on 11/25/02 10:43, Marc Jaeckle at email@hidden wrote:
> I can't remember it exactly at the moment but wasn't the dynamic
> switching between different data rates somewhat limited in WM8 because
> of limitations of the asf file format (only one audio track per file or
> something like that - I know, I shouldn't read your book during the
> night)? Provided that I'm right, have there been changes in WM9
> concerning that?
Correct. WM8 required one and only one audio track per file. WM9
supports different audio tracks, and different resolutions per video track.
Definitely the strongest MBR solution today.
>> But dropped packets themselves are mainly
>> a problem for modem users,
> Not to forget those who want to access video via mobile devices in the
> future (ok, it's a little bit questionable if people will really use
> mobile devices to access video on the internet in the near future but
> that's another story). Error resilience also matters when it comes to
> real-time communication over ip-networks.
Correct. However, the architectures just try to make sure as many
packets arrive in time as possible. Its the codecs themselves that
determine what happens when a packet is completely missing. MPEG-4 has a
lot of good tools in this regard.
>> None of the formats will dynamically reduce resolution due to CPU
>> limitations.
> What about MPEG-4 spacial scalability? If you only decode the base
> layer of a multilayer bitstream you get a lower resolution image. So
> wouldn't it be theoretically possible to add or remove the enhancement
> layers dynamically? (just a thought, I'm not saying that it makes sense
> doing this dynamically)
Ah. Well, it's up to the player to tell the server what it can handle.
I suppose a player could just request fewer layers if it is CPU limited.
>> MPEG-4's scalable profiles (not widely implemented yet) and
> Speaking of MPEG-4 scalable profile implementations: Is there a MPEG-4
> scalable profile solution that also supports OS X and Linux?
No. The only one that is actually implemented that I know of is
PacketVideo, which uses Simple Scalable. But that's mobile device and
Windows playback only. And they use the 3GPP audio profiles, so it's not
ISMA compatible.
>> QuickTime's biggest competitive limitation for streaming is its
>> lack of
>> robust mechanisms to deal with varying connection speeds.
> I hope this will improve with adoption of new MPEG-4 profiles. Although
> I fear that it will take quite some more time...
Fingers crossed. Apple has certainly committed to MPEG-4 in a big way,
and this would be the obvious way for them to go forward to making QuickTime
and the Mac be a good platform for authoring and playing back digital media.
Ben Waggoner <http://www.benwaggoner.com>
Compressed Video Consulting, Training, and Encoding
My Book: http://www.benwaggoner.com/books.htm
Cleaner Tutorial: http://www.saferseas.com/navseries/adclean.html
Compression Books: http://www.benwaggoner.com/bookshelf.htm
_______________________________________________
quicktime-talk mailing list | email@hidden
Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/quicktime-talk
Do not post admin requests to the list. They will be ignored.
