**@matteo:**
**Every build** of FFmpeg has its quirks, but I'm surprised such a simple command string doesn't deliver the expected results for you. Even if you have a strong reason to hold on to your current version, you can keep any number of builds at hand. I currently have two in my `%PATH%` directory, named `ffmpeg` and `ffmpeg2`. (Possibly useless if not using a static build.)
**If you would like** to test your build against my input files and batch commands, I have [uploaded everything to a GoogleDrive][1] where they are freely available.
**I have also** uploaded my [FFmpeg console output][2] and some file size/media length information to Pastebin in case it might help with debugging.
**Pastebin links** to:
- [FFmpeg console output][3]
- [MediaInfo for final Flash video file][4]
- [MediaInfo for audio input file][5]
- [MediaInfo for still image input file][6]
**GoogleDrive links** to:
- Input audio file [narrate.wav][7]
- Input image file [still.png][8]
- Batch file [batch.bat][9]
- Final output video file [final.flv][10]
You are also welcome to upload anything to the [folder named Stack Exchange][11], I'll be happy to test your input files against my build. Obviously I've got very little to do over the weekend.
[1]: https://docs.google.com/folder/d/0BxafXIRt8NlPRk94QWd5aDBQdm8/edit "link to complete folder"
[2]: http://pastebin.com/c5uu0upQ "FFmpeg console output"
[3]: http://pastebin.com/c5uu0upQ "FFmpeg console output"
[4]: http://pastebin.com/CxW9s1sz "Flash output MediaInfo"
[5]: http://pastebin.com/Z01yEphW "Audio input MediaInfo"
[6]: http://pastebin.com/UPYnZLi8 "Still image input MediaInfo"
[7]: https://docs.google.com/open?id=0BxafXIRt8NlPSzEwWGxMRmY3RGs "Input audio file"
[8]: https://docs.google.com/open?id=0BxafXIRt8NlPbHZYM0tLWWtzeWc "Input image file"
[9]: https://docs.google.com/open?id=0BxafXIRt8NlPUmxvUmtjYW90LWM "Batch file"
[10]: https://docs.google.com/open?id=0BxafXIRt8NlPREZaZ0dkR3VGVFk "Final Flash video file"
[11]: https://docs.google.com/folder/d/0BxafXIRt8NlPRk94QWd5aDBQdm8/edit "Open folder"