Creating MP4 Files

Software name : Avidemux
Software version : 2.4

This chapter will show you how to create a MPEG4 file from an existing video file.  There are many reasons why you may need to create a MPEG4 file from an existing video file - to make a downloadable preview file for a longer movie that can be viewed in VLC player, for example.

Before we start however it is useful to note that MPEG4 files created by Avidemux won't play in a Quicktime ('QT') player (which makes them unsuitable for wide distribution as podcasts). There are numerous posts on the Avidemux forum about this issue and hopefully a future version will solve this problem. If you want to create a QT compatible file you'll have to use the softwares known as SUPER (Windows only), or FFMPEGX (MacOSX) and FFMPEG in Linux. There is help elsewhere on these applications.

I will assume that you already have a video file which you want to turn encode.

If you don't already have a suitable video file, then you may need to either :

1. export a file from a video editing programme
2. capture a DV tape to a file on your hard drive

Opening the Original File

So, assuming you have a file ready to go...Open the video file you already have. This should be as high quality as you can - this is because every time you convert a video file into another type of file quality is lost. So you want to start with the highest quality file as possible to ensure the newly created file is the highest quality it can be. Ideally it will be a DV file exported from a video editing program or captured from a camera or an MPEG2 file or VOB from a DVD.

Click on 'File' and then on 'Open' :

You will see a window appear that you can use to browse your computer to find the file you want. The file browser should look similar to this (but its look will differ depending on your Operating System, the following image is from Avidemux running on Ubuntu Linux):

Highlight the file you wish to open and either double-click on it or press 'Open'.

Encoding Settings

When you have opened a video, copy the settings shown below by selecting them from the drop down menus on the left. Select MPEG-4 AVC (x264) from the Video drop down menu. Select AAC (FAAC) from the Audio drop down menu. Finally select MP4 from the 'Format' list at the bottom of that section :

If you see neither of these options listed then try another MP4 option for video or another audio option (eg. MP3).

Deinterlacing

The next thing that we might want to do to the video file is to add a deinterlace filter. This would be appropriate if you had a video that was edited from a DV camera and is still interlaced. If we create a DVD that isn't played on a standard TV then we might see the effects of the interlacing which will look like strange horizontal lines through the video.

If you don't know what the effects of interlacing are you can see them in the screen shot below (most clearly visible on the face of the man at the top left).

We can remove this unwanted effect by adding a deinterlace filter.

To do this click on Filters under the Video section.

 

Then click on the Interlace tab, and select yadiff.

Then click on the '+' sign at the bottom of the window :

You will then be shown a pop-up window like this:

Click 'OK' to the default settings shown, and Yadif should appear on the section on the right :

It's important that the deinterlace filter is the first filter you add.

Then click Close on the bottom right of the screen :

Screen size and Bitrate

The screen size and bitrate you use really depends on what you want to do with the MP4 file you are creating. There are some simple things to keep in mind:

The higher the bitrate the larger the actual size of your video. This means that if you use a very high bitrate then it will be slower to download, this may or may not make a difference to you. You may want to try and imagine what kind of internet connection your audience may have (if you are indeed making a MP4 for delivery over the net). If they have fast connections then the final file size isn't as important. The final choice is yours and it usually means balancing a compromise of quality vs download time.

The actual size (height and width) of the movie will also affect file size. Additionally of course, the height and width affect the playback experience for the viewer. The larger you make the height and width the easier it is to watch but also the file size will increase. The compromise you strike is also one of judgement.

If, for example, you want the video to be downloaded over an internet connection but you want it to retain a good quality image then perhaps choosing the following might be a good idea :

1. 300 kp/s bitrate
2. 320 (width) x 240 (height) size

If you want a high quality 'Internet TV' file then 640 x 480 and 1000 kp/s (or higher) is more suitable.

The decision is yours as to the most appropriate height and width, bitrate, and resulting file size. Lets assume you have made that decision and look at how to change the bitrate and height / width.

Changing Bitrate

Click on the Configure button on the left of the Avidemux interface.

You will see a pop up window appear

Make sure the 'Encoding mode' is set to 'Two Pass - Average bitrate' from the drop down menu. Change the setting in the text box ('Dual pass, avg bitrate') to 300. Then click on 'OK'.

Change Screen Size

Now click on Video and choose Filters:

Choose the transform tab on the left, this should be the default view :

Then double click on 'Resize' and a pop up window will appear.

So, let's assume we wish to change the video to 320 (wide) by 240 (high). Enter '320' in the text box next to 'Width' and '240 ' into the text box next to 'Height'. Next choose the correct aspect ratio (the shape of your video file - normally 4:3) from the 'Source' and 'Destination' drop down menus. Then , when you are finished press 'OK'.

Click 'Close' to return to the main screen.

Saving the file

To save the file click on the 'Save' button.

You will see a pop-up box that may look a little like this:

Choose a place to save the file by browsing your computer using the list of folders displayed. Then in the name field:

 

write in the name you want the file to be called and end the name in ".mp4". When you are finished press 'Save'.

You should see a box which lets you know how long you have to wait for the encoding to finish and shows the encoding progress.

You'll get a success message if the encoding works correctly. You can now play the file in a media player.

Trouble?

It might be that Avidemux does not save your file, or shows an error when you try and save the file. To work around this try a different combination of settings for the Audio and Video and Format boxes as shown :