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• NDK r8c warning for asm objects regarding "Cortex-A8 erratum" - should I be worried ?

  7 décembre 2012, par Alex Cohn

  Question : What is the meaning of this warning ? If there are no real-life consequences, I can live with it for a while... But I am concerned with what will happen if our program gets loaded on one of the faulty chips.

  Background : With NDK r8c, linking of X264 encoder issues warnings :

  cannot scan executable section 1 of libx264.a(dct-a.o) for Cortex-A8 erratum because it has no mapping symbols

  ... same warning for all assembly files in libx264.

  libx264.a itself was cross-compiled on the same machine with the same 4.6 toolchain taken from NDK.

  Here are the instructions to easily reproduce the problem (Ubuntu or MacOS) :

  1. Download x264-snapshot-20121203-2245 from ftp://ftp.videolan.org/pub/x264/snapshots/last_x264.tar.bz2

  2. Run ./configure --enable-pic --enable-strip --enable-static --cross-prefix=~/android-ndk-r8c/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86/bin/arm-linux-androideabi- --sysroot=~/android-ndk-r8c/platforms/android-14/arch-arm --host=arm-linux

  3. Run ~/android-ndk-r8c/prebuilt/linux-x86/bin/make

  It will build the static library, and after that display the Cortex-A8 warning while linking the x265 executable. I am not worried about the compiler warnings, because building libx264.a is done offline, it is not part of our official daily build.

  I have reported this as http://code.google.com/p/android/issues/detail?id=40794.

  I tried to add the mapping symbols manually to dct-a.S following the ARM.com instructions, but this had no effect.

• Can you "stream" images to ffmpeg to construct a video, instead of saving them to disk ?

  8 juillet 2016, par Brandon

  My work recently involves programmatically making videos. In python, the typical workflow looks something like this :

  import subprocess, Image, ImageDraw
  
  
  
  for i in range(frames_per_second * video_duration_seconds):
  
      img = createFrame(i)
  
      img.save("%07d.png" % i)
  
  
  
  subprocess.call(["ffmpeg","-y","-r",str(frames_per_second),"-i", "%07d.png","-vcodec","mpeg4", "-qscale","5", "-r", str(frames_per_second), "video.avi"])

  This workflow creates an image for each frame in the video and saves it to disk. After all images have been saved, ffmpeg is called to construct a video from all of the images.

  Saving the images to disk (not the creation of the images in memory) consumes the majority of the cycles here, and does not appear to be necessary. Is there some way to perform the same function, but without saving the images to disk ? So, ffmpeg would be called and the images would be constructed and fed to ffmpeg immediately after being constructed.

• scalable looping slideshow ffmpeg command

  15 avril 2024, par Martin

  I have the below ffmpeg command which takes a 2 hour mp3 file and four image files and combines them to renders a single mkv video file where the 4 images appear in a slideshow where each image is displayed for an equal amount of time.
I am using these files : https://file.io/XjYl2DDrLn6b

  


  Since the video is 2 hours long ( 7200 seconds ) and there are 4 images, each image gets displayed for 7200/4 = 1800 seconds.

  


  The logic for determining how to loop these image files is within the 'filter_complex' part of my ffmpeg command.

  


  [0:a]concat=n=1:v=0:a=1[a]; Use the only audio file.

  


  [1:v]scale=w=2000:h=2000,setsar=1,loop=3615.91:3615.91[v1]; Use loop filter for repeating img1 3600 times ( 1800 seconds * 2Hz = 3600 )

  


  [2:v]scale=w=2000:h=2000,setsar=1,loop=3615.91:3615.91[v2]; Use same loop filter logic for img2

  


  [3:v]scale=w=2000:h=2000,setsar=1,loop=3615.91:3615.91[v3]; Use same loop filter logic for img3

  


  [4:v]scale=w=2000:h=2000,setsar=1,loop=3615.91:3615.91[v4]; Use same loop filter logic for img4

  


  [v1][v2][v3][v4]concat=n=4:v=1:a=0,pad=ceil(iw/2)*2:ceil(ih/2)*2[v] Final combination of audio/images

  


  So each image is displayed for 1800 seconds, making up the total 7200 (2 hour) runtime of my audio file.

  


  But if I want each image to be displayed for 3 seconds, looping through all 4 images for the entire 2 hour duration, how would I do that ?
I can't include hundreds of these concat lines, how can I achieve this looping slideshow effect scaleably ? For use with extremely long audio files and hundreds of images.

  


  Full uncommented ffmpeg command (copy paste it inside web browser search window to turn into one line)

  


  ffmpeg.exe 
-r 2
-i "C:\Users\martin\Documents\projects\rendertune\test-files\mp3\frankie knuckles mix.mp3"
-r 2
-i "C:\Users\martin\Documents\projects\rendertune\test-files\mp3\FRONT.jpg"
-r 2
-i "C:\Users\martin\Documents\projects\rendertune\test-files\mp3\BACK.jpg"
-r 2
-i "C:\Users\martin\Documents\projects\rendertune\test-files\mp3\side 1.jpg"
-r 2
-i "C:\Users\martin\Documents\projects\rendertune\test-files\mp3\side 2.jpg"
-filter_complex "
[0:a]concat=n=1:v=0:a=1[a];
[1:v]scale=w=2000:h=2000,setsar=1,loop=3615.91:3615.91[v1];
[2:v]scale=w=2000:h=2000,setsar=1,loop=3615.91:3615.91[v2];
[3:v]scale=w=2000:h=2000,setsar=1,loop=3615.91:3615.91[v3];
[4:v]scale=w=2000:h=2000,setsar=1,loop=3615.91:3615.91[v4];
[v1][v2][v3][v4]concat=n=4:v=1:a=0,pad=ceil(iw/2)*2:ceil(ih/2)*2[v]
"
-map [v]
-map [a]
-c:a pcm_s32le
-c:v libx264
-bufsize 3M
-crf 18
-pix_fmt yuv420p
-tune stillimage
-t 7200 "C:\Users\martin\Documents\projects\rendertune\test-files\mp3\Equal_Slideshow_Time.mkv"


  


  Ffmpeg command in one line : ffmpeg.exe -r 2 -i "C:\Users\martin\Documents\projects\rendertune\test-files\mp3\frankie knuckles mix.mp3" -r 2 -i "C:\Users\martin\Documents\projects\rendertune\test-files\mp3\FRONT.jpg" -r 2 -i "C:\Users\martin\Documents\projects\rendertune\test-files\mp3\BACK.jpg" -r 2 -i "C:\Users\martin\Documents\projects\rendertune\test-files\mp3\side 1.jpg" -r 2 -i "C:\Users\martin\Documents\projects\rendertune\test-files\mp3\side 2.jpg" -filter_complex " [0:a]concat=n=1:v=0:a=1[a]; [1:v]scale=w=2000:h=2000,setsar=1,loop=3615.91:3615.91[v1]; [2:v]scale=w=2000:h=2000,setsar=1,loop=3615.91:3615.91[v2]; [3:v]scale=w=2000:h=2000,setsar=1,loop=3615.91:3615.91[v3]; [4:v]scale=w=2000:h=2000,setsar=1,loop=3615.91:3615.91[v4]; [v1][v2][v3][v4]concat=n=4:v=1:a=0,pad=ceil(iw/2)*2:ceil(ih/2)*2[v] " -map [v] -map [a] -c:a pcm_s32le -c:v libx264 -bufsize 3M -crf 18 -pix_fmt yuv420p -tune stillimage -t 7200 "C:\Users\martin\Documents\projects\rendertune\test-files\mp3\Equal_Slideshow_Time.mkv"