[bpowley]

We have a J2ME MMAPI application which plays streaming (RTSP, H.264) 3gp video. Intermittently, we only get audio playback, but no video.

The video is streaming from our own Darwin Streaming Server, and the phone we are testing with is a 6220C. The problem is intermittent -- most of the time, video will play with no problems. However, occasionally, a video which was previously playing fine will play with audio only.

What is likely to be the cause of *intermittent* streaming video playback problems?

[psamick]

There are two things you can try:
(1) Make sure you have the latest version of the Darwin server. You may also want to compare the RTSP chat with a working session and a non-working session for differences.
(2) If possible, get any updates to the 6220 software. I don't know what version of Helix is on your phone, but there have been some updates to H.264 processing and display handling.

I am assuming your Java App just uses an instance of the Helix plugin to play the content. You may also want to check your display window handling for any issues.

[bpowley]

> Make sure you have the latest version of the Darwin server.

Got that.

> You may also want to compare the RTSP chat with a working session and a
> non-working session for differences

I did this, and logged both the RTSP chat and RTP packets, for working and non-working sessions. I didn't see anything obviously different. My guess at the time was port numbers, but there didn't seem to be pattern of certain ports working and others not.

Is there anything else to look out for?

> If possible, get any updates to the 6220 software. I don't know what version of Helix
> is on your phone, but there have been some updates to H.264 processing and display handling.

I'll look into that, although last time I checked there weren't any updates (Nokia did release one and then pulled it).

> I am assuming your Java App just uses an instance of the Helix plugin to play the content.

I'm assuming that too :-) I think that MMAPI uses RealPlayer under the covers, and I have actually since tested with RealPlayer on its own and seen exactly the same behaviour.

In the case of RealPlayer, the audio-but-no-video sessions stop at "Loading".

> You may also want to check your display window handling for any issues.

As far as I know I have eliminated any bugs in this -- I did find early that drawing into the video area caused issues. The problem I'm seeing now happens in both RealPlayer and our Java app.

I noticed some Nokia/Real - specific stuff in the Darwin Streaming Server configuration, but couldn't find any documentation about what they were for. I did wonder whether this might be an issue too.

[psamick]

The problematic clips, are they live or on-demand?

[bpowley]

> The problematic clips, are they live or on-demand?

They're on-demand. That's one of the perplexing things: exactly the same clip will sometimes work and then sometimes not work.

[psamick]

Does the same problem occur when using RealPlayer (the native App for streaming playback)?

[bpowley]

>Does the same problem occur when using RealPlayer (the native App for streaming playback)?

Yes, it does. With RealPlayer, the audio starts playing but the display stops at "Loading".

[psamick]

If, when using the RealPlayer App, it stops at Loading then either (a) it isn't getting data for one or more streams or (b) it thinks it has to throw away data for one or more streams.

For (a), you can check the IPdump. You said you saw nothing obvious, so check that (1) they are coming to the port(s) specified in the SETUP Requests and from the ports in the SETUP Responses. Also make sure the Session IDs are correct. You could also look at the Receiver Reports and see what the client is claiming it is seeing (packets received count).

For (b), look at the RTP-Info line in the PLAY Response. Compare that info with the sequence numbers and timestamps of the first few packets received. They should be close.

Also, please describe what happens after Loading. Does it stay in loading forever? Does it eventually time out? Loading forever indicates that it is receiving data. If it times out, then it isn't seeing data.