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Old Jan 07, 2011, 10:13 PM
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Tips For Editing with AviDemux

I have done some editing of the HD key cam .MOV files using the latest version (V2.5.4) of AviDemux, and have the following tips that might save you some time and/or frustration:

Main Window Configuration

I like the two-pane display showing the Input Video and Output Video after your edits, like Vdub does. AviDemux can do this, but it doesn't default to that mode, nor can you save it in a configuration setting. The Window top tool bar has the pane orientation selection icons, and the pane sizes have to be set using the "View/Zoom Ratio" menu. Pretty clumsy at best.

"H.264 Detected" Alert

This alert box pops up whenever a video is opened that uses the H.264 video codec like this camera uses. I've always clicked on "no" to reply to this with no problems, fearing what the "loss of frame accuracy" might do. I found that doing this when I loaded back in a file I had just output which had been re-encoded with the MPEG-4AVC (H.264) codec option caused the program to crash! When I reloaded it and selected "yes" the file loaded fine, so sometimes you don't have a choice. I need to do some more testing to see how/if selecting "yes" every time affects the final video.

Sound Issues

The audio codec used in the .MOV file is not a mainstream one in the PC world. I've had troubles with it not working when using the direct "Copy" selection in the main editing window. I now routinely output all my files by selecting the "MP3 (lame)" option in the selection dropdown box under the Audio heading. It is NOT "lame"... EVERYTHING today plays MP3 files!

Sometimes when re-encoding the native .MOV file the sound is intermittant and breaks up while playing the video during editing. Not to worry... it always seems to play fine in the final saved video. Similarly, reloading a file that you just saved can result in some strange sound during playback in the editor, like the sound track plays at several times normal speed! Again, it always plays fine after you save out that revamped file.

Output File Naming

When you output a file you will be prompted for a file name and location. Be sure to add the file type suffix for the format you chose to the end of the file name when you type it in. AviDemux does NOT do this automatically (but it should!), so if you leave it off, there is no file suffix to call up your media player to play when you click the icon. You can also change the file name after you save it to add the suffix if you forget.

Simple Trimming

Clipping of unwanted sections of a video can be done without re-encoding the video... just leave the default drop down box set for "Copy" under the Video heading.

Use the orange "A" and "B" icons at the bottom of the window to set the beginning and end of the section you want to trim. The selected range will be highlighted with a blue outline on the timeline slider. Hitting the "Delete" key or selecting the Edit/Delete menu option will delete that portion. You can drag the timeline slider to quickly get near your trim points, or take short steps to get there with the left or right arrow keys. I've had an alert pop up on occasion when saving a file after trimming the first part of a file, saying the "the video does not start on a key frame". A key frame is the first full image that is used to define the next series of compressed frames, so if it's not there, the subsequent frames have no reference and the program will abort the output. The easiest way to make your cuts at a key frame seems to be to use the arrow keys to step to your final trim point before setting your "A" or "B" markers.

When outputting a simple trimmed, direct copy video file, DO NOT use .AVI file format... it will not work properly. You will need to re-encode the video to do that. Set the output to "MP4" in the dropdown box under the Format heading.

Improving Video Fidelity With Filters

Most of these cameras are set to record with over-saturated colors and with a high contrast setting. While this produces very vivid colors, it also looks somewhat un-natural, increasing the visibility of a central "hot spot" and darkening of the corners in the video. Applying several filters built into AviDemux editor can eliminate most of these undesired artifacts.

Some users prefer the very vivid colors the #11 camera produced. This post gives novices step-by step instructions for boosting the #16 colors to more closely match the #11 camera.

Re-encoding Video

It is necessary to re-encode the video whenever a direct copy into a different file format doesn't work properly (e.g. .AVI), or when you want to use a filter to modify the final video characteristics. Some useful filters you might consider are sharpening, color correction, brightness/contrast tweaks, cropping, and re-sizing. There are a lot more. Access them via the Video/Filters menu, highlight the ones you want, and click the green "+" icon to activate them for the output. I won't try to explain their individual settings that will pop up when you select one... best suggestion is to play with them to see what they do.

My best advice is to always output to the MP4 Format using the MPEG-4AVC (i.e. H.264) Video Codec and the MP3 (Lame) Audio codec. This will produce the most consistent and reliable results. All my video players and editors for Windows 7 will import and use MP4 files except Vdub. You can output the re-encoded video into an .AVI format so Vdub can load it, but there's really no need to unless Vdub can do something better than AviDemux. I haven't found anything yet other than interact with AviSynth scripts to do some fancy combining of multiple videos. But I have a commercial editor that I would normally use for that.

The "Configure" button under the Video Heading gives important toggles for the MPEG-4AVC codec. The only ones that need changing from the default settings for good results are the "Encoding Mode" under the "General" tab. The dropdown box gives 5 options. I have tried them all, and the two that produce slightly better results are the "two pass" options. I think the "Average Bitrate (two pass)" option is just a tiny bit better and easier to configure. Select that one and type in "7000" for the value in the "Average Bitrate" box. That is the approximate average bit rate that this camera normally produces, and will make your final output quality virtually identical to the the original.

If you need to reduce your final file size, you will need to reduce the average bitrate number which will reduce the video quality. An easier way to get a specific file size is to select the "File Size (2 pass)" Encoding Mode, and enter your desired file size in the Target File Size box.
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Last edited by Tom Frank; Jan 31, 2012 at 12:37 AM. Reason: added more sound peculiarities.