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I have videos in different formats (wma, mkv) with several audio tracks (one by language). I would like to make these videos available in streaming for video-on-demand.

One told me that the flash video format cannot handle more than one audio track. If this is true, what are my options to provide these videos ?

I have two probably working ideas and one for which I'm not sure because of flash players capabilities. The first idea is to create for each mkv, N flash videos, one for each sound track. This is probably easy to do with ffmpeg for example. This solution has the advantage of simplicity but requires much more storage, since the video part will be stored several times.

The second solution would be to dynamically generate the flash video with the desired language once the customer has paid for it. I think this would be very tricky to implement correctly. It may also not be fast enough to do the conversion. So I probably forget this one.

The third solution would be perfect but I don't know if it is possible at all. It consists on spliting audio and video apart and let the flash player mix the correct audio track with the video on the customer computer. I have no idea wether this is possible with adobe flash, nor if there are existing implementations.

What do you think about the third option ? Do you have better suggestions ?

Thanks !

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2 Answers 2

up vote 2 down vote accepted

It looks like Flash Media Server 4 supports multiple audio tracks. From their new features page:

Absolute timecode NEW

Ensure that existing timecodes persist within media files to allow for richer synchronization between streams, improving interactive experiences (such as switching audio tracks or camera angles) with multibitrate and multistream video and synchronized playback events.

It appears that you can use it to synchronise one video stream with a choice of audio tracks in a separate stream.

If you're not able to use Flash Media Server 4, you might like to consider providing one audio track with music/sound effects and your main language only, then offering captions as text over the video for multiple language support. (YouTube's captioning page has more information about this.)

Beyond that, storing multiple versions of the same video, each with a different embedded audio track, is probably the best way to go. Yes, it uses more disk space, but storage is pretty cheap these days, and you wouldn't have to worry about synchronising multiple streams.

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We have an article about Flash audio tracks implementation techniques. Please check it: http://blog.denivip.ru/index.php/2011/09/implementing-audio-tracks-in-flash/?lang=en

Short answer: OSMF 1.6 (Adobe video players framework) supports alternate audio tracks.

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