Multiple streams playing at the same time?

Consider breaking the video into smaller manageable chunks and provide an interface for user to select these smaller pieces. With smaller media you have an easier time starting a swf with the video.

You could record the timestamps when you start to record a voice stream , while you are playing the downloaded FLV.

E.g. your progressive movie starts to play.

At timestamp 1 minute and 15 seconds you start to record voice stream A
At timestamp 3 minute and 2 seconds you start to record voice stream B
At timestamp 3 minute and 29 seconds you start to record voice stream C

Store those 3 timestamps in a database.

When a user wants to see and hear the result you need to download the movie. Download the data-timestamps from a database. Download the voice-streams.

Then have a fast interval running.

Start your movie.

Let the interval check if the play-time of the movie is matching one of your recorded timestamps. If it does ; play the voice-stream.

Et voila.

But don't expect this to be flawless. The resolution of the interval is pretty good (you can have an interval run 50 times a second) but the resolution of the FLV is not so accurate.

command: time (NetStream.time property)
public time : Number [read-only]
The position of the playhead, in seconds

Flash only lets you time this way on whole seconds.

Normally ppl would record a movie and insert cuepoints. See the Video Encoder tool that's installed when you installed Flash 8.

This requires "editting" of the movie before you can use it ; but you only need to listen for an event on your client. Ofcourse you can only use this method if you want to use fixed cuepoints in your main-movie (like points for a voiceover/comment or something)

from the docs:

command: onMetaData (NetStream.onMetaData handler)
onMetaData = function(infoObject:Object) {}
Invoked when the Flash Player receives descriptive information embedded in the FLV file
being played.
The Flash Video Exporter utility (version 1.1 or greater) embeds a video's duration, creation
date, data rates, and other information into the video file itself. Different video encoders
embed different sets of metadata.
This handler is triggered after a call to the NetStream.play() method, but before the video
playhead has advanced.
In many cases the duration value embedded in FLV metadata approximates the actual
duration but is not exact. In other words it will not always match the value of the
NetStream.time property when the playhead is at the end of the video stream.