How to replace FLV’s audio?

Hi
I want to replace sound of FLV video with a mp3. What software I can use? I know about Sony Vegas and Adobe Premier but It always use converter (rendering). I don’t want them to do this. I just want to replace audio. As you might know, rendering will reduce quality of video and take a lot of time. I want a software that will keep original video quality without conversion but just replace a new audio. I found some software that did this job but it don’t allow me to edit timeline. So sometime, the video and sound playback do not synchronize (Sound start before people speak). Can you recommend me a good one?
Answer #1
whatever you choose , you will have to use a video editor to load the mp3 over the top of the existing soundtrack into the video … and you might have to convert the flv to mpeg or avi … and you could possibly then have a problem with the sync of video / audio
Answer #2
convert it to a .ts as whatever you use will make another video file (conversion) and then use tx muxer which also has a time delay to get your video and audio in sync.
Answer #3
As I mentioned in the first post, Conversion will reduce video quality and take a lot of time. I don’t want to convert back and forth.
Answer #4
Use avidemux it will just convert the audio.
Answer #5
Look good but do you know how to remove and replace new audio file such as mp3?
Answer #6
Look good but do you know how to remove and replace new audio file such as mp3?
avidemux can do that open the app drag the video into it once it opens then goto the menu bar and click audio then select track select the track and then click add audio track the choose the mp3
Answer #7
Can I move audio to synchronize with video with the program? So speech start at the time people speak.