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A report from OSCON 2007

A report from OSCON 2007

Posted Aug 3, 2007 16:48 UTC (Fri) by Hanno (guest, #41730)
Parent article: A report from OSCON 2007

> Arjan suggested 20 minutes of video or a minute of audio.

Mixup?


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A report from OSCON 2007

Posted Aug 3, 2007 17:19 UTC (Fri) by arjan (subscriber, #36785) [Link]

video tends to come from a cd/dvd (one of those rotating energy slurping thingies) while audio tends to come from the harddisk (or usb). For cd/dvd the "spin the disk up" is a much higher cost so you tend to want to do it much less frequent than for in core storage...

A report from OSCON 2007

Posted Aug 4, 2007 13:56 UTC (Sat) by man_ls (guest, #15091) [Link]

How can you store 20 minutes of video? On DVD this can amount to more than 700 MB, is it practical to cache that much information?

A report from OSCON 2007

Posted Aug 4, 2007 20:21 UTC (Sat) by arjan (subscriber, #36785) [Link]

that depends on how much ram you have (free)....

(and on the actual datarate you have)

A report from OSCON 2007

Posted Aug 5, 2007 1:05 UTC (Sun) by drag (subscriber, #31333) [Link]

well the problem I have is that it should discriminate based on disk type, not on format.

As often as not I am reading audio from a cdrom and video from the harddrive. :)

A report from OSCON 2007

Posted Aug 9, 2007 12:08 UTC (Thu) by arafel (guest, #18557) [Link]

What you say is true, but it's also true that if you're prepared to buffer 20 minutes of video, buffering the whole audio track (whether MP3 or raw audio) should be possible. What was the reason for saying 1 minute, rather than just 'all of it'...?

A report from OSCON 2007

Posted Aug 14, 2007 8:01 UTC (Tue) by nim-nim (subscriber, #34454) [Link]

However mostoptical drives make a loud noise during spinnup or at maximum spin speed. This is highly conterproductive when reading audio or video (and a huge power drain besides)

It's much better to spin the media at a slow constant rate rather than stop and restart it all the time. Unless you can buffer long periods (at least 15-30 min of content)

video buffering

Posted Aug 5, 2007 5:54 UTC (Sun) by akanaber (subscriber, #23265) [Link]

> > Arjan suggested 20 minutes of video or a minute of audio.
> Mixup?

I'd guess it was "20 seconds of video".

video buffering

Posted Aug 5, 2007 6:05 UTC (Sun) by akanaber (subscriber, #23265) [Link]

> I'd guess it was "20 seconds of video".

Whoops. I just noticed that some of the comments above were from arjan. Never mind, and sorry for the noise.

I was just a bit surprised at the idea of buffering 20 minutes of DVD video. That's certainly a large buffer.

video buffering

Posted Aug 11, 2007 0:43 UTC (Sat) by giraffedata (subscriber, #1954) [Link]

I can't understand how there could possibly be a rule of thumb for this. Besides the fact that it's far from reliable to assume video is on optical storage and audio is on magnetic storage, there seems to be a huge assumption about how scarce memory is on the system.

If buffering 700MB means you have to push out of memory other stuff so that you then have to spin up a disk and get it back multiple times, it probably doesn't make sense.

But if there is 1400MB of memory essentially unoccupied, stopping at 20 minutes of buffering doesn't make much sense.


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