Ask for help on streaming

[tiger007]

Hi,

I am a student developing a research project which requires to stream two 15 FPS videos of the resolution (1024*768) at teh same time. But unfortunately I am having the problem of frame-dropping even after using swap-buffering like approach. I am using firewire B cameras and SATA harddisk, and also I am using multiple trheading to take advantage of the mullti-core CPU. I know the possible cause if the harddisk. But my supervisor said it should be okay for 2 such videos.

Since you guys are video gurus, I am hoping to get your value comments on the possible bottleneck and any possible way to do the fast video-2-disk-streaming.

Thank you very much.

[Principher]

I am by no means an expert (more like a beginner) but the simplest way of figuring out if the framedrop is caused by slow harddisk access is (as far as I know) to simply check the CPU usage. I the usage is high (close to 100%) it most likely is not due to your harddisk. Writing to the harddisk is so slow, that it can hardly be seen on a modern PC.

I may be wrong in this assumption, in that case someone enlighten me in my ignorance. :)

[DarkZell666]

You'll have to supply more information if you want more advice ^^'

What's your CPU ?
What's the video bitrate (peak and/or average if you know them) ?
(Just to confirm, you're recording both your cameras onto your computer right ?)
To what format are you actually capturing your video's ? Does the cam do live encoding and it sends you encoded video ? Or do the cams send raw uncompressed video, and your host application (the project you wrote ?) does the encoding ?

Anyhow, 1024*768 is quite a high resolution, even if it only needs to be 15fps. The only case you would manage to do that real-time is if you are encoding to MPEG-1/-2 (and having a multi-core CPU is great, but if the mpeg2 encoder doesn't support multicore it's useless).

Actually, you might even be capturing raw uncompressed video and saving raw uncompressed video. This is the only case the HDD would be the bottleneck, since raw uncompressed video is like ... well over 60mbps. Since you're writting two video's at the same time, the HDD needs to change writting positions very often, and that slows down the maximum HDD throughput ENORMOUSLY (so even a 200mbps SATA couldn't write faster than 100mbps in your situation).

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