6 Replies Latest reply on Apr 19, 2007 3:37 PM by Peter Lorent

    Streaming issues

    Peter Lorent Level 2
      Hi all,
      I'm streaming (progressive download) video with no soundchannel so I can stream voice-overs in the chosen language. Doesn't work well. Either the sound plays, it plays to late, it plays a small bit and stops, doesn't play all together. Sometimes the video stops when the sound kicks in, then plays again. And this occurs with only one small video in the FLVPlayback and a small mp3 for the voice-over. I'm starting to think that this won't work at all. So, will I need to edit the video to contain the voice-overs... any thoughts?
        • 1. Re: Streaming issues
          Greg Dove Level 4
          I've never tried what I think you're attempting to do but if I did, I would aim to preload the audio. Then also make sure that the video buffer would be sufficient to never stall the video playhead on a progressive streaming download.

          I assume those would be the best conditions to make the attempt to do it. I don't know how easy it is to try and synch the audio like that or how you would try to check for synch periodically - because I've not really done much with audio by itself. The playheadTime property of the FLVPlayback will give you the timecodes.
          • 2. Streaming issues
            Peter Lorent Level 2
            Well, setting the buffertime for a progressive download is ignored. Only works for real streaming. So, I'm already preloading the video. Preloading the audio could be an option when using just a few files but I must handle quit a number of files and do not know beforehand what the user is going to do in the website. So, it just isn't manageable. But setting the buffertime for the audio might help. The sound gets triggered by an AS cuepoint in the video so I was thinking to put the cuepoint backward in time by the buffertime for the audio. Then again, that obviously wouldn't work when audio has to kick in simultaneously with the video...
            • 3. Streaming issues
              Greg Dove Level 4
              So you need to 'buffer' both the flv and the audio.

              You can 'buffer' the progressive download by keeping the FLVPlayback in pause while checking the current percentage downloaded.

              EDIT: Oh sorry I see you're preloading the video already

              For the audio, I'm not really familiar with it as I said... just haven't done much with it by itself.

              In terms of using cuepoints to trigger the audio, you just want it to start at a known synch point I would imagine, and make sure you have enough of it to continue smoothly in parallel with the flv.

              Cuepoint accuracy for what you're doing is probably 'quite' important. Hard-coded cuepoints are more accurate that AS ones...but you can improve the normal situation for AS cuepoints: {livedocs excerpt}

              ActionScript cue points are accurate to a tenth of a second. You can increase the accuracy of ActionScript cue points by lowering the value of the playheadUpdateInterval property because the component generates the cuePoint event for ActionScript cue points when the playhead updates. For more information, see FLVPlayback.playheadUpdateInterval.
              • 4. Re: Streaming issues
                Peter Lorent Level 2
                Yes, I choose the AS injected type for the cuepoints because then I can create a complete stream dynamically and the because the accuracy is acceptable in this case. But yet another issue pops up. The audio somehow degrades (not in terms of filesize by any publish settings but just a funny transformation). Has nothing to do with CBR btw or compression settings, that's all in order. Hmmm, it keeps me of the streets....
                • 5. Re: Streaming issues
                  Greg Dove Level 4
                  If I get a chance I'll try to do a test tomorrow - out of curiosity. It'll be off local so I can't simulate real-world but I'll see if I can replicate or avoid your audio problems. I'll have to do it with a FLV with an audio track and just mute its volume... don't think I've got too many silent flvs around!
                  • 6. Re: Streaming issues
                    Peter Lorent Level 2
                    To test whether I could seamlessly play a number of flv's I downloaded a QT-movie from the Apple website and (QuickTime Pro) exported to flv without the audio track. I'm very curious if you can replicate the problem. Of course I will be working on this tomorrow (and probably the weekend :) ) and if I come up with a solution I'll let you know. Better yet, I hope you can post a solution :) . A weekend without work... sounds like heaven.