VideoHelp Forum
+ Reply to Thread
Results 1 to 6 of 6
Thread
  1. Member
    Join Date
    Dec 2008
    Location
    Germany
    Search Comp PM
    I am just experimenting at the moment with converting movie trailers, and I found one that i'd forgotten existed on my external drive which is an AVI file.
    I'm using ffmpegX and selecting MP4 as a Quick Preselect, without changing any other video parameters, the settings show up (under video parameters) as video size: 624x256 (same as the original file), and next to Autosize it says: 2.35:1, Framerate is: NTSC FILM.
    So basically, the problem is, the converted movie that I end up with is a different size to the original, even though i'm not changing the video size after selecting the original file.
    Any ideas anyone?
    Quote Quote  
  2. file size = bitrate * running time

    But, if the codecs are suitable, rather than reencode try remuxing the audio and video streams from the AVI to an MP4 file. AviDemux can do it.
    Quote Quote  
  3. Member
    Join Date
    Dec 2008
    Location
    Germany
    Search Comp PM
    Thanks jagabo, but for my sake and the sake of the other newbs here, can you explain that in more simple terms?
    Quote Quote  
  4. AVI and MP4 are containers, vessels for holding audio and video data. Within the containers are streams of audio and video multiplexed (muxed for short; a little video, a little audio, a little video, a little audio...) together along with some organizing data.

    Not all containers can hold audio and video compressed with every possible codec. But if your AVI file uses codecs that are suitable for MP4 (and will work on your intended playback device) you can simply demultiplex the streams from the AVI file and remultiplex them into an MP4 file. Remultiplexing is much faster than re-encoding (a few minutes vs a few hours), there will be no quality loss and the resulting file will always be almost the same size as the source (different containers have a little different overhead so it won't be exactly the same size).

    AviDemux can remux audio and video from an AVI container into an MP4 file. Start AviDemux, then:

    1) File (menu) -> Open... select AVI
    2) Format (pulldown) -> MP4
    3) File (menu) -> Save -> Save Video...

    AviDemux doesn't automatically append file extensions so be sure to add .MP4 to the end of the output filename.

    AviDemux can also reencode the audio and/or video if necessary.
    Quote Quote  
  5. Member
    Join Date
    Dec 2008
    Location
    Germany
    Search Comp PM
    Sorry jagabo, I just reread my first post, and I didn't make clear what the problem was, the problem is with the frame size of the re-encoded file. So without changing any of the automatic settings that ffmpegX calculates, I am ending up with a picture that has a changed picture ratio.
    Sorry for the confusion.
    Quote Quote  
  6. Explorer Case's Avatar
    Join Date
    Feb 2004
    Location
    Middle Earth
    Search Comp PM
    So your source is 624x256. What is the video size of your converted output, i.e. how is it different?
    Quote Quote  



Similar Threads

Visit our sponsor! Try DVDFab and backup Blu-rays!