Audio for Video using Avidemux
I have a lot of fun with Flip Mino HD camcorder. I’ve already done a few music videos with it and in my opinion the audio is far behind the quality of the video. Of course, even with expensive video equipment, having the mic on the camera keeps it some distance from the subject. Having a separate mic, much closer to the subject, gives a much better result.
A Free Video Editor – and a Good One
In the past I’ve used Windows Movie Maker to combine my audio and video streams, but WMM is not compatible with the MP4 720P file created by the Flip. I was happy to find Avidemux, a free video editor. The program comes with a wide range of codecs and works on the compressed files without decompressing for simple operations like trimming length and replacing audio. And since that’s almost all I do to my music videos, it’s perfect for the job.
Avidemux is simple both in concept and use. You can peruse and search the Wiki and ask questions in the forum but there’s no substitute for a little experimenting.
For a simple music video I replace the camera audio with my separate recording and trim the start and end points of the clip. Naturally, when I shoot the video I clap in front of the camera so I have an obvious point to synchronize the two streams. As funny as it seems, getting a good clap important because it makes synchronization so much easier. Try to face the camcorder directly so the instant of contact is easy to see.
Synch Video with External Audio
To sync the video first File : Open the video file and find the “clap” point. Note the time. Then load the external audio file by going to the Audio : Main Track menu selection, choosing the format for the external audio file, and open the file. Now when you play the video, the external audio will play instead of the audio recorded by the camcorder. Find the “clap” on the audio track and note the time.
Take the difference between the two “clap” points in milliseconds. Check the Shift option box, and enter the difference value in the milliseconds value field. If the clap happens first on the external audio file, enter the difference as a positive number. If the clap happens first on the video stream, enter the difference as a negative number, with a minus sign preceding.
Now play the video the audio and video “clap” should be synchronized.
Trim the Video
Next, trim the video to length. Avidemux provides two markers, the A and B marker, which can be placed at any frame in the video. After the markers are set, any save, delete, cut, or copy will affect the section between the markers. My technique for trimming a video is to set the “A” marker to the beginning of the good stuff, and the “B” marker to the end of the portion I want to keep. When I save the video only the portion between the markers is saved.
Before saving, confirm that the Format field is set to the proper container format. If you’re not converting to a new format, it should be the same as the input video. You may need to set a codec for the audio stream, depending on the container format and the format of the external audio file. Once again, the format used in the original video file is a good choice.
When saving files, Avidemux has a quirk – probably because it’s a port from a Linux implementation – it does not automatically insert the extension on the saved file. You need to specify an extension that matches the container format when you save the video, and you should choose the appropriate extension for audio files and frame exports as well. And one more tip, I always save the file to a new name, so I can re-use the original file if needed.
Here’s a video demonstrating all the steps I’ve described. A few moments watching the procedure should make things much more clear. Try the full screen option in the lower right hand corner of the video control bar.
I’ve had a lot of fun learning and using Avidemux. If you need a nifty video tool that works quickly with minimal resources and minimal damage to your video quality, you should give this program a try.
This entry was posted on Wednesday, June 10th, 2009 at 7:53 pm and is filed under Tutorials, Video. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
Homebrewed Music − Audio for Video – Avidemux and Wavosaur said in post # 1,
on June 11th, 2009 at 1:41 pm
[…] my last blog entry I described the process for merging audio and video recorded on two different devices, for […]
Carl said in post # 2,
on July 15th, 2011 at 4:41 am
Great tutorial, I will try this when I get home as Reaper seems to be damaging the quality of the video when I render. I briefly tried it last night but I think I got an error message opening an MP4.
Thanks.