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Author Topic: Cant understand why playback speed is so much faster than record speed  (Read 24663 times)

KDR

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Re: Cant understand why playback speed is so much faster than record speed
« Reply #15 on: November 17, 2006, 03:33:58 PM »

What you might be seeing in file size I think has to do with they type of compression. A higher res image would compress more because of more like pixels then a low res image where it can't compress as much. (Just a thought)

I will have to look when I get home but I think theres an option to record with no compression at all? If so that would be a good test to see what file sizes the 2 resolutions create.
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tjdavj

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Re: Cant understand why playback speed is so much faster than record speed
« Reply #16 on: November 17, 2006, 04:22:37 PM »

KDR,

Actually that's a great idea! I'll give it a try too, and we can compare notes.
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ajleduc

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Re: Cant understand why playback speed is so much faster than record speed
« Reply #17 on: November 17, 2006, 07:11:47 PM »

I think I can help with the file sizes.
I made a mistake in my previous post where I indicated streaming video.
What I should have said is constant bit rate. 
When ever I see constant bit rate I think streaming.
One of the purposes behind constant bit rate is to guarantee a bit rate for a stream.
--- Anyway ---
Whether you specifically setup it up or not the codec is using constant bit rate in its encoding.
My proof of this is as follows.

Quote
640x480 = 3.7 mb w/ 35 secs of viewing with 1 minute of recording
320x240 = 6.2 mb but with 1 min of viewing with 1 minute of recording

6.2mb / 60 seconds = 0.10333333 mb/s
3.7mb / 35 seconds = 0.10571429 mb/s

The numbers are to close to not be significant. 
Therefor you are recording at a constant bitrate and the problem is dropped frames.

Further I am guessing the 35 seconds reported is more like 35.8 seconds.
I am assuming the 320x240 number is accurate at 6.2mb.
Back to algebra (sorry!)
  6.2mb/60seconds = 3.7mb/x
 
  (6.2mb/60seconds)/3.7mb = 1/x
 
  3.7mb / (6.2mb/60seconds) = x
 
  35.8 = x

As for the reason you are dropping frames that appears to be from a previous post the hardware.
I suspect also the amount of work you are asking the computer to do also plays a roll.

On my computer a 4.3ghz hyperthreaded 1gb ram 160gb sata harddisk bought specifically for video software development.
I am seeing numbers like 40% cpu usage with the display showing.
Upwards to 100% or more (more being when I hit 100% and start sucking down ram) when I turn on recording.

I have just started setting up my system to work with x10 and have a long way to go.
One thing that occurred to me that may be obvious to you ---
I figured I would get a external harddisk put it in the rafters store video to that. 
That way if someone ripped me of I would still have the harddisk hidden.
The other night while I was testing I realized I just created a huge bottle neck.
Not only is the external disk slow(er) than my sata drive its USB same USB controller as the VA11A.
da...
newbies do become users but sometimes these things take time.
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tjdavj

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Re: Cant understand why playback speed is so much faster than record speed
« Reply #18 on: November 17, 2006, 08:06:03 PM »

Thanks for the explanation, makes a lot of sense..

Quote
On my computer a 4.3ghz hyperthreaded 1gb ram 160gb sata harddisk bought specifically for video software development.
I am seeing numbers like 40% cpu usage with the display showing.
Upwards to 100% or more (more being when I hit 100% and start sucking down ram) when I turn on recording.

Interestingly, I see the about 40% usage when viewing display @640x480, but it goes to about 65% when recording, and I'm using a 2.2Ghz Athlon64 3400+, 512M of ram, 250Gb SATA. As I previously stated, when capturing live video @ 720x480 from my Satellite receiver, using MS Movie Maker and Nvidia VIVO, I typically see around 35% usage.  Doesn't make a lot of sense to me.

Quote
Not only is the external disk slow(er) than my sata drive its USB same USB controller as the VA11A. da...

Are you saying that it's plugged into the same USB controller as the VA11A, whereas bus speed is dropped to USB 1.1 [11Mbps]?
or that it only supports USB 1.1 [11Mbps]?

Quote
newbies do become users but sometimes these things take time.

Hey, if you're not a newbie, you're not learning anything..   LOL
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ajleduc

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Re: Cant understand why playback speed is so much faster than record speed
« Reply #19 on: November 17, 2006, 09:33:14 PM »

Quote
Interestingly, I see the about 40% usage when viewing display @640x480, but it goes to about 65% when recording, and I'm using a 2.2Ghz Athlon64 3400+, 512M of ram, 250Gb SATA. As I previously stated, when capturing live video @ 720x480 from my Satellite receiver, using MS Movie Maker and Nvidia VIVO, I typically see around 35% usage.  Doesn't make a lot of sense to me.
I haven't done anything to improve the performance of the computer yet as far as x10 is concerned.
To be honest I am that new to x10.  I am still just getting through the, O I need this software package, O I need this hardware, O now I need this software package......  I think I have finally got all the pieces to start getting things up and running.
As far as capturing video from the Satellite, is it possible that the compression is being done on the video card in hardware.  Where x10 is using a software codec using some of your CPU time?

Quote
Are you saying that it's plugged into the same USB controller as the VA11A, whereas bus speed is dropped to USB 1.1 [11Mbps]?
or that it only supports USB 1.1 [11Mbps]?
Yes I plugged it into the same USB controller and dropped it to 11 Mbps. 
It supports USB 2.0.
Thats the Da...
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tjdavj

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Re: Cant understand why playback speed is so much faster than record speed
« Reply #20 on: November 17, 2006, 09:54:44 PM »

Quote
As far as capturing video from the Satellite, is it possible that the compression is being done on the video card in hardware.  Where x10 is using a software codec using some of your CPU time?

You are correct, the nVidia VIVO has a hardware encoder, but so does the VA11A.
here's the link to the spec sheet:
http://mxhaard.free.fr/spca50x/Doc/Sunplus/spca506a/ca506a1v10.pdf

video compression is done "on chip" so as to minimize bandwidth requirements thru the USB interface.

At this point, I'm kinda confused as to how the codec figures into this, since I see very little or no difference when using different codecs in AHP.. The differences can easily be accounted for as I am recording live video. I think I have to use a "canned" video feed as a "standard" to test the various codecs against.

Quote
Yes I plugged it into the same USB controller and dropped it to 11 Mbps. 

I'm surprised that you don't have more USB controllers on the motherboard, at least a PCI USB card is fairly inexpensive.
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ajleduc

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Re: Cant understand why playback speed is so much faster than record speed
« Reply #21 on: November 18, 2006, 06:23:12 AM »

Quote
You are correct, the nVidia VIVO has a hardware encoder, but so does the VA11A.
here's the link to the spec sheet:
http://mxhaard.free.fr/spca50x/Doc/Sunplus/spca506a/ca506a1v10.pdf

video compression is done "on chip" so as to minimize bandwidth requirements thru the USB interface.

At this point, I'm kinda confused as to how the codec figures into this, since I see very little or no difference when using different codecs in AHP.. The differences can easily be accounted for as I am recording live video. I think I have to use a "canned" video feed as a "standard" to test the various codecs against.
YUV420 is some compression but the codec compresses further.
From the TV decoder you are getting 24 bits per pixel
YUV420 compression - for each group of 2x2 pixels it drops 6 bytes of data. 
Basically you end up with 12 bits per pixel.
But that still needs to be compressed further.
For example, if you were to take a 640 x 480 video at 30 frames per second, 12 bits per pixel that would be 13 almost 14 mb per minute.
With the codec they get it down much further.

I was thinking your NVIDA card may do codec style compression in the hardware which MS Video Maker is taking advantage of. 
I am not totally sure of that though, the more I think about it I am guessing not.

To give you an idea of what can be done, and this does push the limits of the computer.
I have taken the feed from 4 firewire video cameras producing 640 x 480, 30 fps (BW image 8 bits per pixel) at the same time.  Converted, Filtered, Analyzed, saved (compressed) the data and displayed the results.  The app can run for hours and is still responsive to the user.

I think the real problem is x10 handling of video.

In there defense, in order to get the speed described above we basically said.
We will specify the computer, one similar to mine described in previous post, and we only support 1 operating system XP. 
Its a lot easier when you can do that vs trying to support every operating system in the world. 
Whats optimal for one OS isn't for the other etc. 

But it still comes down to, they are only taking the feed from one camera.

Quote
I'm surprised that you don't have more USB controllers on the motherboard, at least a PCI USB card is fairly inexpensive.
I do have more controllers 4 to be exact.
I just plain wasn't thinking.


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tjdavj

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Re: Cant understand why playback speed is so much faster than record speed
« Reply #22 on: November 18, 2006, 10:21:59 AM »

Thanks again for the info, I think further testing with the codecs is the next step.

Quote
I think the real problem is x10 handling of video.

I couldn't agree more!!

Also, glad to hear that you don't have to buy any USB cards.
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