mp4

• TV audio extracted using ffmeg does not work in iOS (but it works in the simulator)

  26 janvier 2014, par Genar

  I can process a TV signal (well I have a .ts video which comes from a TV channel), using ffmpeg but the audio cannot be understood in an iPhone/iPad. The most strange is that the audio (and video) works properly in the simulator (and also in an Android real device, but this is another point), but in a real iPhone/iPad device the video is OK but the audio sounds like a metallic box and nothing can be understood.

  I have created the ffmpeg libraries for iOS (I have tried the version 2.0.2 and also the version 2.1.3) using the information provided in the following link :

  Installing ffmpeg ios libraries armv7, armv7s, i386 and universal on Mac with 10.8

  The aforementioned link explains how to create the ffmpeg include folders and the universal libraries which I have included into my project (the libraries created are : libavcodec.a, libavdevice.a, libavfilter.a, libavformat.a, libavresample.a, libavutil.a, libswresample.a and libswscale.a).

  The sampling frequency used is 48000.

  The audio got from ffmpeg is then stored into a buffer and then "inserted" using OpenAL ; but, from the same TV content (the same .ts video file) the audio data which is generated from ffmpeg in an iPhone/iPad is totally different from the audio data generated from ffmpeg in the simulator (which can reproduce both the audio and video perfectly).

  Thanks in advance,