Date: Sun, 29 Oct 2000 15:48:37 +0100 (CET) From: Oliver Fromme <olli@secnetix.de> To: freebsd-multimedia@FreeBSD.ORG Subject: Re: Streaming MPEG.. Message-ID: <200010291448.PAA17996@monos.secnetix.net> In-Reply-To: <Pine.BSF.4.21.0010241912550.495-100000@moritz.alleswirdgelber>
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Heiko Recktenwald <uzs106@ibm.rhrz.uni-bonn.de> wrote: > On Tue, 24 Oct 2000, Oliver Fromme wrote: > > Note that "I-frame crippled" MPEG has pretty poor > > compression/quality, compared to "real" MPEG streams > > (with I, B and P frames). > > This is the old Xing streaming, I think. Correct. > man vic, from 1995, says, that MPEG isnt supported yet, > contrary to former plans, and I saw a big SGI Media server, > that can stream 100 MPEG streams...but this is broadband. Well, MPEG streams are (unfortunately!) not very well-suited for transmission via lossy media, like mbone (vic etc.). This is because of the inter-dependencies embedded in the MPEG streams. For example, when you lose some data while transmitting an MPEG video (or system) stream, _all_ the following data is useless till the next I-frame. Similarly for audio: when you lose data within a layer-3 stream, it not only destroys the current frame, but also the two next frames (worst case). Of course, you could restrict (or rather: cripple) your MPEG streams to I-frames only and layer-2 audio, but then you'll lose a good deal of compression/quality capability. One of the _really_ big strengths of MPEG is the ability to perform motion interpolation and prediction, which require B- and P- frames. Therefore I'm not surprised that MPEG is not on top of the to-do list for the vic developers. MPEG is better suited for reliable media such as TCP connections. There are other formats which are better suited for streaming via multicast (mbone). Regards Oliver -- Oliver Fromme, secnetix GmbH & Co KG, Oettingenstr. 2, 80538 München Any opinions expressed in this message may be personal to the author and may not necessarily reflect the opinions of secnetix in any way. "All that we see or seem is just a dream within a dream" (E. A. Poe) To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-multimedia" in the body of the message
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