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info needed for G1X video override bitrate

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Offline moroz

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info needed for G1X video override bitrate
« on: 20 / August / 2013, 21:27:50 »
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Hello,
i read that we can control the bitrate in the new CHDK-SVN Autobuild g1x-100e-1.2.0-3037
i would like to have more information about the bitrate contol in the video mode but i can't find any thread / documentation explaining this in details
could you please tell me if we can increase the video bitrate ? and by how much in numbers please

Thank you very much!
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Offline reyalp

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Re: info needed for G1X video override bitrate
« Reply #1 on: 20 / August / 2013, 21:45:47 »
Quote from: moroz on 20 / August / 2013, 21:27:50
could you please tell me if we can increase the video bitrate ? and by how much in numbers please
As far as I know, CHDK bitrate control is only available in the cameras that save video in mjpeg format. Modern cameras use H264 .mov files. The "video quality" option adjusts the compression level, but it doesn't necessarily correspond to a specific bitrate.
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Offline moroz

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Re: info needed for G1X video override bitrate
« Reply #2 on: 20 / August / 2013, 22:02:51 »
i downloaded the Autobuild from : http://mighty-hoernsche.de/bins/g1x-100e-1.2.0-3037-full.zip
in the "Read me" you can read the following:
Main features:
* a higher compression movie mode, and double the maximum video file size
??
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Offline waterwingz

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Re: info needed for G1X video override bitrate
« Reply #3 on: 20 / August / 2013, 22:06:34 »
Quote from: moroz on 20 / August / 2013, 22:02:51
i downloaded the Autobuild from : http://mighty-hoernsche.de/bins/g1x-100e-1.2.0-3037-full.zip
in the "Read me" you can read the following:
Main features:
* a higher compression movie mode, and double the maximum video file size
??
The readme is a generic document and sometimes not completely correct.  Asking a question here in the forum will get you a more accurate answer.  As indeed it did with reyalp's previous post.
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Offline moroz

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Re: info needed for G1X video override bitrate
« Reply #4 on: 20 / August / 2013, 22:08:27 »
Quote from: reyalp on 20 / August / 2013, 21:45:47
...The "video quality" option adjusts the compression level...

could you please be more specific about this option?
thank you
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Offline reyalp

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Re: info needed for G1X video override bitrate
« Reply #5 on: 21 / August / 2013, 02:24:32 »
Quote from: moroz on 20 / August / 2013, 22:08:27
could you please be more specific about this option?
thank you
You can adjust the compression level in some arbitrary unit. Lower numbers = lower quality. Higher numbers = higher quality. If you go too high, the camera won't be able to keep up and will probably shut down. In general, you probably can't go a lot higher than the stock setting.

The best way to understand it is to try it.
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Offline philmoz

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Re: info needed for G1X video override bitrate
« Reply #6 on: 21 / August / 2013, 05:59:21 »
Quote from: moroz on 20 / August / 2013, 22:08:27
Quote from: reyalp on 20 / August / 2013, 21:45:47
...The "video quality" option adjusts the compression level...

could you please be more specific about this option?
thank you

The G1X (like other Canon cameras that record H.264 video) attempts to maintain a constant quality in the video rather than a constant bitrate. The bitrate (and file size) will depend on the content being recorded - using the default camera settings I've seen 1920 video recorded as low as 50MB / minute up to 250MB / minute.

CHDK allows you to override the 'quality' factor applied. The values you can enter range from 1 - 99, where 1 is the lowest quality and 99 the highest. The default camera setting is approximately equal to 84 in the CHDK override.

A setting of 99 will roughly double the average file size, a setting of 1 will be around 1/2 - 1/5th the average file size; but the actual size can vary greatly as I said depending on content.

A high speed class 10 card should be able to keep up even at quality level 99 - I use a Lexar 400x card with no problem.

The last issue is the 4GB file limit - at quality 99 you can easily reach the 4GB limit in around 8 minutes recording 1920 video.

Phil.
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Offline moroz

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Re: info needed for G1X video override bitrate
« Reply #7 on: 21 / August / 2013, 06:15:32 »
thank you reyalp and philmoz !
i found on  http://www.imaging-resource.com/PRODS/G1X/G1XVIDEO.HTM that the average bitrate is 34Mbps

so if the camera setting of "84 " is equivalent to 34Mbps
can we conclude that 99 will be equivalent to  40Mbps (99/88 = 1.179 x 34mbps = 40Mbps)
which is an acceptable bitrate for H264
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Offline philmoz

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Re: info needed for G1X video override bitrate
« Reply #8 on: 21 / August / 2013, 06:23:52 »
Quote from: moroz on 21 / August / 2013, 06:15:32
thank you reyalp and philmoz !
i found on  http://www.imaging-resource.com/PRODS/G1X/G1XVIDEO.HTM that the average bitrate is 34Mbps

so if the camera setting of "84 " is equivalent to 34Mbps
can we conclude that 99 will be equivalent to  40Mbps (99/88 = 1.179 x 34mbps = 40Mbps)
which is an acceptable bitrate for H264

As I said 99, will roughly double the file size - so an average bitrate of 68Mbps is quite possible. I've seen it go higher than 70Mbps at times.

Phil.
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Offline moroz

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Re: info needed for G1X video override bitrate
« Reply #9 on: 21 / August / 2013, 07:19:27 »
thank you Phil
can we hope for a new autobuild that will:
- uncripple the automatic movie mode ? (it will be great to shoot full manual with this camera)
- increase the Fps from 24Fps to 30Fps ?
i don't understand why Canon blocked these features!! i mean Digic 5 + 1" sensor are great specs for video recording !!
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