High-quality video in versatile camera?

External Since: Aug 16, 2005 Posts: 57

"John Turco" <jtur.DeleteThis@concentric.net> wrote in message
news:453B0E6E.1C2D99E@concentric.net...
> PTravel wrote:
>>
>> "Dave Martindale" <davem.DeleteThis@cs.ubc.ca> wrote in message
>> news:eh9oe0$sqn$1@swain.cs.ubc.ca...
>> > "PTravel" <ptravel.DeleteThis@travelersvideo.com> writes:
>> >
>> >>Sorry, but the measure of video quality is the frames per second.
>> >>Still
>> >>cameras must use very high compression rates to store video on an SD or
>> >>CF
>> >>card. All of the ones that I've seen use either mpeg1 or mpeg2.
>> >
>> > The Canon digicams I've used produce motion-JPEG encoded video. Each
>> > frame is independently compressed, much like DV encoding. Yes, the
>> > files are large.
>> >
>> > Your comments about the undesirability of MPEG1 and MPEG2 don't apply
>> > to
>> > motion-JPEG video.
>>
>> Only with respect to the need for multi-pass analysis and lack of ease of
>> editing. Because mjpeg doesn't use intraframe compression, like mpeg, it
>> cannot compress as efficiently. That results in far higher compression
>> ratios being required to accomodate the limited amount of storage media
>> available, far lower data bandwidth and a corresponding decrease in
>> quality.
>>
>> Also, unless the camera comes with software that will transcode captured
>> mjpeg to DV-codec-encoded AVI (which will result in still more quality
>> loss), the mjpeg-encoded AVI (or whatever it produces) will not be
>> readily
>> editable in most consumer and prosumer editing programs. At best, every
>> single frame will have to be rendered before it can be worked with. At
>> worst, it won't be imported at all without transcoding and subsequent
>> quality loss.
>>
>> >
>> > Dave
>
>
> Hello,
>
> My ancient (circa 1999) miroVIDEO DC30 (MJPEG PCI card) can capture in
> S-VHS/Hi8 and 44KHz, 16 bits stereo (CD) quality. Its user's manual
> states:

SVHS and Hi8 are physical recording formats. I don't know what you mean by
"can capture in." The DC30 was an analog capture card. If your point is
that the mjpeg that it produced supported stereo, that's fine -- the
difference between 48 khz and 44 khz probably wouldn't matter much.

>
> "For capturing video, you need a hard disk with sufficient capacity.
> When capturing, for example, S-Video approximately 120-200 MB per
> minute has to be saved."

200 mb/minute is 1.2 gig/hour, less than 1/10 of the 13.7 gig/hour required
by DV-25.
>
> It was bundled with Adobe Premiere, which gives it advanced editing
> capabilities. Both the hardware and software cost several hundreds of
> dollars apiece, when new.
>
> I got my DC30 ($106.50) and Premiere 5.1 ($31.52), separately
> (secondhand), off eBay, in 2002.

Again, I'm still not sure of your point.

>
>
> Cordially,
> John Turco <jtur.DeleteThis@concentric.net>

External Since: Aug 16, 2005 Posts: 57

"Dave Martindale" <davem.DeleteThis@cs.ubc.ca> wrote in message
news:ehe3bi$qbf$1@swain.cs.ubc.ca...
> "PTravel" <ptravel.DeleteThis@travelersvideo.com> writes:
>
>>> Where do you get "half the bandwidth" from? Digital still cameras write
>>> to flash cards, which can have quite high bandwidth - higher than DV25
>>> tape. That's why you can copy video clips off them faster than real
>>> time, for one thing.
>
>>I'm going by what someone else posted to this thread, i.e. 9 minutes on a
>>1
>>GB card.
>
> Well, even that is more than half the bandwidth of DV25. But you're
> making statements that *no* digital still camera can produce high-quality
> video, without even apparently being aware of some of the better ones.
>
>>First of all, the NTSC standard for digital video is 720 x 480, not 704 x
>>480.
>
> That's the DV standard for NTSC-format digital video, which is somewhat
> based on the Rec. 601 standard for digital NTSC video, neither of which
> is actually the "NTSC standard", which describes only the analog signal.
>
> Although 720 pixels per line are captured, that includes the "ramp up"
> and "ramp down" areas outside the clean aperture area. But the pixel
> aspect ratio is 10/11, so the 4:3 aspect ratio image 480 lines high
> occupies 480 * 4/3 * 11/10 = 704 pixels. The "extra" 32 pixels are
> just an artifact, probably because there's some slop in the analog NTSC
> timing spec, and PAL is slightly different, and the original D-1 video
> recorder designers wanted to capture the active video wherever it was.

I was looking through google and noticed we had the same exact discussion
about a year ago when you were advocating that digital still cameras could
capture video as well as dedicated camcorders. You were wrong then and
remain wrong now. The frame size for DV-25 digital video is 720 x 480,
period. When displayed on a digital monitor, it remains 720 x 480.

I'm not going through this nonsense again with you again. Just do a google
search.

>
> But if you're editing video on a computer screen or non-overscan
> monitor, surely you've noticed that some of those 720 pixels are just
> black for some video sources? If they're outside the 4:3 picture area,
> that's just fine.
>
> Anyway, if you want your frame captures from DV to have exactly square
> pixels (which is the standard for still images), you either need to
> crop the capture from 720 to 704 wide before resampling to 640, or you
> need to resample 720 to 655 pixels (but then you may include some of
> those black pixels).
>
> None of this nonsense is necessary for the HD video formats; all of the
> pixels are active, and they're also square.
>
>>Second, the additional 12% resolution may not be "terribly useful" to
>>you, but it is certainly useful to those of us who care about the quality
>>of
>>our video.
>
> Why is it useful to have horizontal resolution that is greater than
> vertical resolution? There are 720 pixels instead of 640 because 13.5
> MHz was a nice round number for a single sample clock in the D-1
> recorder, giving slightly tall pixels in NTSC and slightly wider than
> square pixels in PAL - a good compromise.
>
>>As for a data rate that's 2/3 of DV-25, sorry, the more
>>efficient compressor is not going to make up for the data loss.
>
> Perhaps not, but it's apparent that the very first camera whose specs I
> looked at does somewhat better than what you said the best still camera
> could do for video.
>
> Dave