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Streaming Video: Adobe Encoder

Tips and tricks for better quality in Streaming Video

Adobe Media Encoder

ADOBE ENCODER SETTINGS

Adobe Media Encoder can be used to create another version of a computer video file, changing the file format or video characteristics. In the example here, a .wmv (Windows Media Video) file, created from PowerPoint slides, is used as input, and the output will be a file in .flv (Flash Video) format. 

The screenshot above shows what Adobe Media Encoder looks like after the input file is selected, and the program is waiting for further settings before proceeding. Settings near the top of the screen indicate the name of the input file, and the output setting for Flash Video. The Preset tab, controlling width, height, and bit rate is set for Custom.


DO THIS FIRST!

Adobe Encoder is not very good at telling the user which options will retain the aspect ratio of the input file and which will not. For this reason, it is important to begin by hovering the cursor over the input file name. This will produce the pop-up display shown  below. The width and height of the input are shown, in this case 960x720. Divide the width by the height to get the aspect ratio: 960/720 = 1.333, approximately.  


THE NEXT STEP IS TRICKY!

Clicking on the down-arrow just under the word "Preset" will produce a list of possible widths, heights, and bit rates for the output. Many of these choices will produce poor results, because the aspect ratio of the output will not match the aspect ratio of the input. The options are listed with aspect ratios such as 4x3 and 16x9. Quick arithmetic shows that 4/3 = 1.333 while 16/9 = 1.7778. Since the aspect ratio of the input is 1.333, all of the options listed with an aspect ratio of 16x9 (=1.7778) should be dropped from consideration. Using any of them will produce an output file with black bars burned into the program.

The options that are marked as "Match Source Attributes" will respect the aspect ratio of the input file, but will not reduce the width and height, if that is desired. 

Assuming a recommended target width of 600 to 640, there is only one option on the list that meets requirements: the option of 640x480 for the output file has an aspect ration of 1.333 (640/480 = 1.333 and 4/3 = 1.333).


FOR MORE DETAILED CONTROL:

If none of the options listed by Adobe Encoder are desirable, click on the words just to the right of the down-arrow that is below the word Preset. The words might by "Custom," "Match Source," or some other value. Clicking on the words will bring up a set of options to control the details of the output file explicitly. In the screen that pops up, click on the Video tab and then use the slider to move the details up or down until the screen width and height are displayed.

Click the box labeled "Resize Video," then overwrite the height and width values with the desired settings. It is up to the user to ensure that the entered values have the correct aspect ratio.

To reduce the width of 960 to 640, for example, divide 960 by 640 producing a scaling factor of 1.5. The same scaling factor must be applied to the height if the aspect ratio is to be maintained. In this instance, dividing the input width of 720 by the scaling factor of 1.5 produces the target of 480 (=720 / 1.5). 

Note that an Estimated File Size is displayed on the screen. That figure will be updated automatically as height and width are changed. Reducing 960x720 to 640x480 reduced the Estimated File Size from 573 megabytes to about 266 megabytes.

Using the slider again, find the bit rate setting:

Clicking on the box labeled Bitrate Level will allow selection between High, Medium, Low, or Custom. High or Medium are recommended settings. Again, as these settings are changed, the Estimated File Size figure will be adjusted automatically.


Lastly, click the Audio tab and make sure the audio type is set either to Mono or Stereo, and not some kind of audio with more than two channels: