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Offline RAW Compress (ZIP / DNG)

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Offline eliavecellio

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Offline RAW Compress (ZIP / DNG)
« on: 18 / January / 2008, 00:49:43 »
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We all know that the CRW raw files are quite big because they either have no compression, or very light compression.

People have argued against real-time compression (eg into DNG) because it would slow down the shot-to-shot time.

My suggestion, if possible, is that CHDK include an offline compressor of RAW files, either into ZIP format, or DNG (depending on which one is easier to code, I guess ZIP would be easier).

In this way, the compression is not done in real-time (as the photo is taken) but later on. When you are having a rest from taking photos, you can just go to the CHDK menu and launch the Compressor option that can then compress either a single CRW file, or batch process the whole folder of CRWs. It could have an option as to whether to keep the original CRW or delete it to make more space on the card.
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Offline hydrogen

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Re: Offline RAW Compress (ZIP / DNG)
« Reply #1 on: 19 / January / 2008, 20:19:49 »
Quote
My suggestion, if possible, is that CHDK include an offline compressor of RAW files, either into ZIP format, or DNG (depending on which one is easier to code, I guess ZIP would be easier).

In this way, the compression is not done in real-time (as the photo is taken) but later on. When you are having a rest from taking photos, you can just go to the CHDK menu and launch the Compressor option that can then compress either a single CRW file, or batch process the whole folder of CRWs. It could have an option as to whether to keep the original CRW or delete it to make more space on the card.

I like this idea.

+1 from me
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Offline martinF

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Re: Offline RAW Compress (ZIP / DNG)
« Reply #2 on: 23 / January / 2008, 12:04:13 »
Im trying to implement a lossless compression using ZLIB, but the raw sensor data can be compressed only by 20%
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Offline vit40

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Re: Offline RAW Compress (ZIP / DNG)
« Reply #3 on: 23 / January / 2008, 12:44:49 »
I suppose lossless jpeg iz better, since it is used in dng and cr2 format (real cr2, not CHDK crw/cr2) and file size is reduced about a half or even more
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Offline Barney Fife

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Re: Offline RAW Compress (ZIP / DNG)
« Reply #4 on: 24 / January / 2008, 01:09:40 »
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« Last Edit: 22 / April / 2008, 09:51:50 by Barney Fife »
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Offline GrAnd

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Re: Offline RAW Compress (ZIP / DNG)
« Reply #5 on: 24 / January / 2008, 06:57:05 »
Quote from: Barney Fife on 24 / January / 2008, 01:09:40
When looking at the code for the video compression it appears he rewrote the whole compression routine.

Nope. He did not. He just copied it from the original firmware to be able to pass some variables to the procedure.
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Offline martinF

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Re: Offline RAW Compress (ZIP / DNG)
« Reply #6 on: 24 / January / 2008, 09:44:47 »
What compression rate can be done using DNG? Is the lossless JPEG realy lossless? Is no data lost due to quantization and colorspace conversion (RGB->YUV)? The Adobe SDK for DNG, which is used also by DNG4PS is written in C++
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Offline vit40

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Re: Offline RAW Compress (ZIP / DNG)
« Reply #7 on: 25 / January / 2008, 02:38:00 »
Don't know about details, but lossless jpeg compression algorithm is entirely different than lossy jpeg compression. In raw, there is no color space conversion - data remains linear in color space of sensor (value at each pixels is proportional to voltage read from pixel location
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Offline kwf

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Re: Offline RAW Compress (ZIP / DNG)
« Reply #8 on: 25 / January / 2008, 07:55:00 »
Quote from: eliavecellio on 18 / January / 2008, 00:49:43
We all know that the CRW raw files are quite big because they either have no compression, or very light compression.

People have argued against real-time compression (eg into DNG) because it would slow down the shot-to-shot time.

My suggestion, if possible, is that CHDK include an offline compressor of RAW files, either into ZIP format, or DNG (depending on which one is easier to code, I guess ZIP would be easier).
Maybe it is possible to utilize some RAW compression code from cameras which support CR2-files in the firmware, e.g. the DSLR? Maybe even real-time is possible, if these cameras use hardware support which just isn't utilized by the current firmwares.

If not it may still be possible to utilize this code for off-line compression (although it might be easier to port existing code like zip,dng2ps, etc.). Compressing in DNG would be the best, because you could directly handle them with Lightroom etc.  without needing DNG4PS, exiftool etc.
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Offline Lilien

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Re: Offline RAW Compress (ZIP / DNG)
« Reply #9 on: 27 / January / 2008, 15:01:08 »
One question:
Is the picture data in a DNG file (created by DNG4PS) still in the form of Bayer matrix data (RGBG, not RGB)?
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