This is exactly what we're trying to do, except for with a dozen TV
channels. The 3ivx D4 4.5 MPEG-4 codec actually seems to be the best
right now (www.3ivx.com). But it doesn't come close to the quality of
what some of the competitive solutions we've looked at are turning out,
and I haven't really been able to get a real answer as to why.
Even Cisco's MPEG-4 software-only codec running on an old Pentium III
can be set up to give us near-perfect quality at under 2Mbps. I don't
think the issue is letting the bitrate go higher: we get quality almost
undistinguishable from live TV out of MPEG-1, -2, and -4 on other
platforms at 1 to 2 Mbps; there's no reason to go any higher than that.
I think the issue is more that the codecs currently suitable for
live-encoding use with QuickTime aren't optimized for or geared toward
very-high-quality, high-bandwidth output. They're wonderful at almost
every other speed and for every other application up to moderate
quality for live streaming; but "TV quality" doesn't seem to be
attainable.
For what it's worth, here are some comparisons I did a while back:
(The Cisco example there isn't a good one; when paused, the video got
"blocky"...when it's playing, it's almost crystal clear.)
Everything else about the QuickTime solution - the hardware, the OS,
the software itself, the flexibility and featureset, cost, etc - is
fantastic...it's just that there seems to be no software codec solution
for high-quality live streaming. (Also, we'd want to stick with
MPEG-4...since Cisco's IP/TV MPEG-4 software codec is amazing on even
old hardware, we know it can be done.) I'm just hoping that Apple will
surprise us all with an amazing H.264/MPEG-4 AVC live streaming
software solution that blows everything else away...
I would love to get some kind of official response from the QuickTime
team on this...
(As an aside, we're using Canopus ADVC-100 analog -> FireWire
converters and industrial tuners to get the video into the machines. A
couple weeks ago, I got the first Xserve- and G5-compatible PCI TV
tuner card from Miglia. It supports QuickTime, and works with QuickTime
Broadcaster! It's a great solution because everything is self-contained
completely within one box. And multiple cards can even be installed in
one machine for streaming multiple channels!)
- Dave
On Jan 21, 2004, at 7:21 PM, Jason Gaiser wrote:
Hello Everyone,
I've assigned the task of getting a OSX 10.3/Dual G5 server to produce
a real time video stream with near TV quality. I've played around
with Quicktime Streaming Server/Quicktime Broadcaster a bit and
haven't been able to come close. I'm using a Sony TRV-520 camcorder
connected via 1394 for the video source. I can view the incoming
video using Vidi and it looks great.
I've tried every codec on the system, including the Apple MPEG-4 and
DivX Pro 5.11. The best results came from the Apple MPEG-4, set to
640x480, 'Best' Quality. I've tried changing FPS from 10 to 60, key
frame interval from 1-100, and Bandwidth limiting from 10,000 to none.
The resulting stream ranges from 5-10 Mb/s, with the CPU's running
around 55%. I've viewed the results on a local Quicktime player using
the loopback address, as well as Quicktime and VLC on various
computers on the LAN. On every client, the video is blurry, and
subject to a fair amount of macroblocking and fringing.
Is there something I'm missing, or am I running up against a
limitation of software codecs in general? I would expect that I could
simply crank the quality up even more, with a resulting increase in
bitrate. However I can't get the codecs to use more bandwidth.
