A big part of the developers worldwide, who have dealt with video converting, sooner or later have been used FFMPEG. In fact I’d say that two of the main software on the video converting scene are FFMPEG and Mencoder. I began to use Mencoder back in 2005 and I used it as a DVD ripping tool, but my experience with it ends there, while now I use FFMPEG.
However FFMPEG is a converting program and many things depend on what kind of video files come as an input and what do you want to achieve as an output. Here comes the codec question, where various libraries can help. In my case, as I wrote few posts ago, I use MP4 as output encoded with h.264, both encoded with ffmpeg/libx264. So far so good, but there is one main problem that anyone used this pair knows.
Flash Player and MP4
As far as I know Flash Player 9 and beyond plays video files encoded with MP4/h.264 except the typical FLV (flash video files). This can help video sites not only to share their video content via web – within browser based flash players, but also to show them via some mobile device interface where MP4/h.264 is perhaps the only one reasonable solution. In this case the file is accessible in both medias.
By default Flash Player can play such FFMPEG encoded .mp4 files, but fist the whole file must be downloaded by the browser and only than the playback can begin. That’s because the FFMPEG puts meta info at the end of the video file, while the flash player needs it at the beginning and only than to begin playing while the file is still downloading.
As the name of this software says this program helps you move the important meta info from the end to the beginning of the file. This helps the video to playback as early as possible. In an ideal circumstances everything works just fine, but there is a serious problem in fact.
qt-faststart and Server Crash
qt-faststart is responsible to move the meta info where it must be – at the beginning of the video file, but cannot finish execution when the video file is broken or the meta info doesn’t exists. Actually this is not a problem of qt-faststart, but to the video file. However this was a critical problem in my case, because the video files remains stuck for hours of execution and 99% of CPU usage.
Thankfully there is a solution and it can be found in the qt-faststart wrapper – qtfaststart.py
written on Python this script overcomes the disadvantages of qt-faststart. As described by his author Daniel G. Taylor:
- Works everywhere Python can be installed
- Handles both 32-bit (stco) and 64-bit (co64) atoms
- Handles any file where the mdat atom is before the moov atom
- Preserves the order of other atoms
- Can replace the original file (if given no output file)
With its help not only qt-faststart doesn’t crash, but also the video files remain progressive as desired. The installation process is as difficult as copy/paste on the server where Python must be installed.