Canon MJPEG color space for SD950 IS is TV.601. What is yours? - General Help and Assistance on using CHDK stable releases - CHDK Forum

Canon MJPEG color space for SD950 IS is TV.601. What is yours?

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Offline foton

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PowerShot SD950 IS DIGITAL ELPH (US market) / DIGITAL IXUS 960 IS (Europe) / IXY DIGITAL 2000 IS (Japan) use TV.601 (ITU‐R BT.601/SMPTE 170M/NTSC) color space for all MJEG videos, even 1024x768. Probably other older cameras, which are using MJPEG use these color space too.

Procedure to check your video color space for Windows users:

1. Using tripod or stable surface, record few second of motionless video with big green solid object. Latter take a shot from the same point at exactly the same settings (including white balance, color settings and aspect ratio). Use sRGB color space for photo.

2. Install AviSynth (http://avisynth.org/mediawiki/Main_Page)

3. Install ResampleHQ(http://svn.int64.org/viewvc/int64/resamplehq/doc/index.html) plugin for AviSynth (you will have to unpack it to plugins directory in AviSynth directory. Dll and exe files must be directly in this directory)

4. Install FFmpegSource2 (http://code.google.com/p/ffmpegsource/) plugin for AviSynth. Unpack exe file and dll file directly to plugin directory.

5. Install any version of VirtualDub.

6. You also need an graphic program with resizing capability. It maybe IrfanView (it has buggy resizing resulting in more aliasing/less details but we don't care about it here).

7. Create scipt.avs:

FFVideoSource("MVI_5368.AVI", threads=1)
ResampleHQ(dstcolorspace="RGB32", srcmatrix="TV.601", dither=false, kernel="Robidoux", chroma_kernel="Robidoux")

and put it into directory with your recorded video file. Change "MVI_4773.AVI" to name of your video file, and "TV.601" to color space you wish to check from http://svn.int64.org/viewvc/int64/resamplehq/doc/index.html#matrices. Probably you will need to check only TV.601 and TV.709.

8. Open script.avs with VirtualDub. Limit range in "Video/Select Range" to one good frame similar to your photo. Select "File/Export/Image sequence" and export selected frame to bmp in directory of script. Program will export only limited range of frames even if it is displaying something else.

9. Open taken photo with your image editing program and rescale it to the resolution of video. Save such rescaled image as photo.bmp.

10. Open photo.bmp and frame from VirtualDub in two windows with Paint. Compare colors, especially green, if it's the same (http://forum.doom9.org/showthread.php?t=164378) the chosen color space in scipt.avs is the color space of your camera. You may maximise both windows to align them. You may also crop fragment of one image and put it in another, if it makes task easier to you.

11. If you checked video color space of your camera please post it here. Note that video space for HD may be different then for SD. The standard is to use TV.709 with HD and TV.601 with SD. Some cameras, as SD950 IS, use the same color space for all resolutions.

If you already converted MJPEGs from video camera to x264 you can change information about color space using http://forum.doom9.org/showthread.php?t=152419. It is working best with RAW wideo. Example (changing color space to TV.601):

ffmpeg -i "T1_Video - .h264" -vcodec copy -an -vbsf h264_changesps=colorprim=6/transfer=6/colormatrix=6 sample.h264
« Last Edit: 02 / August / 2012, 13:04:56 by foton »

 

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