Is CHDK worth it for video?

And the short answer is… NO.

I installed the CHDK firmware on my Canon SX200 IS (1.00c) tonight, and made some video tests. I shot high-detailed objects with the normal firmware (default video quality is 75%), and with the CHDK firmware at video quality “99%” (and with all its video quality-related options set to ON).

The result was that the 99% quality setting would produce over 50 mbps bitrate videos (instead of the default 24 mbps). This is good. Problem is, after inspecting the footage, there was only about 2% visual quality gain. I tried with a small moving object too, same result. You can view the test images below yourselves (saved as full quality, with decoder at full quality too).

Test image 1, default 75
Test image 1, CHDK 99

Test image 2, default 75
Test image 2, CHDK 99

The other problem was that with any quality over 85%, the SD card (or was it the DSP/CPU of the camera?!?) could not keep up. Sometimes the video would bail out after 1 second of recording, sometimes after 6-7 seconds. Only below 85% it was stable with a Class 6 SDHC card. And this made that 2% of gain, disappear too.

Here’s an actual JPEG image, captured in AUTO mode, and then resized to 720p and re-saved again with only 75% quality. Even after such harsh treatment, that image is zillions of times better than any still from the videos I captured.

If the CHDK developers did not actually have any bug in their video tweaks, it means that the Canon digicam videos lose tons of quality DURING capture/resizing, internally, before the footage even reaches the encoder! So that would be a weak DSP they use, rather than a weak encoder.

Finally, the histogram, and zebras did NOT work on video mode with the CHDK firmware! Obviously, the video mode gets very little love from the CHDK developers. Which is sad. I mean, one other big feature that filmmakers would love is additional 24p/25p support. But this feature is not even on their todo list!

So, unless you’re interested in CHDK for its photography features, don’t touch it for video. It offers nothing of note to us videographers.

UPDATE: I shot one more test, under better lighting conditions this time, during daytime. As you can see, the quality gain was still minuscule.

Test image 3, default 75
Test image 3, CHDK 99

5 Comments »

Frank wrote on August 26th, 2010 at 3:58 AM PST:

Another great review, spot on. Thank you, Eugenia.
I lusted for the 7D Magic Lantern (a CHDK variant) firmware patch Canon’s too vision-challenged to provide. Have given up since it looks like it won’t happen. Currently working with a Canon HF-S200 – not too bad – better than my 7D. Will still use the 7D for specialty takes – nothing like an 8 MM or a 640 or a macro when it is needed. For me, for now, it’s the S200.


NK wrote on August 26th, 2010 at 6:48 AM PST:

Hi, I own an S2IS myself and I think what’s limiting the quality here is the lighting conditions. With only 1/15 or 1/30 of a second for exposure, the camera probably turns up ISO, which in my experice visibly reduces sharpness. The chip is probably doing some processing too. For example – if I were a canon programmer, I’d try and filter out the noise by computing a weighted average of the frame in question and the the frame before and after.
That’d explain why the still image is so much better.

I too had the problem of the cam/card not being fast enough to handle 99% quality.


This is the admin speaking...
Eugenia wrote on August 26th, 2010 at 11:54 AM PST:

I updated the article with your suggestion, there was no improvement of note to speak about.


NK wrote on August 26th, 2010 at 5:49 PM PST:

Yeah. I wouldn’t even be able to tell them apart if they weren’t labeled.


reyalp wrote on September 2nd, 2010 at 10:17 AM PST:

@Frank
Magic Lantern is not really related to CHDK, the DSLRs are too different for code to be usefully shared with the P&S

@Eugenia
I would expect Canon to set the default quality to something fairly near to the maximum the hardware can sustain. On the older cameras that used MJPEG (like the S2IS NK has) I think there was a bit more of a gain.

Available readout modes tend to be dictated by the hardware, so I’d guess 24p is unlikely.

Histogram in video mode should be possible, actually I don’t know why it’s turned off there. Probably zebra too, although it’s a bit of a CPU/memory hog so it might break something. I’ll look into that.

As for what gets love from the developers, it’s pretty much whatever individual coders find interesting. There isn’t an over all direction.

Fudgey did some experimental work with shutter/aperture/iso control in video and ISO control in video mode which might be of interest http://chdk.setepontos.com/index.php/topic,5295.msg54071.html#msg54071 but it’s pretty raw at the moment.


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