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• How do I generate a color screen for the duration of an MP3 in ffmpeg ?

  25 février 2019, par yaggelee

  I have successfully generated a blue screen to add to an mp3. But, I have always needed to include the length of the clip to match the mp3. When I don’t include a timecode it continues to generate footage until I cancel the command.

  ffmpeg -f lavfi -i color=blue:s=1920x1080 -i input.mp3 -t 00:02:08 output.mp4

  How do I specify that I only want color generated during the length of the mp3 that I am adding ?

  ffmpeg -i <.jpg> -i <.mp3>

  This worked too but I don’t want to rely on a jpeg file.

• Concatenate multiple videos with a black screen loop into one video

  23 février 2020, par Marcel

  I am using ffmpeg to join a bunch of videos together.
  I am using the classic join ffmpeg code :
  

  ffmpeg -f concat -i joinlist.txt -c copy joinedfile.mp4

  but the problem is that the videos are of different formats, encodings, but the same size : all 640x480. I want to join them all and put a black screen video with no sound every other video :

  video1 + black_screen_video + video2 + black_screen_video + video3 ...

  I generated a black screen video of 2 seconds duration using :

  ffmpeg -f lavfi -i color=c=black:s=640x480:d=2 black_screen_video.mp4

  so all of the videos are of the same size : 640x480, and 25 fps but different codecs. The videos have sound, except for the black screen video.
  I can’t do anything manual, because the number of videos are around several hundred. So it has got to be an automatic way to do all this.

  When I joined them together using the above code, the resulting video does not play correctly at all.

  I know that I have to re-encode them, but how to do this to all these videos at once, with one line of code ?

  Update :
  I am already using with success this code to join them together, but only three, if I have more than one hundred, it is time consuming to write down one by one :

  ffmpeg -i vid1.avi -i vid2.avi -i vid3.avi -filter_complex "[0:v:0] [0:a:0] [1:v:0] [1:a:0] [2:v:0] [2:a:0] concat=n=3:v=1:a=1 [v] [a]" -map "[v]" -map "[a]" output.mp4

  but this is joining only the videos, not looping the black screen video. When I do with black screen, ffmpeg gives me stream matching errors.

  update :

  here is the console image :
  

  2nd update :

  a very long list of errors in red, of which a screenshot here :
  

• Android NDK w/ ffmpeg library - error running project

  11 novembre 2014, par ynnadkrap

  Using this guide, http://www.roman10.net/how-to-build-ffmpeg-with-ndk-r9/, I successfully compiled ffmpeg-2.4.2 with Android NDK 10, but now I’m having issues using it in my eclipse project.

  The error I’m getting :

  *** Android NDK: Aborting    .  Stop.

  which points to this in prebuilt-library.mk :

  ifndef prebuilt
  
  $(call __ndk_info,ERROR:$(LOCAL_MAKEFILE):$(LOCAL_MODULE): LOCAL_SRC_FILES points to a missing file)
  
  $(call __ndk_info,Check that $(prebuilt_path) exists, or that its path is correct)
  
  $(call __ndk_error,Aborting) <----- ***** This line is specifically pointed out by the error log
  
  endif

  Here’s my ...jni/Android.mk :

  LOCAL_PATH := $(call my-dir)
  
  
  
  include $(CLEAR_VARS)
  
  
  
  LOCAL_MODULE    := VideoTest
  
  LOCAL_SRC_FILES := videotest.c
  
  LOCAL_LDLIBS := -llog -ljnigraphics -lz -landroid
  
  LOCAL_SHARED_LIBRARIES := libavformat libavcodec libswscale libavutil
  
  
  
  include $(BUILD_SHARED_LIBRARY)
  
  $(call import-module,ffmpeg-2.4.2/android/arm)

  Here’s my android-ndk/sources/ffmpeg-2.4.2/android/arm/Android.mk :

  LOCAL_PATH:= $(call my-dir)
  
  
  
  
  
  include $(CLEAR_VARS)
  
  LOCAL_MODULE:= libavcodec
  
  LOCAL_SRC_FILES:= lib/libavcodec-55.so
  
  LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/include
  
  include $(PREBUILT_SHARED_LIBRARY)
  
  
  
  include $(CLEAR_VARS)
  
  LOCAL_MODULE:= libavformat
  
  LOCAL_SRC_FILES:= lib/libavformat-55.so
  
  LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/include
  
  include $(PREBUILT_SHARED_LIBRARY)
  
  
  
  include $(CLEAR_VARS)
  
  LOCAL_MODULE:= libswscale
  
  LOCAL_SRC_FILES:= lib/libswscale-2.so
  
  LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/include
  
  include $(PREBUILT_SHARED_LIBRARY)
  
  
  
  include $(CLEAR_VARS)
  
  LOCAL_MODULE:= libavutil
  
  LOCAL_SRC_FILES:= lib/libavutil-52.so
  
  LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/include
  
  include $(PREBUILT_SHARED_LIBRARY)
  
  
  
  include $(CLEAR_VARS)
  
  LOCAL_MODULE:= libavfilter
  
  LOCAL_SRC_FILES:= lib/libavfilter-3.so
  
  LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/include
  
  include $(PREBUILT_SHARED_LIBRARY)
  
  
  
  include $(CLEAR_VARS)
  
  LOCAL_MODULE:= libwsresample
  
  LOCAL_SRC_FILES:= lib/libswresample-0.so
  
  LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/include
  
  include $(PREBUILT_SHARED_LIBRARY)

  Here’s my project structure :

  http://imgur.com/2vMryOS

  So it seems to me that the project isn’t building because the LOCAL_SRC_FILES doesn’t point to anything, but is it referring to LOCAL_SRC_FILES in jni/Android.mk or the one in ...ffmpeg-2.4.2/android/arm/Android.mk ? Either way, it seems like they are actually pointing to something. I’ve also tried looking at this solution, Android NDK : Aborting stop ?, but I’m having a hard time understanding it. Which Android.mk file needs changing ?