video plays abnormally fast for a short time while streaming from FMS (issue appears on iPad)

Question

I am streaming (live, no recording) video using Flash Media Server 4.5. I created to 2 applications -

1) Publisher: Publishes (streams) video using FMS. 2) Receiver: Plays the published stream.

Everything works good as expected because its very simple application on WEB or in (Desktop) browser.

But when I port Receiver app to iPad, video, it plays fine but in between it plays fast (like you are fast forwading in VCR or DVD player) for few mili seconds and then back to normal.

Note: I tried using Wowza server in place of FMS but no luck.

To resolve this issue I played with some settings like - lowering the camera fps to 10, quality to 50, favoring to false. It results lil bit improvement but my client cannot compromise on low quality video, that too on iPad.

Thanks in advance!

Answer 1

This is actually the intended behavior for live streaming. There is no "one size fits all" answer to this question.

If you use RTMP (a TCP protocol) the network layer is going to ensure that all packets are delivered. This is not necessarily ideal for live streaming. Using RTMFP (a UDP protocol) is generally preferred.

I can't find where I've read this before (NetStream documentation?). But Flash Player will do it's best to keep up w/a live stream. It may play the video slightly faster or drop video frames in order to do so.

This usually happens b/c of network issues and so your approach to lower the quality of the video feed is a good approach. However, the best thing to play with is the capture resolution of the camera (using Camera.setMode()).

Lowering the capture resolution will reduce the bandwidth required to transmit the video. You can use a smaller capture resolution (like 320x240) and still display it at a larger size in the Video object (480x360). Obviously, there is a trade off you will have to make. Maybe give your users some options to set quality based on their network conditions.

The other useful method is Camera.setQuality(). If bandwidth is the issue, you might specify a bandwidth target to let Flash manage the quality based on bandwidth. Again, providing users an option to configure this.

Finally, if the problem only seems to happen on an IPad and you're confident bandwidth is not the issue, then it could be hardware related. Again, Flash will do what it can to keep the live stream as "current" as possible (my gut feeling is that it would drop frames, not play faster in this scenario).