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• FFMPEG performance when reading directly from s3 vs local

  16 janvier 2020, par user1147070

  I have a usecase where I need to transcode a s3 file. I have two options

  Option a : Download the file to local, then run ffmpeg on it

  Option b : Provide a presigned URL as ffmpeg input eg -
  "./ffmpeg -loglevel debug -y -i "https://mybucket/key?signedParams" -threads 0 -map_chapters -1 -f mp4 -movflags faststart -map 0:0 -acodec libfdk_aac -ac 2 -ar 44100 -b:a 48k -sn -vn /output.mp4"

  I tried running both and comparing the time but I don’t see any much performance improvement in #b as compared to #a.

  I have 2 questions

  1. Is #b is better in performance than #a ? Or both of them are same ?

  2. In case of #b does ffmpeg wait for complete download and then start transcoding or it start downloading and transcoding simultaneously ?

• Revision 5ab920d2ae : Using local variable for token_cache. The difference with the old code is that

  3 décembre 2013, par Dmitry Kovalev

  Changed Paths :
   Modify /vp9/decoder/vp9_decodeframe.c

  
   Modify /vp9/decoder/vp9_detokenize.c

  
   Modify /vp9/decoder/vp9_detokenize.h

  
   Modify /vp9/decoder/vp9_onyxd_int.h

  
  
  Using local variable for token_cache.

  The difference with the old code is that originally the whole token_cache
  was initialized with zeros at the beginning of decode_coefs() function.
  Now we set several zero values explicitly with "token_cache[scan[c]] = 0".

  Change-Id : I88cc5031f01d13012d1a4491739c36cb44f9401e

• android - ffmpeg - making crossfade between 5 videos

  24 juin 2016, par LuongTruong

  I want to make a small slideshow app which is able to do some effect like fade in, fade out, and crossfade between multiple videos by using ffmpeg4android.

  After a few hours researching, I am still getting stuck in doing crossfade. Following this suggestion, I am able to create a crossfade but it is not work perfectly.

  The problem is that I want to combine 5 videos with crossfade effect between them and the duration of each video is 5 seconds. As a result, the output file is only 5 seconds instead of 25 seconds and there is a crossfade effect in the end of output file.

  Here is my command :

  String commandStr = "ffmpeg " +
  
                  "-y " +
  
                  "-i /sdcard/videokit/big_buck.mp4 " +
  
                  "-i /sdcard/videokit/big_buck.mp4 " +
  
                  "-i /sdcard/videokit/big_buck.mp4 " +
  
                  "-i /sdcard/videokit/big_buck.mp4 " +
  
                  "-i /sdcard/videokit/big_buck.mp4 " +
  
                  "-filter_complex " +
  
                  "[0:v]setpts=PTS-STARTPTS[v1];" +
  
                  "[1:v]format=yuva420p,fade=in:st=0:d=1:alpha=1,setpts=PTS-STARTPTS+(4/TB)[v2];" +
  
                  "[2:v]format=yuva420p,fade=in:st=0:d=1:alpha=1,setpts=PTS-STARTPTS+(8/TB)[v3];" +
  
                  "[3:v]format=yuva420p,fade=in:st=0:d=1:alpha=1,setpts=PTS-STARTPTS+(12/TB)[v4];" +
  
                  "[4:v]format=yuva420p,fade=in:st=0:d=1:alpha=1,setpts=PTS-STARTPTS+(16/TB)[v5];" +
  
                  "[v1][v2]overlay[v12];[v12][v3]overlay[v123];[v123][v4]overlay[v1234];[v1234][v5]overlay,format=yuv420p[v] " +
  
                  "-map [v] " +
  
                  "/sdcard/videokit/result.mp4";

  UPDATE 1 : ADD LOG

  Please download the log file here

  Please let me know if I did something wrong in my command. Any help would be appreciated.

  Thank you in advance !