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• Concatenating 30fps video with audio using ffmpeg

  29 juillet 2012, par Olumide

  In essence, my question is about how to specify the framerates of an input video file and the resulting, output video file when concatenating a video and an audio file.

  I am trying to concatenate a 30fps video with a 44k audio file but the video and audio parts of the result/output are out of synch. (This does not happen, or less obvious, when the framerate of the video is 24fps, suggests to me that ffmpeg has a default framerate.) I've tried specifying the framerate of the output video as well, like so

  ffmpeg -i inFile.avi -i audio.wav -b:v 2500k -r 30 outFile.mpg

  but that doesn't seem to help.

  What am I doing wrong ?

• libx264 in Visual Studios 2010 - Memory error in Release Build

  21 décembre 2011, par DeusAduro

  I am building an application and using the x264 library as an encoder. I have built the library for my windows system using MSys/MingW. The library works fine under debug build (note both debug and release builds are using the default VS2010 settings). However, under release an access violation error is thrown at the first call to the x264 library, specifically :

    Unhandled exception at 0x00905a4d in StreamTest.exe:
  
    0xC0000005: Access violation.

  The error is thrown at this line :

  x264_param_default_preset((params), "veryfast", "zerolatency");

  While I was figuring out how to compile the library I came across a lot of talk about memory alignment in Windows/Visual Studios and how it wasn't particularly compatible with the alignment expected by x264. For example when compiling in MSys I had to enable —enable-memalign-hack. I am wondering if the source of this error might stem from a memory alignment issue which only manifests itself through some setting in my release build. Unfortunately I know almost nothing about the specifics and so have come here.

  Can anyone give me some more information regarding the memory alignment issues and any Visual Studio settings which might cause this ? Any other tips/pointers to fix this issue are very welcome.

  Thanks.

  Edit

  From answer below :

  1. From the linked SO question I get the impression he added "build with debugger info" to the OpenCV build ? Since I'm building the x264 library through MSys with G++ I'm not sure I can do this. I have checked the build settings for my project, and under both release and debug it has debugger info. Not sure if I missed something in that post, please let me know.

  2. I tried the application verifier. It seems that x264 is trying to execute code from non-executable memory as per the App verifier output :

     VERIFIER STOP 0000000000000650: pid 0x1B18: 

     Attempt to execute code in non-executable memory (first chance).

     0000000000905A4D : Address being accessed.
     
     0000000000905A4D : Code performing invalid access.
     
     000000000021EA90 : Exception record. Use .exr to display it.
     
     000000000021E5A0 : Context record. Use .cxr to display it.

  Anything to be gathered from this output ?

  Thanks again.

• Batch statement to convert mp3 to aac

  20 décembre 2011, par Soham Dasgupta

  My question is straight forward. I have tow commands to convert a single mp3 file to aac in tow pass. Here are the commands -

  ffmpeg -i input.mp3 -f wav - | neroAacEnc -ignorelength -q 0.5 -if - -of output.m4a
  
  
  
  ffmpeg -i output.m4a -y -vn -acodec libvo_aacenc -ab 128k -ar 48000 -ac 2 final.aac

  Please guide me to some script where I'll be able to convert a folder full to mp3 files in one shot. Suppose if its a VBScript then would it ask for the folders where mp3 are kept.

  Also a question about libvo_aacenc codec, is it the best codec to convert to aac if not then what codec should I use for the second pass for converting m4a to aac with highest compression but good quality. The above settings does not produce too good compression. Please help. Am very new to audio encoding.