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Old Nov 2, 2005, 11:37 AM   #1
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Hi

I have had an Olympus 490Zoom for a few years. I am happy with the photo quality but video quality is very poor. This is partly due to the 320x240 max. resolution but I think also due to the compression used in the camera. An analysis of single frames show "blocky" images, which I feel certain causes the "mottled effect" on my vidoes. The compression is described as "Motion JPG".

I have compared results with those on a friend's Canon Ixux ( 3 MPixel ) under identical Resolutio/FrameRate conditions and his are much better. There appears to be no blockyness in his frames.

The compression on my Olympus MOV files is "Motion JPG" The Canon I compared appears to use "Motion JPGincluding Huffman Tables" ( according to a Gspot analysis of the AVI files it produces ).

So, please which current cameras produced relatively good videos ?

Aremy conclusionsaboutmy current problems being due to bad compression likely to be correct ? If so, which current cameras are best in this respect ?

Are there other specifications which I should carefully check with respect to video quality ? - apart from the obvious ones of Resolution and Frame Rate ( current camera rate 15 )

I am not expecting the same quality as from a digital camcorder but something which is very much better than my current Olympus. Itrust that Olympus have now moved on and their cameras produce much better compression results than my current one.

Thanks

Phil







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Old Nov 2, 2005, 11:52 AM   #2
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As one who does videography for a business, if you are concerned about quality of your video, why are you using a CAMERA for video? I have not used alot of different digital cameras, just Olympus and Panasonic, but the video quality outof any camera is going to be minimal at best and usually half the resolution that you would get from the cheapest video camera. What can I say, cameras are designed to take still pictures.

Rather than continuing to frustrate yourself with the poor quality video from your camera, purchase a real camcorder, one with a firewire (IEEE1394) port would be best them you can go straight into your computer.

Jeff
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Old Nov 2, 2005, 12:19 PM   #3
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Well, the current crop of Digicams almost universally support 640x480 at 30 fps. I have the canon S2, which is considered to have one of the best video modes of most current cameras, with 640x480/ 30 fps and full stereo sound. Optical zoom and image stablization available during use. It takes video on par with my MiniDV camera (JVC GRD290). I dont even take the video camera now most places if im taking short clips and such (with a 2 gb card you get about 15 min of video) But that is the problem, storage. With each miniDV tape you get 60+ minutes.

There are cameras around that use the MPEG4 codec, which compresses the video, so for example the Casio Z750 get >45 minutes per gb. The video looks good, but not as good as the motion JPG codec, there are noticable atifacts, especially with fast moving subjects. Diffeerent cameras use diffrerent compression ratios, so some Mpeg4 llok worse than others, etc. Its hard to find that info though as they dont always post it, so the best bet is to look at samples yourself.

So for most uses, I use my canon S2 for video, and it looks great. If I need the 25x optical or long video, I use my MiniDV. For playback on TV, DVD you wont notice a difference.
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Old Nov 2, 2005, 12:28 PM   #4
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You are using a camera that came to market in early 2000, and the video feature was never a strong point for anybody 5 years ago. When I want video, I use a camcorder. You don't take a knife to a gunfight.

Anyway, current video is better on the newer models. I've owned a D-490, and the video quality on my current C-8080 is much better.
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Old Nov 2, 2005, 12:40 PM   #5
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If you want to record video, better get those with Mpeg4 compression or else you will need to get lots of memory cards... models like Casio S500, Z750, S600(not launch yet...) or Pentax S5z, S6 or Kodak V550, V530 or Samsung i5 or etc..... As for Sony's model with Mpeg VX, the compression is not as small as Mpeg4, can still expect big video file size.

Cos for a 1GB card @ normal video (@ 640x480 30fps) can only hold about 7-9minutes, while a Mpeg4 video (High Quality, 640x480 30fps) can hold about 30-35minutes, about five times more. i.e. if you want to get a 2GB, for normal video models, you will need 5x 2GB cards to record the same duration of video....

I've seenthose movie clips of models i mentioned above, Casio gives the best movie quality (so far...), the rest have a little 'noise' in the video due to high compression. But Kodak and Samsung model can zoom during recording (Kodak ones can hear the motor zoom noise when zooming, video a little 'coarse') (Samsung zoom noise very very soft, very good, but the video bitrate is slightly less then Casio, so video quality not as good when compared).

So in the end I bought EX-Z750... Ha Ha (just need to disable the alternate 'power on' feature (via the REC/PLAY button) to prevent accident turning on the camera in pocket which will cause the 'Lens error'. So far I have no problem with it.) The video quality is as good as my Ixus40 @ 640x480 30fps, but the file size of Z750 is much smaller, don't have to be worry when taking movie.

You can go and search the web and download all the sample videos to compare... Cheers.
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Old Nov 2, 2005, 1:37 PM   #6
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It's just a question of time... Digicam graphics engines are getting more powerful, compression techniques are improving and flash memory capacities are constantly increasing. When you consider MPEG-4 SP or ASP, it can already achieve very high quality video at bit-rates as low as 1Mbps. The problem is that to achieve such high quality compression a very powerful processor is required. On a PC you can compress aDVD movie into a CD (700MB) utilizing an MPEG-4 SP or ASP codec like Xvid orDivx with little noticeable loss of quality at the same resolution. However this requires a two-pass analysis of the source video and is not achieved in real time even on the most powerful PC. Digicams have to perform MPEG-4 compression in real-time,havelittle to no analysis time, let alone two passes, andmustsurvive offbatterieswhile doing so.Differences inthese real-time encoding graphics engines ultimately determine the quality of the encoded video.

When, in a year or two, either flash memory capacities have increased significantly to make lower compression methods viable (like the S2's MJPEG)and/or digicams have graphics engines powerful enough to encode in real-time in the newfangled MPEG-4 AVC (H.264), then they will begin to rival camcorders.

My personal opinion after viewing as many sample videos as I could find from digicams, the Sanyo C5 at this time appears to have the best quality vs. file size, file size having a definite role because of the limited flash storage capacities available at this time.
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Old Nov 3, 2005, 5:50 AM   #7
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Hi All

Thanks guys for all those comments - food for thought.

The Sanyo C5 , wih its MPEG4 certainly looks worth investigating.

If I go for a different make which uses "MOTION JPG" compressionthen I still have some uncertainties.

A lot of cameras appear to use "Motion JPG" compression, as does my Olympus and the Canon Ixus 30 I tried and the specifications just seem to say "Motion JPG". It was only when I used GSPOT to identify the Codec for the Canon 30 AVI files that I came across the Codec description "Motion JPG using Huffman Tables".

I am not sure if the "Huffman Tables" bit is the significant feature of Canon's compression techniques which avoids Blockiness which leads to the "Mottled Effects" which I get in my videos.Maybe this is just a red herring and ALL current cameras which use "Motion JPG" are now better in avoiding Blockiness compression artifacts.
From what I can ascertain the "Motion JPG using Huffman Tables" Codec is an old IBM one developed before MJPEG was finalised.

Once I have bought a camera, however, it is too late.

So, should I be trying to ascertain which Codec camera manufacturers use when I am trying to choose a new digicam ?

Anyone have any comments on this please ?

Phil

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Old Nov 3, 2005, 6:59 AM   #8
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Just a note about Huffman tables. All forms of JPEG, including M-JPEG, employ Huffman tables. What they are is this: after you have applied the lossy filtering to the frequency domain DCT data (well, you DID ask...), you apply the compression (notice that the lossiness is not actually part of the compression -- even lossless JPEG uses Huffman coding for its compression. What the lossiness does is make the compression more effective once it's applied). The way motion JPEG does compression is by means of pre-defined Huffman tables. They work like this: the Huffman table is a list of bit patterns. Assume, for example, that typical data has 43 0 bits in a row more commonly than any other pattern. That bit pattern is given the first Huffman table entry. So, whenever you find that pattern, you replace the 43 bits with the two (if memory serves) bit key to the first Huffman table entry. The keys get longer as you move down the list of entries, so it is possible for Huffman tables to actually increase the size of a "compressed" file over an uncompressed file -- although the lossy step makes that virtually impossible in practice. The next most common pattern is given the next Huffman table entry, etc.

Now, standard M-JPEG does not actually contain a Huffman table at all. It assumes the default M-JPEG table, which may not be optimal for the particular images you are compressing. As a matter of fact, you can typically double the effectiveness of compression by analyzing the bit paterns of your actual data and creating an optimal Huffman table for that data. This violates the M-JPEG standard, but is a big win on storage.

So, why would the standard not generate its own Huffman table? Because it is stunningly processor-intensive to analyze the data and create a dedicated table. It is beyond most processors' power to do this in real time. My suspicion is that this camera isn't generating a dedicated table, either. It just takes too long to do. What doesn't take any time is using a table once it exists. So, in all likelihood, they will allow you to upload a non-standard M-JPEG sequence into the camera that contains a Huffman table, and still play it back. It's just as fast to get the Huffman entry on decompression from a custom table as from a default table.

If all those assumptions are correct, supporting using a Huffman table on decompression is not very interesting. If, on the other hand, it generates a dedicated Huffman table for your data, you will get noticeably better storage efficiency on the camera, at the cost of creating non-standard M-JPEG that many video players will not be able to replay correctly. You can decide for yourself which is the better possibility.


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Old Nov 3, 2005, 9:23 AM   #9
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Specs on paper are one thing, actual performance is another. You won't be able to determine the quality ofa camera's video capabilities purely based on it's specs or it's compression method,just like the number of megapixels say nothing about the quality ofthe photos taken by adigicam.The compression method should simply give you a ball park idea of the file sizes. For video, given the same compression method andeven the same bit rate, differentdigicam enginescould yield significanlty different results. You need to look at actual results to make a call.
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Old Nov 4, 2005, 8:02 AM   #10
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I agree that you need to see results before buying.

Ihave now had a look at the Sample Movie for the C5 on the Sanyo website and it is very impressive in terms of quality & file size. I have seen other clipsat a reviewer's site and these are pretty good too in good light but less good in poor light. That reviewer's overall opinion however seemed to be only average.

I see that the Olympus C-770 also uses MP4 compression but have not yet found any sample movies.

MP4 really seems to be the way to go and no doubt there will be quite a selection of MP4 digicams on the market soon

However, is anyone aware of any others, apart from the 2 above, on the market at the moment. I am too old to wait too long before buying

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