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View Full Version : Communicating with webcams through ADSL.


pirata
20th January 2003, 07:44
Hi everybody. I post this one in PC Hardware section. NO ANSWER AT ALL. I still it is interesting, and it's all about new technologies, so I'll try my luck in this section. I have edited it a bit.

I am an engineer currently based in France. I have a ADSL connection and I thought I could enjoy a tighter and warmer contact with my relatives and old frends in Germany using a Webcam and a Netmeeting-like program. Unfortunately I haven't ever had any experience with this kind of hardware/software, so I need some insight from the savvy people before using the Visa.

Many of my relatives and my friends are also getting into the mood for webcamming, but we all agree that good quality is a must for really having a warn and nice webcam experience. Most webcam demonstrations I have seen were 384x288-15fps, even using 128/256 ADSL. Is that really true?

The problem can be divided into parts (if any of my statements is not true, don't hesitate to tell me so):

1-the captured video and audio are sent down to the PC via USB1.0 (are there USB2.0 webcams?), in UNCOMPRESSED format. That really eats up the USB bandwidth and limits the video quality you can get. I think usual resolutions are somewhere near 384x288 at 15fps. Correct me if I am worng, please.

2-Once you get the video in the PC, you want to stream it to your mate in the other country. Of course it is necessary to compress it first. And here begins the second problem: you need realtime video and audio codecs that are able to squeeze the data to fit in in a little bit less than 128kbs (up and down). And you also need a streaming application that is able to interface with those codecs and stream their outputs to Internet. This streaming application should also be able to store the incoming data in HD (for later reviewing) and also allow to chat with 2 mates at the same time (since the down stream rate is 256 in ADSL, which provides for 2 inbound streams and one outbound stream).

As for realtime codecs I've found dicas mpegable codec (look for it in the web). Although it is MPEG4 (good quality at low bitrates), the image size is no bigger than 384x288. I don't know of any other realtime codec (MJPEG codecs and similar stuff can't do a great job at compressing). I also don't know of streaming apps interfacing with user-selected codecs.



Well! That's a starting point. I can hardly wait for your contributions!

Cheers, Marc

thijs
20th January 2003, 13:13
Hi Pirata,

I have a webcam (philips Toucam pro, USB 1), But unfortunately I don't have ADSL yet, so I can't give you much advise on that subject. I can tell you something about the video-dimensions: with my webcam I can easily capture a 640x480 video @ 25 fps. This is on an Athlon 1400 Mhz, 256 MB Win XP system.

Hope that helps.
Thijs.

alexcyn
19th February 2003, 10:00
Having ADSL 128/256 Kbps your video stream should fit into ~100 Kbps.
It is very strict limitation. From my experience, if you want to have good quality video, the max resolution for 100 Kbps is SIF (320x240) at 10-15 fps.
No codec can compress acceptable video into 100 Kbps at higher resolutions :-(. Then the quality will depend on codec. New upcoming H.264 standard will give you the maximum quality at this bitrate, but it is very CPU intensive.
=Alexei

Sirber
19th February 2003, 17:14
RealVideo + RealAudio seems to be the best choice. It can do realtime encoding and is optimized for streaming. I think you should ocntact Helix Community about licensing options.

I encode animes at 250kbps (sound included) and the image is as good as a MPEG1 or DIVX @ 500+kbps. At 100kbps, 320x240 is correct, at 10fps, with 8kbps voice audio codec.

Good luck :)