What is "Total bit rate"?

Question

Level 7

24,455 points

What is "Total bit rate"?

I have a reasonable idea of what bit rates are, measured in MB/sec or Kb/sec, but whenever I use "Get Info" on a video clip I get something like . . . . "Total bit rate: 26,571" . . . . just that - nothing else.

What exactly is it?

It's too low to be b/sec.

I am sure it is too high to be Kb/sec ?

What do they mean by "Total"?

I understand "Average" and "Maximum" but what is "Total"?

24" 2.8 GHz (Penryn) 4GB RAM iMac, Mac OS X (10.6.4), FCE 4 + FCS 3 . . . Little Knowledge, Many Opinions.

Posted on Sep 7, 2010 1:47 AM

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Answer 1

Tom Wolsky

Level 10

152,816 points

Sep 7, 2010 4:28 AM in response to Ian R. Brown

It's kilobits per second. No idea what total means. Don't use Get Info. Use Movie Inspector in the QT player.

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Answer 2

Ian R. Brown Author

Level 7

24,455 points

Sep 7, 2010 4:31 AM in response to Tom Wolsky

Thanks Tom.

So it is Kb/sec.

Big mystery about the "Total".

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Answer 3

Tom Wolsky

Level 10

152,816 points

Sep 7, 2010 4:36 AM in response to Ian R. Brown

kb/sec. Not to be confused with KB/sec.

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Answer 4

Ian R. Brown Author

Level 7

24,455 points

Sep 7, 2010 4:43 AM in response to Tom Wolsky

Sorry, that's what I meant.

I assumed the small "b" was all I needed to signify "bits". Didn't realise the "K" also needed to be lower case.

That's what comes of being lazy and not writing it out in full!

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Answer 5

RedTruck

Level 4

2,145 points

Sep 8, 2010 1:37 PM in response to Ian R. Brown

The K doesn't matter, it's only the b or B that matters.

The total bit rate is exactly that. You may have a video with an average or constant bit rate of 5Mb/s, and then an audio file with 768Kb/s, and and a subtitle stream of however many kb/s that is, and maybe another audio stream for secondary audio, and maybe something else that contributes to the TOTAL bitrate.

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Answer 6

Ian R. Brown Author

Level 7

24,455 points

Sep 8, 2010 1:46 PM in response to RedTruck

That makes sense as most video clips consist of video plus separate audio. I tend to forget that, except when making videos for the web, when I specify AAC audio to keep the files small and Dolby Digital Professional 2.0 with DVDs.

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Answer 7

RedTruck

Level 4

2,145 points

Sep 8, 2010 5:04 PM in response to Ian R. Brown

I can't tell you how many people use my studio and compress their video to fit exactly on a DVD-5, and then go over because they can't fit their audio or menu graphics, or subtitles, or anything else. They go over literally by about 1-2 MB, and don't understand that you can't just stuff it in there… One byte over is too big. That's a tough one for a lot of people to grasp, but always funny when they ask if there's anything they can do to make it fit without recompressing it. I just tell them to hit it with the hairdryer.

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